SPL got different result in Mac and Win ?

[julian9593]

Hi All,
In Mac I get 75dB SPL , but in Win version I can only got 56dB. Please see below two screen shot:

I send 1K tone to a bluetooth speaker then use miniDSP UMIK-1 to measure SPL.
I wonder why different OS has different result.

Thanks.

 

[John Mulcahy]

You have left the input settings on the Windows version as default, so REW doesn't know that the input is a UMIK-1 and will not apply the cal file sensitivity factor. You should also make sure you are running 5.20.6 or later, see this item from the 5.20.6 release note:

• Recent UMIK-1 (which have a USB-C connector) have a different volume curve, so the SPL figure shown for them was only correct at the 0 dB gain setting (54% volume on Win10). When an ASIO wrapper is used the volume control is bypassed for these mics, so the input volume correction should no longer be applied. REW now checks the mic serial number to determine the correction to apply.

 

[julian9593]

Hi John,

Thank you for pointing the mistake, I re-test again and select the correct input device and make sure the software version is 5.20.7.

Though SPL is better than first trial, the SPL still lower than Mac version. We only interesting in the 1K tone energy.
Mac 1kHz value is: 66.9dB
WIN 1kHz value is around 55 dB

The audio source is iphone bluetooth 1kHz to a speaker, the volume set to 77%.

What do you think about this difference ? Is it correct ?

Thanks.

 

[John Mulcahy]

If the source and speaker are in the same places the results should be the same. Testing with tones is unreliable though, very small changes in position can significantly change the results. Better to use a wider band signal, such as the speaker cal signal of the Pink PN or Pink Random noise signals. If you can't get the same results that way save each measurement using the button to "save current" and attach the mdat files.