Sweep Truncating @ ~14kHz?

[NeilBlanchard]

Hello,

When I do a 10Hz-20kHz sweep, the first time all is as it should be. But today, when I do a second sweep - the response measured is being cut off at about 14kHz. It is dropping almost straight down, and is about -60dB or more at 20kHz. What would be causing this?

I have changed out the tweeter, and have used two other speakers. I have swapped out my preamp, and my power amp. Each time, the first sweep I take is fine, but then the next/subsequent sweeps are truncated like a brick wall filter is in there ...

I am using a miniDSP UMIK-1, and a Framework laptop running Windows 10; if that matters.

Thanks - Neil

 

[John Mulcahy]

Could be that something in the system has a high latency causing the end of the sweep to be missed. Try using the acoustic timing reference to synchronise capture with the detection of the timing signal.

 

[NeilBlanchard]

Hello John,

Now that you mention it, the DAC I am using - the Denafrips Ares II - does have very high latency. And unfortunately, it seems to vary - so I think I will switch DACs, when measuring with REW.

Because I need to figure out how to do gated measurements, so if I have to futz with the Ares II latency, that won't be fun.

 

[John Mulcahy]

Using the acoustic timing ref eliminates any latency in the playback path.

 

[NeilBlanchard]

Thanks, I should try that - I would assume that using the Ares II would negate any soundcard calibration, right?

For the moment, I used the headphone jack on the laptop into the preamp, and I had no frequency truncation.

 

[John Mulcahy]

You could include the DAC in a fresh soundcard calibration if you liked, though the latency might cause issues with the cal. 'Soundcard' cal can generally include everything handling the electrical (as opposed to acoustic) signals that isn't part of the system being measured.