Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 486 - AVS | Home Theater Discussions And Reviews
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post #14551 of 14558 Old Today, 06:07 AM
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Quote:
Originally Posted by AustinJerry View Post


Both measurements are of the center channel + subs with variable smoothing. At 20Hz, the 80dB measurement shows 2.1% THD, while at 105dB, the figure rises to 26.4% THD. At 80dB, there is negligible distortion at 75hZ (.7%), but at 105dB, something significant happens, with a huge distortion bulge (8.8%) developing for an unknown reason.

Interesting...
Another insight to apply to this is that 3rd order distortion occurs at 3X the frequency in question. While one might say 8% distortion isnt audible at 74.9hz, this isnt where it occurs. It occurs at 224.7hz (74.9 X 3). And that, I would wager IS audible.

Along these lines, 10th order distortion happens at 10X the frequency in question. So if one had high 10th order distortion at 30hz, it would occur at 300hz! And so on....

In another illustration, 10th order distortion at 4K wouldnt be significant. Why? Because it would occur at 40,000hz. (you may notice the 10th order line stops around 2K for this reason for a X-20k measurement).

This is why looking at higher order distortion is important.

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post #14552 of 14558 Unread Today, 12:06 PM
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Simple questions

Hello,
Sorry for such basic questions, to me I believe them important enough to ask. On my laptop when I configure in windows the output device (my Onkyo receiver) in advanced settings I have several options, I chose 16 bit 48000Hz, when I configure my recording device (UMIK-1) it only has one option and that's 24 bit 48000Hz. My question is it OK to use the 16 bit rate in the output device and the 24 bit rate in the recording device (UMIK-1) as long as both use the same 48000Hz cycle. Or should I set both to 24 bit 48000Hz. Again please forgive my ignorance.

The other question is my UMIK-1 has a 18dB gain structure, I would like to physically change that gain inside the mic to 0dB, it seems fairly easy to do. Then I must also change the sensitivity as well. Here is my mic's sensitivity parameters:

"Sens Factor =0.6814dB, SERNO: 7005070" I would then subtract this number by -18, correct? Does look like the corrected 90 degree cal file, if not please tell me what the corrected file is after -18dB. TIA

"Sens Factor =-17.3186db, SERNO: 7005070"

Thanks Guys, Jeffrey
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post #14553 of 14558 Unread Today, 01:00 PM
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Originally Posted by ahblaza View Post
Hello,
Sorry for such basic questions, to me I believe them important enough to ask. On my laptop when I configure in windows the output device (my Onkyo receiver) in advanced settings I have several options, I chose 16 bit 48000Hz, when I configure my recording device (UMIK-1) it only has one option and that's 24 bit 48000Hz. My question is it OK to use the 16 bit rate in the output device and the 24 bit rate in the recording device (UMIK-1) as long as both use the same 48000Hz cycle. Or should I set both to 24 bit 48000Hz. Again please forgive my ignorance.

The other question is my UMIK-1 has a 18dB gain structure, I would like to physically change that gain inside the mic to 0dB, it seems fairly easy to do. Then I must also change the sensitivity as well. Here is my mic's sensitivity parameters:

"Sens Factor =0.6814dB, SERNO: 7005070" I would then subtract this number by -18, correct? Does look like the corrected 90 degree cal file, if not please tell me what the corrected file is after -18dB. TIA

"Sens Factor =-17.3186db, SERNO: 7005070"

Thanks Guys, Jeffrey
I would set both devices to the same bit depth.

Why do you want to set the mic to zero gain? Most of us here have UMIK-1's with 12dB gain. I predict if you adopt this different, non-standard setting, you will encounter anomalies that will be difficult to explain. And, of course, we won't be able to help because you are not using a standard setting.
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post #14554 of 14558 Unread Today, 02:38 PM
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Quote:
Originally Posted by AustinJerry View Post
I would set both devices to the same bit depth.

Why do you want to set the mic to zero gain? Most of us here have UMIK-1's with 12dB gain. I predict if you adopt this different, non-standard setting, you will encounter anomalies that will be difficult to explain. And, of course, we won't be able to help because you are not using a standard setting.
Thanks Jerry for the bit depth, I'm glad I asked. I just thought going to 0 dB would give more headroom for taking higher compression sweeps. Ok I will do 12 dB gain then, I didn't know that was the default gain used by all here. So then I would just subtract -6dB from the SENS FACTOR, did I have it set right (sens) for the 0dB gain in the above post?

So this is what it looks like now, would it be much of an inconvenience for you to display the correct cal file with lowering the gain 6dB from 18dB to 12dB. I would really appreciate it. Again Thanks for all that you do.

"Sens Factor =0.6814dB, SERNO: 7005070" After change "Sens Factor =-5.3186dB, SERNO: 7005070" correct?

Sincerely, Jeffrey
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post #14555 of 14558 Unread Today, 04:07 PM
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Originally Posted by ahblaza View Post
Thanks Jerry for the bit depth, I'm glad I asked. I just thought going to 0 dB would give more headroom for taking higher compression sweeps. Ok I will do 12 dB gain then, I didn't know that was the default gain used by all here. So then I would just subtract -6dB from the SENS FACTOR, did I have it set right (sens) for the 0dB gain in the above post?

So this is what it looks like now, would it be much of an inconvenience for you to display the correct cal file with lowering the gain 6dB from 18dB to 12dB. I would really appreciate it. Again Thanks for all that you do.

"Sens Factor =0.6814dB, SERNO: 7005070" After change "Sens Factor =-5.3186dB, SERNO: 7005070" correct?

Sincerely, Jeffrey
I believe that would be the correct adjustment to the sensitivity parameter. Here is how you could test it out:

- While the mic is still configured for 18dB gain, launch REW, and using the signal generator, output a test tone (say pink noise), and adjust your AVR master volume so the mic is reading a specific value (say 80dB). Note the MV level.
- Open the mic and set the dip switches to 12dB gain.
- Launch REW again, output the same test tone, set the MV to the same value you determined above, and use the REW SPL meter to see how loud the test tone is. If the sensitivity parameter is correct, the level will measure the same as in the previous test.
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post #14556 of 14558 Unread Today, 04:26 PM
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Are there disadvantages to changing it to 12? I thought that change was only needed (recommended?) if you have input clipping with PC mic gain set to 100.
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post #14557 of 14558 Unread Today, 04:36 PM
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Are there disadvantages to changing it to 12? I thought that change was only needed (recommended?) if you have input clipping with PC mic gain set to 100.
Search this thread for the previous conversations. No need to re-hash it all over again.
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post #14558 of 14558 Unread Today, 04:43 PM
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Quote:
Originally Posted by AustinJerry View Post
I believe that would be the correct adjustment to the sensitivity parameter. Here is how you could test it out:

- While the mic is still configured for 18dB gain, launch REW, and using the signal generator, output a test tone (say pink noise), and adjust your AVR master volume so the mic is reading a specific value (say 80dB). Note the MV level.
- Open the mic and set the dip switches to 12dB gain.
- Launch REW again, output the same test tone, set the MV to the same value you determined above, and use the REW SPL meter to see how loud the test tone is. If the sensitivity parameter is correct, the level will measure the same as in the previous test.
Thanks Jerry as always, that makes perfect sense. I will do it now. I really appreciate all that you contribute to this forum especially for the likes of myself
Best, Jeffrey
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