Bass Traps: How Many?

Hi Ethan, it's good to see you here.

When calculating how much absorptive material to place in a room for an "ideal" room response, it is fairly easy to calculate for mid and high frequencies. As an example, here's a Sabine calculator I have seen:

Sabine Calculator

However, when it comes to low bass frequencies, I don't have the answers. Do you know of any methods to make a preliminary estimate as to how many square feet of bass traps are needed and to which frequencies the traps should be tuned? It would be great if there was a formula I could plug in, but perhaps it's not that simple???

Blair,

> Do you know of any methods to make a preliminary estimate as to how many square feet of bass traps are needed and to which frequencies the traps should be tuned? <

It's even simpler than a formula.

As far as I'm concerned you cannot have too much absorption at low frequencies. Of course you can definitely have too much at mid and high frequencies.

To reassure myself that this assessment is correct I recently installed 20 bass traps in my living room home theater. It's not a small room, but at 16x25 it's not huge either. I found that as I added more and more traps, the low end just got better and better. So all those traps are staying, no matter what my wife says!

As for tuning, I believe very strongly that tuned bass traps is the wrong approach. I have an article coming out next month in EM that explains this in detail. But briefly, all rooms have peaks and severe nulls at all frequencies. Not just those frequencies that are related to the room's dimensions. So to treat only the modal frequencies ignores half of the problem. Further, there are dozens of modal frequencies in all rooms. So which specific ones would you treat and which would you have to leave alone? For this reason, broadband low frequency absorption is the best solution.

--Ethan