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REW phase alignment procedure.


jay michael

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Hey everyone. I'm going to first off admit that I am not an expert REW user. I've drudged around the internet for a few years trying to find a reliable procedure for executing a proper phase alignment between tops and subs without spending money on something like Smaart. There have been some tools added to REW recently to assist in this, but I've never come across a proper explanation or tutorial on how to do it. Piecing together some bits and pieces i've found from a few different sources I think I may have it somewhat figured it out. Warning, I filmed this after a LONG hot day and was pretty burnt out. You'll notice I miss-spoke a few times towards the end using the wrong descriptors for what I was trying to say. Otherwise It should be easy enough to follow what I was doing. I've since used this procedure a few more times setting up my system in different configurations and I've been getting repeatable results that seem to make sense and sound really good. Perhaps this is old news to some of you but I thought I would share it to see if you might find it useful, or absolutely shoot holes in it if you think its out to lunch. End goal is I want a repeatable process that I can rely on, and maybe do a proper tutorial down the road to help others out.  It seems like its one of those mystery processes that people ask a lot about. Let me know what you think, good or bad. 

 

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A little to ad to this. When you start playing with different delay values you may find a couple that gives good additive summation, maybe even 1 or 2 with positive polarity and others with polarity inverted. What I've been doing is taking screen shots of each and at the end looking at each screen shot and seeing which one has the best or smoothest frequency response as well as the best phase traces that line up both at the crossover frequency and as far away above and below the crossover frequency. You really want to keep an eye out for null ripples forming above and below the crossover point. There should be 1 particular delay value that has the best combination of additive summation and alignment of the phase lines below and above the crossover point, that point should be your ideal place to set the system. Note: It may be worth trying a handful of crossover points as well, saving screen shots of all of the different delay values as each crossover point may give slightly different results. 

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Great video mate...

Been checking out a heap of info and tutorials on this lately and quite often I find people can get carried away going way too in depth with technical theory and precision results while breezing over the important info for people who have absolutely no experience like which button does what and demonstrating easy to make mistakes.

Also repeating the steps several times while showing the workflow that got you to where you ended up helps with my retention heaps I think.

Couple of things I thought of while watching (based right now on my pretty much completely theoretical regurgitated youtube knowledge)

Can your processor run allpass filters? I think once you've gotten the delay dialed in this is your next step in phase aligning things either side of the X-over as they allow you to (i believe) modify the phase response slope and do this relative to frequency (i.e. constrained to a certain bandwidth) rather than just shifting the whole plot forward and back in time.

Also applying eq to your plots will have effects on phase so trying this at frequencies where you're not getting summation may help to get the alignment there closer while not messing up where you've got it dialed in?

Anyways great work keep it up!

Also just btw I absolutely love (am insanely jealous of) your system... been following you on youtube for a while. Cant see myself finding the small fortune for anything danley anytime soon but gonna have a go at some DIY MEH horns to go on top of my Othorn/ES18 combo this year :)

 

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On 8/9/2021 at 10:53 PM, jay michael said:

Hey everyone. I'm going to first off admit that I am not an expert REW user. I've drudged around the internet for a few years trying to find a reliable procedure for executing a proper phase alignment between tops and subs without spending money on something like Smaart. There have been some tools added to REW recently to assist in this, but I've never come across a proper explanation or tutorial on how to do it. Piecing together some bits and pieces i've found from a few different sources I think I may have it somewhat figured it out. Warning, I filmed this after a LONG hot day and was pretty burnt out. You'll notice I miss-spoke a few times towards the end using the wrong descriptors for what I was trying to say. Otherwise It should be easy enough to follow what I was doing. I've since used this procedure a few more times setting up my system in different configurations and I've been getting repeatable results that seem to make sense and sound really good. Perhaps this is old news to some of you but I thought I would share it to see if you might find it useful, or absolutely shoot holes in it if you think its out to lunch. End goal is I want a repeatable process that I can rely on, and maybe do a proper tutorial down the road to help others out.  It seems like its one of those mystery processes that people ask a lot about. Let me know what you think, good or bad. 

 

The auto anything (frequency, gain, delay, etc.) in REW is always interesting - the RTA-like simulations seems to be very accurate. 

I too have taken the manual approach you have with eq, but never did the alignment reference...I know this is 2 years old, but appreciate the share. I'll have to give this a go. 

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Cool video, I haven't seen that before. Gotta do this too, been too lazy to phase align my PAs but I really should.
The alignment tool in REW looks super cool, this is the first time I see it. I used to take a bunch of sweeps changing delays until things looked right lol.

Btw you don't need to run the timing reference to a speaker, you can do a straight (electrical) loopback instead.

When integrating multiple drivers via dsp in speaker designs, I do it in the following order:

  1. Apply corrective speaker/driver EQ (minimum phase)
  2. SPL align
  3. Apply Xovers
  4. Take another measurement of the individual components/speakers now with everything that changes phase already applied
  5. Phase align
  6. Take another measurement for validation

And then when the PA is set up I'd probably align the PA with the Snare drum, because that will likely be the loudest sound coming from the stage and in smaller venues that will actually dominate the overall sound. Not applicable to DJ gigs of course, but something to keep in mind if you're working with acoustic sound sources.

I'll be rocking Powersoft soon so I'm looking forward to getting all of this running.

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