What is 'estimate IR delay' in REW?

Use estimate IR delay to the adjust the zero time reference to make the phase graph readable.

From the REW manual:
Using a timing reference allows REW to eliminate the variable propagation delays within the computer and interface so that separate measurements have the same absolute timing. A Timing offset can be set that will shift the response relative to the timing reference, allowing the time of flight delay to be removed if using a loopback connection, for example. The timing offset can be set manually or from the figure calculated using the Estimate IR Delay function.

And: For speakers the delay estimate is based on the location of the peak of the impulse response. Subwoofers have a broad peak and a delayed response due to their limited bandwidth so the delay is instead measured relative to the start of the impulse response. The start of the impulse response cannot be located as precisely as the peak, however, so delay values are less accurate for subwoofer measurements.
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I love to geek out about the physics of sound. This channel focuses on the growing opportunity for live sound engineers to improve their confidence and consistency through the understanding of the principles of sound system design and optimization. My goal is to make this channel upfront and honest about my success and failure, so you can learn from both.

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[johnschalk]

This was helpful to me as I am trying to compare the phase traces for two bookshelf speakers. One is a coaxial design and the other is a traditional two driver speaker. I noticed that the estimated IR offset is nearly identical to the loop back timing reference value for the measurement. Why shouldn't we just use that value? FWIW, while my two phase traces are smoother now, I still can't really understand what they're showing me! The unwrapped phase plot for the traditional 2 driver design is flatter from 700 Hz to 24 kHz than the line for the coaxial speaker which is the opposite of what I was expecting. I'll conclude by saying that I enjoy all of your videos Nathan. Thank you for providing so much good content on all things audio for us.

[shanefoss]

This was timely and very helpful for me. Thank you ❤

[fascination.sound.and.groove]

*Thanks for the great video.*
Andre from Hamburg, Germany

[Nonamehere]

Is it possible or correct to also align the phase using the overlay screen (phase) in rew, unwrapping the phase and placing the two phase curves coplanarly? That's how I've been doing it so far.

[mfkhometheater]

I don't know what I'm doing wrong but my impulse response doesn't look anything like it should. What you have at 2:10 looks fairly normal like what I would see using ARTA but what I'm getting in REW is not an impulse response. I don't know what it is.

[rlopezrb]

Hi Nathan, i want to ask a question: I measure independent each way, lows and highs, only 1 channel. ¿I must apply estimate delay in the measured highs and put the delay for next measurement (bass)? i can remove the xover in bass to measure well but later i have to put it ona and filters PEQ too and phase will move. i want to estimate delay between bass and fullrange. 0.5 ms physically.
with initial delay is easy to align with alignment tool the problem is to know if the delays are ok. thanks

[johnschalk]

Does anyone else have trouble with REW retaining the Timing Offset value even after starting a new session? This caused me at least 20 minutes of "what the heck" when I was trying to time align some front fills to the mains at a gig. I kept getting a negative time, which wasn't possible given the relative positions of the speakers. I finally realized that there was an old value in the Timing Offset box and once I zero'd that out, everything proceeded normally. Is there a config setting to not retain this value?

[guillaumerebmann]

Hi Nathan, i have an issue and no clear explanations.
I would like use the Merlijn Van Veen's absolute/relative method to do the aligment between my subs and Tops. I use for this method the REW software with a USB mik-1.
During the absolute step: the top is plugged on the left side and the sub on the right side. The timing reference is the left side (the top speaker).
I measure first the top and then use to "estimate IR delay" and correct the delay. Then I mesure the sub (timing reference Left side).

Now is the By using the REW alignement tool without sub IR estimation delay the delay i have to apply to the sub is -16, 8 ms! With sub IR estimation delay and shift, the delay to apply on sub is only 5.03 ms which make more sense to me.

What is your opininon?

Hello from France.

[Dont_Gnaw_on_the_Kitty_]

Gradient a bit high here, what does IR stand for, what is it and then finally why would you need to correct for the delay.

[zechariahblevins]

Is it fair to say this is a similar function to “delay locate” in smaart?

[halrichard]

Is there any REW instruction for Dummies? :D Thanks for your efforts Mr Lively.

[kuriakos]

I didn't understand anything 😢 how i will make alignment and phase alignment my subs?? 😕

[tcmixman]

How does REW compare to Smaart, Systune etc?