3 way active crossover - why delay?

[nonsubscriber]

So I setup this device over a decade ago. Digital in, active crossover, 6 channels out.

For some reason I added a 1.5ms delay for the high channels. The crossovers are LR-12db/octave, LR-12db/octave and LR-24db/octave.

I probably cannot tell the difference listening but there must have been a reason I set this delay (probably someone's advice.)

Anyone have an idea? Thanks!

 

[DWPress]

The tweeter is delayed to match the woofer in time (the physical driver is shallower than the depth/source of the woofer). If you can measure your speakers with REW you would see the effect on the impulse response.

 

[somebodyelse]

1.5ms is about 18" worth of delay which seems excessive for the difference in driver depth.

 

[valerianf]

What is the best way for measuring the needed delay for the tweeter?

 

[Devnull]

What is the best way for measuring the needed delay for the tweeter?

Look at how the phase changes at the xover freq and adjust the phase to reduce the mismatch

 

[levimax]

What is the best way for measuring the needed delay for the tweeter?

I like this method using REW. It is written for a miniDSP but will work with any active crossover. https://www.minidsp.com/applications/rew/measuring-time-delay

 

[Keith_W]

What is the best way for measuring the needed delay for the tweeter?

I prefer to use the tweeter delay method. Assuming you are using a MiniDSP:

1. Take an initial sweep of the driver under test (DUT) with your tweeter and keep it aside.
2. Dial in the maximum delay for your tweeter. I can't remember offhand what this is, but let's say 30ms.
3. Do a sweep of the DUT together with the delayed tweeter.
4. Examine the impulse response. You will see two impulses - on the left is the DUT arriving earlier, and on the right is the tweeter. Measure the distance between the two impulses from impulse START (not impulse peak!). You will need to adjust the zoom settings to see the two impulses clearly! If it is exactly 30ms, the two drivers are perfectly aligned. If its > 30ms, then the DUT is arriving early. The solution is to delay the DUT by (measured distance minus 30ms). If it's <30ms, the DUT is arriving late. The solution is to delay the tweeter.
5. Set these delays in your DSP and repeat the sweep. Compare it to the sweep you took in step 1.

 

[nonsubscriber]

Thank you for the great replies!