Precision Measurement Microphone (4 replies)
I’m considering a precision measurement microphone. Specifically one that will measure the noise floor of ultra quiet home theaters. I’ve measured a hand full of high end theaters using the behringer ECM 8000 mic.
Even when connected directly thru the iAudioInterface2 (by passing the multiplexer) the lowest noise floor I can record is 30db. I’m guessing this is a limitation of the microphone? My first question is: Is that correct? Is the mic the limitation or is that a limitation of iAudioInterface 2?
If it’s the mic, my second question is, what quality measurement mic will measure the true noise floor of a ultra quiet theater? I’m looking at the Earthworks M30 or M50. Are those mics a good choice for measurement of the true noise floor? Is the M30 good enough? Because the M50 is about twice the cost.
I don’t see myself ever doing measurements for live music, so home theaters is all I’m considering.
HI! The use of a Type I mic is required for low noise floor measurements. Your mics are the limiting factor as the iAudioInterface should be up to the task of low noise measurement. 25dB to 30 dB is a typical noise limitation for most Type II mics. Of course, you should remember to bypass your MUX as it is pretty noisy. That's OK because we use the MUX for low frequency response measurements with a test tone set to play well above any noise from any source.
I’d be interested to hear what precision mic’s are preferred when a precision mic is needed. Good reviews of precision mic’s are difficult to come by. A recommendation from a calibrator would be worth it’s weight.
I've been underwhelmed by any of the Earthworks mics that weren't their top-of-the-line models ...I mean, yes they're certainly better than a Behringer ECM8000, but their shortcomings are still evident when compared to the better measurement mics that Earthworks offers.
But frankly, other than the one titanium diaphragm omni made by THE (Taylor Hohendahl Engineering) I've never encountered a measurement mic that made me want to use anything other than a B&K (aka DPA). And they are not cheap.
Sadly, the two qualities you need a precision measurement microphone to possess -- low self-noise and flat frequency response -- are extremely difficult to achieve inexpensively. Damn transducers! 🙂