Second Input Device for Loopbback selection

[SPo]

Hi John,

in my setup i use an ordinary Realtek onboard Soundcard with line out and line in and a calibrated miniDSP UMIC-1 for acoustic measurement.

But with this setup i am not able to select my realtek soundcard input als loopback, because you offer this selection only for the chosen input device which is my microphone.

Couldn`t you add a device-selection possibility for the loopback channel ?

A screenshot from my laptop - only for reference:

Kind regards,

SPo

 

[John Mulcahy]

Windows doesn't maintain any synchronisation between different devices so a loopback on a different device wouldn't serve any purpose. The acoustic timing reference was added to deal with this situation.

 

[SPo]

Ok - didn`t thought about that. But if i am using the acoustic timing reference i dont`t get the 'time-of-flight' from different speaker chassis. This is calibrated out of the signal.

In my case i wanted to adjust the delay times for each of my three chassis to compensate in in my nanoshark dsp. I did this with audacity now. But it would be good to measure it in REW with a not-timealigned dirac impulse.

For this scenario i do not really need an accurate AND absolute timing information. A relative timing information would be enough - just set the fastest as 0 delay and the rest follows.

Let`s say the sampling frequency of the mic has an acceptable stabilty over a short time. And you wouldn`t close & open the mic driver for each measurement and instead leave it open and sampling and you discard the samples only.
The constant recording and discarding wouldnt harm anything (except performance). The timing reference should then be taken from OUTPUT device.

The sampling of the measurements wouldn`t have a correct absolute timing offset. But inbetween the measurements taken in that session, the timing is steady - depending of the sampling stability of the mic.


So an option as requested in the 1st post and an option to constantly sample via the mic may be useful for doing timealignments with an USB mic.

What do you think ?

SPo

 

[John Mulcahy]

if i am using the acoustic timing reference i dont`t get the 'time-of-flight' from different speaker chassis. This is calibrated out of the signal.

The acoustic timing reference provides timing relative to the reference driver's arrival. If the distance from the reference driver to the mic needs to be included a tape measure will quickly show what time to add, otherwise relative timings are readily available using the existing options. Input and output paths have variable delays relative to one another so keeping devices running doesn't really help since there is still an unknown delay to take into account.