Timing Reference Selection Not Retained - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 16 Old 01-13-17, 02:47 PM
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Re: Timing Reference Selection Not Retained

Wayne,

The last time I tried that ( your configuration ) I ran into significant timing differences ( REW ran in succession within a single REW session ) on a fixed speaker driver ( ie; & the distances measured were unreliable and not to be trusted ) .

This was no doubt due to the two sound-cards having different internal clocks ( & not being synchronized to each other ).

So now I'm curious, can you achieve a consistent answer ( in distance ) when taking multiple successive readings with your composite SC, timing setup ?

If so, I think it's an aberration / and still believe Johns builtin "Positive opt-in Selection for a setup that's inherently inaccurate" makes good sense ( since it ought to cut down on questions from those who don't understand the issues at play here ).


Last edited by EarlK; 01-13-17 at 03:29 PM.
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post #12 of 16 Old 01-13-17, 03:30 PM Thread Starter
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Wayne Myers
 
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Re: Timing Reference Selection Not Retained

Quote:
EarlK wrote: View Post
Wayne,

The last time I tried that ( your configuration ) I ran into significant timing differences ( REW ran in succession within a single REW session ) on a fixed speaker driver ( ie; & the distances measured were unreliable and not to be trusted ) .

This was no doubt due to the two sound-cards having different internal clocks ( & not being synchronized to each other ).

So now I'm curious, can you achieve a consistent answer ( in distance ) when taking multiple successive readings with your composite SC, timing setup ?

If so, I think it's an aberration / and still believe Johns builtin "Positive opt-in Selection" makes good sense ( since it ought to cut down on questions from those who don't understand the issues at play here ).

So you have tried it too? Cool!

I love it when you guys get super thorough about this stuff!

My initial response to your question is that it is enough trouble to get this application working that it will not be undertaken lightly or accomplished accidentally. It is an advanced application, if you will. Anyone using a USB mic and an audio interface for timing reference will probably (???) know the risks.

For measuring drivers within a single system, the technique might not be appropriate. For relative speaker placement

How accurate or inaccurate can it be? I thought I remembered it being in the range of a few microseconds, but did not save a project I can refer to quickly. I am getting ready to make some measurements and will respond to your question in the next day or so.
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post #13 of 16 Old 01-13-17, 03:42 PM
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Re: Timing Reference Selection Not Retained

I'll be curious to hear of you experiences with this setup .

I'd also like to know whether ( or not ) the Mac OS is truly more accurate regarding timing drift ( since OS10 allows it's own version of a composite driver, called "Aggregate Devices" that will follow a single clock.

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post #14 of 16 Old 01-13-17, 05:05 PM
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Re: Timing Reference Selection Not Retained

In general I have not found Windows to maintain any relative timing relationship between different soundcards from one measurement to the next, but perhaps an ASIO4All-managed composite device gets around that. However, I think there are more people that could end up trying to make measurements with Loopback selected whilst using a UMIK in conventional fashion (and getting results that won't reflect what was intended) than people doing it deliberately to take advantage of a composite device setup. Given that, the once per session impact and the placement of a timing ref mode selector on the measurement dialog since 5.17 allowing easy change of mode, I think it is better leaving the behaviour as is.
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post #15 of 16 Old 01-13-17, 06:05 PM
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Re: Timing Reference Selection Not Retained

WHOA, I guess it is high time I read the directions and get mine to work properly !!!!

Good Listening

Jack

"For those who believe no proof is needed for those who don't believe no proof is possible"
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post #16 of 16 Old 01-13-17, 09:33 PM Thread Starter
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Wayne Myers
 
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Re: Timing Reference Selection Not Retained

You guys win, big time. I glanced at it once, in another system, I don't remember it being this bad.

I ran 10 sweeps. The impulses ended up in two clusters. Total spread about 8 mS. The technique is totally unusable.

Thank you, John.
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