REW Beta Release Large (24 dBSPL) difference with and without API server

[jvanriel]

Hi,

I'm using REW V5.40 Beta 57 (Pro upgrade) with miniDSP EARS with calibration files. I've measured a signal (1KHz and 2KHz at various volumes) with and without the API server.

* dBFS values are identical
* dBSPL values show a difference of 24dBSPL

It drops immediately when starting the API server but does not raise when stopping the server. It is repeatable when quitting/starting the app.

Why is there this constant offset?

Thanks,

Jan Van Riel

 

[John Mulcahy]

The current 5.40 beta build is beta 75. When REW is started it may alter the Windows input volume setting for USB mics to select the volume corresponding to unity gain, depending on whether the option to allow REW to control input volume is selected. Any change to input volume should not affect SPL readings unless there has been some change to the behaviour of EARS or EARS has not been selected as the input device and input or the cal files are missing the SENS FACTOR line.

 

[jvanriel]

I've upgraded to the latest beta version (on a Mac BTW) but with the same result. Just starting the API server I see the dB SLP measure drop with 24 dB SPL. But 24dB SPL is exactly the EARS and UMIK-1 gain at maximum volume. Could it be possible that this value is not taken into account when using the API?

 

[John Mulcahy]

What SPL measure are you referring to? Displayed where or read from where?

 

[jvanriel]

Here are screenshots and a recording.

 

[jvanriel]

Here are the EARS cal files that I'm using

 

[John Mulcahy]

Thanks, bizarre stuff. Your EARS unit is from a later build than the one I have and has a different gain curve. REW checks for that using the serial number, but the format of the serial number entry in the EARS cal files differs from the format in the UMIK cal files, so that detection probably isn't working. That doesn't explain why starting the API server has any effect, however. I'll see if I can work out what is going on, and fix the serial number detection.

 

[jvanriel]

Cool. Let me know if you want me to try anything else.

 

[John Mulcahy]

Can you attach a screenshot of the Audio Midi Setup entry for your EARS unit showing the volume controls, please?

 

[jvanriel]

Here you go