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SPL Calibration problem with UMIK-1 8 years 9 months ago #10763

  • mcmahongg
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Hi

I'm using a UMIK-1 (Ser #700-0107, unmodified) with REW v5.01 beta 17 Build 2967:
Lenovo T61 running Win7 Ultimate (64 bit)
ASIO4ALL v2.11 beta 2

When I check the SPL using a B&K 4230 Calibrator I get a value with the REW SPL tool that's about 6 dB too low. I've independently verified that the calibrator is outputting very close to its specified output (94 dB SPL, 1000Hz) and I've ensured a good seal between the UMIK-1 and the calibrator using modelling clay.

Screenshots of REW Preferences, ASIO4ALL display and REW SPL tool attached.

Any advice appreciated.

thanks

Gerry
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10782

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Have a look at the calibration file and check the Sens Factor figure, the cal file download tool shows it should be -16.005dB for that mic but an older cal file may have a different figure.

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10783

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Thanks John

The first line of the original cal file that came with the mic is:

"Sens Factor =-14.705dB, SERNO: 7000107"

Gerry

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10784

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In the REW soundcard preferences what is the input volume control set to? What SPL do you get with the calibrator if you set the input volume to 1.0?

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10785

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I've been using ASIO setting - no volume control present - there's a screenshot of the configuration with my fist post (#10763).

I've just changed it to JAVA and re-ran the test. REW Preferences screenshot attached. I'm getting 87.8 dB (with original calibration file) which is close to the figure I was getting with ASIO - i.e. about 6 dB below the expected 94 dB SPL.
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10786

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What is the dB FS figure on the SPL meter in that state?

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10787

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See screenshot of SPL meter attached.
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10788

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See screenshot of SPL meter attached.

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10804

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That's interesting - you have the same -27.8 dB FS input level with Java drivers and input volume set to 1.0 as you had with ASIO4All? What was the Windows level set to when you were using ASIO4All? It looks like the windows input levels controls are still used with ASIO4All, which makes sense I guess since ASIO4All is creating a pseudo ASIO interface rather than natively going ASIO to the device. The actual level is still strange though, since the cal file sensitivity figure is the dB FS input level when the mic is driven by a 94 dB calibrator with the Windows volume set to 1.0, so with -27.8 dB FS coming in and a -14.7 dB cal figure your readings should be off by 13 dB rather than 6. From a practical point of view you can just change the cal file sensitivity figure to get the mic to read correctly, but it would be good to understand what is happening with the various levels in the system. A Windows input level of 1.0 should correspond to +24dB of gain, you can check that by right clicking on the volume control figure on the Levels tab and selecting decibels rather than percent.
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10805

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Thanks John

Attached are screen shots of the REW Preferences - with Java and with ASIO (ASIO4ALL), also the ASIO4ALL control panel.

I'll be away for the next week but will look at this again when I get back.
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10940

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John

Screenshot of SPL Meter attached. This was captured in Java mode.

Whether using Java or ASIO i get very close to the same result - which is close to 6 dB below the expected 94dB SPL. I could of course alter the calibration file but I'm curious about that 6 dB figure and why it's there.

regards

Gerry

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SPL Calibration problem with UMIK-1 8 years 9 months ago #10980

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OK, so dB FS levels are consistent with the cal figure and the SPL figure, which is good. From an REW perspective it would be handy if you had an opportunity to try the mic and cal file on a Windows 8 machine, just in case something has gone awry between Win 7 and Win 8, but I appreciate that having extra PCs lying around isn't the norm. It does look as if the cal file figure is wrong for that mic.
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SPL Calibration problem with UMIK-1 8 years 9 months ago #10981

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Thanks John

Unfortunately i don't have access to a Win8 PC.

I could add the correction to the cal table but I don't have a means of checking the SPL results at frequencies other than 1000Hz however.

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SPL Calibration problem with UMIK-1 8 years 9 months ago #11025

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Only the sensitivity figure in the first line of the file would need to change, the calibration data values and the shape of the calibration curve would (and should) stay the same.
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SPL Calibration problem with UMIK-1 8 years 7 months ago #11703

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John,

I am experiencing the same problem with my new Sony Pro 13 running windows 8 pro. If it is just a matter of adjusting the sensitivity file then what figure should I change it to. Will this cause any problems with the overall operation of the REW software.

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