Phase shift function

1audiohack

In the end of section 4.12 on page 38 of the DBX260 manual is a little explained phase function adjustable from 0 to -175 degrees.

What is this intended to do?

I have played around with it in attempt to level the group delay of an acoustically small direct radiator in order to maintain its acoustic center with falling frequency.

I measured the T.F. of 0 and -45 degree on a Nyquist plot with my TEF and both plots match at origin and rotate clockwise ending with a 45 degree difference increasing with frequencey as expected. When applied to the driver however the final value of phase is increased.

I may have just answered my own question, how ever I could use some insight. I am just a novice. What is the intended purpose of this control?

Thank you,
Barry

Dennis

\"An additional parameter that can be found in some frequency dividers is phase alignment circuitry. This can come in the form of standard signal delay or as a specialized form of phase filter knowen as an all-pass filter. The standard delay can be used to compensate for the mechanical offset between high and low drivers so that the most favorable construction design can be utilized. The all-pass filter is a tunable delay that can be set to a particular range of frequencies. The band width and center frequency are user selectable. All-pass filters can be found in dedicated speaker controllers and active speakers, where conditions are sufficiently controlled such that the parameters can be optimized. The all-pass filter is of extremely limited practical field use since the field conditions make clear discernment of the phase response extremely challenging.\"

This quote was stolen without permission from Bob McCarthy's book, \"Sound Systems: Design and Optimization\"

Dennis

1audiohack

Thank you Dennis.

I need to horse around with this some more.

Any additional help would be most welcome.

Thank you,
Barry.

Dennis

I have had little success with all-pass filters. It's probably a lack of knowledge on my part but they seem to move things in directions other than where I want to go. I usually just use delay and deal with the latency. This might be a question to post on the forum at ProSoundWeb. There's lots of people there that are smarter than me.

Dennis

1audiohack

I can concur with that! I am just trying to get a better handle on something that could be usefull, if I can wrap my head around it.

I will give the ProSoundWeb guys a try.

Thanks again,
Barry.

Dennis

If you post at ProSoundWeb, come back here and post a link to your thread there.

Dennis