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Ethan Winer · 15th March 2004

Steve,

> I guess I should question whether anyone ever tested the corner traps. <

This is a huge problem with DIY acoustic projects in general. I see all kinds of stuff ranging from great to incredibly lame, but nobody ever tests their plans because it's so difficult and expensive. When I published my panel trap plans in 1995 I had no clue about the absorption specs, though I knew they worked well because I'd built so many in a lot of different studios. Since then I paid to test panel traps, when I used to sell them, so now I know for certain how well they work.

> they are proposed as being broadband due to their variable depth. <

As far as I can tell the variable depth is irrelevant, and just makes it more difficult to calculate the center frequency. A panel trap is basically a shock absorber for low frequency sound waves. It has a mass (the panel) and a spring (the air inside). So I assume the air has some amount of springiness, but the shape of the cavity should not be a factor. That is, there can be only one sum total of springiness. Versus corner mounted fiberglass or foam where the varying depth does broaden the absorption curve. But porous absorbers work on an entirely different principle than panel traps.

Again, this is all "how it seems to me," and it's not based on anything more scholarly than that!

--Ethan

15th March 2004	#13
Ethan Winer Gear Guru Joined: Oct 2002 Location: New Milford, CT, USA Posts: 12,331	Steve, > I guess I should question whether anyone ever tested the corner traps. < This is a huge problem with DIY acoustic projects in general. I see all kinds of stuff ranging from great to incredibly lame, but nobody ever tests their plans because it's so difficult and expensive. When I published my panel trap plans in 1995 I had no clue about the absorption specs, though I knew they worked well because I'd built so many in a lot of different studios. Since then I paid to test panel traps, when I used to sell them, so now I know for certain how well they work. > they are proposed as being broadband due to their variable depth. < As far as I can tell the variable depth is irrelevant, and just makes it more difficult to calculate the center frequency. A panel trap is basically a shock absorber for low frequency sound waves. It has a mass (the panel) and a spring (the air inside). So I assume the air has some amount of springiness, but the shape of the cavity should not be a factor. That is, there can be only one sum total of springiness. Versus corner mounted fiberglass or foam where the varying depth does broaden the absorption curve. But porous absorbers work on an entirely different principle than panel traps. Again, this is all "how it seems to me," and it's not based on anything more scholarly than that! --Ethan __________________ Ethan's audio book is now available!