# CM-140 Accuracy and how to get it calibrated?



## jmcomp124 (Feb 27, 2007)

I have an Integra DHC 40.1 with MultEQ. After Audyssey calibration, the pre-amp test internal test tones are supposed to read 75dBC at listening position, but mine reads 70dB. With REW measurements, things look consistent. Is my CM-140 off by 5dBC?
I am in Portland, OR. If it is off, is there a place I can get it calibrated locally? Can I calibrate it myself and if so what is the procedure? If not, where do I send it in for calibration?
Has anyone else gone through this before?
BTW, with REW, I use the CAL fine of course. 
Thanks,
-Jai


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## Wayne A. Pflughaupt (Apr 13, 2006)

I doubt the meter is off a full 5 dB. I don't see where it's that big a deal if the meter doesn't read 75 dB after calibration, but you might run your concerns past the folks at our Audyssey MultEQ Discussion Thead and see what they say.

Regards,
Wayne


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## jmcomp124 (Feb 27, 2007)

Wayne A. Pflughaupt said:


> I doubt the meter is off a full 5 dB. I don't see where it's that big a deal if the meter doesn't read 75 dB after calibration, but you might run your concerns past the folks at our Audyssey MultEQ Discussion Thead and see what they say.
> 
> Regards,
> Wayne


Wayne,
Just posted there and hoping for a response. 
What do folks here notice in SPL levels after Audyseey calibration at listening position?
Thanks,
-Jai


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## jmcomp124 (Feb 27, 2007)

Wayne A. Pflughaupt said:


> I doubt the meter is off a full 5 dB. I don't see where it's that big a deal if the meter doesn't read 75 dB after calibration, but you might run your concerns past the folks at our Audyssey MultEQ Discussion Thead and see what they say.
> 
> Regards,
> Wayne


Also compared it side by side to the old analog Rshack meter and they both read exactly the same 70dBC.


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## glaufman (Nov 25, 2007)

Many things can affect this. Are you hand holding the SPL meter when taking measurements? Your body produce some weird effects. Is the mic of the meter in exactly the same place as the Audyssey mic was?


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## jmcomp124 (Feb 27, 2007)

glaufman said:


> Many things can affect this. Are you hand holding the SPL meter when taking measurements? Your body produce some weird effects. Is the mic of the meter in exactly the same place as the Audyssey mic was?


Hi Greg,
I have tried it on a tripod and also at the first position of the Audyssey mic. It is consistently around 70dBC at listening position. The pink noise is 500Hz to 2KHz and less prone to reflections.
Thanks,
-Jai


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## glaufman (Nov 25, 2007)

How about absorption?
If you have MultEQ, yo umeasured at several locations, yes?


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## jmcomp124 (Feb 27, 2007)

glaufman said:


> How about absorption?
> If you have MultEQ, yo umeasured at several locations, yes?


Yes, 6 locations. Where can I get my CM-140 calibrated?
Thanks,
-Jai


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## jmcomp124 (Feb 27, 2007)

CMC-200 costs $250. Are there places that do calibration for a small fee?


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## glaufman (Nov 25, 2007)

I'm not sure which mics he can/can't do, but Anechoic (Cross Spectrum Labs) is pretty reasonably priced.


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