MB 4000C for broadband sweep? - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 3 Old 09-28-08, 03:08 PM Thread Starter
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Jeff
 
Join Date: Jul 2006
Location: Chicagoland
Posts: 22
Unhappy MB 4000C for broadband sweep?

OK, let me preface this by saying I have almost no idea what I'm doing. Any help would be appreciated.

I am trying to run some broadband REW tests using my SB 24 Live and REW. I borrowed this mic which I know fits the specs. The thing I don't know is whether or not it requires a preamp to operate. I bought an XLR-> mono 3.5 cable to hook it directly into the line-in of the soundcard. Because the mic is powered by a battery, it was my hope I didn't need the preamp.

When I did some quick testing, I noticed that I had sound, but it was far too quiet to pick up test tones. I turned up the mic level as high as possible on the PC, and I could see it picked up something, but not nearly enough for a measurement.

I'm wondering if someone can tell me what I need to make this work. My guess is a preamp, but then my question is - why is this mic any different than using the RS meter, which works fine without it? I'm also wondering if my issue is the fact that the 3.5mm side of the mic cable is mono, but I did set REW to the correct input (left) and it clearly picked up something there vs nothing on the right side. I have to wonder, however, if a stereo converter would fix my problems?

I guess the last issue is that I don't have a calibration file...but I'm still hoping this would work for relative measurements (before/after shots for my treatments) even if its not a perfect representation.

Thanks,
Jeff
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post #2 of 3 Old 09-29-08, 06:16 AM
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brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: MB 4000C for broadband sweep?

The microphone requires a preamp (with phantom power) to bring the voltage to a line level. A Radio Shack meter outputs line level and so is compatible with the line level inputs of the soundcards line-in port. Note, you cannot use a mic-in port of the soundcard with REW.

The standard mic preamp use around here is the Behringer preamp, and is usually combined with the Behringer ECM8000 microphone. These are both relatively inexpensive and we provide a calibration file on our download page for the ECM8000. A calibration file is required for accurate measurements as most microphones drop off in their response at high and low frequencies.

Hopefully, you have read and are completely familiar with REW Cabling Basics and the REW HELP files.

brucek
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post #3 of 3 Old 09-29-08, 06:52 PM Thread Starter
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Jeff
 
Join Date: Jul 2006
Location: Chicagoland
Posts: 22
Re: MB 4000C for broadband sweep?

Yup, I've read the guides and I knew about the Behringer. I was just hopeful this mic might have worked since it had an internal power source, similar to the RS meter.

Thanks
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