single driver double bass array ( a.k.a. bow your heads )

[Borat]

i was thinking yesterday about what DBA and multiple subs have in common and arrived at a double bass array solution consisting of just one subwoofer in the corner of the room.

you simply take the 3 dimensions of the room and calculate the time delay it takes for time to travel both ways along these dimensions. this creates 3 time delays ( one for each dimension ).

then you add to the original signal the time delayed and inverted versions of the same signal. this will produce comb filtering that will automatically take care of all the standing waves ( except oblique ones ).

by adjusting the gain on the inverses you will be able to tailor the response depending on the degree of severity of the standing wave modes.

in effect the system will be canceling its own reflected sound. actually it will even provide automatic compensation for room gain ! ! !

no it won't be perfect but considering the simplicity YOU CAN'T BEAT IT.

NOW BOW YOUR HEADS FOR THE ALMIGHTY BORAT ! ! !

[InclinedPlane]

[CLS]

So, you have to get three 'copies' of the original signal, then give them different delays and reverse the phase, and then mix them all together with the original signal for the only one subwoofer to play.

You call that simplicity. OK, a mixer is no big deal I guess, but what about the delay?

[thadman]

Interesting

[gootee]

Yeah but the real solution is to play your music outside, with tall towers for your speakers, and a tall tower for your chair. <grin>

Or, I guess you could cover all of the other room surfaces with speakers, each with a microphone, so they could play cancellation signals for whatever hits them. (Wow, that might get messy, fast.)

All kidding aside, maybe you should try it! But, from a corner, the "oblique" signals might be significant.

Maybe you could use something like an audio version of a Time-Domain Reflectometer. Then you could play a test "pulse" signal and see/measure all of the "times of flight" of the reflected returns, on a scope (or PC) display, and see/measure their relative amplitudes. If the three from the room-dimensions were by far the largest, for example, then your idea might start to look very good!

Cheers,

Tom

Go, Purdue!

[MarzZ]

Or you could just use these: E-Trap

[thadman]

Originally Posted by gootee

Cheers,

Tom

Go, Purdue!

+1, Are you an alum?

[gootee]

Originally Posted by thadman

+1:d, are you an alum?

Yup! EE, 1978.5!

[tinitus]

Originally Posted by Borat

i
NOW BOW YOUR HEADS FOR THE ALMIGHTY BORAT ! ! !

I just had a mighty good laugh, thanks

[Don Hills]

I bowed my head... doubled over with laughter.

Your technique is used very day. You're just looking at the problem in the time domain, whereas it is usually looked at in the frequency domain.

Build a circuit (or implement in a DSP) to produce the cancellation effect you desire. Now measure its frequency response. It will look just like a series of notch filters, such as would be produced by a multi-band parametric equaliser, one band per mode.

In fact, for any given mode, the required correction is easy.

Measure the mode Q and size. For example, you might find a Q of 0.6 and a peak of 10 dB. Adjust the parametric equaliser for a Q of 0.6 and a dip of 10 dB. Sorted.