I am working on the construction of my rigid fibreglass 3 pcf panels and debating between the varying widths available to: primarily 2" and 4".

To help, I am curious:

1) Which will provide greater overall (and low/high) NR - a 2" panel spaced two inches away from a flat wall or a 4" panel sitting flush against a wall?

2) Which will provide greater overall (and low/high) NR - a 4" panel sitting flush or a 1-2" panel arranged with a spaced 1/4" plywood facing and optional back air gap? (http://www.ethanwiner.com/BTPlans.gif)

Thanks for any thoughtful feedback you can provide. I hope this may stimulate a bit of discussion about the relative merits of different treatment approaches.

Mike,

I can't help with your fabric question, but I can answer these.

> Which will provide greater overall (and low/high) NR - a 2" panel spaced two inches away from a flat wall or a 4" panel sitting flush against a wall? <

By "NR" you mean absorption? In that case 4 inches thick is a little better than 2 + 2, but only a little.

> a 4" panel sitting flush or a 1-2" panel arranged with a spaced 1/4" plywood facing and optional back air gap? <

A wood panel bass trap is a specific device that must be built exactly as shown in those plans. If the goal is broadband absorption, rigid fiberglass is the better choice.

--Ethan

Another way to think about it: a 4" panel flush sort of "includes" a 2" panel spaced from the wall, with the additional beneft of another 2" of absorptive mass on the wall. More mass will not equal less absorption, so the 4" one is better.... though a 4" panel 4" off the wall would be better still.

That was really what I was thinking. Like most guys not doing this for pro reasons, I'm looking for the cheapest, easiest approaches possible, so I think for now I'll stick to broadband 4" and 2" flush panels.

Just from trying a few in my basement I noticed a dramatic change. I'm hoping once I get the furnace treated and computer silenced (ala Ethan's Dell) it will be pretty sweet. Also a few QRD's probably wouldn't hurt ...

Thanks.