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Vikash 3rd June 2004 09:54 PM

Standing waves again...
 
Designing a three way with L shaped bass cab (it will be once mid and tweet cabs are inside).

How would you most effectively calculate standing waves to determine acceptable dimensions for my L shaped enclosure?

Mudge 3rd June 2004 10:39 PM

Instead of an L-shape, why not make separate cabinets for the bass and the mids? I too am building a 3 way at the moment, and am using separate enclosures a la Wilson X-1 for the bass and the mid/treble. The bass enclosure is designed so that the first standing wave is above the crossover between the drivers, and the mid/treble is totally overstuffed with acoustic foam to kill any box resonances in it's operating range.
Now I have the tricky task of eliminating panel resonances:bawling:

Timn8ter 3rd June 2004 10:51 PM

I thought the same thing. Enclose the mid, tweets are usually sealed these days. Use the remaining volume for the woofer. I think that keeps it simpler.

GM 3rd June 2004 10:59 PM

The whole cab as if it were straight for the LF BW up to the frequency where the long vertical dim. is 2x its length. For the base of the "L", its 1st eigenmode begins at 2x its longest dim.

Since it's doubtful you will find a good compromise, just concentrate on the 'pipe' as a whole and use damping material at the top, one side, and back to attenuate the higher frequency eigenmodes.

GM

BillFitzmaurice 3rd June 2004 11:25 PM

You want to totally line the woofer section. While damping material is unnecessary below 100 Hz, above that it's hard to use too much. As was suggested go with a sealed sub-enclosure on the mid and the same for the tweeter (unless either or both has a sealed basket) and fully line the woofer section with an inch of high density polyfill.

The idea of supressing 'standing waves' is fallacious; there's really no such thing inside of a speaker cabinet. But you do want to be sure there are no reflective surfaces inside off of which midbass and higher frequencies can reflect back to the cone, which would cause response anomalies.


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