Strange measurements

[Aqua_HeaD]

Apologies my bad English.

I have suddenly run into problems with REW and especially the RTA function. I am using an UMIK-1 together with my laptop to measure my car.

When I make RTA measurements the curve will drastically drop down after 3000Hz and no frequencies over that will be measured. It almost look like the microphone is broken but it’s not. Sweep measurements seems to be okej. Even over 3000Hz.

Another strange thing is that when I use the tone generator in REW through my AUX input on the head unit no sound at all will come out from my sub base. It doesn’t matter if I use PN or separate tones. No sound at all will be played through the sub. The sub works fine through the USB (with other tone generators), BT and from the HU itself but not from the tone genarator in REW.

It seems that some settings have failed because everything worked fine in the beginning.

any suggestions?

 

[Wayne A. Pflughaupt]

I have suddenly run into problems with REW and especially the RTA function. I am using an UMIK-1 together with my laptop to measure my car.

When I make RTA measurements the curve will drastically drop down after 3000Hz and no frequencies over that will be measured. It almost look like the microphone is broken but it’s not. Sweep measurements seems to be okej. Even over 3000Hz.

Check the graph settings under the “Limits” icon. You may need to broaden the SPL Top and Bottom settings.

Hopefully John will weigh in for the other problem.

Regards,
Wayne

 

[Aqua_HeaD]

Check the graph settings under the “Limits” icon. You may need to broaden the SPL Top and Bottom settings.

Hopefully John will weigh in for the other problem.

Regards,
Wayne

Thanks but I have trtied to change those settings but it will not do anything about the maesurment problem or the sound problem from the sub when using REW´s tone generator.

 

[DanDan]

Pink Noise drops in level by 3dB per octave.

 

[John Mulcahy]

There are no settings in REW to stop signals going to your sub, so that issue is either in the way the HU is handling the Aux input, or the way the laptop is handling signals passing through whatever output you are using. Is it a Windows laptop? Using the headphone output? Windows laptops often come installed with various kinds of audio utilities that can have default settings which alter the output, usually they can be disabled by selecting "Disable all enhancements" on the Enhancements tab of the Windows audio properties for the playback device or output, but sometimes a separate software package has the settings (Waves MaxxAudio is an example).

For the RTA drop-off it would be helpful to see some examples of what you are talking about, ideally mdat files from using the Save button on the RTA but even just screenshots. I can't think of a way to get a drop off at 3 kHz with a UMIK, unless it was being used with a broken cal file, but if the UMIK had become disconnected the laptop could revert to the default input, which might be an internal mic with an 8k default sample rate. All just speculation though, really need to see some examples of what you are talking about.to see if there are clues in those.

 

[Aqua_HeaD]

There are no settings in REW to stop signals going to your sub, so that issue is either in the way the HU is handling the Aux input, or the way the laptop is handling signals passing through whatever output you are using. Is it a Windows laptop? Using the headphone output? Windows laptops often come installed with various kinds of audio utilities that can have default settings which alter the output, usually they can be disabled by selecting "Disable all enhancements" on the Enhancements tab of the Windows audio properties for the playback device or output, but sometimes a separate software package has the settings (Waves MaxxAudio is an example).

For the RTA drop-off it would be helpful to see some examples of what you are talking about, ideally mdat files from using the Save button on the RTA but even just screenshots. I can't think of a way to get a drop off at 3 kHz with a UMIK, unless it was being used with a broken cal file, but if the UMIK had become disconnected the laptop could revert to the default input, which might be an internal mic with an 8k default sample rate. All just speculation though, really need to see some examples of what you are talking about.to see if there are clues in those.

Thanks for your answer. It is good to know that REW settings cant make those strange issues. I am using an old laptop with Windows 7 installed at the moment. The "drop" issues that I am talking about have appeared latley and I have used the same laptop with the same REW version installed toghether with the same microphone during the whole tuning process. I will of course take a screenshot and post it here so you can see how it looks like. Maybe I will try to reinstall REW and see what is happening.

 

[John Mulcahy]

Include screenshots of the REW generator.

 

[Aqua_HeaD]

I have now made some different measurements through my portable CD player and through my surround system at home.

Yellow curve: Sweep measurement with laptop and portable CD-player via cable. REW generator.

Cyan curve: PN measurement with laptop and portable CD- player via cable. REW generator.

Blue curve: 3000Hz sinus tone with laptop and CD-player via cable. REW generator.

Red curve: PN from tone generator App via BT from iPhone to Samsung surround system.

You can see that significant drop on the red curve. I have the same drop when I make measurement via iPhone with USB-cable and Carplay in the car.

This is really strange. I always use Carplay with cable when I listen to music in the car an all the frequencies will be heard in the speakers. I don’t really understand why those frequencies above 3000Hz will be cut off when I use the phone as a signal source for the measurement in REW.

It is also strange that those sub tones not will be heard in the car when I use the tone generator in REW though the AUX input of the head unit. When I play sub tones from REW generator through my portable CD-player at home everything will work as it should.

 

[Aqua_HeaD]

Forget everything that I have been written before. I now feel very embarrassed since I have made a “huge” mistake.

It was just a setting in the tone generator app that had been changed. I had the sample rate set to “match source” instead of “48000hz”.

 

[John Mulcahy]

Glad you worked it out, now you can get back to measuring!