Old 05-10-2007, 11:22 PM   #41
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Originally Posted by chip mcdonald View Post
How big is that room? It looks really tiny.. if it's *really* small, bass trapping is probably going to be fruitless.
. . . .

Otherwise, in a tiny room you'd have to figure out exactly which frequency in the bass is dominant through analysis, and then build a custom-dimensioned Helmholtz resonator to stop it.
Quite the opposite, actually. I've treated many very small rooms with bass traps, including small vocal/isolation booths. And you really need broadband bass trapping for this.

Just for example:

A 4' x 5' x 7' vocal booth will have axial modes at 141.25, 282.50 and 426.75 Hz related to the width (4 ft) dimension, 113.00. 226.00, 339.00 and 432.00 Hz for the length (5 ft) dimension and 80.71, 161.43, 242.14, 322.86, 403.57 and 484.29 Hz for the height (7 ft) dimension.

Those axial modes will create the strongest peaks and nulls, but you may also be more exposed to the effects of tangential modes in such close quarters.

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- get that right monitor away from the side wall; get both monitors away from the back wall...
Yes . . . definitely! He's basically got that one monitor seriously corner loaded, and is probably getting at a good 6 to 12 dB or so additional in the low frequency range from that corner loading.

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Otherwise, in a tiny room you'd have to figure out exactly which frequency in the bass is dominant through analysis, and then build a custom-dimensioned Helmholtz resonator to stop it.
For most small rooms, you simply need broadband trapping to cover all of the room modes (which can cause both extreme peaks AND extreme NULLS!). If, after broadband trapping, you still have one particular peaky/resonant frequency that is very stubborn, then maybe that is the time to use a tuned absorber like a Helmholtz resonator or tuned panel absorber.
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Old 05-12-2007, 07:06 AM   #42
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Default hmmm

i'm curious.

I have alot of that thin carpet (about 1/8" thick) that is used to cover cabs. would that work for covering? or should I get something thinner? it's going on a bass trap that is going to be positioned behind the drummer who is also behind a shield in a 80x 25 room.
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Old 05-12-2007, 07:43 AM   #43
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i'm curious.

I have alot of that thin carpet (about 1/8" thick) that is used to cover cabs. would that work for covering? or should I get something thinner? it's going on a bass trap that is going to be positioned behind the drummer who is also behind a shield in a 80x 25 room.
Can you blow through the carpet? If not, it wont work as well.

Also, broadband traping is even more important in smaller rooms. Trap as much as you can. make the room COMPLETELY dead. There is no good reflections in a small room.
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Old 05-14-2007, 09:09 AM   #44
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Just for example:
113.00. 226.00, 339.00 and 432.00 Hz for the length (5 ft)
Where can he get a broad band absorber that *evenly* reduces 4 octaves at those *specific* frequencies, while not creating a valley elsewhere, that will also fit in a 4x5 room and still leave room for other stuff...?

If he's got a tiny (4x5) room, it's always going to have bass problems at appreciable volumes, even if he puts some of Winer's broad band traps in the corners - and then, he's not going to have a "room" left over.



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then maybe that is the time to use a tuned absorber like a Helmholtz resonator or tuned panel absorber.
Sort of like "in a tiny room you'd have to figure out exactly which frequency in the bass is dominant through analysis, and then build a custom-dimensioned Helmholtz resonator to stop it."
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Old 05-14-2007, 08:49 PM   #45
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Does'nt have to evenly absorb, or target, specific frequencies.

It has to absorb as much as you can fit/afford. You cant over do it.

That idea relates to killing the high frequency "air" in nice sized and shaped rooms. At lower frequencies, you want maximum absorbtion in any room. More so for the small ones.

You are correct in assuming that a 4x5 room is going to sound crappy no matter what, its just a matter of how crappy.

Traping can go on the cieling to wall corners just as well.
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Old 05-14-2007, 09:04 PM   #46
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Where can he get a broad band absorber that *evenly* reduces 4 octaves at those *specific* frequencies, while not creating a valley elsewhere, that will also fit in a 4x5 room and still leave room for other stuff...?
Chip, broadband absorbers DO NOT create nulls/dips in the frequency response. Rather, they actually REDUCE the severity of, or eliminate, nulls/dips in frequency response, as well as reducing peaks.

The peaks and nulls are BOTH caused by the phase interference of the room reflections with the direct source sound at various points in the room. If you put broadband absorption in a room, you reduce the reflections that cause both peaks and nulls, and therefore your entire frequency response evens out, and the decay time becomes more uniform.

If you can reduce the amplitude of those reflections by even as much as 6 dB or so in relation to the direct sound from source, you will noticeably reduce the severity of both peaks and nulls.

A lot of people get confused and think that putting absorption in a room can cause you to end up with LESS bass . . . but indeed you will get MORE bass where before there were nulls, and you will of course reduce the peaks.

Tuned absorption targets only one frequency or frequency range, and ignores all the rest . . . and therefore does not take care of all the other peaks and nulls that are absolutely there across the frequency spectrum (in ALL small rooms) whether you notice them or not. Most small rooms have peaks and nulls across the entire frequency spectrum somewhere in the range of 30 to 35 dB from top to bottom.

Some of those peaks and nulls occur in very narrow bandwidths, so a lot of times people do not notice them (especially the nulls) when they are listening in a room . . . but you will most certainly notice how much you were missing when you treat the room properly with broadband absorption, and you get back so much of the sound that was previously inaudible due to phase cancellation at modal frequencies. The other thing is that so many of those very narrow band peaks and nulls will get entirely missed by 1/3-octave band pink noise testing which so many people traditionally use for room acoustics analysis/RTA. That's simply not fine enough resolution to get an accurate sense of what's *really* going on in your room.

The bottom line is that ALL small rooms NEED broadband absorption to get anything even remotely close to an even frequency response. That is simply the best and most cost-effective way to treat small rooms, and I think pretty much any acoustician worth his salt will tell you the same.

So . . .

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then maybe that is the time to use a tuned absorber like a Helmholtz resonator or tuned panel absorber.
Sort of like "in a tiny room you'd have to figure out exactly which frequency in the bass is dominant through analysis, and then build a custom-dimensioned Helmholtz resonator to stop it."
My point being that your assertion that bass trapping (i.e. broadband bass trapping) would most likely be "fruitless" is *entirely* incorrect, as is your recommendation for a tuned trap (which, again, only addresses a very narrow band) to the *exclusion* of broadband trapping.

And back to this:

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Originally Posted by chip mcdonald View Post
Where can he get a broad band absorber that *evenly* reduces 4 octaves at those *specific* frequencies, while not creating a valley elsewhere,
Off the top of my head, I can't think of ANY absorbers/absorption materials on the planet (at least not that could reasonably be used for interior acoustics treatment ) in that have a flat absorption curve (unless you count an open window or doorway), and it is a huge (and unfortunately widely held) misconception that a flat absorption curve is needed (even if in certain instances it might be preferable), because of the principles I've discussed above.

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that will also fit in a 4x5 room and still leave room for other stuff...?
Typical panels made from at least 3-4 inch thickness of OC 703/705 (or the rockwool equivalent), be they commercially manufactured or DIY will offer SUBSTANTIAL improvement across the entire frequency range in a room like that (most definitely *including* even the lowest frequencies I listed as axial modes for that room). This will give you a MUCH flatter frequency response across the entire spectrum than using tuned traps in a small room such as this, and even using tuned traps you don't just use one and call it good . . . you have to have such absorbers evenly distributed throughout the room for best results, and preferably in the corners, where ALL of the room modes are present. This is where you need to break those wave fronts to get the most effective reduction of room modes.

Tuned traps are most often an inefficient use of space in small rooms, because the tuned traps will typically take up as much or more space as a typical broadband panel absorber, and will not lead to an *overall* flatter frequency response in the room unless used *in addition to* broadband traps.

So . . . if you treat a small room such as this with broadband bass traps and you STILL have one very stubborn low frequency peak, then -- and ONLY then -- you might consider adding a tuned trap . . . if you have room.

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Old 05-16-2007, 12:02 PM   #47
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My point being that your assertion that bass trapping (i.e. broadband bass trapping) would most likely be "fruitless" is *entirely* incorrect, as is your recommendation for a tuned trap
He's talking about wanting to put something flat on the wall, and having basically a non-existent budget since he's talking about "trading up" to KRK 8's for the difference in what he has now - which I think is probably around about a $200 difference.

He can buy one broadband absorber from Ethan Winer for about that much.

So, in one situation he's got crappy speakers in a crappy room, but with *how much* of a low-frequency improvement? On the other hand he could have less crappy speakers in the crappy room that might have +/- *how much* of a difference - in an area where his crappy monitors has a sketchy/rolled off response to begin with?

If he gets the monitors he'll have a slight more accurate mid/high direct sound, same crappy room response (but maybe a better low end from the monitors to begin with); one presumes he won't be straddled with a 4x5 room forever, in which case skills learned on the better monitors would translate to a larger room AND he'd still have the monitors he's used to using.

I'd rather be in that situation, than to have a nice bass trap but having to listen to crappy monitors with my slightly-better-bass response-but-still-crappy room.


Quote:
if you treat a small room such as this with broadband bass traps and you STILL have one very stubborn low frequency peak, then -- and ONLY then -- you might consider adding a tuned trap . . . if you have room.

.. of course, he should have just had Storyk design his teeny tiny room to begin with, and he wouldn't have any problems to begin with. Simple!

The guy is obviously on a tight/non-existent budget and has crappy monitors. A $200 monitor upgrade is going to yield more returns than a $200 bass trap in his situation.

IMO.
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Old 05-17-2007, 06:32 AM   #48
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The guy is obviously on a tight/non-existent budget and has crappy monitors. A $200 monitor upgrade is going to yield more returns than a $200 bass trap in his situation.
I have to disagree. $200 will buy a lot of 703 or rockwool. Better monitors will suffer the same room problems. The differance between the peaks and nulls in the monitors will not be even close to as wide as what the room is doing.

I would rather have $300 monitor is aroom treated with $1000, than have $1300 monitors in an untreated room. The results will be more reliable that way.

You CANNOT mix acuratly in an untreated room.
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Old 05-17-2007, 08:16 AM   #49
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Can you blow through the carpet? If not, it wont work as well.
i can feel the blown air behind it, but not nearly the same force. i'll try and find that under the sofa fabric...that should work mo better
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Old 05-17-2007, 09:04 AM   #50
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I have to disagree. $200 will buy a lot of 703 or rockwool. Better monitors will suffer the same room problems. The differance between the peaks and nulls in the monitors will not be even close to as wide as what the room is doing.
$200 of 703 or rockwool is not going to fix a 4x5 room.

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I would rather have $300 monitor is aroom treated with $1000, than have $1300 monitors in an untreated room. The results will be more reliable that way.
If the room is 4x5, I'll take the $1,300 monitors. *My* results will be more reliable because I can learn what the room sounds like and adjust accordingly, and then I've at least got a good starting point with the decent monitors.

A crappy starting point/bad monitors in a room that *is still going to be bad* is worse IMO. We disagree. Sorry.

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You CANNOT mix acuratly in an untreated room.
"Accurately" is relative. Many people mix in effectively untreated rooms and have good results.
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Old 05-17-2007, 09:22 PM   #51
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We can disagree..............but you'll still be wrong. ;-)
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Old 05-17-2007, 10:02 PM   #52
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We can disagree..............but you'll still be wrong. ;-)
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