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UMIK-1 dropping high frequencies 6 years 1 month ago #29357

  • skypickle
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UMIK-1 sn: 7017021
First room: macbook pro early 2008 running REW 5.17 beta 14,
NAD T175 preamp connected to macbook with mini plug stereo jack to stereo analog in
Cinepro amp
PSB gold tower speakers


Second room: macbook pro late 2013 running REW 5.17 beta 14
sonos connect: amp connected to macbook with a different mini plug stereo jack to stereo analog in
duevel speakers

Measurements of each room using REW are attached below and in each case the SPL curve drops off by 4khz even though the sweep was set to go to 20khz.

Is the microphone broken? I purchased it not too long ago and just started using it. There has been no damage. Is there a way to test the UMIK-1?



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UMIK-1 dropping high frequencies 6 years 1 month ago #29360

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Did the sweep actually run to 20 kHz?

Perhaps try an RTA with pink noise and see what that shows.

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UMIK-1 dropping high frequencies 6 years 1 month ago #29368

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I would perform a loopback test on your REW setup to verify it's sweeping over the full range.

It's highly doubtful the microphone itself has an issue. In fact, your two measurements indicate a 1khz difference.

Dave.

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UMIK-1 dropping high frequencies 6 years 1 month ago #29369

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how do i do a loopback test on a macbook pro? There is no microphone port!

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UMIK-1 dropping high frequencies 6 years 1 month ago #29370

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well, i ran the measurement on the macbook without the UMIK-1 attached. Even though I turned down the output volume of the speaker to 50% and the mic input to 30% I still got a peak of 117 db!! LOL! prob because the speaker is right next to the mic on the laptop. Anyway the sweep ends a t 3.5 kHz . Why is that? The prefs are set to use 'main speaker signal' under sound card tab and 'use acoustic timing' under analysis tab.

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UMIK-1 dropping high frequencies 6 years 1 month ago #29371

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I reiterate Johns question. Do you actually hear the sweep going above 4khz??? (That should be easily audible.)

Edit: (You posted nearly at the same time.) :)
It seems your problem is with the REW setup and not the UMIK.

Dave.

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UMIK-1 dropping high frequencies 6 years 1 month ago #29372

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and here is an rta using only the laptop and sine wave at 12 kHz. clearly the laptop CAN generate a 12 kHz signal.



and here is the measurement dialog window clearly showing the sweep to 22khz

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UMIK-1 dropping high frequencies 6 years 1 month ago #29373

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and here is an rta with pink noise


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UMIK-1 dropping high frequencies 6 years 1 month ago #29374

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well, it seems setting the 'length parameter' to 512 or 1M improves the situation




Why would that be??
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UMIK-1 dropping high frequencies 6 years 1 month ago #29379

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The prefs are set to use 'main speaker signal' under sound card tab and 'use acoustic timing' under analysis tab.


Are you using an acoustic timing reference? Perhaps try turning that off for now.

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UMIK-1 dropping high frequencies 6 years 1 month ago #29382

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If I do not use the timing reference, I get the error dialog below:




With this setting, I get a full trace only if I set the sampling to 1M . As I make the samples less, the trace ends earlier.




In the chart above, The short gold trace is a 256k sample and the green trace is the 1M sample.
If I turn on 'use acoustic reference' I get the magenta graph (full trace) with the 1M sample.
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UMIK-1 dropping high frequencies 6 years 1 month ago #29384

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Might be better to use the stable release (5.16) until you sort things out?

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UMIK-1 dropping high frequencies 6 years 1 month ago #29385

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How does REW know to start without a timing reference? I guess the latency in the macbook results in the trace ending in the program but it is still being played by the output. I see this during the measurements:


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UMIK-1 dropping high frequencies 6 years 1 month ago #29387

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The timing reference is not to tell REW to start, it is so that it can measure relative time delay.

I would suggest you get things going with the stable release and without using a timing reference. Once you learn the basics then you can try more advanced things and/or "live on the edge" with the beta releases ;)

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