Time and phase alignment with a USB microphone - a REW tutorial 

another gold mine of information. i have none of the necessary equipment to do this, but knowledge is power, and someday...

Thanks! Peter Hermanns and THANKS RAW CAt!!!

Beautiful, just beautiful 👏 Thank you for sharing this information and glad I am a Patreon supporter. Personally I felt the video relayed the desired information correctly.

Another very informative video. Thanks a ton for knowledge sharing 😊.

Thank You Very much for taking the time to make this very helpful and informative video ! The way you explain things is very straight forward and well done. This is pure gold.....

Thanks for your sharing！You are great!

Thank you for sharing

sound is fascinating, this is a great channel. i'm about to write a long reply for whoever is interested in the distinction between phase and delay as it's potentially confusing... hope it helps :) the phase shift of a Particular speaker is a delay at a Particular frequency. 90 degrees phase shift at 100Hz is not the same amount of delay in ms as 90 degree shift at 1000Hz. it's a 10x shorter delay in ms because the fq is 10x higher... that's key to internalize. two speakers that are not the same model will have different phase graphs, meaning different delays at different frequencies. (crossovers also alter the phase by a given amount depending on their order, how quick they attenuate the signal) so even if they are aligned in time (say they're positioned in front of you at the same distance) their phases will not be aligned over the entire fq. that means at Some frequencies one of the speakers will have a 'small delay' and play later in time but at Some other frequencies the other one will be behind. it's kind of strange but that's how things are... so just to underline, two different speakers being at the same distance from you and starting to play a sound at the same time is not guaranteed to work together over a frequency range. in that case, there are options on how to make them work best together one being actually time misalignment to a degree that compensates for the delay present in the phase at certain fq. this would align them over a certain frequency but not over the entire frequency range. another option is to delay both speakers by the maximum amount one of them has (at a given frequency) and then adjust the delay for multiple frequency ranges giving a chance to the 'slower' speaker to catch up.. in other words we modify the phase at a particular fq by applying filters that do not change the tone only the phase. (these are called "all pass filters", whatever sound goes in comes out but w/ a slight delay. just as a curiosity, all filters introduce delay measured in degrees, a change in phase. passive crossovers alter the phase depending on their order. EQs in general alter the phase, in fact that's how they work by creating constructive or destructive interference -there are special EQs that only alter the tone or only the phase ) ---------------------------------- in practice: for two or more speakers that are meant to play the same frequency range (say you have 4mids), you want the sound from each one of them to reach you/the mic at the same time. you align them in time w/ your ears being the "finish line". because the speakers are usually identical, the phases will be identical and the the sound reaches you in phase. for two or more speakers that are meant to play different ranges of frequencies (say 4 mids and 1 bass) you want the sound they all play in common, (the crossover frequency range) to reach your ears in phase. and because the speakers are not identical their phases are usually not identical, so the time alignment between the mids and the bass is not the priority but the phase is for a fuller sound. in sound most things are compromises between two or even more aspects. things can't be 'perfect' and the challenge is to trick our ears. one 'perfect' example is having two speakers in a stereo configuration, at different distances and tricking our ears/brains into believing the sound is actually coming from someplace in front of us from a mono sound source. the compromise is that for it to work we can't change our position and if we do the trick doesn't work anymore. so it's far from perfect but we can work w/ it :).

Thanks for this video! I could never get the loop back and xlr mic working properly to do it

I notice you rarely do the "estimate IR delay' step of Peter's guide, which he says is required at the beginning of every new measurement set, ie between L/R tweets as well as between tweets/mids. Basically to remove the system delay and get accurate measurements, Peter explains to make sure to have the timing offset in the measurement tab be set to 0, do your initial measurement, then 'estimate IR delay', click the middle option 'shift and update timing offset', re-do that same measurement now with the updated system delay removed, then quickly measure the other speaker you are aligning the first one to. So for tweets it'd be first sweep R, second sweep R, third sweep L. Then the same for mids, rears, etc. Then to align them together it'd be first sweep tweets, second sweep tweets, third sweep mids. So on and so forth. Its actually alot more time consuming than this video demonstrates. I'm not sure how accurate your measurements could be if skipping this step entirely, you instead choose to 'set t=0 at cursor' which doesn't avoid the clock drift you get between components when using a usb mic. At least that's my understanding of the process.

This will be very informative for a lot of people and I appreciate all your hard work. But after paying out for a Focusrite and XLR mic it would be great if you can do a video using REW as I am more familiar with that software. Keep up the good work !! Thanks !!!

Awesome video again from you! Only having a UMIK-1 and no focusrite-loopback system this helps a lot to trust the data of the measurements. I wonder, if you have to decide between perfect IR start OR perfect phase angle/slope in crossover point: from a listening experience what is better, or do you do a "in between" IR start AND phase match?

Thanks, I will try this today. Very good info. I like your amp testing videos as well, and especially your A-B testing of different amps. I’m very curious how much the quality/price of an amplifier actually matters. It seems for subwoofers, it doesn’t matter. And maybe for mids and highs, it doesn’t really matter down to a certain point. I bought a cheap Skar 4 channel to temporarily replace a Diamond Audio D5 300.2 while I repaired it, and I can’t tell the difference in my daily driver. I also wonder if I would be able to tell the difference between tuned EQ and tuned as close as possible without EQ, basically just tuning the levels. I have an alpine 0850x and it takes too long to switch between tuning presets to do a proper A-B test. I also probably can’t tell the difference between hi-res lossless and lossless or even hi-res and Bluetooth.

Great info as always! Iam just wondering when you made video of allpass, where the timing offset value "comes" and in analysis tab what were impulse calculations settigs? If I put estimate IR timing reference, it gives me a "default" value of 39ms, which is very high?

Hey RAW-CAt, many thanks for all the helpful videos you've uploaded, much appreciated. I just installed my first car audio upgrade, next step will be to try and tune the car myself with the help of your videos. I'm now deciding what mic to get. Since I already have a sound card, would any cheap measurement mic do, does it need to come with a calibration file ? Or would you recommend getting a umik and a tape measure for simplicity? Thanks and take care!

Okay, shifted away from trying to do the XLR one as I didn't have a way to access the amp via RCA or high level inputs. Couple questions: 1. I assume this TA should be done after getting the cross overs dialed in? Do you recommend also doing it after EQ? 2. On my vehicle which has a Match Up 10 under the carpet area under the seat, to get a signal from REW into the amp, do I have to connect somehow directly to the amp? The car's headunit does not have a line in, and the Match 10's only optical in is used by the Nav TV Zen V. Is it even possible to get a signal from the PC to the car via the USB input on the car to your knowledge? Otherwise I guess I'm stuck with the auto time alignment function in the AF DSP tool, or old fashioned tape measure. But I don't think I can adjust phase.

Thanks for so much informative video. Accordingly i made alignment for front midbass and tweeters and same centre imaging is much better than previously made by tape measurement. But when rear passive speakers running along with front active aligned ones, centre imaging is not that good. Whether is it require to time align rear passive speakers and if so then which to consider midbass or tweeter ?

I enjoyed the video. I am curious about how the measurement method differs when using an audio interface. Thankyou so much ~~

I’ve did this method before a few month back when if I tried to match the phase and the end result don’t turn out right. So I ended just to match the impulse rather than phase.

@11:00 when you measured the Left reference tweeter you muted the Right tweeter and selected in Rew output L+R. Is there a reason that you didn't select in Rew output just L?

to output the chirp to the cars speakers we must be directly hardwired into the dsp ? cant use bluetooth to my headunit?

I don't know if anyopne else has experienced this but I've noticed my DSP.2 will andomly changes EQ from time to time when the car starts up. It seems mostly on initial start if it's been left a lone for a while (overnight) but when/if I cut the car off and start it up again , the sound has a lot of mid and likes to digitally clip. Is there a setting that's changing or is my DSP defective? It's using High in from a Renault stock headunit without the Bose amp. I've put everything flat and off on the headunit too.

I read the pdf and it says if the dsp does not have virtual channels that you must measure each side individually and then both sides together. I've been trying to wrap my mind around how you would do that. I have a Dayton audio dsp and I'd love any suggestions. Your videos are simply amazing and I'm grateful for your expertise!

I get wildly different timed measurements each time, even for the same driver. I can get 4 ms between tweeters, make that change, re-measure and then they are 15 ms apart in the other direction. All speakers do the same thing even when taking L/R measurements within seconds of each other. Also, every time I measure, I get a Clock error message saying that the ppm were way too high, often over 1,000.

@RAW-CAt So basically I do all this time and phase alignement after setting xovers and a little bit of eq? Or only xovers? Could you point a list of steps what comes first, that would be perfect for a newbie. Thanks in advance 😊

Why would you use time alignment to phase align instead of aligning time and then using the phase adjustment on the DSP?

So if we are supposed to set time alignment before xovers, I assume there is a function in REW where we can set the range of frequencies we want the sweep to consist of. Otherwise how do you protect tweeters and midranges from low frequencies? I would hate to make the mistake of sending a full 20-20k sweep to my tweeters inadvertently.

Hi.. nerijus, what about small RTA mic dayton imm6, output using cable jack 3.5 mm to AUX DSP, is good with this method?

I believe you can play it from the file (and even add timing reference sound to it)

Have you tried using a battery powered speaker with an aux input plugged into the headphone jack of the laptop as a reference? I'm guessing this would remove the need to use the tweeter.

What do you recommend to do as the first step? EQ or T&P allignment?

Hello, I'm Michael from Germany. the video is great. can you repeat where I can get the PDF from? Thx

Hi, used smlc p100pro ,output coaxial to dsp ?

Would you help me how to ssl2 external audio interface is calibrated using room eq wizard

Why did you delay the subwoofer channel? Is the subwoofer in your car located in the front of the cabin?

The only thing that keeps frustrating me is my Audiocontrol D6.1200 has left and right channels paired, and no virtual channel routing. So the I/O routing is what I struggle with the most.

Hi mate, wonderful.. Been looking for this kind of method to do TA Anyway, how do u find the result compare to loopback method ?? Which one better ? What i found still confusing is that , We would add delay to phase align between drivers (tweet to mid, sub to bass, ) at XO frequency. It will affecting the time alignment (impulse).. bit confuse on this part. Unable to download the pdf docs from fb group .. Anyway, thanks for your effort making this kind of videos Peace from Indonesia

I didn't fully understand something - why do I need to measure my timing reference element? It's already supposed to be in the right timing.

About time lol.... jk thank you

Holy shit this is a process! You need a phd!😂😂

Great video, I realized one important things. Being able to do TA with rew, is pointless without a dsp. The built-in TA and EQ in aftermarket head units are worthless!! Ass im not able to select the individual speakers. The f#$ is the point of having TA adjustment if i cant measure it!

how to download pdf

So basically this is a helix DSP video

Idk about this. Just wasted four hours. The measurements were never consistent. The more I meausred, the more wrong it became. I tried the headphone jack and an audio quest dragonfly for speaker output. Did measurements right away. Clock drift I guess.

Midbass