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RE: time alignment for coax...........

Posted by tomservo (M) on July 25, 2007 at 08:01:28

In Reply to: time alignment for coax........... posted by Norman Bates on July 24, 2007 at 20:45:50:

Hi

You are dealing with multiple things.
If you actually measured the time of origin (the equivalent location front to back, in time), you normally find the cone driver is behind the HF section, this is usually still true with the type having the Compression driver behind the woofer.

The other “thing” is that the crossover itself introduces delay, delaying the LF section more than the HF section, showing up as a phase rotation of 180 degrees for a 2nd order slope and 90 degrees more per order increase.

Sadly, many measurement popular systems show acoustic phase incorrectly and so it has lead people to think the all pass filter is more useful than it is in this application.
It is what is already wrong with a loudspeaker, it is an all pass filter already, it delays the lf side more than the hf side.

One can do better than the normal relationship if you go active DSP and use linear phase crossovers (which do not have the normal phase shift) or “find” a passive arrangement, which also results in no phase shift. This can be done, is done in the SH-100 and SH-100B commercial speakers we sell at work.
Best,

Tom Danley

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