There have been a lot of comments about this mic in the DIY mic thread. Could a moderator move them here:
http://www.diyaudio.com/forums/multi-way/144306-diy-measurement-mic-7.html#post2011834
http://www.diyaudio.com/forums/multi-way/144306-diy-measurement-mic-7.html#post2017983
Several people, including myself, have confirmed that the output is not truly
balanced - not an issue just good to know. The internal circuit looks a bit odd
in that it looks as if designed to be balanced but not quite right:
http://www.hometheatershack.com/for...techniques-usage-discussion-5.html#post217237
I'm wondering if anyone has noticed high noise levels from these mics below about 100 Hz? I've got
to look into it more but was just wondering what to expect if anyone already has the data.
I'm also looking for a small low cost USB mic pre with phantom power
to interface to a laptop computer. This looks like it, but I've not tried it
yet. It is very basic, USB 1.1, no higher sampling rates but should do the
trick for basic measurements - anyone know from practice if it works well:
http://www.artproaudio.com/products.asp?type=86&cat=9&id=150
http://www.diyaudio.com/forums/multi-way/144306-diy-measurement-mic-7.html#post2011834
http://www.diyaudio.com/forums/multi-way/144306-diy-measurement-mic-7.html#post2017983
Several people, including myself, have confirmed that the output is not truly
balanced - not an issue just good to know. The internal circuit looks a bit odd
in that it looks as if designed to be balanced but not quite right:
http://www.hometheatershack.com/for...techniques-usage-discussion-5.html#post217237
I'm wondering if anyone has noticed high noise levels from these mics below about 100 Hz? I've got
to look into it more but was just wondering what to expect if anyone already has the data.
I'm also looking for a small low cost USB mic pre with phantom power
to interface to a laptop computer. This looks like it, but I've not tried it
yet. It is very basic, USB 1.1, no higher sampling rates but should do the
trick for basic measurements - anyone know from practice if it works well:
http://www.artproaudio.com/products.asp?type=86&cat=9&id=150
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I can't say I am very happy with my M-Audio Audio Buddy. Overloads way to easy. Might look into building one, or maybe the demo board form Linear Tech. I just gave up on cheap preamps and ADC, and ordered an e-mu 1616.
Can't comment on LF noise, as I live half a mile from Rt 50, so my LF noise is loud and steady anyway. You would think it was mic noise unless you went outside on a quiet night and realized what horrible din you live in. I suspect the actual mic noise is below 100dB.
There are several threads on "improving" the sound of the mic, but it was not made to be musical, it was made to be an instrumentation mic.
Can't comment on LF noise, as I live half a mile from Rt 50, so my LF noise is loud and steady anyway. You would think it was mic noise unless you went outside on a quiet night and realized what horrible din you live in. I suspect the actual mic noise is below 100dB.
There are several threads on "improving" the sound of the mic, but it was not made to be musical, it was made to be an instrumentation mic.
Based on specs and reports I'd choose the E-mu0404 for a USB device but it is fairly costly and has a lot of controls that leave the opportunity for errors in settings. The 0202 does not have phantom power but gets an excellent review here:
A Winner
I also have the M-Audio Transit but it is line only, no mic pre or balanced XLRs - some say the drivers can cause issues:
ESI and AUDIOTRAK SOUNDCARDS for PRAXIS
I could use it with this low cost mic pre, there is a schematic here and it looks fine to me or at least easily modded:
Parts-Express.com:*Rolls MP13 Mini-Mic Preamp with Phantom Power | xlr rolls preamp power amps power amp power mini mics microphones mic leds LED ic clips clip amps amp
These mics are probably very similar to the popular Panasonic - interesting that Linkwitz's mod brings the MaxSPL to 141 dB for a 5 Vpp output! But yes these are probably limited to about 120 dB.
Linkwitz also mentions a noise level of 30 dBA SPL:
http://www.linkwitzlab.com/sys_test.htm
The calibration report for my ECM8000 indicates a noise level of 36 dBA which is in the ball park. Linkwitz mentions that his measurement is above 80 Hz and that there is 1/f noise below - this probably partly explains what I am seeing but not the fact that the rise starts below about 1K in my setup.
A Winner
I also have the M-Audio Transit but it is line only, no mic pre or balanced XLRs - some say the drivers can cause issues:
ESI and AUDIOTRAK SOUNDCARDS for PRAXIS
I could use it with this low cost mic pre, there is a schematic here and it looks fine to me or at least easily modded:
Parts-Express.com:*Rolls MP13 Mini-Mic Preamp with Phantom Power | xlr rolls preamp power amps power amp power mini mics microphones mic leds LED ic clips clip amps amp
These mics are probably very similar to the popular Panasonic - interesting that Linkwitz's mod brings the MaxSPL to 141 dB for a 5 Vpp output! But yes these are probably limited to about 120 dB.
Linkwitz also mentions a noise level of 30 dBA SPL:
http://www.linkwitzlab.com/sys_test.htm
The calibration report for my ECM8000 indicates a noise level of 36 dBA which is in the ball park. Linkwitz mentions that his measurement is above 80 Hz and that there is 1/f noise below - this probably partly explains what I am seeing but not the fact that the rise starts below about 1K in my setup.
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Looked into the LF noise a bit more, waited for the forced hot air heat to stop and the refrigerator to cycle off.
Now the rise starts at about 200 Hz, where the worst case LF noise between about 10 and 50 Hz bounces around averaging 15 to 20 dB higher than midband with short term random peaks to about 25 dB higher. This is probably mostly flicker or Johnson noise from the electret but I'm not very familiar with noise in electret mics so I welcome comments from microphone experts.
There was a 60 Hz component about 30 dB above the midband noise level, but when I listen to the noise spectra I could not hear it. It seemed to come from the rush of the forced hot air and went away when it shut off.
Now the rise starts at about 200 Hz, where the worst case LF noise between about 10 and 50 Hz bounces around averaging 15 to 20 dB higher than midband with short term random peaks to about 25 dB higher. This is probably mostly flicker or Johnson noise from the electret but I'm not very familiar with noise in electret mics so I welcome comments from microphone experts.
There was a 60 Hz component about 30 dB above the midband noise level, but when I listen to the noise spectra I could not hear it. It seemed to come from the rush of the forced hot air and went away when it shut off.
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I went back to the MXL MIC-MATE USB MIC Preamp:
http://www.bhphotovideo.com/c/product/522285-REG/MXL_MICMATE_BASIC_USB_Mic_Mate_.html
And, as expected it does not seem to contribute significant noise, about the same as with the M-Audio Transit.
I used my 114dB calibrator to check if the MXL clipped at this level and it did with the gain switch set to high, but not with it set to low. Switch is about 5dB/step.
The MXL MIC-MATE provides phantom power and seems to work fine for my intended portable application using a Laptop. Probably not a good choice if you need to do near field high SPL testing unless you use an attenuator and a source for phantom power.
http://www.bhphotovideo.com/c/product/522285-REG/MXL_MICMATE_BASIC_USB_Mic_Mate_.html
And, as expected it does not seem to contribute significant noise, about the same as with the M-Audio Transit.
I used my 114dB calibrator to check if the MXL clipped at this level and it did with the gain switch set to high, but not with it set to low. Switch is about 5dB/step.
The MXL MIC-MATE provides phantom power and seems to work fine for my intended portable application using a Laptop. Probably not a good choice if you need to do near field high SPL testing unless you use an attenuator and a source for phantom power.
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