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Thread: Open Sound Meter RTA/Phase/ETC Program

  1. Back To Top    #21
    Noob Jdunk54nl's Avatar
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    Re: Open Sound Meter RTA/Phase/ETC Program

    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

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    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by Jdunk54nl View Post
    Anyone else try it out yet? Post your thoughts/results after using it!

    It really is a game changer to be able to measure phase in real time! You can do fun things with this to get it to align the best possible.

    I was eq'ing some speakers I built (PE C notes as can be seen here) and a sub.

    This was the best I could get at first:
    Note: These are Smaart pictures but open sound meter does the same thing.

    You can see in the middle the real time phase. The orange is the sub, the green and pink are each speaker individually and the blue is both speakers. Everything was lined up the best I could get it by just introducing time delays. This is what I would normally just do in REW and get it the best possible after HOURS of work in sweeps and small adjustments. This was after spending countless hours trying to figure out how to get REW to properly measure phase that was useable. It is not the easiest process.






    I would have never thought of doing this if I hadn't seen the phase in real time (and thanks to @dumdum for the suggestion, but he wouldn't have been able to suggest this without seeing the phase picture either).

    The picture below, I flipped the polarity of the sub because this aligned the slope of the phase better, and then used time delay to get them to line up. The next step would be all pass filters, but this wasn't needed after doing the polarity flip. You can see, the sub phase, left speaker phase, and right speaker phase are all locked on to each other VERY well.

    This is how you properly integrate subs with mains.
    This also took me like an hour or so to learn to use the program and about an hours worth of time to do this. In REW, this would have been at minimum a few hours probably over the course of a few days to get not even close to this. There is no more guesswork here. This is about the best it is ever going to get.





    out of interest where the timings off to the tape measure with the flipping of the phase on the sub, I have tried to help the odd person, but one disagreed and insisted I prove it to him as he didn’t believe there could be two ways to time a sub and both would work...

    I always start with a tape, but often find swapping phase and adjusting the ta to bring it back in time works better than the tape and normal phase

  3. Back To Top    #23
    Noob Cathul's Avatar
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    Re: Open Sound Meter RTA/Phase/ETC Program

    I did that with the last iteration of my tuning. I didn't measure phase and flipped the midbass, which gave me much better and more even summation at both ends of the driver to the sub and tweeters.
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    Re: Open Sound Meter RTA/Phase/ETC Program

    I'm going to try and learn how to use this tool. I have a UMIK-1, Audiofrog UMI soundcard (came with the microphone) and I just ordered an aux splitter. I do have a couple of questions:

    1. When I do the measurements, should I just place the UMIK in the headrest and stand outside the car?
    2. Do I need to configure the UMIK cal file anywhere like I do with REW?
    3. Can I just connect the output AUX to my OEM Aux In instead of the DSP?
    Last edited by swrocket; 04-23-2021 at 05:40 AM.

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    Noob Jdunk54nl's Avatar
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    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by swrocket View Post
    I'm going to try and learn how to use this tool. I have a UMIK-1, Audiofrog UMI soundcard (came with the microphone) and I just ordered an aux splitter. I do have a couple of questions:

    1. When I do the measurements, should I just place the UMIK in the headrest and stand outside the car?
    2. Do I need to configure the UMIK cal file anywhere like I do with REW?
    3. Can I just connect the output AUX to my OEM Aux In instead of the DSP?
    1. When I do the measurements, should I just place the UMIK in the headrest and stand outside the car?

    Definitely keep the microphone in a single position the ENTIRE time. Where you are doesn't really matter, just don't interfere with the microphone (so don't just be holding it right in front of you).


    2. Do I need to configure the UMIK cal file anywhere like I do with REW?
    You can and if you go to open sound meter and read the manual it shows you how I believe. In reality, it doesn't seem to make that much of a difference in my small window of testing.

    3. Can I just connect the output AUX to my OEM Aux In instead of the DSP

    Yes, you want the output from your laptop going through EVERYTHING in your system, that way the ultimate signal delay is accounted for and any oddities within your HU.

    I also posted this up a little bit, but read this and watch the videos. This applies to all speaker pairs even though they are working on the Sub - Midbass alignment. That one just proves to be one of the hardest due to the wavelengths of sub frequencies.

    https://www.merlijnvanveen.nl/en/stu...bsolute-method
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  6. Back To Top    #26

    Re: Open Sound Meter RTA/Phase/ETC Program

    I have used OSM a little while ago for phase and it is brilliant. I tried at the weekend using it for frequency EQing, and I could not get consistent results. I was ripping my hair out...

    I might have been slow to realise this, but it also might be useful to point out to others - *your usual target curves do not apply to the Magnitude plot*. This is because, of course, magnitude is the difference between electrical input to your sound card (loopback) and acoustic input (measurement mic). Normally, you measure with pink noise - and that is the same here. Pink noise "rolls off" at 3db per octave, so if you EQ "flat" you are actually EQing a 3db/Oct roll off. Now, because it's the difference we're looking at, that 3db roll off is on both the loopback and mic signals - and is therefore "removed". So if you want a +5db/oct rise down from 160Hz (Harman) that is actually a +2db rise... If you want it flat from 160-2k, that is actually a 3db/oct rise, etc.

    This is for sure possible to work around - you could easily create compensated target curves. But overall I just don't see the benefit over REW RTA, and it's integrated EQ simulation etc. OSM is great for phase, and using the magnitude plot to get maximum summing a crossover frequency when using all-pass or tweaking delay. But for me isn't a one-stop-shop.

  7. Back To Top    #27

    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by PurpleBass View Post
    I have used OSM a little while ago for phase and it is brilliant. I tried at the weekend using it for frequency EQing, and I could not get consistent results. I was ripping my hair out...

    I might have been slow to realise this, but it also might be useful to point out to others - *your usual target curves do not apply to the Magnitude plot*. This is because, of course, magnitude is the difference between electrical input to your sound card (loopback) and acoustic input (measurement mic). Normally, you measure with pink noise - and that is the same here. Pink noise "rolls off" at 3db per octave, so if you EQ "flat" you are actually EQing a 3db/Oct roll off. Now, because it's the difference we're looking at, that 3db roll off is on both the loopback and mic signals - and is therefore "removed". So if you want a +5db/oct rise down from 160Hz (Harman) that is actually a +2db rise... If you want it flat from 160-2k, that is actually a 3db/oct rise, etc.

    This is for sure possible to work around - you could easily create compensated target curves. But overall I just don't see the benefit over REW RTA, and it's integrated EQ simulation etc. OSM is great for phase, and using the magnitude plot to get maximum summing a crossover frequency when using all-pass or tweaking delay. But for me isn't a one-stop-shop.
    That isn’t accurate... you eq with pink noise with rew so rew will also have the same lowering of level by default that you describe... magnitude is fine to use to set up eq, I frequently do this on smaart with below 400hz

    thats because pink noise is how we hear and is made to be the correct level, white noise is recorded flat from 20-20khz

    it also won’t be why you couldn’t get consistent results as it’s definitely consistent... it is equal and so consistency is down to measurement techniques not the software or signal input

  8. Back To Top    #28

    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by dumdum View Post
    That isn’t accurate... you eq with pink noise with rew so rew will also have the same lowering of level by default that you describe... magnitude is fine to use to set up eq, I frequently do this on smaart with below 400hz

    thats because pink noise is how we hear and is made to be the correct level, white noise is recorded flat from 20-20khz

    it also won’t be why you couldn’t get consistent results as it’s definitely consistent... it is equal and so consistency is down to measurement techniques not the software or signal input
    I appreciate that we want to use pink noise because that is how we hear, and that REW RTA showing "flat" will have a -3db roll off in terms of power.

    As for OSM, if I turn up the signal going into the sound card, the audio level rises but so does the loopback level. So the magnitude stays the same. If the output level is raised in a non-linear way (e.g., using white noise not pink) magnitude still stays the same, because the amplitude of each frequency has risen on both loopback and acoustic inputs.

    I can say, that keeping everything the same, taking a measurement in REW and then in OSM, importing the OSM magnitude measurement into REW and level matching, they were not close to the same. Measuring was consistent. The displayed FR was not consistent. I can make multiple measurements in REW and they are consistent with themselves. I can make multiple measurements in OSM and they are consistent with themselves. I can use sweeps or RTA in REW, and they are consistent with each other (with a db or so more HF roll off from a sweep - but I guess this is how it responds to reflections and comb filtering). But OSM magnitude is way lower in the bass and higher in the treble, compared with REW.

  9. Back To Top    #29
    Noob Jdunk54nl's Avatar
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    Re: Open Sound Meter RTA/Phase/ETC Program

    The magnitude aspect should definitely work for tuning....Yes, you need to set levels between your microphone and loopback appropriately to use it. But if you get a flat line across the magnitude then you have a flat response (according to pink noise if you are using that). It is telling you the difference between what pink noise is on the loopback and what your microphone is measuring. If you don't believe me, switch one of the graphs to RTA mode and you get RTA measurements just like in REW. Flat on RTA will be a flat line on magnitude (when using pink noise). The magnitude will just show the level according to the loopback and RTA will be an "absolute" level.

    Saying that, I still like REW for EQ. I like to take my measurements in REW, go back inside the house, sit in a comfy chair, and use it's EQ panel for crossover and filters. Then go back out, input that stuff, remeasure, adjust where needed then be done with EQ and finally open smaart (or open sound meter) and check phase relationships and adjust appropriately.

    How to measure and EQ (In smaart but same principle)

    https://www.youtube.com/watch?v=ub7gRvhAUEM

    Resource Guide: How do I EQ my Speakers?

    https://www.youtube.com/watch?v=93pHuHLZuPc
    Last edited by Jdunk54nl; 04-26-2021 at 10:11 AM.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  10. Back To Top    #30

    Re: Open Sound Meter RTA/Phase/A Bunch of Other Program

    I would eventually like to try this out. Can you go over the details about how I need to do this with a USB mic? I think you mentioned some piece of software that is needed somewhere in order to make this work with a USB mic? I'll have to go back through the thread.

    I'm very familiar with REW, but mainly for pink-noise RTA measurements. I've take sweeps a few times, but it was a major PITA, to be honest - I would MUCH rather be able to measure "live" phase instead of trying to use sweeps.

    I'm just looking for an idea of what I need hardware and software-wise - in order to use this app with a USB MIC successfully. Or would you recommend an XLR MIC instead? If that makes it easier, I don't mind spending the money if the USB mic method is "hack'ish".

    Thanks!

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