audio interface bug?

Hi all
I am trying to calibrate my ultralitemk5 at 192kHz.
and frequency response looks like below.


It shows a lot of dips.

I check the other sample rate below 192kHz and they looks good.
For example 176.4kHz and setting below.


I have turn off all eq stuffs in interface's software and mk5 can deal with 192kHz sample rate so I am not if it is issue of rew or audio interface?
What is your opinion?
Thanks all

John Mulcahy said:

Looks like you need to increase the ASIO buffer size in the ASIO control panel.

Click to expand...

actually I decrease the buff size and make this flat.
I test a lot of settings then I find buff size<=1024 when fs=192kHz.
However the measurement is not stable. sometime works and sometimes not so I am not sure if it is bug of beta version?

John Mulcahy said:

Strange if larger buffers make things worse, that's the largest buffer you tried? I have used it at 768 kHz with an RME ADI-2 Pro without issues, so I don't think there is any inherent issue in REW. You could try the Java drivers WASAPI exclusive mode as an alternative (device entries starting EXCL).

Click to expand...

well the largest buffer in ASIO is 4096 while largest buffer in java is 512, so maybe some issue conflict between motu app with rew for buffersize>512 in 192K? but anyway 44.1k sample rate is good enough for acoustic measurement.