UMIK-1 timing reference and Phase - Page 5 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #41 of 82 Old 03-07-16, 02:47 PM
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Re: UMIK-1 timing reference and Phase

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jtalden wrote: View Post
I see the measurement sweep signal is modified a little so I intend to update my external sweep file accordingly.
The measurement signal hasn't actually changed, just the way that start and end are shown in the signal generator controls to make them consistent with the measurement window settings.

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I looked to see if the measurement sweep export feature now includes a new option to save a stereo version of the sweep with the new acoustic timing sweep on the reference channel. I don't see that option yet. I am thinking that it will make it possible to run external sweeps that provides the capability of the new acoustic timing option.
The meas sweep export needs an additional dialog to choose whether or not to include a timing signal and where, I haven't done that yet. It would also lend itself to a mode where REW can be set to start capturing and wait to see the timing signal before capturing the measurement, removing the complication of trying to time things by hand. On my todo list
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post #42 of 82 Old 03-07-16, 03:24 PM
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Re: UMIK-1 timing reference and Phase

Thanks John!
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post #43 of 82 Old 03-07-16, 11:28 PM
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Re: UMIK-1 timing reference and Phase

Very nice indeed, John! Now I need to go back and research all of the instances in which my measurement accuracy was called into question because of the lack of a timing reference. Serious homework to do!

And I feel an update to my beginners REW guide will be coming soon...
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post #44 of 82 Old 03-10-16, 09:52 AM
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Re: UMIK-1 timing reference and Phase

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Thank you very much. With this addition andyc56 (the creator of Multi-sub optimizer) can make his software work with USB mics which makes it much easier.
Hi all. I'm the guy who wrote the Multi-Sub Optimizer (MSO) software.

I mentioned this in another thread, but it's worth repeating here. I used to have big, bold warnings about using MSO with USB mics, which I've since updated to reflect the current REW status with regard to the new acoustic timing reference feature. I had those warnings there because if one attempted to use measurements taken with a USB mic without an acoustic timing reference, MSO would appear to work fine, but give wrong results. This is an insidious type of "silent failure" error that needs to be clearly warned against in the documentation, especially considering that USB mics now dominate the measurement scene. There are actually no modifications to MSO required for it to give correct results when used with measurements taken with a USB mic, as long as one uses the acoustic timing reference when performing the measurement.

Kudos to John, not only for the quality and breadth of features of REW, but also for his amazing commitment to it.
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post #45 of 82 Old 03-11-16, 01:19 PM
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Re: UMIK-1 timing reference and Phase

JohnM, many thanks for the acoustic timing reference addition for USB microphones. I had the chance to do some measurements today - in preparation for some MSO calculations (thanks andyc56) - and the new system is so much easier to use, previously I had to crawl behind my AV cabinet to disconnect speaker cables and connect up some pre-amp outputs to a Behringer ADC.
The quick high frequency sweep gave identical timing accuracy to my previous method - so I knew I was good to go!!!!

Now, how about a quick access panel for selecting the HDMI output channel, with inc/dec buttons???????????

Regards, Mike.
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post #46 of 82 Old 03-20-16, 04:14 PM
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Re: UMIK-1 timing reference and Phase

A bit more progress on the acoustic reference support, V5.15 beta 4 (available from the installers directory) has added the ability to include the timing reference signal when saving a measurement sweep as WAV and there now is a "Wait for timing reference" check box on the measurement dialog. When that box is checked REW will delay capturing the main measurement sweep until it has seen the timing reference signal, which allows coping with unlimited amounts of latency and makes it easy to measure by replaying the measurement sweep WAV if the REW output cannot be used directly.

I've also made some small changes to the waterfall and spectrogram plots.

The changes compared to beta 3 are:
  • Added option to add timing reference signal when saving measurement sweep as WAV
  • Made the signal generator export filenames more descriptive
  • Show a warning if using a timing reference with ASIO but haven't selected a timing ref output
  • Removed the fade to graph colour at the bottom of the spectrogram to better define the lower parts of the plot
  • Restored Violet as the bottom colour for the Rainbow spectrogram colour scheme
  • Added a cursor frequency line over the surface of the waterfall plot
  • Added a measurement option to wait for the timing reference signal to be detected when using an acoustic reference
  • Bug fix: Spectrogram contours were not redrawn when plot range was changed
  • Bug fix: Frequency axis grid lines were not drawn on floor of waterfall when using linear frequency axis
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post #47 of 82 Old 03-27-16, 03:13 PM
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Re: UMIK-1 timing reference and Phase

JohnM,
Thanks!
I spent the day figuring out how to get this setup correctly. I am using the 'acoustic timing' feature and the 'hold for trigger' function when using an external signal from my DLNA file server. After some confusion and dumb mistakes I finally got it all sorted out. I now have accurate IR timing with foobar fed REW signal files and can thus confirm that close phase tracking is properly retained when the ReRhase FIR phase correction filter activated. Very nice!
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post #48 of 82 Old 03-27-16, 05:44 PM Thread Starter
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Had some success and some failure with this so far. One one of my setups it worked flawlessly once I figured it out. On a second setup I get the test signal also coming from the channel I have setup as the timing reference. Obviously a full range signal from the tweeter Might be I've messed something up in the setup but pretty sure I mirrored the working setup on the other PC. I used the same gear.
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post #49 of 82 Old 03-27-16, 09:57 PM
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Re: UMIK-1 timing reference and Phase

John, just to be clear, when selecting the channel to use for timing reference, there is no requirement that the speaker on that channel be closer to the MLP than the speakers being measured, is there? For example, when measuring my left, right, and center channels, I am using a side surround as the timing reference. That speaker is ~.5 ft further away than the mains from the MLP.
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post #50 of 82 Old 03-29-16, 04:33 PM
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Re: UMIK-1 timing reference and Phase

It doesn't matter whether the timing reference is nearer or further away.
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