# UMIK-1 SPL Calibration



## Slybond (Feb 15, 2017)

Hi, I bought the Mini DSP UMIK-1 microphone and when comparing the SPL meter in REW to the classic radio shack SPL meter, the REW measurement is 5db hotter. I have the correct calibration file loaded for the microphone, could it be something else?

Thanks, 

Sean.


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

When you say “	REW measurement is 5 dB hotter,” are you referring to the left-side markings on a frequency response measurement graph, or that REW’s SPL meter reads hotter?

Regards,
Wayne


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## willis7469 (Jan 31, 2014)

That's funny! My RS spl meter shows lower spl numbers than REW! Yep. I loaded the cal file too.


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## Slybond (Feb 15, 2017)

Wayne A. Pflughaupt said:


> When you say “	REW measurement is 5 dB hotter,” are you referring to the left-side markings on a frequency response measurement graph, or that REW’s SPL meter reads hotter?
> 
> Regards,
> Wayne


Sorry about that, REW's SPL meter reads hotter than the radio shack SPL meter


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

A few things to keep in mind:


* Assuming the calibration file has a sensitivity line, it should deliver accurate SPL readings from REW’s meter. The Radio Shack meters are lower-end Type 3 devices that typically have a +/- 2 dB variance, if not more. 

* That said, I’d have more confidence in a calibration from Cross Spectrum Labs than one from miniDSP.

* Make sure you’re comparing apples to apples. The Radio Shack meters have only A or C weighted options. The C-weighting we normally use rolls out the lows below ~40 Hz. If you’re using REW’s Z weighting, it’s unweighted, which translates to flat response with no low end roll out. Thus with a low frequency signal that has significant energy below 40 Hz, it will read hotter than the C-weighted RS meter.

Regards, 
Wayne


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## Slybond (Feb 15, 2017)

Wayne A. Pflughaupt said:


> A few things to keep in mind:
> 
> 
> * Assuming the calibration file has a sensitivity line, it should deliver accurate SPL readings from REW’s meter. The Radio Shack meters are lower-end Type 3 devices that typically have a +/- 2 dB variance, if not more.
> ...


Thanks for the information Wayne, 

I assume a calibration from Cross Spectrum Labs would require purchasing the UMIK-1 from them?

Sean.


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

Correct, but I wouldn’t go out and buy a second mic just for that. Dead-accurate SPL is not a necessity for anyone except people with professional needs, e.g. enforcing noise ordinances.

Regards, 
Wayne


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## JohnM (Apr 11, 2006)

Cross Spectrum don't calibrate sensitivity for USB mics.


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