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headphones as mic

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LeftyGorilla

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So I've decided I should try making binaural recordings using a pair of Grado 225s headphones. The large, open drivers make them ideal(?) for this, but I am a little worried about damaging them with the DC current from the mic input on my MZ-R700. Can't find a definitive statement of what this plugin power is. I tried it out and got a surprisingly nice recording from them.

Here are the specs for the "microphone:"

Transducer type dynamic

Operating principle open air

Frequency response 20-22

SPL 1mV 98

Normal impedance 32ohms

Driver matched db .05

I started getting paranoid after reading the following from a Sennheiser rep on Head-Fi:

If you want to connect your dynamic headphones to a mic. socket on a PC, MiniDisk, flash recorder, or the like you will need a special adaptor cable. These devices have about 5-Volts of "plug-in power" to power small electret condenser microphones. The adaptor cable will therefore need to have blocking capacitors in it to prevent this DC power getting to the headphones. Do this (or switch off the plug-in power) and you can then use your headphones as microphones (how good they will actually be is another thing as they were designed to be headphones and not microphones and the impedance may not be the best match - but it should work.)

I did find one reference to 1.5V of plugin power:

Your extension cord should work fine.

But plug-in power and phantom power are two different things. Plug-in power is a little bit of current at the mic jack--as above, 1-10V.

The plug-in power from the MD is only 1.5 volts.

Phantom power is 48V, usually from an external device for mics that need it. (Some recorders, not MD, also provide it),

Phantom power can replace battery power for mics that need all that power. Plug-in power probably won't give your MS907 what it needs--hence the battery. I don't have the MS907, but my guess is that if you try recording with it plugged into the mic jack, but with batteries removed, you won't get much of a signal. I'd be very curious to hear otherwise.

Any thoughts? Will the mic-in eventually burn out my phones? Safer to use the line-in? Is the whole idea wrong-headed?

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Any thoughts? Will the mic-in eventually burn out my phones? Safer to use the line-in? Is the whole idea wrong-headed?

Line-in would give you silence. The plug-in power is only 1.5V, and I have no idea how much damage it would do (if any) but...it's kind of nuts to use big, expensive Grados as microphones. It's not what they are made for. Their drivers are designed to drive sound out into your ears; vibrating to incoming sound is a sideline.

Get binaural mics that are made for the job, at a place like www.soundprofessionals.com . They're cheaper than a new pair of Grados. Also much smaller, and likely to be much more hi-fi.

Binaural just means placing omnidirectional mics where a pair of ears would be. It's not about headphones.

For what it's worth, I recorded a song through my Shure earbuds once. It worked--about as well as listening to the concert through a telephone. It was in the Live Recordings gallery on the old minidisc.org site--I don't know if that has been transferred to this new server.

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