Guitar pick percussiveness and speakers

For absorptive traps, the thicker they are, the lower the frequency they will act upon. They are generally reckoned to be effective down to a point at which the active trap depth equals 1/4 of the wavelength. But there is no point in trying to control frequencies lower than those that the room itself will support, because they cannot be present anyway. And the point at which that happens is determined by the longest length in the room - in your case the diagonals. And that's why you have to put bass traps in corners - that's where the problem has to be intercepted. So, the bigger the room, the deeper the traps need to be. To a first approximation, if you have an absorptive trap 15" deep, it will control down to about 65Hz, and that's quite a comfortable figure for a lot of rooms - because to get much deeper than this, you have to extend the depth considerably; to get down to 40Hz the trap would have to be 24" deep.

Ok, I know I said I was done with this one, but you have a way of keeping me hooked. I'm calculating 1/4 wavelength at 65Hz to be 4.3 feet, but you indicate a depth of just 15" to gobble up 65Hz (or close to it, anyway). I guess there's more to the math than just this simple calculation, perhaps because it's in a corner vs. against a flat wall maybe? (Are we getting into modes at this point?) You mentioned placing an entire roll of roof insulation in the corners. Those bad boys would certainly be deeper than 15", and yes, I'd most likely throw a curtain or something in front of them, if for no other reason than that stuff is the itchiest material I've ever encountered!

Ok, I know I said I was done with this one, but you have a way of keeping me hooked. I'm calculating 1/4 wavelength at 65Hz to be 4.3 feet, but you indicate a depth of just 15" to gobble up 65Hz (or close to it, anyway). I guess there's more to the math than just this simple calculation, perhaps because it's in a corner vs. against a flat wall maybe? (Are we getting into modes at this point?)

You are of course quite correct! I have a chart which has two scales on it - one in feet and one in metres. Guess which scale I read it off... I should have done the sum, because then I wouldn't have got it wrong. Also, it makes sense - you really do need a very thick absorber to control deep bass, but most of the ones you can easily buy aren't that deep, and therefore can't work that low at all. Perhaps I should drink the coffee first... Oh, and the whole thing is about modes.

You mentioned placing an entire roll of roof insulation in the corners. Those bad boys would certainly be deeper than 15", and yes, I'd most likely throw a curtain or something in front of them, if for no other reason than that stuff is the itchiest material I've ever encountered!

You don't have to take it out of the wrapping for it still to work - fortunately. The plastic wrapping has absolutely no effect at all at low frequencies, and all the air vibration passes straight through it. Since it's the air particle velocity that you are damping, all that happens is that the air on the inside is excited almost identically, so the interception is the same. If you had a big enough roll, and enough deep bass, you'd see the plastic vibrating, and the vibration would be damped by the material inside. Same thing happens at the frequencies that a smaller one would be controlling, but I doubt that you'd see it!

Looks like I'm off to Home Depot. My studio is about to get really small! Thanks for everything. This was quite an education.

If you want to see how it works... (just be careful how you read it first thing in the morning!)

Very cool and simple, thanks.