How do I ask a question? - Home Theater Forum and Systems -

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post #1 of 24 Old 11-02-13, 06:41 PM Thread Starter
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How do I ask a question?

I'd like to know how to calibrate a USB mic (Dayton Audio UMM-6) and a Cord Async USB controller? Where do I ask that question? I tried to search on "Calibrate USB mic" using the double quotes to get that phrase, but the search engine returned no hits. I don't know how to plug the analog output from the Cord DAC into the mic USB line.
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post #2 of 24 Old 11-02-13, 07:14 PM
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Re: How do I ask a question?

I would post your question in the calibration forum here..

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post #4 of 24 Old 11-02-13, 09:48 PM Thread Starter
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Re: How do I ask a question?

OK, thanks for moving the post to the right thread. Looks like brucek may have answered my question several years ago.

Last edited by Oldears; 11-02-13 at 09:54 PM. Reason: spelling
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post #5 of 24 Old 11-02-13, 11:55 PM Thread Starter
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Using the USB mic

Well, I thought this would happen. REW or RealTek failed to detect the USB mic. I have attached a screen shot of the error message. When I click on the Input Devices, the only device listed is the default device. I made sure the check box was unchecked on the mic/meter tab asking about SPL weighting. I've spent an hour trying to trouble shoot this to no avail. The output device, the built in sound card on my PC (Windows 7) is working because when I play a test signal from the mixer, accessed by clicking on the speaker icon in the lower right corner of the desktop, I hear it through the speakers.

How do I get the software to recognize the USB mic? Please don't assume I know anything about computers and audio. Although that is not true, my knowledge may be different than yours.
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post #6 of 24 Old 11-03-13, 01:42 AM Thread Starter
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No volume control

I unplugged the USB cable from the mic and plugged it back in, and now the sound card recognizes it. Except now I have no volume control. I can hear the 1 kHz signal, but there doesn't seem to be a way to increase the input volume. It is greyed out and the RealTek volume is set for maximum. I have included another screen shot. FYI, I can crank up the volume on the preamp to the point of driving me out of the room, but there is no effect on the REW display. I've gone into control panels and looked at RealTek, but that is just for the speakers, and I've gone into the Sound panel. There the microphone is the UMM-6, and properties tabs are Level: set to 100; Advanced: 1 channel, 16 bit, 44100Hz (CD Quality).

I've now got 3 hours into this project and suspect anyone else would have taken about 30 seconds to get this far.
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post #7 of 24 Old 11-03-13, 04:38 AM
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Re: How do I ask a question?

For USB mics it is best to use the latest beta version of REW, which has extra features to support them. You can find that here. The help files in the beta version (also available as a PDF at the beta download thread linked above) have been updated to cover USB mics. Make sure the mic is plugged in before you start REW, otherwise Java can take a couple of minutes to realise there is a new USB device present.
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post #8 of 24 Old 11-03-13, 05:04 PM Thread Starter
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How loud do I have to turn up the volume?

Wow! That was a piece of cake. Took about two minutes to calibrate everything using a different computer, the latest version of REW, and using the external desktop speakers plugged into the computer. Looks like the little speakers don't go below 100Hz! It was great having the program ask me if the mic it detected, the UMM-6, was the one I wanted to use, and then asking for the calibration file, which I had. I felt confident everything was going to work. And it did. I've included a screen shot with a warning. BTW, it is really helpful having the additional information about using USB mics in all the steps.

When I was checking levels, I had to turn the volume up much louder than I ever have to get the input levels up to -30 dB. Is that normal? The UMM-6 mic is about 9' away from the right speaker and pointing straight up. I'm now going to try downloading the beta version of REW on the main computer downstairs, which is where I want to do the measurements and where I was having all the trouble last night. If I still have problems with that computer, I'll take this desktop down there.

Thanks for the link to the beta version. I didn't know where to find it on the website. When I opened REW last night, I saw a dialog box telling me there was a newer version available, and if I wanted it to click here. I did, and I was taken to the home page of the forum. I couldn't figure out what to do next.
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post #9 of 24 Old 11-04-13, 08:43 AM
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Re: How do I ask a question?

That warning is for the soundcard calibration process. That process is not used with a USB mic like yours.
The soundcard calibration file should be left as "none".

Your measurements should be made at about 75-80 dB SPL. If you get a low level warning when you take measurements just ignore it. Many USB mics have an output level which will trigger this warning, but it has no effect on the SPL or most other measurement types.
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post #10 of 24 Old 11-04-13, 12:55 PM Thread Starter
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Re: How do I ask a question?

The new version of REW was really easy to set up on the computer that was giving me fits before, and I spent about 8 hours making all kinds of measurements, checking different sitting positions, stacking pillows and cushions up to 5' high in every corner, draping quilts over walls, mirrors and pictures, wedging cushions between the tops of bookcases and the ceiling, and covering horizontal hard surfaces with blankets. (Yes, my wife is out of town for a week.) The best results seem to be just cushions in the corners so I'm a bit suspicious about the numbers.

I can upload the files if necessary, but the first thing that jumps out is the frequency response drops off pretty sharply around 10 kHz in every single measurement. When I play test tones from a CD that go from 20 Hz to 20 kHz, I don't hear anything above 8 kHz, but the free app on my iPhone registers a signal for every test tone up to 20 kHz. Why is the SPL meter showing such different results than the frequency plot in REW?

Do I need a better SPL meter or app? I read the thread "Spl meter/Worth it" which concludes with the statement that the iPhone is sufficient. (Unfortunately the link to the Cross Galaxy meter goes to a device for calibrating a meter, not the meter itself.) I'm using a free app from 10th Decibel. I picked it at random, and I have an external mic for the iPhone, the IMM-6 from Dayton Audio which I bought just to get free shipping since shipping was more than the cost of the IMM-6.

Of course I don't want to buy anything I don't have to, but I do want to get meaningful results. Using REW, I see almost no effect of different seat positions further away or closer to the speakers, nor do I see any effect of toe in, although the sound stage is much clearer when I listen with the speakers aimed at me rather than straight ahead, but maybe that's just my ears deceiving me.

Ah, I just remembered REW is using only one speaker so of course it cannot detect sound stage effects, not to mention the test tones are probably equal in each speaker, but I would think the orientation of the speaker would have a noticeable effect on the room frequency response. We're talking about 30 degrees to the side from pointing straight ahead.

And remember, I really don't have much of a clue what I'm doing with an SPL meter or with REW. I understand an SPL meter measures the pressure of the sound waves which we associate with volume, and the frequency plot in REW shows how far from a perfectly horizontal line my room acoustics are. That's it.
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