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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Brian, please help clarify... posted by DMW on July 26, 2003 at 08:21:05:
I did not scroll down far enough to see the part of your post addressed to me.I started using QSO filters in 1984 at the suggestion of James Bongiorno, who touted their well-known advantages. The constant phase shift of 90+ degrees is relatively benign. You have limited choices in filter poles, as most drivers mass-limit or exhibit roughness at a frequency which is dependent on driver diameter. A fourth order filter would have the same behavior as a first plus a considerable delay from the 360 degree displacement; I too combine 4th order with 6 dB hipass filters, but no sloping baffle has anywhere near enough offset between drivers to compensate for said delay. Rather than worry about theoretical advantages of certain filters over others I would spend time worrying about maintaining that constant phase shift and preventing zero output frequencies from popping up due to rolloff/rollins summing to -180 degrees. I've seen numerous "phase and time coherent" designs with mids in inverted polarity relative to woofer and tweeter, which gives you the desired response in the crossover region but a 180 degree phase inversion in the passband.
Ideally first order networks should combine with constant directivity drivers utilized well above or below their roughness region. That should yield excellent results. In the meantime I prefer the low loss and lack of ringing of the simpler first order network.
Big B
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Follow Ups
- Re: Brian, please help clarify... - Brian Cheney 07/27/0320:38:27 07/27/03 (0)
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