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Thread: Time alignment issue

  1. #1
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    Time alignment issue

    I have an issue with not getting constant results with time delay using audiomulch for processing. I am using Smaart 6.1 with the m-audio mobile pre USB sound card with behringer mic and I have been successful with using that combination in all of my previous setups. This is the first with having the computer do all the processing though so I dont know if this is normal but here is my issue.

    When I have the mobile pre connected directly to the amps I can get constant results using the time delay function in Smaart, but when outputting through the mobile pre into my sound card (asus xonar D2x line in) and then processing through audiomulch the time delay is never anything constant. I will get a result something around 2-300ms and then if I wait a few seconds/minutes and test the time delay again the result will increase 1-2ms from previous and every result after that will continue to increase, it increases consistently but its difficult to do any kind of time alignment for obvious reasons, I am basically guessing and trying to compensate for that 1-2ms change. Does anyone have any idea what could be causing this? I am totally stumped, I can only imagine its gotta be something in audiomulch because if I take the program out of the equation I am getting constant and consistent results for time delay. I am using Rubber filter for crossover, Gdelay for gain and delay and Electri_Q for EQ. Any help would be Much appreciated as I am at my wits end.

    PC specs are as follows incase anyone needs to know:
    Zotac GeForceŽ 9300-ITX-WiFi
    Asus Xonar D2X
    Intel Core 2 Duo E7500 2.93Ghz
    OCZ Platinum 4GB (2 x 2GB)
    OCZ Vertex 30GB SSD
    Hitachi 1TB HDD
    Windows 7 professional

  2. #2
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    So how about just plugging the Mobile Pre into your amp and doing your measurement that way, since you say you get consistent results that way. Then hook your Xonar back up to the amp, start Audiomulch and plug your delay value into Gdelay.

  3. #3
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    Quote Originally Posted by kross View Post
    So how about just plugging the Mobile Pre into your amp and doing your measurement that way, since you say you get consistent results that way. Then hook your Xonar back up to the amp, start Audiomulch and plug your delay value into Gdelay.
    Yep, tried that as well and its totally wrong. With those numbers the stage is entirely to the right side of the vehicle, no where near center. Also the onboard sound which sends the signal for my rear midbass is completely off as the delay on the onboard sound is much higher than the asus card for some odd reason, talking close to 50ms.

  4. #4
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    Well your initial problem sounds like the Audiomulch clock and the sound card clock are slightly out of sync (one slightly faster than the other), causing a cumulative error. Try different sampling rates in Audiomulch. 48 kHz, 44.1 kHz, 96 kHz, etc. And prefer ASIO over DirectSound.

    BTW I'm not an expert in this by any means, just tossing out ideas. But I've read that many sound cards claim they support 44.1 kHz but really just resample to 48 kHz. It's best to use a sample rate that your sound card natively supports.

  5. #5
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    I think if the sample rate was off by that much it would cause more then a few ms difference. Not familiar with audiomulch but I know alot of audio processors use a self generated clock (aka cpu generated) which can vary very slightly from the sound cards hardware clock. theres another forum member more knowledgeable on the subject that will probably jump in.....

  6. #6
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    Yeah, I made sure to set VAC, and all sound cards to the same 16-bit 44.1k rate so I couldnt imagine that being it.

    The crazy thing I noticed today was that the onboard sound that the rear midbasses run off, are changing, I will do a rough T/A on them and they will appear in the front center, but after I shut it down and boot it back up they will be off again, we are talking by 60ms or so, but give it a few minutes, like 10-20 (maybe less) and they will eventually delay back down to be back in line with the rest of the frontstage, its really weird.

    But anyway, anyone else can suggest something?

    I basically just set the left side as close as I can by guessing the increment in between testing delay and then adjusting the right side by ear to center it as best I can, but its still not right, better but not right.

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