Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 738 - AVS Forum | Home Theater Discussions And Reviews
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post #22111 of 22127 Old Yesterday, 01:46 PM
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Hi guys -

I was making some adjustments to my miniDSP after moving one of my subwoofers and ran into some unexpected results with REW. Here's what I did:

I setup REW with a timing reference (using the center speaker) and ran a frequency sweep
I then ran sweeps with the same center speaker as a timing reference for the front and rear subwoofers, intending to use the delay differences in my miniDSP setup.

Oddly - my initial sweep went wrong somehow: showing a delay of 7.5ms for the center speaker using the center speaker as a timing reference. That obviously doesn't make any sense. Any insight as to why this happened? I re-ran the test with the sweep running from 80Hz to 300hz (eliminating the subs) and ensured my receiver was set to pass the signal directly through.

Thanks,
Mike

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
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post #22112 of 22127 Old Yesterday, 01:48 PM
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Quote:
Originally Posted by mjmcmahon67 View Post
Hi guys -

I was making some adjustments to my miniDSP after moving one of my subwoofers and ran into some unexpected results with REW. Here's what I did:

I setup REW with a timing reference (using the center speaker) and ran a frequency sweep
I then ran sweeps with the same center speaker as a timing reference for the front and rear subwoofers, intending to use the delay differences in my miniDSP setup.

Oddly - my initial sweep went wrong somehow: showing a delay of 7.5ms for the center speaker using the center speaker as a timing reference. That obviously doesn't make any sense. Any insight as to why this happened? I re-ran the test with the sweep running from 80Hz to 300hz (eliminating the subs) and ensured my receiver was set to pass the signal directly through.

Thanks,
Mike
Post .mdat.

Markus

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post #22113 of 22127 Old Yesterday, 01:56 PM
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I'd dumped the originals, but here's another test with the same issue - speaker 1 1 (Left Front) used as timing reference, yet shows a system delay??

zip file attached
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File Type: zip Timing reference issue.zip (191.6 KB, 13 views)

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
Speakers - B&W 683S2/ HTM61S2 / 685 Surrounds / Fluance Signature Bi-polar Rear Surrounds/ PSA S1500 & XS15se subs
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post #22114 of 22127 Old Yesterday, 02:21 PM
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OK, what are we looking at here? Hint: label your measurements if you expect feedback.
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post #22115 of 22127 Old Yesterday, 03:30 PM
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Originally Posted by AustinJerry View Post
OK, what are we looking at here? Hint: label your measurements if you expect feedback.
Sorry Jerry - I thought I'd explained it thoroughly but obviously not. The first measurement is the reference timing - in this case the Front Left speaker. The second is the subwoofer using the front left as a timing reference. I was following the instructions provided here for measuring time delay - https://www.minidsp.com/applications...ing-time-delay

Under the section "Tabulate your results", it points out that you should have a zero System Delay for the first speaker - which would make sense when you're measuring the same speaker as you use for a time reference. In my case, the system delay showed 6.92ms for a system delay on the same speaker?

I've updated the .zip file with labels to help clarify things.

Thank you,

Mike
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File Type: zip Timing reference issue.zip (192.1 KB, 11 views)

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
Speakers - B&W 683S2/ HTM61S2 / 685 Surrounds / Fluance Signature Bi-polar Rear Surrounds/ PSA S1500 & XS15se subs
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post #22116 of 22127 Old Yesterday, 03:55 PM
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Quote:
Originally Posted by mjmcmahon67 View Post
Sorry Jerry - I thought I'd explained it thoroughly but obviously not. The first measurement is the reference timing - in this case the Front Left speaker. The second is the subwoofer using the front left as a timing reference. I was following the instructions provided here for measuring time delay - https://www.minidsp.com/applications...ing-time-delay

Under the section "Tabulate your results", it points out that you should have a zero System Delay for the first speaker - which would make sense when you're measuring the same speaker as you use for a time reference. In my case, the system delay showed 6.92ms for a system delay on the same speaker?

I've updated the .zip file with labels to help clarify things.

Thank you,

Mike
Thank you for clarifying. Yes, if the Left front is set as the timing reference, and the first measurement is the left front, then these should be a zero delay. What kind of speakers are these?
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post #22117 of 22127 Old Yesterday, 04:08 PM
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Originally Posted by AustinJerry View Post
Thank you for clarifying. Yes, if the Left front is set as the timing reference, and the first measurement is the left front, then these should be a zero delay. What kind of speakers are these?
Jerry -

the mains are B&W 600 series - the reference speaker is a 683S2.

Is there anything I should be adjusting in the REW setup for the timing reference? I ask because I thought I remembered seeing something about 1M Groundplane? The UMIK was placed at the primary listening position.

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post #22118 of 22127 Old Yesterday, 04:18 PM
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Quote:
Originally Posted by mjmcmahon67 View Post
Jerry -

the mains are B&W 600 series - the reference speaker is a 683S2.

Is there anything I should be adjusting in the REW setup for the timing reference? I ask because I thought I remembered seeing something about 1M Groundplane? The UMIK was placed at the primary listening position.
I guess I could have looked in your sig...

There are no adjustments required to use the acoustic timing reference. Two recommendations: first, let's see what @markus767 has to say. He is in Europe, so we may not hear his feedback until tomorrow AM. Second, you could open a thread in the REW Forum on HTS titled, "Under what circumstances would a measurement of the speaker set as the timing reference produce a non-zero alignment delay?"
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post #22119 of 22127 Old Yesterday, 04:59 PM
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Thanks Jerry - I'll wait and see what Markus says and engage on HTS if necessary.

I'm also going to step through the 'Getting Started with REW' tutorial again to ensure I get the same results.

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
Speakers - B&W 683S2/ HTM61S2 / 685 Surrounds / Fluance Signature Bi-polar Rear Surrounds/ PSA S1500 & XS15se subs
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post #22120 of 22127 Old Yesterday, 05:24 PM
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The sweep only goes from 80 Hz to 300 Hz. Do the sweep again from at least 20 Hz for the sub woofer.
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post #22121 of 22127 Old Yesterday, 06:30 PM
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Quote:
Originally Posted by mjmcmahon67 View Post
Thanks Jerry - I'll wait and see what Markus says and engage on HTS if necessary.

I'm also going to step through the 'Getting Started with REW' tutorial again to ensure I get the same results.
Since I authored that document, I can assure you that there is nothing magic about a measurement with a timing reference.
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post #22122 of 22127 Old Yesterday, 07:56 PM
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Originally Posted by AustinJerry View Post
Since I authored that document, I can assure you that there is nothing magic about a measurement with a timing reference.
Didn't think that there was - I do know that occasionally things can become corrupted - either thru user configuration or otherwise. I figured starting with a clean slate was a good way to start. Unfortunately, it didn't make any difference.

Hopefully Markus will have some insight!

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
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post #22123 of 22127 Old Yesterday, 11:23 PM
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Quote:
Originally Posted by mjmcmahon67 View Post
I'd dumped the originals, but here's another test with the same issue - speaker 1 1 (Left Front) used as timing reference, yet shows a system delay??

zip file attached
You're seeing a difference because you've limited the sweep to 80-300Hz.

Markus

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post #22124 of 22127 Old Today, 05:32 AM
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Originally Posted by markus767 View Post
You're seeing a difference because you've limited the sweep to 80-300Hz.
Doh! Too simple. When the OP tries this, I am sure the delay will be zero as expected. But I believe he is trying to use the impulse to determine sub delays. The sub is typically measured 15-300Hz. Would this mean that the sub impulse measurement will not be accurate as well? Or what should the sub measurement sweep be?
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post #22125 of 22127 Old Today, 05:46 AM
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Quote:
Originally Posted by AustinJerry View Post
Doh! Too simple. When the OP tries this, I am sure the delay will be zero as expected. But I believe he is trying to use the impulse to determine sub delays. The sub is typically measured 15-300Hz. Would this mean that the sub impulse measurement will not be accurate as well? Or what should the sub measurement sweep be?
Well, the impulse response reflects the frequency response. So it is an accurate representation of that particular frequency range.

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post #22126 of 22127 Old Today, 09:12 AM
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Thanks guys - this is what I was talking about when I talked about "user configuration corruption" - in other words, there was a loose nut behind the keyboard

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
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post #22127 of 22127 Old Today, 10:25 AM
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Originally Posted by markus767 View Post
Well, the impulse response reflects the frequency response. So it is an accurate representation of that particular frequency range.
So just to make sure I'm on the right track here:

I was attempting to time-align my subs. Using REW and delay settings on my miniDSP, I was attempting to get the delays to match as closely as possible. Am I correct that doing so would time-align the subs?

PJ - Sony VPLHW45ES / Screen - EliteScreens 120" CineGrey / BD - Sony BDP-S5100 / AVR - Yamaha RX-A3030
Speakers - B&W 683S2/ HTM61S2 / 685 Surrounds / Fluance Signature Bi-polar Rear Surrounds/ PSA S1500 & XS15se subs
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