Author Topic: REW question  (Read 3251 times)

Offline wechnivag

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Re: REW question
« Reply #60 on: November 05, 2018, 11:57 »
Nice illustration that explains what happens with a bare wall reflection, vs absorption and diffusion.

Absorption based treatment focus the attention on direct sound from the speakers only, yielding a more precise, pinpoint imaging.

A direct reflection from a bare wall, if it is very close to the direct sound, and very high level, can cause comb filtering dips and peaks. Depending on frequency and severity, this will always show up on measurements by a microphone, but not necessarily audible due to how our ears are able to differentiate between the direct sound and the delayed reflection sound (within fusion zone) , which is integrated with the direct sound to provide timbre and tonality. It is this mechanism that is exploited by diffusers.

The lower peak of a diffused reflection, as well as the spread out time domain really complements the hearing mechanism and provides a lot of timbre, richness of tone and body to the direct sound.






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« Last Edit: November 05, 2018, 12:09 by wechnivag »

Offline Boxerfan88

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Re: REW question
« Reply #61 on: November 05, 2018, 12:48 »
Thanks for sharing, very informative.


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Offline ronildoq

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Re: REW question
« Reply #62 on: November 05, 2018, 13:50 »
Nice illustration that explains what happens with a bare wall reflection, vs absorption and diffusion.

Absorption based treatment focus the attention on direct sound from the speakers only, yielding a more precise, pinpoint imaging.

A direct reflection from a bare wall, if it is very close to the direct sound, and very high level, can cause comb filtering dips and peaks. Depending on frequency and severity, this will always show up on measurements by a microphone, but not necessarily audible due to how our ears are able to differentiate between the direct sound and the delayed reflection sound (within fusion zone) , which is integrated with the direct sound to provide timbre and tonality. It is this mechanism that is exploited by diffusers.

The lower peak of a diffused reflection, as well as the spread out time domain really complements the hearing mechanism and provides a lot of timbre, richness of tone and body to the direct sound.






Sent from my X9009 using Tapatalk

as long as within the 1st 40ms, beyond that it we hear it as echo..... Nice Sharing Gavin! "Depth" is exactly the word to describe it, i noticed....

Comb filtering is the worst, that is the last thing we want... Keep the listening area as simple as possible, the lesser the items and things in the surrounding bubble, the better it is....

Offline Boxerfan88

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Re: REW question
« Reply #63 on: November 06, 2018, 22:20 »
Today I started to measure the HT multi-channel system via HDMI, and I hit a very very weird problem. Intermittently when doing "Check Levels" or Measurements, I hear random click/pop/stutter; and if I continue, ASIO4ALL will hang along with REW, and the only way out is to reboot PC. Switch back to JAVA mode, all is good - but can only measure L-R.

After some serious troubleshooting, I think I found the fix (recorded here for the benefit of all):
1. Open elevated CMD window
2. bcdedit /set disabledynamictick yes
3. Reboot PC

So far so good, managed to complete the measurement of all 5.1 speakers without ASIO4ALL hanging.

ps: it wasn't PC capability, it's quite a powerful box (i7-6800K + 32GB RAM)  -  Stupid Win10!!
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Offline Jag

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Re: REW question
« Reply #64 on: November 07, 2018, 05:16 »
Nice sharing, boxerfan.
ATMOS and Auro ready! 15 surr spkrs . Time to optimize

Offline Boxerfan88

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Re: REW question
« Reply #65 on: November 19, 2018, 16:01 »
Received my UMIK1 shipment...happie.  :)

Was re-measuring the HT system, and I got some questions on "system delay". It is supposed to show the time delay for the various speakers (referenced against the acoustic timing reference signal). I used the center channel as the acoustic timing reference for the measurement, and I notice the "system delay" jumps around quite a bit. I kind of expected the "system delay" for CC to be close to zero, and consistently close to zero; but it is not the case. Any ideas why it is so?

CC-Center Channel


FL-Front Left Channel
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Offline Jag

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Re: REW question
« Reply #66 on: November 19, 2018, 16:38 »
I would not suggest to use the CC as your timing reference Channel. Use one of the other surrounds as the timing reference.
ATMOS and Auro ready! 15 surr spkrs . Time to optimize

Offline ronildoq

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Re: REW question
« Reply #67 on: November 19, 2018, 18:33 »
Received my UMIK1 shipment...happie.  :)

Was re-measuring the HT system, and I got some questions on "system delay". It is supposed to show the time delay for the various speakers (referenced against the acoustic timing reference signal). I used the center channel as the acoustic timing reference for the measurement, and I notice the "system delay" jumps around quite a bit. I kind of expected the "system delay" for CC to be close to zero, and consistently close to zero; but it is not the case. Any ideas why it is so?

CC-Center Channel


FL-Front Left Channel


All speaker settings need to be set to 0 or same distance in your AVR before measuring.

Pick the speaker that is nearest in distance from where you put the MIC (MLP) as your reference speaker for ATR, so you wont have negative delays..

Make sure speakers are in Full Range when taking measurement.

Make sure the mic is exactly at the same spot without moving, even a slight movement affects the impulse response and time

Offline Boxerfan88

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Re: REW question
« Reply #68 on: November 19, 2018, 22:16 »
I would not suggest to use the CC as your timing reference Channel. Use one of the other surrounds as the timing reference.

Will try measuring with surround as timing reference, and post back results.
Any reason why not to use the CC as timing reference channel?
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Offline Boxerfan88

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Re: REW question
« Reply #69 on: November 19, 2018, 22:22 »
All speaker settings need to be set to 0 or same distance in your AVR before measuring.

Should I not run YPAO first?
What's the reason to reset to blank before using REW?
Thanks for sharing.

Quote
Pick the speaker that is nearest in distance from where you put the MIC (MLP) as your reference speaker for ATR, so you wont have negative delays..

I see. My surrounds are nearer to MLP than CC. This kind of explains Jag's comment about using Surround instead of CC for the acoustic timing reference channel.

Quote
Make sure speakers are in Full Range when taking measurement.

It is full range for FL, CC, FR; but not SL,SR.
I see where you're going with this...pure speaker performance measured without bass management.
I will try.

Quote
Make sure the mic is exactly at the same spot without moving, even a slight movement affects the impulse response and time

Yep, mic is exactly same spot when doing all the measurements.
Mic is at ear level, and facing ceiling.
I am using the 90degree correction file.

Thank you for the pointers, much appreciated.
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Offline ronildoq

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Re: REW question
« Reply #70 on: November 20, 2018, 23:07 »
Should I not run YPAO first?
What's the reason to reset to blank before using REW?
Thanks for sharing.

I see. My surrounds are nearer to MLP than CC. This kind of explains Jag's comment about using Surround instead of CC for the acoustic timing reference channel.

It is full range for FL, CC, FR; but not SL,SR.
I see where you're going with this...pure speaker performance measured without bass management.
I will try.

Yep, mic is exactly same spot when doing all the measurements.
Mic is at ear level, and facing ceiling.
I am using the 90degree correction file.

Thank you for the pointers, much appreciated.

Depends on what you are trying to achieve. Are you measuring delays to check if YPAO sets the distance correctly post EQ?
 
If it is, then yes set all speakers to 0 distance settings (take a pic before that) , use the nearest speaker to MLP as the one for acoustic timing reference. Then measure all other speakers (except for subwoofer) and determine the delays/distance. See if YPAO sets them correctly . If the differences in delays Is marginal , ie <0.1ms, trust  the room correction software.

In order for the above to be effective, the mic must be placed at the same exact location , run a one point YPAO eq. Then compare with one without any eq 0 distance,see if YPAO sets it correctly.

Audyssey, accueq, Dirac, all does it quite accurately

The only difference between the above is how the software integrates mains with subs, that is where Dirac takes the lead....

A lot of this is to do with the subs being EQ’ed as 1.

When the subs are already phased matched with a good response, this then frees up resources for the EQ programs to work out the best delay combinations for mains with subs, this is how I approach EQ

Offline Boxerfan88

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Re: REW question
« Reply #71 on: November 21, 2018, 16:25 »
Depends on what you are trying to achieve. Are you measuring delays to check if YPAO sets the distance correctly post EQ?

Yes, exactly my objective. Thank you for your sharing. So much to learn...
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Offline Boxerfan88

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Re: REW question
« Reply #72 on: December 02, 2018, 21:35 »
Playing around with REW today. I thought I'd compare UMIK microphone facing ceiling vs. facing front.
Similar (shape) yet different (peaks) -- interesting how 90 degrees can differ.
Question: for HT why measure facing ceiling when our ears face front?

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Offline Jag

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Re: REW question
« Reply #73 on: December 02, 2018, 22:28 »
Facing ceiling allows for all 7 ear level speakers to be measured with being affected by mic directionality.

If you use front facing, all speakers you xcept L&R speaker’s arrive at the mic’s transducer at different angles. I.e, the rear surrs will be affected by the mic’s base before arriving at the little transducer within the mic it self.

ATMOS and Auro ready! 15 surr spkrs . Time to optimize

Offline Boxerfan88

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Re: REW question
« Reply #74 on: December 03, 2018, 10:01 »
Facing ceiling allows for all 7 ear level speakers to be measured with being affected by mic directionality.

If you use front facing, all speakers you xcept L&R speaker’s arrive at the mic’s transducer at different angles. I.e, the rear surrs will be affected by the mic’s base before arriving at the little transducer within the mic it self.

Thanks for the explanation. Much appreciated.
Soekris dac1541 | DA&T A38  | Usher MD2+X616 | Orisun DD12 | Samsung PS50B850 |
Yammy RXA3030 | RPi3+Kodi | BDP-S5100 | PC+foobar2000 | Chromecast