Sound Proofing Advice

[Elill]

Forget foam or just about any other product sold in Australia like this, they're all rubbish. Unless its 48kg/m^3 its not going to work properly.

Get the WHITE HD batts in 48kg from Acoustica and cover in a acoustically transferent cloth - you want it at leave 100mm deep for a rear wall, preferrably 150mm

http://www.acoustica.com.au/hdbatts.html

I'll also second Toole's book - it is a bible, a must read.

BTW - absorbers like that suggested will only work if you're at least 3ft+ from them (its a sound air partical velocity v pressure issue)

[Craigandkim]

Forget foam or just about any other product sold in Australia like this, they're all rubbish. Unless its 48kg/m^3 its not going to work properly.

BTW - absorbers like that suggested will only work if you're at least 3ft+ from them (its a sound air partical velocity v pressure issue)

Hey Elill,

thats a pretty big statement considering there are many other versatile products which will do "the job" that are not 48Kg/m density.

Another thing to consider is what "job" are we actually trying to address for haygeebaby- first reflection off the rear wall or overall bass absorption? Couple of different approaches here- diffusion or absorption.

Also; flemo has some valid points: find the optimum placement of your speakers first before any treatments- frequency responses as you well may know, are determined by the interaction of the speakers placement and the room boundaries. Different placement will evoke different responses.

You've obviously used and worked with this stuff, whats the price of the Acoustica 100mm sheets and whats it like to work with?

Could you clarify your second statement here, what do you mean (absorbers like those suggested and only work if you're 3ft + away)??

Regards

[Elill]

thats a pretty big statement considering there are many other versatile products which will do "the job" that are not 48Kg/m density.

Density is important in terms of how the product absorbs sound across the spectrum. Because these bass traps are resistive in their design (not membrane), different densities will absorb or reflect sound accordingly. 48kg or 3pcf is the universally accepted “norm” as its coefficients have been found to perform best for the typical treatment options i.e. corner traps or reflection points – as “broadband bass traps”. Some studies have shown increasing density works better. Thickness is key however 4” or 100mm minimum. Oh and too dense and it’ll start reflecting high frequencies (not a bad thing in certain circumstances, but beyond my skill to determine).
Check out BOB GOLDS for specific material data.

first reflection off the rear wall or overall bass absorption? Couple of different approaches here- diffusion or absorption.

Also; flemo has some valid points: find the optimum placement of your speakers first before any treatments.

Agree – speaker placement is crucial, although in some cases (like mine) the room will largely determine where they go as it is small…..wider the better in my opinion. Placement of subs is even more important.
Diffusers need to be big and have a significant distance to work - unless its something like an RPG BAD Panel...even then they need a good distance from the listener to be effective.

You've obviously used and worked with this stuff, whats the price of the Acoustica 100mm sheets and whats it like to work with?

The Acoustica stuff is cheap relative to say the CSR/Fibreglass alternative which is called Ultratel – that is about $350 a bag (3 50mm thick panels, I think you get about 3sqm a bag). I can’t recall the exact price, but it’s very affordable.

Could you clarify your second statement here, what do you mean (absorbers like those suggested and only work if you're 3ft + away)??

Sure, resistive trap performance is maximised when the sound air particle speed is maximized (not pressure) which is a 1/4 of the wavelength's distance out from a wall. So at 100Hz the wavelength is about 3.4m so one-quarter equals 85cm.