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Acoustics Crash Course 1 - Room Modes

By marktaw in Media
Sun Jun 09, 2002 at 05:50:41 PM EST
Tags: Music (all tags)

With the proliferation of home recording studios, many more people have questions about room acoustics than before. This article first in a series meant to be a starting point in your understanding of acoustics in rectangular rooms.

The Fun House Metaphor

Imagine a room whose surfaces reflected light to varying degrees. These surfaces don't reflect light perfectly, but they all reflect light. Some of them reflect more blue than red, others are sort of greenish*. You go in with protective glasses so you can watch light rays fly around the room without worrying about damaging your sight or being temporarily blinded by flashing lights.

Light travels much too swiftly for us to see it go by. If someone took your picture in this room, the camera's flash would send out light in all directions, much like a speaker, and these would bounce off, travel through, and be reflected by various objects in the room - the walls, you, the camera, etc. until every frequency had been absorbed by one of the surfaces. It would be too quick for you to see every reflection, but you might get a brief impression of "this room seems sort of blue" and by usingcolored light, or sophisticated measuring equipment,you could verify that indeed it is more blue than other rooms you've been in.

This metaphor, while not totally accurate, can help you learn about the problems affecting rooms.

Standing Waves, Room Modes, and Eigentones

All of those phrases mean more or less the same thing. If you take a flashlight and shine it straight at one of the walls, it will bounce off of one wall and hit the opposite wall. Minor movements by your hand will cause radical movements of the beam of light as it bounces several times between the two walls.

In audio these are known as Standing Waves - a wave of sound that bounces between two or more surfaces emphasizingone frequency over others. The area between two parallel walls resonate at certain frequencies.

Light waves are tiny. Audio waves are gigantic by comparison. A bass wave can be several feet long. This is important, especially below 300hz or so. Above 300hz, the waves become small enough that they aren't affected by the room size as much. They bounce around every which way.

Treble waves are small and fast like those created by a rock dropping into a pond. Bass waves are long like the ones that sweep you off your feet when you go to the beach.

If you've ever seen a leaf floating on wavy water, you'll know that the waves don't actually move the water anywhere. The leaf rises and falls, but doesn't move in any direction. Sound waves are very much the same, increasing and decreasing in pressure without really moving anywhere. Otherwise sound would be accompanied by a wind, and you would feel a breeze every time John Bonham hit his kick drum.

Whena speakermoves forwards it compresses the air a bit, when it moves back it creates a bit of a vacuum. These are known as Compression and Rarefaction. If one speaker moves forward while the other moves backwards, they cancel each other out. If you can wire your speakers out of phase you'll hear this - all the low end will drop out and it will sound tinny.

Standing Waves are sounds that reinforce each other, like two speakers wired in phase, as they bounce back and forth between walls, the build up areas of high and low pressure that areconsistently in the same places in the room.

If your walls are 14 feet apart and the wave is 13 feet long, it won't get the reinforcement it needs and it'll die down quickly. If the wave is 28 feet long, or 14 feet long, 7 feet long, etc., it will keep bouncing back and forth between the walls until it encounters a corner and dies off. Because of this, unless you have a very square room, the modes will terminate in the edges and corners. Once that 14 foot wave encounters your 8 foot ceiling, it will die off.

You can calculate the length of a sound wave fairly easily. You just take the speed of sound in feet-per-second, and divide it by the frequency (waves per second).


speed of sound (distance per second)
------------------------------------ = length of wave
frequency (cycles per second)

The speed of sound is around 1130 feet per second, or 344 meters per second. Do not mix feet and meters in your calculations. To make these calculations work you must keep the units of measure consistent. Either feet or meters, cycles or distance must always beper second.

Axial Room Modes

Axial Room Modes involve two parallel walls. In the imaginary reflective room, take your flashlight and point it directly at the wall and it will bounce back and forth between the two walls. These are Axial Room Modes.

If you're standing in the room and shine the light at one of the walls it will bounce back and forth between the walls. Remember sound will zig-zag around the room, and that sound sources aren't directional like flashlights. A speaker is more like a bare light bulb, or a light bulb in a box.

Because of this zigzag, room modes are actually a range of frequencies centered around the number given in our calculations.

Calculating the resonances that will be favored between two parallel surfaces isthe inverse of the calculation to determine the length of a sound wave. Since a room can enforce a wave twice as long as it is, you can multiply the length of the room by two - usually we divide the speed of sound by two because it's an easier calculation to remember - 585/feet, or 172/meters.


Speed of sound / 2
------------------------- = standing wave frequency
distance between surfaces

My living room is 18 feet long, so it will enforce a frequency of (1130/2) / (18)= 565 /18 = 31.39. Multiples of this will be a problem too. You can reverse this calculation easily enough - 1130 / 31.39= 36 = twice the length of my room.

It will also enforce frequencies based on it's width and height (11 feet and 8 feet). The other walls are modes of 51.36 and 70.625. Since I know multiples will be a problem, I know at a glance that frequencies around 150 and 210 will be a problem. How do I know? Because both 30 and 50 go into 150, and both 30 and 70 go into 210. Calculating the exact frequencies using the calculator I can confirm this. The following are several modes I found by multiplying the original mode two or more times: 156.94, 154.09, 219.72, 211.875, 282.5, and 282.5. Since these modes are close to each other I know they will be problems. I'm not concerned with modes above 300hz.

Tangential Modes

Tangential Modes involve four surfaces (two sets of parallel walls) and have about half the energy of Axial modes.

Sound, like a rubber ball, bounces off a surface at about the same angle it arrives at. In tennis the angle is normally very shallow, maybe 15 degrees. On the other hand, throwing a ball straight at the wall, it bounces off at roughly 90 degrees.

Now imagine you're standing in the middle of one wall and you aim the flashlight at an angle towards the center of the wall to your side. No matter what the dimensions of the room it will bounce off of that wall and hit the center of the wall opposite you. Then it will bounce off that wall and hit the wall to your other side. It will bounce off of that wall and come back towards you. If you weren't there to block the light, it would do the same thing again. Aim it up slightly and it will spiral up the room.

The distance between bounces is not arbitrary. Since sound waves that are out of phase cancel each other out, they must be multiples of each other in order to support the wave throughout the circuit.

The calculation for a tangential mode is similar to a that of axial modes, but you have to calculate the length of the ray of sound. Since we know the dimensions of the room, and assuming your walls are perpendicular to each other, we're calculating the triangle formed by two adjacent surfaces and the sound ray.

If you remember your geometry you'll remember that the calculation for a right angle triangle is a^2 + b^2 = c^2. (^2 is the symbol for squared) We know the values for a and b - these are parts of the lengths of the walls at the point where the sound wave bounces off of them, so we're solving the equation for C.

The calculation is:


Speed of sound / 2
------------------------------------ = frequency
square root of (x^2/l^2) + (y^2/w^2)

l and w are the length of the two surfaces involved in the calculation - length and width or length and height or width and height. This is essentially the same as the Axial Room Mode calculation, where the bottom is the equation to find out the length of the of the wave based on the triangle. Note that "x" and "y" can be different numbers. Figuring out for x=1 and y=1 yields the first mode. x=2 and y=1 or x=1 and y=2 would give you different shaped triangles that are also valid. x=2 and y=2 would give you an octave of x=1 and y=1.

Oblique Room Modes

Oblique Modes are the most difficult to describe. They involve all six surfaces, and have about half the energy of Tangential Modes, one quarter of the energy of Axial modes. This mode looks something like the Tangential Mode, except instead of just moving around on a flat plane, it bounces off of the ceiling and floor on it's way around.

Again, the calculation is similar to the previous ones, but you're solving for a 3 dimensional shape, a pyramid of sorts. In the diagram above all lengths are the same, though they don't look it because of foreshortening in the 3D diagram.


Speed of sound / 2
------------------------------------------------ = frequency
square root of (x^2/l^2) + (y^2/w^2) + (z^2/h^2)

"l" "w" and "h" are Length, Width and Height. This is actually a sort of master equation, and you'll often see Room Modes in the format "1 0 0" which symbolizes the X, Y, and Z values for the equation. Setting any of the values to 0 essentially removes that value from the equation (0/1 = 0). This means that two positive numbers and one zero is the calculation for tangential, three positive numbers is the calculation for oblique, and one positive number is the calculation for axial. There are no negative numbers as there are no negative room dimensions.

Some Final Notes

So Axial Modes are the easiest to compute, and they're the most important, which is very nice. Tangential Modes are about half as loud, and Oblique about a quarter as loud, but if an oblique room mode occurs near another mode, that frequency may still be a problem. It's best to calculate all room modes, Axial, Tangential and Oblique to see where any overlap may be.

I've added a Room Mode Calculator to my site to prevent you from having to do all this number crunching by hand.

These modes actually hit the whole wall surfaces, so don't think you can treat just the center of every wall as depicted in the diagrams. For example, there's nothing that says a Tangential Mode has to happen halfway up the wall, and it and does spiral up the wall until it hits a corner where the angle change and the mode dies out, unless it becomes an oblique. Axial Modes can and do happen at any and every part of the wall.

Also, since there are sleight angles involved - nothing is exactly like this simplified mathematical model - the numbers you get from these equations are the center of a band of frequencies that are affected. Which is why modes that happen close to each other are a problem. It's like boosting 140 and 150 Hz on two EQ's, the "Q" is likely to overlap causing a larger buildup of sound in the area of 140-150hz.

Since waves above 300hz are so small (282hz is a four foot wave) there is a much more even spread and much less of a build up in certain areas. A four foot wave can get into lots of places, while a 20 foot wave doesn't fit in may places. Above 300hz, sound is more influenced by what the room is made of and things that are in the room than the shape of the room.

* More on material reflectivity in a later article

Sound Wave quick reference. These are the frequencies of the lowest notes on a piano. A = 27.5, A# = 29.135, B = 30.868, C = 32.703, C#, 34.048, D = 36.708, D# = 38.891, E = 41.203, F = 43.654, F# = 46.249. G = 48.999, G# = 51.913.

These will allow you to quickly test the room modes without sophisticated equipment. Simply play a note at one of these frequencies or their octaves to see whether or not it's emphasized in your room. Using your ears isn't as precise as other measuring equipment, but it's a step in the right direction.

I hope this answers some of your questions and gives you a starting point for some more research. Remember that real life is more complicated than mathematical models, please don't do anything stupid or spend any money just because you "read it online."


Voxel dot net
o Managed Hosting
o VoxCAST Content Delivery
o Raw Infrastructure


Related Links
o Room Mode Calculator
o Also by marktaw

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Acoustics Crash Course 1 - Room Modes | 114 comments (111 topical, 3 editorial, 0 hidden)
Good article (3.00 / 2) (#1)
by tombuck on Sun Jun 09, 2002 at 03:01:02 PM EST

Just be an arsehole, though, which tuning are you referring to with regards to the piano. I assume you're using the ugly, ugly "equal" temprement, but don't forget the controversy surrounding the tuning area of music...

Give me yer cash!

You got me! (none / 0) (#2)
by marktaw on Sun Jun 09, 2002 at 03:14:57 PM EST

You're right, I am referring to Equal Temperment - this is the temperment most people are going to have access to. Besides, that was a can of worms I didn't want to open. It's not something I had thought of since it was an almost last minute add on to the article.

[ Parent ]
I know. It's fun to ask :-) (none / 0) (#3)
by tombuck on Sun Jun 09, 2002 at 03:20:08 PM EST

I've just started really investigating this area of music, as my new electronic piano has seven-odd tuning methods, ranging from meantone to pythagorean and so on. It's strange, but after playing with (fuck, what's his name? Student of bach, came up with a temprement)'s method to play bach, it really does make a difference, which really rather disturbs me to  say the least.

I'm thinking about writing a history of (western) tunings and explanations to boot. Perhaps. Lots of work for a fairly niche section.

Give me yer cash!
[ Parent ]

Does it really matter (none / 0) (#4)
by i on Sun Jun 09, 2002 at 03:46:51 PM EST

for mode calculations? The difference between equal and natural (pythagorean?) tuning is about, oh, 0.1% at most. Your room measurements will probably have more error.

and we have a contradicton according to our assumptions and the factor theorem

[ Parent ]
I don't know his name... (none / 0) (#6)
by fluffy grue on Sun Jun 09, 2002 at 03:58:17 PM EST

But the temperment is called "well-tempered"
"trhurler: he's a bright ray of sunshine shoved right up your ass" -- Misery Loves Chachi

[ Parent ]

Quick google (none / 0) (#7)
by tombuck on Sun Jun 09, 2002 at 04:06:11 PM EST

(that'll teach me)

The one I was referring to was the Werckmeister III. It sounds fabulous.

Give me yer cash!
[ Parent ]

WerkMeister? (none / 0) (#8)
by pwhysall on Sun Jun 09, 2002 at 04:29:23 PM EST

Sounds like my boss...
K5 Editors
I'm going to wager that the story keeps getting dumped because it is a steaming pile of badly formatted fool-meme.
[ Parent ]
Temperament is fascinating (4.00 / 1) (#29)
by gidds on Sun Jun 09, 2002 at 10:28:25 PM EST

In some ways it's a shame that Equal Temperament has become almost universally popular, now that we have the technology not just for many other temperaments, but for variable temperaments and pure harmonies even through many different keys...

And there are loads of misconceptions; firstly, that equal temperament was what most composers used.  False: it only started to become widely used through the latter half of the 1800s, and became the most popular method of tuning in the 20th century (the first true ET tuning method was invented in 1917).  Mozart, for example, is reported to have said that he'd kill anyone who played any of his work in equal temperament!

Secondly, that Bach's `Well-Tempered Clavier' refers to ET.  False: it referred to `well' temperaments such as those developed by Werkmeister, Rameau, and Silbermann, which are closer to equal temperament than the meantone tunings used before that, and so allow a range of keys and modulations, but still have relatively pure harmonies.  In any case, ET would have completely ruined the point of the book, which was to demonstrate and exploit the subtly different `colours' that well temperaments give to the different keys.

And third, that we even know which tuning he was referring to!  He may have meant Werkmeister III (one of the most popular), and he certainly used Quarter-Comma Meantone earlier in his work, but although there's been lots of research, and people like Barnes and Kellner have their own suggestions, no-one really knows for sure.

The effect of temperament can be subtle, but it's well worth investigating.  Equal temperament works because every harmony is equally out-of-tune!  We should get used to the purer harmonies that other temperaments allow.

[ Parent ]

Hold it just a second... (none / 0) (#72)
by gauntlet on Mon Jun 10, 2002 at 06:04:42 PM EST

I've never heard of temperment. However, some of the things that I'm hearing here ring true (Oh, the punnage!) for me. I have spent a lot of time singing in choirs, and I have noticed that for certain types of music, a given interval will be out of tune unless you sing it slightly sharp or slightly flat.

Now am I to understand that the method popularly used for dividing up an octave is not set in stone? That there are other ways of doing it that produce harmonies differently? Oh PLEASE Oh PLEASE refer me to a website that has sound files that demonstrate these "temperments." This could explain a lot.

Into Canadian Politics?
[ Parent ]

No websites but... (4.00 / 1) (#79)
by marktaw on Mon Jun 10, 2002 at 11:50:37 PM EST

It's true. The even temperment is a system of comprimises, fifths are a little flat, thirds are a little sharp. Essentially, it boils down to issues like "The 5th of E is not the same note as the third of G." If you play keyboards, look for a keyboard that handles multiple temperments. Antares Auto Tune handles multiple temperments. If you play guitar or bass look into the Buzz Feiten system, or check out his website.

[ Parent ]
Temperament websites (none / 0) (#84)
by x31eq on Tue Jun 11, 2002 at 07:42:10 AM EST

This is indeed interesting, but off topic.

If you want sound examples, try Understanding Temperaments which has MIDI files and a Java applet. Also, have a look at this other site that gives explanations that I like.

[ Parent ]
Not set in stone (none / 0) (#112)
by gidds on Sat Jun 22, 2002 at 08:15:52 PM EST

Harmony is based on harmonics: multiples of a frequency that `harmonise' well with it.  If you play one note, and another with exactly twice the frequency, they'll fit well together with no `beats'; and the second will be exactly an octave above the first.  If you add another note at triple the frequency, it'll also fit well, and be a fifth above that.  And so on.

However, if you make a scale based entirely on the harmonics of one note, you'll get something that sounds perfect in that key, and terrible in all others.  So what you do is compromise somehow.  In equal temperament, you divide the scale up into twelve equal semitones.

If we look at that fifth; the pure harmony gives a ratio of 3:2, or 1.5.  Equal temperament gives a fifth of 2^(7/12), which is about 1.4983 – extremely close to the pure fifth, but not quite.  Other intervals aren't quite so close, with thirds and sixths particularly problematic.  The pure major third is 4:3, or 1.3333; the equal-tempered major third is 2^(5/12), or 1.3348, which is sharper than the pure one (although equal-tempered minor thirds are flatter than pure ones).

This can easily affect choirs (I sing in small groups where it's especially noticeable).  If you sing a pure harmony major chord, the third will be a little lower than the equal-tempered third.  So if you're not thinking, you'll measure the next note you sing from that third, and go flat.  It's not a massive difference, but the effects can mount up over a piece.  (For some reason, you always seem to go flat, never sharp, though I suspect the reasons for that are human rather than musical.)

Other temperaments make different compromises, making some intervals closer to pure, and others less so.  Because fifths are so basic a ratio, and the equal-tempered fifth is so close to pure, most temperaments are based around fifths: for example, you can make a good scale by having eight fifths pure, and splitting the difference (the `comma') across the other four; that's quarter-comma meantone.

In a way, tempering is a mathematical hack rather than a musical one: the result of approximating rational fractions by fractional powers of two.

I don't know any web sites with sound samples, but I'm sure you'll be able to find some with Google.  (As long as you remember the `a': it's `temperAment'!)

[ Parent ]

Excellent article (2.00 / 1) (#11)
by osaka aquabus on Sun Jun 09, 2002 at 06:18:33 PM EST

As someone who is attempting to construct a home studio this summer this article is very helpful. Please keep going with it.

Subwoofers and tweeters (3.00 / 1) (#12)
by imrdkl on Sun Jun 09, 2002 at 06:24:53 PM EST

I guess it probably depends on the room-shape, but is there a general rule of thumb regarding subwoofers? Facing the room, or the wall? I've always wondered. Also, is it always the case that separating the tweeters and placing them higher up will enhance the overall sound-quality? Higher end speaker systems seem to follow this rule, but I have wondered sometimes if it really helps. Great article, btw. The light analogy was helpful to start off with, even if your intro could have been just a bit more informative.

Bass isn't extremely directional (5.00 / 1) (#23)
by marktaw on Sun Jun 09, 2002 at 09:49:39 PM EST

A lot of woofers are designed to be placed nearly anywhere. They aren't very directional. Some even fire downward at the floor.

That said, putting them near edges and corners make them even bassier.

[ Parent ]
Corners and edges (none / 0) (#53)
by vectro on Mon Jun 10, 2002 at 02:49:11 AM EST


“The problem with that definition is just that it's bullshit.” -- localroger
[ Parent ]
Resonation (none / 0) (#57)
by brunes69 on Mon Jun 10, 2002 at 07:14:33 AM EST

Cause the bass box is so strong, it causes nearby surfaces to resonate at the same frequency (put a sub next to a wall, then feel the wall while it is working). This causes the overall effect to be louder. I have my sub under a desk, and I find this makes for a much better setup than when it was just by itself on the floor.

---There is no Spoon---
[ Parent ]
Exciting Lots 'o Modes (4.66 / 3) (#70)
by marktaw on Mon Jun 10, 2002 at 05:57:20 PM EST

All modes terminate in the edges and corners of the room. Sound bounces back and forth between to walls until it either dies off or encounters another wall. When it encounters another wall it bounces off in a new direction and, hopefully, dies off.

When you put a woofer in a corner as opposed to away from the corner you're getting the maximum bang for your mode buck. It'll get to go across the entire wall until it encounters another wall and dies off.

If the amp is in the middle of the room, sound waves have to travel to the wall before it bounces off. Some frequencies will be out of phase by the time they bounce back to where the amp is, others in phase more or less balancing the sound out, within the limits described in the main article.

By putting it right next to the wall, you're allowing frequencies to bounce back immediately with little to no phase shift, increasing the output. All that stuff that would've travelled away from you is just reflected right back. A good metaphor for this would be a flashlight. While flashlights are specially curved to bounce light into a beam, a corner acts the same way but less directionally.

Being a bass player, I used to do this all the time on purpose. I'd stick my bass in one corner and aim it at the opposite corner. This not only allows the longest possible range for the waves to develop, but emphasizes as I just described. If you want more woof in your woofer, you might try moving it into a corner. Your neighbors might disagree with this though.

[ Parent ]
Bose (2.00 / 4) (#13)
by Bios_Hakr on Sun Jun 09, 2002 at 06:54:30 PM EST

Ok, I have always heard commonfolk say that Bose is good.  I have also heard audiophiles say Bose is bad.  Looking at the LifeStyle System (the only Bose either side ever talks about), I can see that it is propritary.  Other than that, is Bose bad?

My own system, Pioneer, came with fairly crappy speakers.  I have often looked at the 301/501/vcs-10 from Bose as a decent upgrade.

I guess what I'm trying to do is understand WHY Bose is bad and what a true audiophile would reccomend vice Bose...In then Bose price range, of course.

Paradigm (4.00 / 1) (#15)
by zerosome on Sun Jun 09, 2002 at 07:50:41 PM EST

I work as an engineer for a company that designs and manufactures amplifiers, pre-amps, and processors for the professional and audiophile markets. Friends often ask what speakers, or amplifiers are "the best." For amps, I generally recommend ours, because for the money, I sincerely believe they are unbeatable. When it comes to speakers, I feel safe recommending Paradigm. They have a wide range of products that suit just about anyone's budget, and I myself own a pair of Studio 100/v2 speakers (and am very happy with them). Their Reference line will be well outside of the "Bose price range," but their Performance and Monitor Series are probably just what you're looking for.

[ Parent ]
While (none / 0) (#35)
by Anonymous 7324 on Sun Jun 09, 2002 at 11:09:54 PM EST

I don't own Bryston, I can testify that in the high-end world, they're definitely the real deal. Don't hear about Paradigm much in the ultra-high-end, but they seem to be a good favorite of people building beginner hi-fi systems.

zerosum: surprised to see a real engineer on K5!   Are you the brains behind the famous 4-BST and 7-BSTs? :-)

[ Parent ]

Nope (none / 0) (#48)
by zerosome on Mon Jun 10, 2002 at 12:49:37 AM EST

Personally, I think Bryston doesn't get the recognition it deserves in "the high-end world." Mostly I think it's because we don't charge an arm and a leg for our amps. Oh, and we don't put gold this, and gold that everywhere on our products. I like the way the amps look, but some people don't seem to want a big black monolith in their listening room.
Stuart Taylor is the man behind the ST line of amplifiers. I do work one cubicle away from him though. I'm not so good with the analogue electronics (C.Eng), so I do microcontroller programming on the Bryston surround processors.
You're right about Paradigm not being mentioned much in the context of ultra-high-end. That's probably because they don't make a $10,000+ pair of speakers. This automatically eliminates them from consideration in ultra-high-end systems. For those of us that don't have more money than brains, a modest $3000US pair of speakers is usually sufficient.
The thing that I really like about the Paradigm line is that they make something for everyone (except those that want really crazy looking, or extremely expensive speakers). If you want entry-level, look at their Performance series. If you want better, look at the Monitor series. Still not good enough? The Reference series incorporates everything Paradigm knows about speaker design.

[ Parent ]
Genelecs... (none / 0) (#82)
by sobcek on Tue Jun 11, 2002 at 02:38:54 AM EST

We're getting a matched set of 8 Genelec 1037s this fall...(drool...) (sorry for all the posts, but electro-acoustic music topics rarely surface (unfortunately))

[ Parent ]
Genelecs eh? (none / 0) (#91)
by marktaw on Tue Jun 11, 2002 at 08:10:33 PM EST

I've never heard them, though I have heard mixed reviews. Love to hear what you have to say about them when you get to them.

I'm thinking of building a music only site somewhere in between audioreview.com, epinions.com and kuro5hin.org... Anyone interested?

[ Parent ]

Actually.... (none / 0) (#93)
by sobcek on Wed Jun 12, 2002 at 02:30:38 AM EST

I've not heard the 1037s either, but, as far as the electro-acoustic community goes, they're pretty much the gold standard.  Extremely flat frequency response, and they put out more than a sorority girl.  

Also, as a handy plug, if you haven't checked out Curtis Roads' The Computer Music Tutorial (runs about $50-60, but worth it) it's a handy reference and big enough to stop any door cold.

[ Parent ]

Flat is good (none / 0) (#96)
by marktaw on Wed Jun 12, 2002 at 04:25:29 PM EST

Flat is good, but everyone seems to have different ideas of what flat sounds like. I think we'd all agree on the definition, and we'd all agree with various graphs that sine waves and white and pink noise produces, but when it comes to listening to them. That's still a very subjective thing. But here in the acoustic world, I don't hear too many good things about the genelecs. Again, all subjective opinion. Thanks for the book reccomendation, I'll check it out.

[ Parent ]
Paradigm: approximate prices? (none / 0) (#71)
by phliar on Mon Jun 10, 2002 at 05:58:19 PM EST

When it comes to speakers, I feel safe recommending Paradigm.
I have a pair of psb 800s that are about eight years old -- hmmmm, I could get new speakers since I have more money now. Their web site makes no mention of approximate prices though. Approx. how much is the Studio series? Say the 60?

Faster, faster, until the thrill of...
[ Parent ]

Very Approximate Prices (none / 0) (#73)
by zerosome on Mon Jun 10, 2002 at 06:38:23 PM EST

From what I can find online, the Studio 60's seem to go for ~$1100US. If that's a little steep, I would recommend the Monitor 11's which can be had for ~$800US(+/-100), or the Monitor 9's, which are ~$750US. Once again, if this seems like too much money to spend on speakers, you could get some Paradigm bookshelves, or maybe some floor-standing speakers from the Performance series. I own the Studio 100/v2's (from the Paradigm Reference line) and I feel they were worth the extra money.

[ Parent ]
Thank you! (none / 0) (#74)
by phliar on Mon Jun 10, 2002 at 07:31:36 PM EST

the Studio 60's seem to go for ~$1100US. ... I own the Studio 100/v2's (from the Paradigm Reference line) and I feel they were worth the extra money.
I'm guessing the Studio 100v2 is the "around $3000" speakers mentioned earlier. Did you listen to the 60s and the 80s?

I really like the psb 800s I have. I guess I need to select some CDs and go listen to the Paradigms and see if I hear an appreciable difference (allowing for my far-from-perfect living room!)

Faster, faster, until the thrill of...
[ Parent ]

Couldn't Have Said It Better... (none / 0) (#75)
by zerosome on Mon Jun 10, 2002 at 07:54:36 PM EST

Without question, a good session with a pair of speakers is the best way to figure out what's right for you. I usually recommend one or two CD's that contain "reference material" that will allow you to asess the sonic capabilities of the speakers. Almost more important though, is a selection of music representative of your listening habits (if they don't happen to coincide with the afore mentioned "reference material").
The Studio 100/v2 is actually priced more modestly than you might think. You'll likely be able to find it for ~$1800US. It has been a while since I purchased mine, so I'm not sure what the current price is.
$3000US was a price that I pretty much pulled out of the air (maybe informed by personal experience). I just feel that there's an "elbow" in the price versus performance graph for speakers that exists somewhere well below $10k. Spending more money will get you a better speaker (most of the time), but the question is: how much better?

[ Parent ]
a little bit of "enlightment" :-P (3.00 / 1) (#16)
by KiTaSuMbA on Sun Jun 09, 2002 at 08:14:06 PM EST

First of all, a principle: no audio system is *best* at reproducing all music genres unless you are ready for serious k$ expenditures (and probably a new living room projected for such purpose). That means you have to decide what music genre you "care most" to listen to with maximal efficiency. Bose presents speakers with a notoriously "dry" sound and a "punchy" bass. Most audiophiles care about lurical/classical/jazz so you can imagine what they feel about punchy woofers... they hate them, it's taking out all the "sweetness" of their sound! On the contrary, a house dude will just absolutely love them. Bose has the same effect on "commonfolk" as Bang&Ulefsen has on the audiophile crowd: impression! Both makes present their goodies with some impressive features that in actual efficiency of sound mean nothing if not negative: Bose's lead line of products tries to make a point with miniaturized speakers claimed to produce a very powerful sound stream (a speaker has to *move air* in order to produce sound, so you can imagine the "beaty" of a narrow air stream violently speeding to your ears in order to compensate for the lack of surface). On the other hand, B&U tries to impress the "classy" people with strange design and looks: most of their expensive technology is needed to support such "looks" and not the quality of sound, a pretty much good hi-fi (not hi end) system will have the same results in sound at half the price.
Another issue here is that you already have a system and just need to replace the speakers. Your pioneer is a medium class system so you can't spend a fortune on speakers for not much of an actual benefit. You should choose speakers that fit your amp. in both power and "style" of sound. Although I do not know the exact configuration and charachteristics of your system, nor the music you prefer to listen to, I would suggest a set of Mission speakers that are a nice round-up and do not cost too much. If you are in the rock scene, JBL might also be a nice option and definately less expensive.

There is no Dopaminergic Pepperoni Kabal!
[ Parent ]

Simple explanation. (4.00 / 1) (#20)
by mindstrm on Sun Jun 09, 2002 at 09:44:11 PM EST

Those funky little Bose speakers are designed to make something that sounds good. Not something that sounds accurate. They shape the sound so that certain frequencies are enhanced, others are taken out to make sure the sound isn't muddy, etc...

They are desgned to reproduce important frequencies very well, and other ones hardly at all.

So.. audiophiles don't like them because they are not at all accurate. They just sound good at first listen.
I have also heard that, because of this, they can be tiring on the ears after a while. I dont'know about that though.

[ Parent ]

Bose... (4.00 / 1) (#54)
by cr0sh on Mon Jun 10, 2002 at 02:52:17 AM EST

When I have listened to Bose's system, I have noticed that for some music it sounds good, but other music it just sounds "wrong". It mainly has something to do with the bass of the system - it seems "tighter", sometimes even tighter than a non-ported speaker cabinet. Others have noted this as well.

Something that I have only seen published once:

Bose's "acoustimass" system is a proprietary, patented design. I haven't actually seen their patents, they might shed more light. But I do remember reading a short article in an older Popular Science magazine that explained the system. Essentially, it is the ratio 3:1. Basically, take a speaker (preferably a woofer), put a tube in front of it (on the face of the speaker) that is three times longer than the tube on the rear of the speaker (sandwitch the speaker between the tubes).

With the speaker configured in that manner, certain resonant frequencies and standing waves develop (at the low end) where the sound is enhanced by the pressure wave from the rear of the speaker, and is arriving at the same time as the sound from the front of the speaker. I am certain that speaker size plays a role as well (ie, the ratio between the diameter of the speaker vs lengths of the tubes). You can play around with this using a Radio Shack 4" woofer and a carpet tube of the proper diameter. Make the initial sizes 3 feet long to 1 foot long, and reduce from there. Now, all you have to do is fold it (the hard part, because you need to maintain the centerline distance), and put it in a cabinet.

You could also try this with an 8-10" subwoofer and some concrete form tubes or ABS sewer piping from home depot (home theater subwoofer?).

One thing you may notice is how this system is similar to a ported speaker, which is true - but it is that ratio and how it is applied that makes it patentable...

Have fun...

[ Parent ]

Lesson 1 (3.00 / 1) (#14)
by dachshund on Sun Jun 09, 2002 at 07:47:27 PM EST

When building a decent recording studio, avoid rectangular rooms. If you look closely at the walls of most professional recording studios, you'll notice that the walls are at slightly unusual angles. This doesn't solve all of the acoustical problems you can encounter in a room, but it does eliminate some of the difficulties mentioned above.

This is an interesting article, but it almost seems too detailed. Perhaps it would be better to start with the basics and work up to specific equations?

Not Quite True (5.00 / 2) (#22)
by marktaw on Sun Jun 09, 2002 at 09:46:06 PM EST

While splaying walls about 1 foot for every 10 feet does help with diffusion, completely non-rectangular rooms don't eliminate modes, they just make them harder to predict.

I got into the math right away because that's what most people seem to be clamoring for. =)

[ Parent ]
DOY (none / 0) (#30)
by fr2ty on Sun Jun 09, 2002 at 10:30:11 PM EST

We used threaded rods to keep an additional heavy chipboard wall away from the "outer" wall of our studio. We can tighten or loosen the nuts whenever we want to "reconfigure".

Angles matter. Let the signal travel a bit before it returns to the point of emanation.

There is no perfect room. There's zillions of beautiful rooms, big and small, unequally suited for many kinds of audio drama. You won't always find them at the movies or in your favorite DSP-Gizmo.

I like things like flexible studio angles and changing surfaces. Its not only fun to play around with virtual ones,
even if real walls are a subtle business, as they require calm
and open ears and come without "dry/wet" control.

No links this time, sorry.
Please note that are neither capitals nor numbers in my mail adress.
[ Parent ]

Wind (4.00 / 1) (#17)
by tzanger on Sun Jun 09, 2002 at 09:26:46 PM EST

Otherwise sound would be accompanied by a wind, and you would feel a breeze every time John Bonham hit his kick drum.

With ported speakers at sufficient SPL you do feel wind :-)

No.. (4.00 / 1) (#19)
by mindstrm on Sun Jun 09, 2002 at 09:38:31 PM EST

You feel a push and then a pull. That's not wind, it's an oscillation.

[ Parent ]
The oscillating fan (4.00 / 1) (#24)
by tebrow on Sun Jun 09, 2002 at 09:56:00 PM EST

    a : a natural movement of air of any velocity; especially : the earth's air or the gas surrounding a planet in natural motion horizontally
    b : an artificially produced movement of air
Merriam-Webster Online.

[ Parent ]
push/pull port perceptions (none / 0) (#76)
by phossie on Mon Jun 10, 2002 at 08:29:30 PM EST

it sure feels like wind.  :)  keep in mind that the 'push' out the ports is fairly directional, while the 'pull' back in is diffused.

[ Parent ]
Oscillator and DB Meter (5.00 / 1) (#18)
by thirstyfish on Sun Jun 09, 2002 at 09:34:09 PM EST

I've used this Radio Shack Tricorder looking thing for years to flatten the speaker/room aspect.

For microphones, I've usually gone with raising the gain to the feedback threshold and using my ears to find the resonating frequencies to squelch.

Now, what a friend of mine did once when setting up a studio - having found out the resonance etc., was to build these little wooden boxes with holes drilled in one end which captured or baffled the specific frequencies that he wanted to eliminate.
If anyone has heard of this I sure would like to know more about it !

Bass Traps (none / 0) (#21)
by marktaw on Sun Jun 09, 2002 at 09:44:32 PM EST

I'll get into this in later articles. You can e-mail me if you need specifics right away.

[ Parent ]
Perhaps Helmholtz resonators? (none / 0) (#83)
by sobcek on Tue Jun 11, 2002 at 02:42:07 AM EST

They're a damn cheap way to make a great sounding room. (That and a bit of sheetrock to take care of that nasty flat celing...)

[ Parent ]
I didn't want to mention this (none / 0) (#90)
by marktaw on Tue Jun 11, 2002 at 08:08:54 PM EST

They may be easy to build, but you have to (a) be able to recognize the frequency that needs to be tuned, and (b) know how to build a tuned resonator. That's why I mentioned the more generic 'bass traps.'

They're a semi specialized tool.

These are sort of like giant coke bottles. Know how you blow across them and they make a tone? Well they can also be used to attenuate that tone in a room as well. They're great for tuning out a specific problem that you absolutely know you have.

[ Parent ]

Slightly OT question (3.50 / 2) (#25)
by mindstrm on Sun Jun 09, 2002 at 10:01:15 PM EST

I am a headphone guy. I like a good pair of headphones over speakers. Cheaper, more portable... better sound.

One thing I constantly read when it comes to headphone enthusiasts is the concept of soundstage... meaning... making headphones sound like speakers.

Headphones provide 100% isolation between left & right channels.  SO the theory is that something recorded to be listened to on speakers won't sound right... because with speakers, both ears get all the sound, just with a time delay (and other accoustic shaping due to the shape of the head/outer ear)

THe idea is that with headphones, it sounds like music coming through 2 holes in the side of your head.

Now, it could be because I mostly listen to electronica... where this is probably preferable, and not recorded live performance, where you actually want positional audio.. but.. anyone have any experience with this?

On another note.. if you want high quality audio at low cost.. find some good headphones.


Grado rocks (none / 0) (#28)
by calimehtar on Sun Jun 09, 2002 at 10:15:08 PM EST

For context, I'm hardly an audiophile... but went into BayBloor Radio a couple months back and tried some random headphones. My God, Grado headphones are like discovering a 5th dimension or learning to fly or something... I had no idea that headphones could sound so good. I almost convinced myself they'd be worth the $160-$800... but then I didn't...

[ Parent ]
Grado's DO ROCK (none / 0) (#34)
by marktaw on Sun Jun 09, 2002 at 10:57:15 PM EST

My review of them can be found on my site here.

[ Parent ]
:-) Yep (none / 0) (#37)
by Anonymous 7324 on Sun Jun 09, 2002 at 11:12:56 PM EST

they're not bad. The SR-60 and SR-80 are amazing values. The higher end ones less so. As you go up in the price, you find that the Sennheisers, while listing for $450, can be had for $200 or so on eBay and Audiogon. IMO, this means that at the prise of the SR-225 and above, you're better off with the Sennheiser HD-600s unless one happens to like a more colored sound.

I also wanna try the Stax sometime, but I don't have $7 grand to blow on headphones. >:-)

[ Parent ]

Stax Rox (5.00 / 1) (#51)
by jismay on Mon Jun 10, 2002 at 02:39:50 AM EST

My father has a pair of Stax electrostatic earspeakers, and the associated Stax preamp. I have listened extensively to many types of high-end headphones and the Stax remain the best sounding pair I have listened to bar none. Since they are a semi open air design some ambient noise will intrude during periods of quiet. Also, the bass is not nearly as boomy as most people prefer it in these parlous times. My everyday headphones are an old ~20 year pair of Realistic Nova Pro's. They are nowhere near as good as the Stax, but they do stack up quite favorably with several pairs of brand new headphones in the $300-400 dollar range.
"How do you fight such a savage?" "With heart, faith, and steel. There can be only one." -MacLeod and Ramirez, "Highlander"
[ Parent ]
Right. (none / 0) (#102)
by mindstrm on Thu Jun 13, 2002 at 10:41:33 AM EST

And how much is a pair of Stax electrostatic phones?

Bass shouldn't be boomy.

Open phones are generally considered better. Adding noise isolation colors the sound, and messes with it. You *want* ambient noise to filter in, it's more natural.. the only time you don't is if the ambient noise is too loud.

[ Parent ]

You don't need to spend a ton of money (none / 0) (#45)
by CarryTheZero on Sun Jun 09, 2002 at 11:55:19 PM EST

My Grado SR-60s, which are, I believe, the very bottom of the Grado line, sound fantastic to me (although I'm no professional audiophile or anything -- I just like music) and cost maybe $70. Not cheap, but also not staggeringly expensive.

You said I'd wake up dead drunk / alone in the park / I called you a liar / but how right you were
iTunes users: want to download album artwork automatically? Now you can.
[ Parent ]
SR40 (5.00 / 1) (#69)
by marktaw on Mon Jun 10, 2002 at 05:40:36 PM EST

The SR40 is the bottom of the line model. In this series, the number seems to correspond with price. The SR60 and SR80 are comparable, though I've never heard the SR60. I'm told that the SR80s have a better bass response. The SR40's are build in China and have a very different housing than the others, and these boost the bass a lot. More info and reviews can be found on their website, gradolabs.com.

[ Parent ]
Hmm. (none / 0) (#100)
by mindstrm on Thu Jun 13, 2002 at 10:37:46 AM EST

The 80's have better base response than the 60's, yes.

The 40's, actually, from what I hear, are very similar to the 60's. Not quite as good, but VERY good for the price and market they are in. Probably smoke anything else on the shelf in the same price range.

The 40's use the same drivers as the 60's, just a different housing.

[ Parent ]

Grado (none / 0) (#101)
by mindstrm on Thu Jun 13, 2002 at 10:39:53 AM EST

Yep. Grado SR-60's are about the same as my Sennheiser HD330's. I find the 330's to have a subtly better bass response.. but very subtle. They did cost a little bit (only a little) more than the Grados though.

The Sr-60's are my suggestion to anyone who wants to know what a decent pair of headphones sounds like.

The difference, as I'm sure you know by now, between the average crap people use and a good $60-$100 pair of good name headphones is staggering.

[ Parent ]

DAMN YOU MARK!!! (none / 0) (#61)
by retinaburn on Mon Jun 10, 2002 at 10:33:35 AM EST

As soon as I read the location that f*cking little voice in my head said "At the corner of Bay, and Bloor." ...damn advertising. :)

I think that we are a young species that often fucks with things we don't know how to unfuck. -- Tycho

[ Parent ]
electro-static wonders (none / 0) (#94)
by roju on Wed Jun 12, 2002 at 11:41:05 AM EST

Did you take a look at the crazy electrostatic headphones they have beside the wall of normal headphones?  Wow.  Nothing like having thousands of volts pulsating right next to your brain.

I will admit, I got suckered into a nice pair of Sennheisers.  They were worth it though.  There's nothing like hearing just how crappy your soundcard is, or the nice hum you get since you're too lazy to properly ground your amp.

[ Parent ]

Electrostatic.. (none / 0) (#99)
by mindstrm on Thu Jun 13, 2002 at 10:36:28 AM EST

Is.. somewhat overrated. And somewhat not. It's not a magic bullet. Yes, they have very flat response.. but a good set of grados do as well, at a fraction of the cost.

I can't say I'd go for electrostatic headphones, ever. After all... I can't really see a point in having a frequency response curve even more accurate than the sound engineer who mastered the thing in the first place. It just doesn't make sense.

[ Parent ]

Early Reflections (none / 0) (#38)
by marktaw on Sun Jun 09, 2002 at 11:13:31 PM EST

When sound arrives at the ear, it usually contains quite a bit of directional information. How much reverb you hear gives you a sense of how far away something is - the more reverb you add the further away it will seem, or the larger the room it's in. Even the shape of the ears allows you to tell if a sound is coming from in front of you or behind you. All of this is lost when listening via headphones.

When mixing and mastering a song, the producers and engineers have to do a lot of work trying to approximate all the various ways a song will be played back - an audiophile's living room, a cheap boom box, a car, a walkman, etc.

Some engineers try to remove room sound as much as possible while mixing. They call this "Near Field" monitoring. Essentially, you're so close to the speakers that you drown out the room. You don't get the absolute seperation that you do with headphones, but you don't get as much of "the room."

I'm a big fan of a good sound stage. I like nothing better than listening to music and being able to "see" the room it was recorded in. I don't really know which headphones give you better soundstage. I'm guessing that if you're aware of the difference between listening via speakers and listening via headphones you can appreciate each for what it is. Music is meant to be listened to via speakers and that's what engineers mix for, but there's nothing wrong with listening via headphones.

[ Parent ]
Well.. (none / 0) (#98)
by mindstrm on Thu Jun 13, 2002 at 10:34:50 AM EST

I'm aware of the physics... I understand completely WHY headphones are different....

my point was whether or not people found that the lack of soundstage with headphones on normal recordings was a problem, because so far it's a non-issue to me. So much so that, if the physics didn't make perfect sense, and so many people didn't talk about it, I'd say it was urban legend.

[ Parent ]

Soundstage (none / 0) (#105)
by marktaw on Thu Jun 13, 2002 at 01:50:42 PM EST

Listening in headphones does bug me from time to time. Most recordings aren't going to have directional informationf or headphones, so as a result, everything I listen to sounds like, well, it's coming from a few inches off my ear, not in front of me.

[ Parent ]
headphones vs. speakers (none / 0) (#46)
by startled on Mon Jun 10, 2002 at 12:06:18 AM EST

I love my Sennheisers, but I do find myself longing for a good set of speakers from time to time. They're just different experiences, and no matter how good the headphones you're still missing the other side of the experience. Unfortunately, I can get a fabulous pair of headphones for a few hundred bucks (especially used or refurbs), but I can't even get half a fucking preamp for that.

[ Parent ]
Headphone amps (none / 0) (#47)
by driptray on Mon Jun 10, 2002 at 12:14:27 AM EST

Headphones provide 100% isolation between left & right channels. SO the theory is that something recorded to be listened to on speakers won't sound right... because with speakers, both ears get all the sound, just with a time delay (and other accoustic shaping due to the shape of the head/outer ear)

You can buy special headphone amps that feed a certain percentage of the left channel into your right ear, but with a small time delay. And the same for the right channel and left ear of course.

We brought the disasters. The alcohol. We committed the murders. - Paul Keating
[ Parent ]
Yes. (none / 0) (#104)
by mindstrm on Thu Jun 13, 2002 at 10:45:08 AM EST

It's usually called a crossfeed circuit. There are many techniques for it.

A Soundblaster Live or Audigy, if you tell it your output is headphones, will do the same thing.

My question was more whether people found this to be a problem or not.... I happen to not mind the total isolation at all.

[ Parent ]

I think I'll stick with our 20.2 system... (none / 0) (#80)
by sobcek on Tue Jun 11, 2002 at 02:04:39 AM EST

I'm actually not kidding on this one. For those of you in the Dallas area, come hear a concert of electro-acoustic music at CEMI, the Center for Experimental Music and Intermedia, at the University of North Texas.

Nothing personal, but stereo...well, I've been spoiled, and 5.1 is scarcely enough for anyone, if you ask me... Sound space just can't be done justice with two speakers located directly in your ears. (Though you can do some cool vertical cues with the right filters) I think a lot of the fun is in spatialization, actually...

I can't really be happy with headphones, even AKG 240s (and they do look sweet for the price...). Dunno, but in my opinion, Electronica would be MUCH cooler if it got past two channels.

[ Parent ]
Sweet... (none / 0) (#89)
by marktaw on Tue Jun 11, 2002 at 08:04:07 PM EST

Too bad I live nowhere near Texas. I kinda wished I'd caught Dave Moulton's exhibition with his speakers... He's only in Boston.

I'm sure something like this will come to NY. Heck, it probably has I missed it.

[ Parent ]

Well.. (none / 0) (#103)
by mindstrm on Thu Jun 13, 2002 at 10:43:38 AM EST

It could be me.. but in some simulations, I've heard some *stellar* positional audio using headphones only. Very accurate positioning.. both horizontally and vertically.

[ Parent ]
Possibilities, yes.... (none / 0) (#113)
by sobcek on Thu Jul 04, 2002 at 01:52:28 AM EST

but you still got two channels.  Sure, you can cover the X,Y plane.  If you're really clever (and know the person's shoulder frequency response) you can fake a couple of vertical cues (though this will vary widely in its effectiveness).  If you want overhead, the best way is to put speakers overhead.  I guarantee that 2 channels are no match for 20 <grin>.  Also, you have to realize that the 20 channels provide additional diffusion, as well as intergrating a superior fusing of reverb to the room.

[ Parent ]
Accoustics crash course, Lesson #1 (3.66 / 3) (#26)
by MSBob on Sun Jun 09, 2002 at 10:02:40 PM EST

Before you consider all that the above article mentions remember that before you start spending you first and foremost need a detached house, preferably with an acreage lot.

I have had enough of all 'music fans' intruding my peace with your frigging stereos listening to your favourite band of the month crap. I know some of yous are polite and considerate but unfortunately you are in minority.

Soo... before you splash on your new audio system make sure you first have a house to put it in. Otherwise you're in the market for a decent pair of headphones or you'll have me call the cops everytime you turn up your f***king stereo so that I can hear it in my apartment.

I don't mind paying taxes, they buy me civilization.

True (none / 0) (#36)
by Anonymous 7324 on Sun Jun 09, 2002 at 11:11:04 PM EST

research Etymotics for noise-isolation headphones.

And agreed, a shotgun takes care of noisy neighbors real quick!

[ Parent ]

Shotgun, heh (5.00 / 2) (#40)
by MSBob on Sun Jun 09, 2002 at 11:26:37 PM EST

Actually one of the coolest pieces of advice on noisy neighbours I ever heard came from a friend of mine. What he suggested was basically that upon moving to your apartment as you go round greeting your new neighbours you start talking about your gun arsenal and the new 'toys' you're planning on buying. Then you make up some stories of shooting sprees you were involved in and you tell them in such a way that they make you look excitable and quite unpredictable when it comes to your handling of deadly weapons. Even if they sense your past stories are bullshit, it doesn't matter. So long as you come across as a wacko who might one day act upon his fantasies, all is well...

The first time there is any amount of noise you go complaining straight to your neighbours with that mad look in your eyes that would make Jack Nicholson from 'The Shining' blush. Your wishes are guaranteed to be respected very promptly!

Never tried this approach myself but the whole idea of trying to come across as a wacko so that your neighbours will genuinely fear you is just hillarious... Not really sure whether this would work with me and my round, boyish face, though. It's in situations like these when an appearance like that of Eric Raymond may actually be a positive thing to have.

I don't mind paying taxes, they buy me civilization.

[ Parent ]
All this... (none / 0) (#52)
by vectro on Mon Jun 10, 2002 at 02:43:14 AM EST

And people say that community is dead in America.

“The problem with that definition is just that it's bullshit.” -- localroger
[ Parent ]
Same here (none / 0) (#58)
by am3nhot3p on Mon Jun 10, 2002 at 08:34:32 AM EST

Well, kind of.

When I moved into my university accommodation, I gave them the impression that I was a psychopath. I suggested that I should remove my flatmate's feet if he couldn't stop them from smelling so bad - and explained in detail the theory of battlefield amputation.

When they saw me hacking some chicken legs up with my Chinese cleaver, I think that they began to imagine me actually doing it!

I always found it helpful to have the reputation of being a latent psychopath. My 'suggestions' carried more weight that way.

[ Parent ]

Well (none / 0) (#62)
by farmgeek on Mon Jun 10, 2002 at 11:15:31 AM EST

you can always do what I do.  

When the neigbors get too noisy, I just start firing the pistol out the back deck.

Not only will this remind your neighbors to shut the hell up, but it will also remind them to keep their damn kids from tearing up your back forty (in our case the back one).

We saw a lot more dogs kept chainedon leashes after my wife shot the mutt in our front yard and left it there all day for me to dispose of when I came home from work too.

Guns really do help to insure a polite society.

[ Parent ]

polite? (5.00 / 1) (#65)
by mlong on Mon Jun 10, 2002 at 02:07:19 PM EST

We saw a lot more dogs kept chainedon leashes after my wife shot the mutt in our front yard and left it there all day for me to dispose of when I came home from work too.

Guns really do help to insure a polite society.

I wouldn't call shooting someone else's dog "polite".

[ Parent ]

Loose Dogs (none / 0) (#97)
by Bad Harmony on Wed Jun 12, 2002 at 10:08:10 PM EST

In many rural areas, you can shoot any dog that is running loose on your property. Dogs have a bad habit of harassing and killing livestock and wild animals like deer. If allowed to multiply, they may form packs and become even more of a problem. Most of the people that I know who live in rural areas don't have a problem with this. If they recognize the dog, they will probably say something to the owner the first time that it happens. The next time, fido doesn't get a free pass.

5440' or Fight!
[ Parent ]

re: Loose Dogs (none / 0) (#107)
by HDwebdev on Fri Jun 14, 2002 at 12:41:02 AM EST

I lived in Colorado during the late 70's and early 80's.  In most areas I frequented, pets that wandered onto others properties outside of the city were considered fair game for shooting at.

[ Parent ]
re: Shotgun. heh (none / 0) (#106)
by HDwebdev on Fri Jun 14, 2002 at 12:38:36 AM EST

We have a lot of wild animals that lurk around our area (resort, lots of trash during busy season).

I always greet new neighbors and people looking for places to rent with 'if you hear shotgun blasts after midnight, it'll be over soon, I'm just scaring off the dangerous wildlife'.

Needless to say, the neighbors only bug me with REAL problems, and do it during the daylight hours to boot :)

[ Parent ]

I learnt this the hard way (none / 0) (#63)
by hovil on Mon Jun 10, 2002 at 11:32:32 AM EST

I splashed out on a big amp and speakers, which was fine for where I was living in at the time, but due to a job change I had to move to an apartment close to the city, I had just installed the stereo and turned it on to what I thought was a 'good' volume, and had the neighbour knocking on my door, she was very plesant about it, and hasn't complained since, since I don't turn it up louder than your average TV listening levels. I'm just a bit annoyed that I forked for such equipment when I can't even utilize it to its full potential. the building has very solid walls, so I think the only place that the sound leaks out is the front door, some sound proofing might need to be installed before I can crank it to my hearts desire once more.

I've got a pair of headphones that I use when my girlfriend is watching TV, but I'm one of these losers that likes too feel bass aswell as hear it.

[ Parent ]

Well. (4.00 / 1) (#27)
by mindstrm on Sun Jun 09, 2002 at 10:05:35 PM EST

What about building a dead room?

Walls textured and shaped to baffle/absorb sound, across the board.

I suspect htere is a reason this is not done, probably something to do with deadenning the sound in the room.. but I dunno.

I nkow I like it. I'd love a totall deadroom office.

If you had ever been to such a room, (none / 0) (#32)
by fr2ty on Sun Jun 09, 2002 at 10:39:45 PM EST

you'd know.

It sucks. The walls seem to drink away most of every noise you are used to hear. You can literally hear your blood pumping through your head after a while. It is a strange and highly artificial experience.

Some few people even vomit or seriously loose balance. Some people even like it.
Please note that are neither capitals nor numbers in my mail adress.
[ Parent ]

uhm, sorry (2.00 / 1) (#33)
by fr2ty on Sun Jun 09, 2002 at 10:41:34 PM EST

you said you DO like it.
Are you sure?

What was it like?
Please note that are neither capitals nor numbers in my mail adress.
[ Parent ]

Anechoic Chamber (none / 0) (#44)
by marktaw on Sun Jun 09, 2002 at 11:36:45 PM EST

Yeah, from what I hear those are truly bizarre rooms used to mostly for measuring speaker frequency responses and such. You have no idea how much you depend on your ears to orient you and locate sound sources until you've gone into one of those rooms.

Perhaps you meant a relatively dead room, not an absolutely dead room.

I suspect that if I was in one of those rooms the sound of my tinnitus would drown out the sound of blood rushing through my head. Such is the life of someone close to music.

[ Parent ]
more anechoic fun (none / 0) (#59)
by goosedaemon on Mon Jun 10, 2002 at 09:23:27 AM EST

anechoic chambers are also used to simulate sound from another place; by recording to stereo (or quadraphonic) sound from somewhere else (a concert hall, for example) and then playing it back in the anechoic chamber, with the observer sitting in a certain spot, the sound is exactly as it is in the other place. room reverb and modes and the like don't interfere with the recording.

for purists and professors, obviously. although it is useful for comparing different concert hallfs. imagine, comparing two halls side-by-side with the same piece.

[ Parent ]
Actually, if I might, at least for musicians.... (none / 0) (#81)
by sobcek on Tue Jun 11, 2002 at 02:25:52 AM EST

We don't tend to use it for listening to recordings so much as making recordings. The problem with recording a sound source in a concert hall is that you cannot isolate the instrument's sound from that of the room. (For some of you, this is not a bad thing, but for me as an electro-acoustic composer it's not effective. Recordings are the beginning of a piece rather than an ending for us!) I need to find out what, for instance, the trombone really sounds like outside of the hall's effect. I can do that in an anechoic chamber. What's more, I can get a pure sample, without the 60 cycle hum, the person slamming the door down the hall, the ghetto sled with the booming bass driving down the street, etc. With an anechoic chamber, you don't have to worry about artifacts, which is particularly important since you're going to be using this sound as a source for other sounds. (In some anechoic recordings, they don't even use human players in order to prevent extraneous sound!)

By the way, if you want to compare the same piece in two different halls, it's much better to make a recording in an anechoic chamber and then convolve it with each rooms' respective impulse response pattern. Otherwise you end up with two different performances! (although, as you mention, it is an ideal listening environment in terms of purity (though again, purity will give you a raw dry sound if you're not careful...)

I'd also like to point out that echoes themselves are not bad, and are a very important part of most spatializing programs. (As does reverb) In fact, you will find that a sound source moved around a speaker field without its surrounding reverb and delay can seem very artificial if you're not careful. Anechoic chambers are, as you mentioned, extremely useful testing grounds, as the sound output tends to be significantly less skewed. And yes, they will f$ck with your head after a bit... (the world sounds about 10 times louder after a half hour in an anechoic chamber; remember that your eyes are used to adjusting from light to dark. Your ears are not...)

[ Parent ]
They are useful... (none / 0) (#88)
by marktaw on Tue Jun 11, 2002 at 08:01:53 PM EST

Anechoic chambers are useful in certain applications, though I don't imagine you'd find (a) an orchestra sized anechoic chamber, or (b) an orchestra willing to play in one. I think that if you have use for an anechoic chamber, you're likely to know what they are.

As a composer who uses samples, and who uses reverb convolution to create your reverbs and 'room sounds' then recording in anechoic chambers is useful for you.

I'm not too familiar with convolution, and was wondering if they take convolutions for seperate parts of rooms. Sort of like "microphone in third row center, pistol orchestra left... pistol orchestra center... pistol orchestra right..."

Also, I'm guessing these halls are empty of people... Maybe they should fill them with something that approximates people, becuase the room will sound different with people.

I may contact you off ine with more questions about digital composing.

[ Parent ]

More on convolution (none / 0) (#92)
by sobcek on Wed Jun 12, 2002 at 02:23:01 AM EST

There is software to do this out there, even taking the audience into account.  This is more a job for physical modelling than convolution, however.  (course, if you wanted to do it ultra cheap, find a piece which has a lone pistol shot, and you're a lot closer...Pity about Der Freischutz having orchestration behind it) Just sliiiiightly computationally intensive...  Of course, again, you could simply damp the reverb (by changing the amplitude envelope of the impulse response) a bit more to simulate an audience, and most people would be hard pressed to really tell the difference.

Frankly, if most people can tell the difference between the pistol being twenty feet to the left or right, I'd be damn surprised.  Generally, my understanding is that the microphone is placed in the location where it normally would be in a hall (many choices here, of course, and whether you want a stereo omni X-Y or perhaps MidSide (or something with multi channels) config...).  Of course, for those of us interested in spatialization, the possibility of recording the sound from 8 discrete microphones positioned around the room (and then you could cross-fade the convuluted signals to pan the sound-source location around...)  Also, you have to consider the types of speakers that will be used to reproduce said samples.  For most people, it's not really going to make a significant difference (at least that's my guess)

Of course, it also depends on what microphone you're using to record the impulse...   One of those Neumann dummies would be nice...

[ Parent ]

You're right (none / 0) (#95)
by marktaw on Wed Jun 12, 2002 at 04:17:05 PM EST

My only experience with convolution comes from some winamp plugins. I played some mp3's through a convolution engine and used a club sample/convolution. It really sounded like the recording had been taken inside the club. It gave me some hope for digital reverb, which I mostly abhor. I'm really excited about convolution, at least for reverb. Mic and Amp modelling should be interesting as well, and I know quite a bit has been done in that area as well. You're right, I am getting overzealous about placement within the theater or club or whatever. Less realistically, you can feed odd noises into convolution to create new and interesting sounds. For example outside there's a thunderstorm. Running the music through a convolution based on the thunder would be interesting. A convolution into one of those foam heads would be great. We should start releasing CDs in multiple formats like DVDs - wide screen / pan & scan or for speakers / for headphones.

[ Parent ]
Other fun tricks with convolution.... (none / 0) (#110)
by sobcek on Sat Jun 15, 2002 at 04:27:33 AM EST

There's also the possibility of spectral tricks.  Take a soundstream.  Split it, and delay one by a small amount, and then do an FFT on both of them.  Convolve the two FFTs (via cross multiplication) and you should get some interesting smearing.  (Imagine the possibility of shifting frequency bins...)

This is stuff which can be done in JMax in realtime, by the way.  

[ Parent ]

I've been in such an anechoic chamber (none / 0) (#60)
by vrt3 on Mon Jun 10, 2002 at 10:32:15 AM EST

They're called anechoic because there are no echos (very very very few to be precise). I've been there only during a short time (a few minutes), and with other people there too (acoustics professor + about 10 students), so there was no real silence.

Still, it was a strange experience. Very hard to describe. Makes one realize how much you're used to hear echos all the time.
When a man wants to murder a tiger, it's called sport; when the tiger wants to murder him it's called ferocity. -- George Bernard Shaw
[ Parent ]

some people spend lots of money for this effect (3.00 / 1) (#50)
by krkrbt on Mon Jun 10, 2002 at 01:54:04 AM EST

they're called "sensory deprivation tanks". I've never been in one nor seen one, but here's a description:
a sensory deprivation tank is a twin bed sized chamber in which the user lays in ten inches of water. Eight hundred pounds of Epsom salts is dissolved in the water which allows the user to float like a cork. The chamber is sound proof, emits no light, and both water and air are kept at skin temperature, 94 degrees Fahrenheit.

Many people use the tanks for meditation, self observation, prayer, creativity, visualization, solitude, rejuvenation, rest, and relaxation.

hah, i'll have to try it out this week..

[ Parent ]
Not dead, but neutral (4.50 / 2) (#49)
by Iesu II on Mon Jun 10, 2002 at 01:51:49 AM EST

A dead room is an aesthetically unpleasant listening environment because it's unnatural. It's also incredibly expensive, because really deadening a room takes a heck of a lot of material and extra space.

A neutral room is much easier and cheaper to come up with and doesn't make sources sound isolated. Neutral rooms simply even out reflective characteristics and eliminate standing waves without trying to absorb all of the sound. First, you want the walls and ceiling to be at irrational angles to the floor. Not haunted-house irrational; just a few degrees out of kilter. Perhaps 1-2' of deviation on a 20' wall. Second, you want the walls to be less flat, acoustically. Hard baffles in the centers of walls will disperse treble, and hollow fibreglass columns (bass traps) in corners will prevent bass from resonating too much. Between the wall angles and dispersion adjustments, sound waves will generally be spraying all over the room at random, eliminating resonances and dead tones.

Not that anyone would do the above to a living room. :)

[ Parent ]

Feedback (acoustic, not editorial!) (4.50 / 2) (#31)
by sgp on Sun Jun 09, 2002 at 10:32:59 PM EST

I'd love to understand more about feedback in odd-shaped rooms (I'm thinking in particular about our Church PA system which is in a strange-shaped room (rough diagram). By the nature of the room, sound bounces left, right, and centre. The band tend to be in the left of the diagram, in the non-greyed-out area to the left of the left-most speaker. They have three foldback speakers. The main speakers hang from the ceiling in the locations shown. The room is (guess) 20ft. high, 40ft x 40ft.

It's a feedback nightmare. We tend to use Shure SM58's, though we've a few condensor mikes.Directly under the speakers is a hot-spot for voice mics, anywhere near the foldback is v. difficult, as the foldback tends to be at least as loud as the "main" speakers, to help singers hear instruments over the (unmiked) drums.

There are 10 types of people in the world:
Those who understand binary, and those who don't.

Need Measuring Devices (none / 0) (#41)
by marktaw on Sun Jun 09, 2002 at 11:27:39 PM EST

Odd shaped rooms are a problem. Since this room looks mostly rectangular, you can start there. Actually, if this room is as square as you say it is (20x40x40) there should be a few problem bass frequencies that are easy to identify.

Also, having the mic's so close to the speakers doesn't help much. A de-esser, which is essentially a very narrow band EQ may help with the feedback. Figure out what frequencies are feeding back and cut them out.

The technique for this is simple. You boost a narrow band and sweep it until you start hearing feedback. Then you cut the exact same frequency. If you already have EQ equipment this should be relatively easy and inexpensive to do.

The SM58 has good off-axis rejection. I.e. it doesn't pick up much noise in the directions it isn't pointing in, which one of the things that makes it such a popular mic for live music. I'm guessing that treating the wall behind the peformers will help with the mics a bit as it will cut down on reflections coming off this wall and feeding the mic's.

Also, remember that this article has mostly to do with low frequency feedback, the kind of stuff you can usually cut right out of vocal mics without too much degredation in sound. At higher frequencies it has more to do with what the room is made of, the walls, ceiling, floors, etc. I'm going to address this in another article. Then I'll start talking about solutions. You can e-mail me if you want to continue this conversation.

[ Parent ]
Oh yeah... (none / 0) (#42)
by marktaw on Sun Jun 09, 2002 at 11:31:41 PM EST

As to the measuring devices alluded to in the headline, try to use some of the techniques I mention towards the end of the article. Experiment with musical instruments and find out which notes feed back more than others. Then figure out what frequency it corresponds to by multiplying the numbers I gave. This is another way to find frequencies to cut.

This is a cheap way of identifying problems. Just have a guitar or piano or organ player play a note and see how long it takes to fade out in the house, especially with all of the mic's turned on. Having people in the room will change it's characteristics, and I don't think you want to do this with the whole congregation in there, but this is a place to start.

[ Parent ]
Feedback in PA (none / 0) (#56)
by Sawzall on Mon Jun 10, 2002 at 06:59:28 AM EST

The quick solution (or at least help) would be a processor like the Behringer DSP1124P - cheap, listing at only $159. While there are much better processors out there, few will be cheaper. Beyond the auto mode that makes fast work of feedback, it also offers 24band, parametric EQ. Given the room you describe, the EQ sounds like it would be helpful. If you can afford to go up in spending, Sabine makes a nice unit in the Graphi-Q series for around 1K. Really tight notch filters so you are only pulling down the troubled area, not a big part of an octive. If you have a really good Bingo night, take a look at the Eventide/Lexicon products. PA is not like home stereo - processing is required even desirable.

[ Parent ]
feedback killer... (none / 0) (#66)
by jasno on Mon Jun 10, 2002 at 03:54:22 PM EST

A friend of mine does the audio for our church group and has the same problems.  He's tried the automatic notch filter approach (don't remember the equipment name, sorry) and it's only marginally effective.  

He did mention a rather interesting piece of equipment that might work, though.  He said (and again I don't have manufacturer names) there's a DSP box that simply shifts the frequency up a tiny bit (probably no more than a Hz or so).  Doing this causes any feedback to quickly change frequency which reduces its effect.  Normal sounds only make it through the system a few times and (hopefully) don't get distorted.  I'd imagine you might be able to hear some strange artifacts as the feedback sounds rose in pitch and decreased in amplitude.  Might be something to look at, though.

[ Parent ]

Variable results (none / 0) (#67)
by nosilA on Mon Jun 10, 2002 at 04:07:24 PM EST

Sometimes inserting delays or pitch shifting will help - other times it makes things worse.  The automatic boxes work somewhat, but are insufficient in certain situations.  What you really need is a good engineer with a good ear and a good 31-band graphic EQ (such as a Klark-Teknik DN-360) or a fully parametric EQ (KT and BSS make good ones, and the one in the sound console may be enough) and in most situations, he will be able to remove most of the rings from the system.  

There are other tricks, like inverting the phase somewhere in the system, but those also have varying effectiveness.  You can tinker, but remember that changing the humidity or the size of the audience or the position of items on stage will drastically change the feedback and you have to be flexible.

Vote to Abstain!
[ Parent ]

One More Thing (none / 0) (#68)
by marktaw on Mon Jun 10, 2002 at 05:33:47 PM EST

I don't think I mentioned this before, but moving the mic's is probably your best bet. These types of modes build up energy in specific areas of the room. Simply moving the mic's to another part of the room may have a significant impact. Perhaps the chorus wants to stand to the left of the drums rather than the right, for example?

[ Parent ]
excellent article! (2.00 / 3) (#39)
by florin on Sun Jun 09, 2002 at 11:22:35 PM EST

Thank you. And keep them coming... ;-)

Thank you. (none / 0) (#43)
by marktaw on Sun Jun 09, 2002 at 11:32:14 PM EST

I appreciate it.

[ Parent ]
Equations please! (2.00 / 1) (#55)
by sebpaquet on Mon Jun 10, 2002 at 06:28:41 AM EST

I'd be interested in looking at the derivation of those formulae. Do you know where I can find them (preferably online)?
Seb's Open Research - Pointers and thoughts on the evolution of knowledge sharing and scholarly communication.
You're kidding right? (none / 0) (#87)
by marktaw on Tue Jun 11, 2002 at 07:54:00 PM EST

If you have any questions about the formulas, e-mail me.

[ Parent ]
Why do you think I'm kidding? [nt] (none / 0) (#114)
by sebpaquet on Fri Oct 18, 2002 at 02:22:43 PM EST

Seb's Open Research - Pointers and thoughts on the evolution of knowledge sharing and scholarly communication.
[ Parent ]
Anechoic Chamber (none / 0) (#64)
by tayknight on Mon Jun 10, 2002 at 12:45:15 PM EST

I've spent a lot of time in an anechoic chamber at the National Center for Physical Acoustics back in High School. These rooms are weird. First, you walk on a raised grid of aircraft grade aluminum wires. The floor (under the wires), walls and ceiling are covered in cones that extend out about 2 feet and have a base about 1 foot on each side. They are made of a medium density foam. The cones bounce their echoes in every direction except back into the center of the room. Most of the echo is absorbed by the foam. They are usually isolated from the floor (on springs or cushions of air) and the walls to minimize vibrations from the ground or wind.

These rooms are mostly used to model speakers and for theoretical experiments that require acoustically 'clean situations.

These rooms do allow you to hear very quiet sounds like your own heartbeat. However, acoustic location (from a repeating sound) by our ears is quite good in a room like this since our brain doens't have to discard echoes.

Another cool room was the 'echoic' chamber. This room had very hard, smooth walls. The echoes in this room, for a particular frequency, bounced around and amplified each other. This small room had huge doors and walls since they could simulate jet engines and rocket blasts. Very cool. They could leviate a ping-pong ball in the nodes of a sound.
Pair up in threes - Yogi Berra

Cool! (none / 0) (#85)
by RegularFry on Tue Jun 11, 2002 at 05:39:52 PM EST

They could leviate a ping-pong ball in the nodes of a sound.
Now, for extra points, how the %^&$ does that work?

There may be troubles ahead, But while there's moonlight and music...
[ Parent ]
And you thought I couldn't answer this (none / 0) (#86)
by marktaw on Tue Jun 11, 2002 at 07:43:50 PM EST

I've seen photos of this done with slivers of cork. They take a parabolic resonator, which focuses all of the sound into a single ray down the center.

When they feed the right tone into the resonator it creates a standing wave like you wouldn't believe. Apparently enough to levitage ping pong balls on.

See, that's why they call it a 'standing wave' - it's a wave that doesn't move like normal waves, it just, well, stands there. I guess it's sort of like how clouds float on layers of air pressure.

This is also why cancave surfaces in rooms are bad bad bad.

[ Parent ]

Yeah, but... (none / 0) (#108)
by RegularFry on Fri Jun 14, 2002 at 10:36:26 AM EST

In the standing wave, the nodes are points where the pressure doesn't change at all, and at the antinodes it fluctuates between + and -.  The average pressure over time is constant along the axis of the ray, which leaves me confused as to exactly what the mechanism is, without a gradient to counteract gravity.
Clouds I can understand - there's a static gradient for the vapour to sit on.
Is there a nonlinearity working to make this weird?
Is there a frequency range over which this works particularly well?

There may be troubles ahead, But while there's moonlight and music...
[ Parent ]
Think of a volleyball (none / 0) (#109)
by marktaw on Fri Jun 14, 2002 at 12:31:44 PM EST

The net motion of a molecule excited by a sound wave is 0. They vibrate around a single point in space, and pretty much return there.

Air at the nodes moves quite a bit, while are at the antinodes moves very little. This is sort of counterintuitive, you'd expect the area where pressure changse from +1 to -1 and back to be moving the most, but it's moving the least.

What's causing the pressure build up and release is actually the air at the nodes vibrating back and forth. By rushing in it increases the pressure at the antinode, and by rushing out it decreases the pressure, increasing it in the adjacent antinode.

When you're floating something, you're not floating it at the antinode. The air rushing in gently nudges it up into the more stable antinode. When the node air rushes out, the object being floated is not affected as it's in the stable antinode where air isn't doing much of any moving. As it begins to fall into the antinode, the air comes rushing back in pushing it up again.

This happens thousands of times per second. In my cork example, the slices of cork were floated about a half inch a part, making one wave an inch long yielding a frequency around 14khz, or 14,000 cycles per second.

I guess hail would've been a better example. Hail is rain that begins to fall and freezes, then is blown up by incoming air and accumulates more moisture (& mass) in the upper atmosphere where it begins to fall. It's then pushed up again by updrafts until becomes too heavy to be pushed up again and eventually falls.

Try sloshing water around in your soup bowl. You'll see that the vegetables near the ends move up and down, while the vegetables near the middle move quiet a bit side to side.

Since water doesn't compress the same way air does, the + motion is accompanied by an expansion up, the - motion is accompanied by an expansion down. The area of greatest up/down movement is the antinode. The area of least up/down movement is the node.

Again, water must expand as pressure increases. In air, this isn't true, so air at the node is very stable. What I want you to notice is how wildly the soup in the middle of the bowl is moving side to side.

You'll see that the soup in the node moves back and forth quite a bit, while the soup at the antinodes doesn't move back and forth much at all, just up and down to signifiy increased and decreased pressure.

Let me know if you have any more questions.

[ Parent ]

Cool 8^) (none / 0) (#111)
by RegularFry on Mon Jun 17, 2002 at 01:14:26 PM EST

That makes a lot of sense.  I kind of half got there by thinking about that classic classroom physics experiment with sand in a tube marking out the nodes.
It explains why the object being floated has to be light, too - the object can't fall further down than it gets pushed up, which is only true for things like feathers, pingpong balls, and slices of cork.

There may be troubles ahead, But while there's moonlight and music...
[ Parent ]
Thanks (none / 0) (#77)
by DRAC0 on Mon Jun 10, 2002 at 08:47:03 PM EST

I appreciate this post, and would love to see more.  As of lately I have fallen out of the soundstage scene.  Although I have finally found some time to put some subs in my car for the perfect acoustical back massage. :P

Years past I have worked for churches and small venues in the NW Houston area.  I really enjoy playing with sound systems.


Type-O Alert! (5.00 / 1) (#78)
by marktaw on Mon Jun 10, 2002 at 11:40:04 PM EST

I ran a spell check on this, but it failed to correct a mistyped number. Just above the axial mode calculation that should be 565/feet, not 585/feet.

Acoustics Crash Course 1 - Room Modes | 114 comments (111 topical, 3 editorial, 0 hidden)
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