703 vs cheap mattress foam

[Bevan]

I'm redoing my room treatments with 703 type panels (called Supertel in Oz) for first reflection points.

I have an OB setup with live wall behind the speakers and what I want to be a dead wall behind my head. At the moment I have a king size cheapo foam mattress 5' behind my head.

Now I'm wondering if I should replace the foam mattress with 703 in addition the 703 I'm using up front and sides?

Obviously 703 is better per square inch, but does the fact that mattress foam is 6" thick make it a viable alternative for areas I dont have to look at? It would cost a fair bit to dampen the rear wall with 703 so am looking for a good reason to have to buy all that extra fiberglass.

Any opinions welcome.

cheers
Bevan

[bpape]

You should replace the mattress but keep the 6" thickness - or - use 4" with a 2" gap behind it. Most mattresses are made from closed cell foam which isn't good for acoustical purposes.

Bryan

[Bevan]

Thanks very much Bryan.

That'll cost me a fair bit but I'll aim for that in the long run. I do though have corner bass traps and DEQ on my bass drivers so perhaps I could get away with 2" and gap for a same or better deal than the mattress?

Cheers
Bevan