Hi

Both Radio Shack microphones are condensor types and will be compatible with the car player's input (I think the phantom power supply is about 3V in a car player). There's a data sheet for the KUC1515-01-0850 at http://support.radioshack.com/support_supplies/doc9/9798.htm which specifies a wide voltage range of 2-10Volts. From this, and thinking about how these mics work, I believe the exact voltage isn't critical in general.

We do however need to use an omnidirectional mic, since omni mics measure the pressure due to the sound not the air velocity (hence we get a true SPL).

I also prefer the KUC1515-01-0850 as a "standard" unit because it has wires on. Soldering onto those mics is a bit tedious for someone with "normal" soldering skills like me.

I love the Behringer ECM8000 measurement mic - in fact the idea of AutoEQ came from a rainy day in Somerset with Roger, John Ripley and me in Roger's car with my ECM800 and UltraCurve2496 basically trying to determine how Roger's EQ should be set for a flat response. Sadly the ECM8000 specifies 15-42 volts DC supply (typical for pro equipment). It might just work anyway at 3V, but I couldn't guarantee it would still be flat, making the excercise a bit pointless. Another option might be to pre-amp the mic properly and use that signal.

The frequency ranges specified for the microphones is likely to be a "reasonably flat in this range" type thing. We should be able to compensate as long as the microphone doesn't lose so much sensitivity out of range that its signal drops below the noise floor.

I just looked at the EQ code, and can't find a trace of the limits that I added based on some research by someone on this BBS into which low-frequency settings make the EQ go wrong. It's in there somewhere, I'm sure . Basically it replaced the old 50Hz limit with a combination of limited boost/cut limits at frequencies below 50Hz.

AutoEQ bands are centred on:
  • 25
  • 40
  • 63
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  • 160
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  • 800
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  • 12.5k
In the absence of calibration data you should only rely on the results for bands comfortably inside the mic's flat range. Other bands can be set to 0dB or set by ear.

Best microphone positioning is near your head, because that's where your ears are. You also need to keep background noise as quiet as possible (including handling noise). While AutoEQ is running, the level should be within the range of the cute little VU meter and ideally >=10dB higher than the background noise level. AutoEQ won't do this for you, you have to do it yourself and that may take a few trial runs.

Cheers, John