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Thread: Open Sound Meter RTA/Phase/ETC Program

  1. Back To Top    #11
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    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by BigAl205 View Post
    I was reading over the weekend the Focusrite Scarlet 4i4 has built-in loop-back, so you should be able to do impulse measurements without rigging up a cable and losing an input channel.
    The motu m4 apparently has it too. I didn’t have the option on my
    macbook (running latest os) with driver installed. Justin had the option on his windows computer but I don’t think he could get it to work.
    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

    I've just been messing with this.

    Some things that I can't see how to do, though:
    1. Even setting long buffers, high FFT powers etc, I get quite a bit of variety between measurements. And of course, surely we need to be able to measure several spots. I'd like to be able to average 3 or 4 as per REW. Is that possible?
    2. For aligning drivers/crossovers, I guess I can change and watch realtime, but a way of summing measurements and changing level/time delay would be useful? Or is the workflow with this tool just to do it all real time?

    Seems like it might be a useful final validation or tune of the odd 1/100th or 10th of a ms. But I don't see how I can do what I can with REW?

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    Re: Open Sound Meter RTA/Phase/ETC Program

    Definitely need more options added to be comparable especially in the RTA portion. Phase seems to work decent and measurements were very comparable to Smaart.

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    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by PurpleBass View Post
    I've just been messing with this.

    Some things that I can't see how to do, though:
    1. Even setting long buffers, high FFT powers etc, I get quite a bit of variety between measurements. And of course, surely we need to be able to measure several spots. I'd like to be able to average 3 or 4 as per REW. Is that possible?
    2. For aligning drivers/crossovers, I guess I can change and watch realtime, but a way of summing measurements and changing level/time delay would be useful? Or is the workflow with this tool just to do it all real time?

    Seems like it might be a useful final validation or tune of the odd 1/100th or 10th of a ms. But I don't see how I can do what I can with REW?

    Programs like this are real time measurements programs, that is their benefit. It shows you EVERYTHING REW shows you when you do a sweep (REW RTA doesn't have nearly this info) in real time. You get to see all of that information change in real time compared to REW where you would have to do a sweep, make a change, do another sweep and see if it worked. This isn't just about EQ'ing. That is only a small part of the whole tuning process but what people spend the most time on.

    Rew still has some advantages for taking a measurement than applying EQ in their EQ window. In reality though, Open sound meter isn't made for the home or car users, this is made for a professional that is setting up for a concert, a play, etc. They aren't worried about it being "perfect" and do not get a lot of time to do these things. So it needs to be quick and in real time.


    Now this is another tool in your toolbox if you have a way of doing a loopback. If you don't have a loopback, this program would be pointless. Preferably some audio interface device like the ones mentioned previously for the best results.


    A lot of your questions are answered in the quick start guide: https://opensoundmeter.com/support

    1) You can average up to 100 measurements (Like REW's RTA averaging only with ALL of the info) - Change measurement to FIFO instead of LPF. FFT power determines how much power you are willing to devote to the program via your computer. It just does more calculations with higher power, so there should be some minor changes in your measurements.

    2) The newest version 3.1 has vector averaging of stored results now. Time delay is the phase graph, this is 10000000000x more accurate than any other way to align drivers. Changing levels is super simple but done in real time. Click the measurement icon and adjust the gain appropriately or better yet, use your dsp to do this.
    Last edited by Jdunk54nl; 02-12-2021 at 09:42 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

  5. Back To Top    #15

    Re: Open Sound Meter RTA/Phase/ETC Program

    I have an ECM999 mic and an old Edirol USB sound card. I did use one input as a loopback (headphone O/P of the amp, actually) and the mic into the other. It was working as it should and clearly giving valid measurements. I was just doing at my desk with my near field setup - I didn't bother to go out to the car.

    I did realise after posting that the "math source" can combine measurements - which was the main missing piece. FIFO averaging gives a long time average, but moving the mic removes HF measurements, presumably because the phase is changing so much. So vector averaging solves this. Also, I agree that being able to sum drivers and time shift to get x-over phase right is better than REW, with its timing reference method.

    Still, not being able to model EQ is a big one - and EQ is critically important. Crossover phase and points are largely correct or incorrect - but EQ is subjective. I would not want to start from zero adjusting in real time with pink noise playing.

    It does look like a good tool - and could well be my go to for crossover setting. But I guess partly I am just too happy with REW for a lot of the other workflow, plus it does do stuff that I think this can't and never will - export of averaged responses as a .WAV IR, to use in DRC, for example.

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    Re: Open Sound Meter RTA/Phase/ETC Program

    Quote Originally Posted by PurpleBass View Post
    I have an ECM999 mic and an old Edirol USB sound card. I did use one input as a loopback (headphone O/P of the amp, actually) and the mic into the other. It was working as it should and clearly giving valid measurements. I was just doing at my desk with my near field setup - I didn't bother to go out to the car.

    I did realise after posting that the "math source" can combine measurements - which was the main missing piece. FIFO averaging gives a long time average, but moving the mic removes HF measurements, presumably because the phase is changing so much. So vector averaging solves this. Also, I agree that being able to sum drivers and time shift to get x-over phase right is better than REW, with its timing reference method.

    Still, not being able to model EQ is a big one - and EQ is critically important. Crossover phase and points are largely correct or incorrect - but EQ is subjective. I would not want to start from zero adjusting in real time with pink noise playing.

    It does look like a good tool - and could well be my go to for crossover setting. But I guess partly I am just too happy with REW for a lot of the other workflow, plus it does do stuff that I think this can't and never will - export of averaged responses as a .WAV IR, to use in DRC, for example.
    You can export measurements as osm, cal, txt, or frd.

    If you can loop back your dsp into your computer, you can model eq very nicely in this much like you can with smaart.

    This is from Nathan Lively, he has a lot of videos on using Smaart
    How to set it up
    https://www.youtube.com/watch?v=QwOaqTKvFuk

    How to do it:
    https://www.youtube.com/watch?v=8bi_oZVIJmE
    https://youtu.be/ub7gRvhAUEM


    Also, moving the microphone is always going to impact HF way more than low, you are greatly changing the measurements in the HF by moving it even mere cm right/left/up/down.
    This could also be because on your magnitude graph you are using coherence. If Open sound meter doesn't have a good coherence (how reliable are your measurements) then it won't show those. So click on the magnitude graph and uncheck the "use coherence" check mark. You can also switch one of the three graphs to coherence and see how reliable your measurments are. If it isn't close to 100% across the board, you need to turn up the volume or turn down whatever is causing bad coherence in the room.

    I had terrible coherence in the HF when I was using the usb microphone and external usb soundcard for loopback due to clockdrift. It wouldn't show any of the HF data unless I turned off "use coherence"

    Click image for larger version. 

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    Edit* Video on how to get good coherence
    https://youtu.be/S_A1BVOqNXM?t=312
    Last edited by Jdunk54nl; 02-12-2021 at 12:12 PM.
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  7. Back To Top    #17
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    Re: Open Sound Meter RTA/Phase/ETC Program

    I made these because I was talking to the creator of Open Sound Meter and wanted to better explain the two setups:

    Setup 1: Motu and XLR mic
    Click image for larger version. 

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    Setup 2: USB Loopback and USB microphone:
    Click image for larger version. 

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    Click image for larger version. 

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    Re: Open Sound Meter RTA/Phase/ETC Program

    New version of Open Sound Meter was just released by Pavel (creator of it)

    https://opensoundmeter.com/download


    v0.3.1 is out

    In this update:
    - fixes for MOTU drivers on macOS
    - fix for calibration files (If you already have calibration file created with the software, you need to recreate it)
    - Spectrogram now has options for colours thresholds
    - Math source has an option of operation type: polar or vector
    - Auto notes for stores includes info about applied gain and selected device
    - Data import supports CSV format
    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

  9. Back To Top    #19
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    Re: Open Sound Meter RTA/Phase/ETC Program

    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.





    Last edited by Jdunk54nl; 04-10-2021 at 12:20 PM.
    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    #20
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    Re: Open Sound Meter RTA/Phase/ETC Program

    Here are some videos on helping you do this by Nathan Lively:
    These are using Smaart, but the principles still 100% apply to Open Sound Meter.

    5 ideas to improve Main+Sub phase alignment with SmaartŪ [GSwSST35]



    How to verify main+sub alignment in SmaartŪ [GSwSST34]


    How to phase align main+sub in SmaartŪ [GSwSST34.1]
    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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