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Setting Time Delays in active crossovers


mark1101

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There are 3-4 ways to do it using REW:

 

1) look at excess group delay (after punching the "generate minimum phase" button in the controls dialog box).  It should be flat or gently rising as you go from high frequency to low frequency, with no discontinuities.

2) look at the phase/frequency curve around the crossover point(s)--same thing as above

3) look at the step response--it should be an impulse

4) invert the phase of one driver, and step through increasing or decreasing delays until a local minimum SPL is heard on-axis playing 1/3 octave pink noise around the crossover frequency, then switch the phase back on the inverted driver, i.e., the old school method. (This method suffers from the issue of being 360 degrees off with phase.)

 

There are probably more ways, but I personally use excess group delay first, because you can actually read the delay needed directly.  Then I use step response to see the integrated impulse response, but also how well you selected your crossover filters to approximate a square wave response at midrange frequencies. This will give you the most information.

 

Chris

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In all cases, I'd place the calibration microphone halfway between the two drivers/horns, looking upwards at a 45 degree angle, and at one metre in front of the loudspeaker front face.  For subwoofer/bass bin frequencies, you need to be farther away with the measurement microphone.

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Looks like I need a new PC.  It's time for sure.

 

I have Win XP Home edition 32-bit.  Yes, old.  But only use for music server, surfing, and audio tools.

 

Issue with downloading REW was the java 1.7 or 1.8 which is required.  I don't have that and REW tries to automatically download it and it says JRE file corrupt and stops.  I try to go find Java 1.7 manually (I learned 1.8 won't work after some research)..........well that is as old as the hills and Oracle site doesn't have it anymore as far as I can see (very confusing what they have, a ton).  Other "commercial" download sites get flagged by my virus protection.  Don't trust.  Not even sure you can get the download the way they lead you around.

 

Unless a small miracle in further searches as I have time, I will just get a new PC.

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I use JRE 1.8 (32 bit) with Windows 7 Home Premium (64 bit) to support REW with no problems.

 

The Java version that I use is version 8.

 

Chris

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