No problem Arny. Ethan's measurements still show room influence at low frequency and do not match the manufacturer's data broadband, probably because he could not (well, he could, but maybe did not for lack of time and finances) make a perfect anechoic chamber, but as a relative comparison among mics is a great reference. Along with all the other great stuff on his site, natch!
The QTC (Quiet Time Coherent) series looks similar to the M (Measurement) series but QTC mics target recording, not measurement. I have not looked lately, but when I got my M30 the QTC series was not quite as flat (intentionally) and I don't think they came with an individual cal sheet. However, I think they had a lower noise floor. IIRC, even though the QTC claims time coherency, both were similar in phase response and time response (i.e. durn good!) I thought the QTC-1 was similar to the M30 but do not recall. The current model QTC-30 is similar to the M30. The M50 and M30 are virtually identical through the audio band; the M50 extends out to 50 kHz for noise applications and those who need ultrasonic response. I did not need more than 30 kHz and did not want to pay for it (the M30 is around $650 last I checked). Frankly, I'd have to ask Earthworks for the differences among the M, QTC, and TC (Time Coherent, presumably not as quiet
) series mics.
What is great, as Ethan's plots show, is that today you can get a pretty inexpensive mic that has performance basically the same as a measurement mic. If only I had known about them back then! Actually, I believe Radio Shack had a dirt-cheap electret that was very popular because it had very good (flat) response; maybe it used that Panasonic capsule? I don't know.
You are correct about the iPhone; there have been articles about that in various engineering trade rags. The early models generated a plethora of audio apps ranging from free to several thousand dollars (a friend has one of those) that provided great results. the newer models require processing to compensate the low-end roll-off. Apple said the newer models provide greater vocal clarity with less noise. it is the right trade for vocals, but would have been neat if they had left full-range response and given us the choice (or processed digitally). I suspect the mic was overloading the preamp with LF content.
Nice to have your historical perspective Arny, thanks! - Don