Inconsistent measured volume levels

miniDSP and AV Nirvana
Dmanstarr said:
None of that is in anyway relevant to what is on the graphs. And you can’t see the output levels because REW was not outputting anything.

However, the data offset in the info you sent above shows a 3db offset between the two. I did not add any data offset! REW did that in it’s own.

*I suspect that is the problem*

If you look at the third mdat I sent, I bet it will show a data offset that matches the first file I sent, because when I restarted REW, it went back to the matching recorded volume in the graph.
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Also, I’m measuring inside a vehicle. I’m doing it the correct way for that application. I’m not hear to learn how to measure.
 
Just in case, go to Preferences at the top right of the main screen, set the output and input device, for this device in Windows, disable enhancements in the sound properties. In the same place, turn off all sound devices, except for the two that you use as input and output.
 
R mR 2 has a different data offset. Can you look in C:\Users\<your username>\REW for the file rew_output.txt and attach it?
 
R mR2 and R mR 3 are using different cal files, one normal and one 90 degree. Were they both measured on the same PC? Do both cal file have the same SENS_FACTOR figure?
 
Dmanstarr said:
Also, I’m measuring inside a vehicle. I’m doing it the correct way for that application.
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John Mulcahy said:
R mR2 and R mR 3 are using different cal files, one normal and one 90 degree. Were they both measured on the same PC? Do both cal file have the same SENS_FACTOR figure?
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Same mic, same PC same dedicated cal file specific to the mic serial number.

Cal files being 90 vs normal make a miniscule difference in measurements of the type I’m doing, so little as it literally doesn’t matter when measuring power response at driver’s seat moving mic around head for spatial averaging while using RTA. In the high end, the comb filters due to the vehicle environment are so dense, the slightest head movement changes the measurement drastically. There are no relevant late reflections because a car environment is *not* in essence “a room” as far as our brain is concerned.

I have never manually set a sense factor, but I’m assuming it’s the same since it’s the mics unique cal file.

My measurements are very repeatable with small differences. They never drop across the board by almost exactly 3db, or whatever except when REW does the thing were it adds an offset by itself.

Restarting the program usually fixes this.
 
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Can you attach the cal files along with the C:\Users\<your username>\REW\rew_output.txt file?
 
This is what I see for the cal file name and sensitivity factor in those measurements:

R mR msr 7014612_90deg.txt 2.0838
R mR 2 7014612_Umik1cal.txt -0.9162
R mR 3 7014612_90deg.txt 2.0838
 
John Mulcahy said:
This is what I see for the cal file name and sensitivity factor in those measurements:

R mR msr 7014612_90deg.txt 2.0838
R mR 2 7014612_Umik1cal.txt -0.9162
R mR 3 7014612_90deg.txt 2.0838
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Ok, but why are we talking about the cal file at all?
 
The sensitivity factor tells REW how to convert audio data values from the mic into SPL values. It does not depend on angle, it should always be the same for the same mic. The value in your 7014612_Umik1cal.txt does not match the data for that mic from miniDSP, it has had 3 dB subtracted from it.
 
John Mulcahy said:
The sensitivity factor tells REW how to convert audio data values from the mic into SPL values. It does not depend on angle, it should always be the same for the same mic. The value in your 7014612_Umik1cal.txt does not match the data for that mic from miniDSP, it has had 3 dB subtracted from it.
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Oh lord, I hope that's the problem. I got both of the files from minidsp, though. By serial number as you can see.
 
should I just manually change the text of the cal file for the "normal" one to 2.0838?
 
John Mulcahy said:
The sensitivity factor tells REW how to convert audio data values from the mic into SPL values. It does not depend on angle, it should always be the same for the same mic. The value in your 7014612_Umik1cal.txt does not match the data for that mic from miniDSP, it has had 3 dB subtracted from it.
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The other question, is how did it get changed? I have never messed with the original cal file intentionally.
 
I'd also like to donate, if you have a setup for that. Even if we can't find the problem.
 
I guess someone has changed it for whatever reason, since that is not how miniDSP name the files. They use 7014612.txt, not 7014612_Umik1cal.txt
 
John Mulcahy said:
I guess someone has changed it for whatever reason, since that is not how miniDSP name the files. They use 7014612.txt, not 7014612_Umik1cal.txt
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I see the only difference in the incorrect cal vs the correct one I just downloaded was the sense factor.

It appears the only thing that changes in the measurements with this is the overall SPL level, while relative frequencies in a single measurement remain the same.

Is that the case, or do I need to scrap all my measurements done with the erroneous “normal” cal sense factor?
 
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miniDSP and AV Nirvana

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