First Adventure into Room Treatment

Chris - firstly - Dave Moulton is ONE idea about control room design - He's saying that the sound that goes to the rear should reflect back at you :eek: I say it definitely shouldn't unless your rear wall is over 9 ft from you - in other words it works for large rooms (in a way) but won't work in small rooms IMO.

Slots and Panel absorbers will absorb below 800hz but hey good rigid fiberglass insulation like 703 will absorb down to 250 hz which is far superior to that crappy foam stuff :D:D and as Tex said you have to lift it well off the wall to get any lowering of the absorption frequency.

next time you are at your speakers try cupping your hands up behind your ears to stop the rear sound - you'll hear a definite improvement in imaging etc.

cheers
john
 
Perhaps some clarification is in order on my part.:)

I never meant to suggest that spacing the foam away from the walls would make it more effective from a bandwidth point of view. It will make it more effective at the freqs it does absorb.

You don't want to make your room too dead with foam because you'll just end up with a muddy sounding room. The best thing you can do is kill the worst reflections from the mids up.

Second point was to make the treatment moveable in order to be able to adjust the response of the room to suit the purpose. It's really not a good idea to mix in the same room you tracked in, but if you only have one room you have to deal with it the best you can. Being able to change the acoustics of the room to suit the two different scenarios is a good plan IMHO.:)
 
Thanks alot, Mr Sayers :)


If I were to get ahold of a single sheet of 703 and place it behind my monitors about a foot away from the wall, would it make enough difference to be worth my effort and $35 (us) dollars?

By the way, the back wall is about 11 feet from my speakers, and 9 and a half from my ears.

How about my ceiling? I really am low on budget, so would my foam panels placed around a foot apart on the front half of the ceiling be the best use of my resources?


Rock On
Chris
 
703 is about $7.80 for a 2'x4' x 1.5" You will probably have to buy a minimum amount and from my distributor it was only $50. Some are higher. Get the minimum you can and use it around the room. The best stuff for bass absorbtion is the 705FRK with the foil side facing out.
 
"I never meant to suggest that spacing the foam away from the walls would make it more effective from a bandwidth point of view. It will make it more effective at the freqs it does absorb. "

Actually, MB, you got it backward. What determines the lowest frequency affected by ANY absorbent material, is its distance away from boundaries compared to the 1/4 wavelength of the sound. In order to absorb (convert sound energy into heat energy) the velocity of the wave must be more than zero. For maximum absorption at a given frequency, the material must be at 1/4 wavelength from the nearest boundary. This makes it so that the sound wave has maximum velocity, and therefore tries the hardest to "get through" the absorbent, which results in the most sound energy being converted.

The actual AMOUNT of absorption is determined by the density of the material, and its thickness. 2" foam, for example, can only absorb x amount of sound (convert it to heat) - you can lower the frequency that is affected, by moving the foam further from the wall so that the 1/4 wave length point relates to a lower frequency. However, the AMOUNT of absorption (in joules, BTU, or whatever) won't change unless you change the density or thickness of the material.

Keep in mind Tex's comments about distance off the wall - bass frequencies run into 20-30 foot wavelengths, so 1/4 wave would be 4-5 feet for low bass... Steve
 
Tex-

Are you aware of any online distributors of 703 or the like? The only place I've found is Ethan's site, which is $110 for 6 pieces of 705. Add that to the cost of covering it and getting it away from my wall, and I'm very very over budget.

I 've looked in all my local phone books, and haven't found a commercial insulation dealer anywhere close to me. :(

Thanks
Chris
 
Chrisjob said:
Tex-

Are you aware of any online distributors of 703 or the like? The only place I've found is Ethan's site, which is $110 for 6 pieces of 705. Add that to the cost of covering it and getting it away from my wall, and I'm very very over budget.

I 've looked in all my local phone books, and haven't found a commercial insulation dealer anywhere close to me. :(

Thanks
Chris
Click to expand...

Call up Owens Corning and they should be able to give you a local distributor. Some guys have been able to special order it from Home Depot but that depends on the individual store. Ethan's prices are actually pretty competetive if you are buying small quantities. I would probably have bought from him but I had a wholesaler close by.

It's too bad you already bought all that foam. $300 can go a long way with rigid fiberglass panels.
 
knightfly said:
"I never meant to suggest that spacing the foam away from the walls would make it more effective from a bandwidth point of view. It will make it more effective at the freqs it does absorb. "

Actually, MB, you got it backward. What determines the lowest frequency affected by ANY absorbent material, is its distance away from boundaries compared to the 1/4 wavelength of the sound. In order to absorb (convert sound energy into heat energy) the velocity of the wave must be more than zero. For maximum absorption at a given frequency, the material must be at 1/4 wavelength from the nearest boundary. This makes it so that the sound wave has maximum velocity, and therefore tries the hardest to "get through" the absorbent, which results in the most sound energy being converted.

The actual AMOUNT of absorption is determined by the density of the material, and its thickness. 2" foam, for example, can only absorb x amount of sound (convert it to heat) - you can lower the frequency that is affected, by moving the foam further from the wall so that the 1/4 wave length point relates to a lower frequency. However, the AMOUNT of absorption (in joules, BTU, or whatever) won't change unless you change the density or thickness of the material.

Keep in mind Tex's comments about distance off the wall - bass frequencies run into 20-30 foot wavelengths, so 1/4 wave would be 4-5 feet for low bass... Steve
Click to expand...

In summation: foam is not effective at low frequencies in real-world installations. Spacing it away from the wall a few inches with a denser backing will make it absord more at mid to high frequencies. I don't need a calculator to tell me that. I have ears.
:D
 
M.Brane said:
In summation: foam is not effective at low frequencies in real-world installations. Spacing it away from the wall a few inches with a denser backing will make it absord more at mid to high frequencies. I don't need a calculator to tell me that. I have ears.
:D
Click to expand...

What's a non-real world type of installation?

Again, thanks for all your help.If anyone has any more suggestions, I'd love to hear them :)
 
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