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Acoustic Treatments

FunkySpoo

FunkySpoo

Supporting Member
Feb 6, 2002
4,225
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DMV
#1
You know, those foamy lumpy things on the walls? Is there a method to figuring out where and how many to put up? Or do you just buy a ton of them and cover every flat surface you can. The same goes for bass traps. My rehearsal space is my finished basement and it generally sounds like crap but you guys already knew that. Any links or threads with this info would be helpful. BTW I did do a search but my searchfoo is weak.

Thanks
 
#6
I'm of the opinion that you simply cannot have too much bass trapping. In small spaces this is especially true. Get as much as you possibly can in the horizontal and vertical corners of the room (a rectangular room with a flat ceiling will have twelve corners).

Broadband absorption is not something to simply be placed on every wall. You definitely want it at the first reflection points of your monitors. Beyond that it comes down to taking detailed room measurements and finding the sweet spot. An overly treated room will sound stuffy and dead in a way that's not conducive to tracking or mixing. Additionally you'll start losing high end content. Conversely an under treated room will sound overly reflective, suffer from flutter echo, and have all sorts of phase problems. If I were going to "wing it" I would err on the side of more absorption, but really an RTA program coupled with a calibrated electret microphone will make this job a lot easier and more effective.
 
#8
silky smoove said:
I'm of the opinion that you simply cannot have too much bass trapping. In small spaces this is especially true. Get as much as you possibly can in the horizontal and vertical corners of the room (a rectangular room with a flat ceiling will have twelve corners).
Click to expand...

I agree about bass trapping, but don't expect too much. You don't really eliminate modes, since they are dictated by the room shape, you mostly just shorten their relaxation times, hopefully to the point that they aren't a problem in most musical circumstances.

Also, having just helped one of my kids on this type of math question, I think you will find a rectangular box has eight corners and twelve edges. Put as much trapping in corners and edges as possible.

Otto
 
#9
ofajen said:
I agree about bass trapping, but don't expect too much. You don't really eliminate modes, since they are dictated by the room shape, you mostly just shorten their relaxation times, hopefully to the point that they aren't a problem in most musical circumstances.
Click to expand...
I always under the assumption that changing the shape of the room is an impossibility. Frankly I consider modes to only be of real value when planning the construction of a new room. Once the studs are in place you're pretty much set with what you've got (for all practical purposes).

ofajen said:
Also, having just helped one of my kids on this type of math question, I think you will find a rectangular box has eight corners and twelve edges. Put as much trapping in corners and edges as possible.
Click to expand...
You're arguing semantics. I would define a corner as any intersection of two planes. In the case of the room I described above you would have the following:
4 wall to wall corners
4 wall to ceiling corners
4 wall to floor corners
Total: 12 corners

The eight corners that you're describing is what occurs at the intersection of three planes. While these are absolutely important, and can be very large source of bass build-up, they are not what acoustic treatment books, papers, articles, etc. commonly refer to as a corner. You'll frequently see these referred to by their proprietary name "tri-corner" (thank you Primacoustics, GIK, Auralex, etc.).
 
#10
silky smoove said:
IYou're arguing semantics. I would define a corner as any intersection of two planes. In the case of the room I described above you would have the following:
4 wall to wall corners
4 wall to ceiling corners
4 wall to floor corners
Total: 12 corners

The eight corners that you're describing is what occurs at the intersection of three planes. While these are absolutely important, and can be very large source of bass build-up, they are not what acoustic treatment books, papers, articles, etc. commonly refer to as a corner. You'll frequently see these referred to by their proprietary name "tri-corner" (thank you Primacoustics, GIK, Auralex, etc.).
Click to expand...

I think you are correct that usage in both audio and more commonly doesn't follow the mathematical concept, which M-W defines as "the point where converging lines, edges or sides meet." This will give you the right answer (8) on the math problem.

When I re-read discussion of corner bass trapping, by Everest, Harry Olson at RCA and Art Noxon at ASC, they all think in the more common vernacular terms of the four vertical edges as being the four "corners" of the room. As a practical matter, corner treatments often occupy that space from floor to ceiling or nearly so. That usage that goes well beyond acoustics. We talk the same way about the four "corners" of a boxing ring, for instance.

I'm really not familiar with referring to all twelve edges as "corners", but certainly they are important places that can efficiently be used for bass trapping. From an energy absorbing point of view, all twelve edges are similarly useful, though vertical corners are easier to treat in many spaces.

Otto
 
#11
ofajen said:
I think you are correct that usage in both audio and more commonly doesn't follow the mathematical concept, which M-W defines as "the point where converging lines, edges or sides meet." This will give you the right answer (8) on the math problem.
Click to expand...
As an engineer by trade, I would argue with the supposed "correct" answer to that math problem. It's ambiguous as written. Convergence of lines would certainly only equal 8. Without further definition; lines and edges appear to be the same thing which makes the criteria unclear. Convergence of sides, more correctly called planes, would equal 12. I solve complex geometric math problems all day as a part of my job, and that text book answer is poorly written at best!

ofajen said:
From an energy absorbing point of view, all twelve edges are similarly useful, though vertical corners are easier to treat in many spaces.
Click to expand...
Absolutely. I find the wall/ceiling corners generally easy to treat as well provided you can safely hang whatever medium you're using for trapping. Wall/floor treatment is where it gets tricky as most people can't afford to lose the floor space required for such an installation.
 
#13
There are plenty of resources if you want "professional" sound treatment and a "studio" room. However, if you like a place that sounds good but feels more like a living room then start by covering most walls with carpets and get as many open bookshelves as you can. Fill the shelves with books (buy cheap or get for free) and random stuff in various materials, shapes and sizes. Adjust until you get the sound you like, but a good hint is to try the live-end/dead-end principle.

The result is a nicer and more flexible place to rehearse and record in, while sounding just as good.
 
#15
silky smoove said:
Careful with this approach. What you gain in reflection reduction you also lose in upper midrange and treble content in the room. It can lead to things sounding dull and "boxy." If it's not a critical studio environment your ears are the best judge of when you've got enough in place.
Click to expand...

Absolutely correct, and that's where the next part (bookshelves with books and random objects) comes in. Provides low end reduction, bass trapping (helped by the distance between walls and book pages) while adding nice diffusion for the upper mid/treble.
 

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