I'm looking to build some traps from floor to ceiling... I will be cutting the insulation in 2' triangles... do I push them up against the wall, or keep a space between the wall and the corner piece (like acoustic panels are supposed to have)?
If I keep a space, how many inches from the wall should I keep it?
There is no need to space it off the wall. If the trap is a solid triangle it will not affect absorption at higher frequencies and its going to take a few feet to make any difference at lower frequencies.
Maj, you say that "insulation" is going to be used for "bass traps". The problem, as Fred mentioned, is that simple absorption of sound by fiber glass or similar insulation material isn't very efficient at very low frequencies. There seems to be some enthusiasm on the internet for this type of installation which isn't completely in accord with acoustic principles. The literature indicates(e.g. Toole, Sound Reproduction, p.476)that to be effective at bass frequencies the insulation would have to be about 1/4 wavelength deep. The 100Hz wavelength is about about 11.3 feet and 20Hz about 56.5 feet.
Mechanically resonant membrane absorbers are more efficient at these very low frequencies and electronic equalization may be a more practical approach at these frequencies.
I built some a while back. This is a good thread with a lot of info on them, plus pics detailing how I built mine.
http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=248931&page=2
Sirquack has some in his theater...
mechanically resonant membrane absorbers?? lol!
What's funny about that? It's the principal behind the amazing Tube Traps. They work quite a bit better than stacks of insulation, and cost a whole lot more.
The problem, as Fred mentioned, is that simple absorption of sound by fiber glass or similar insulation material isn't very efficient at very low frequencies.
The corner traps will be quite effective down to about 100Hz. John. Have you seen any designs for resonant membrane absorbers? I did a LOT of research on this topic a while back and was never able to find any sort of design principle to follow.
In the end, I bought a Behringer feedback destroyer to clean up my bass between 20 and 100 Hz.
What's funny about that? It's the principal behind the amazing Tube Traps. They work quite a bit better than stacks of insulation, and cost a whole lot more.
No no.. I'm laughing at my ignorance on the subject, not the subject itself... It was like reading Chinese - I had never heard of that before and when I googled it, the sites it brought me to were thesis-like... so I thought it would be easier to come back here and ask what you meant and where I can get some info in layman's terms.
Is it something I buy as in - is it the name of a product or is it a method I can use? if the latter, then what do I buy to use the method?
You can buy products that make use of the technology here:
http://www.tubetrap.com/ Especially, the upgraded Helmholtz Traps (+25% to the price) absorb more low frequency energy for anything of a similar enclosed volume.
Maj, yes, as you see, the Tube Trap outfit which Chris supplied a link to offers finished products effective at the very low frequencies which are generally the most difficult problem in a typically furnished room at home. As you also see, however, a complete set can run several thousand dollars.
It should be pointed out that one example of a "mechanically resonant" absorber is already present in many listening rooms: a relatively flexible wall surface. Typical drywall construction is sufficiently flexible(in comparison with plaster, etc., walls)that it absorbs significant sound energy at very low frequencies with the result that the room is less "boomy". Though not especially efficient, the large amount of surface area involved allows for an audibly significant effect.
The comment that electronic equalization may be more practical(including the financial aspect)at these very low frequencies still stands, and the use of a built-in equalizer such as Audyssey MultEQ, or a separate unit such as Fred and Dean, among others, have used, can be helpful. The fact is that all our listening rooms(not just Mark Johnson's)suck.
Yeah, that's a little too pricey for me... But I'd love to be able to try it out somewhere; in any case it looks cool - it gives a room a unique look.
So for now I'll stick with the DIY'ers. I read somewhere (sorry, I can't locate the website) that I need to do something about "catching" the fibreglass? I'm not positive, but it seemed the tutorial was saying the fibreglass will come loose with the vibration and such - is this correct? Can someone shed some light on this for me? Or am I completely in left field?