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In Reply to: RE: Stereo Sub-Woofers posted by DavidLD on December 30, 2016 at 11:31:31
David et al.,
I believe there's more to the single sub than just directionality. I also think there's an issue with quality from a couple of factors.
First, there's the issue of exciting room modes. Two subs give a different pattern of room modes, and the excitation ought to be smoother.
Second, in a two woofer set up, switching the bass from mono to stereo sounds different. It could be from room modes, or interaction with the main speakers; or the summing when done electrically is not the same as when done acoustically in the room. For one thing, a single sub will not have the effect of Mutual Coupling. For another, if the original bass source is not centered, it will emerge from the two woofers with some phase shift between them. That phase difference gets wiped out in a summed signal.
My best success in a single sub, was a 12" woofer from Speaker Lab in a 3.25 cu. ft. ported enclosure with a third order low pass filter. But it only worked properly when wall loaded and accurately centered. Turned to the wall, the sound is more diffuse from the woofer, including port noise and woofer harmonics.
Another factor, usually overlooked is the production of harmonics by the woofer. While a 4th order low pass will certainly attenuate the fundamentals above its pass band, the harmonics are generated by the woofer itself and are not attenuated. Similarly, port noise is not attenuated. That argues for significantly higher quality woofers in a mono sub than would be needed in a pair of subs, stereo or not. In my case, I chose an Acoustic Suspension design to eliminate port noise.
Jerry
Follow Ups:
If I recall correctly, Linkwitz recommends multiple open-baffle subwoofers placed around the room to best deal with room modes. I don't have room for additional subwoofers, so my solution is to let my satellites (Spendor BC-1's) run full range and roll the subwoofer in around 40Hz. My room is paneled, with a carpeted concrete floor and one wall of cinderblocks. There is a lot of base boost so the subwoofer is set very low. It work pretty well. There is more than one way to skin a cat.
Dave
The two powered Eosone 12" subs used in the HT have a 12 db / octave low pass crossover switchable from 50 to 120 hz. Even set to 50 hz, I can faintly make out vocal fundamentals.I've yet to hear a single sub not call attention to itself.
Edit: Meant to place above this post, but am traveling and editing with phone is difficult. You get it, but I'm not sure that David does.
Edits: 12/31/16
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