Firstly thanks to everyone who has discussed Moving Mic Measurements (MMM). I'd never heard of the concept before.
I measure for my dedicated listening room with copious amounts of room treatment and I'm the only person listening so I don't mind measuring for one listening position. For that reason it seemed logical to measure using REW's sweep with the mic fixed in the position of the centre of my head. In the past I'd used my exact ear positions doing left and right measurements. The reason I now use the centre of my head and measure both speakers at the same time is that:
- My room is more or less symmetrical.
- I'm mostly concerned with the 0-300Hz range.
- Slight movements in the microphone position can affect the measurements.
- A mic will never exactly detect what my ears /brain hears.
- You can never get ruler flat graphs even if they are desirable. Smooth seems to be the main target.
Real accuracy is therefore impossible to achieve. All we can hope for is to get within one or two dB. As a result my procedure is that once I've implemented the filters for this range I listen with the Real Traps test tone CD (which covers the 10-300Hz range at 1Hz intervals). I then of course listen to music as the final arbiter.
Above 300Hz/400Hz, as Wayne A. Pflughaupt (post 20) and QMuse (post 28) point out, I would only adjust more generally with a wider range of frequencies (lower Q. Does anyone else not like this term Q (quality) and the way it is used when discussing EQ?).
I still get differences if I move my head sideways or forwards, and particularly when I dip my head so the angle of my ears in relation to the speakers is altered. This latter effect is most obvious in the higher frequencies, namely 2kHz and 8kHz. I can't see that any form of measurements will prevent this, particularly as the 2kHz effect is probably to do with speaker crosstalk and their comb filtering (see Toole, Sound Reproduction, p159 onwards).
On the subject of noise when using MMM, presumably the concern is the mic detecting the air movement as it is moved around, like wind on a static mic. I notice on the video linked by m_g_s_g (post 44) they use a foam covering on the end of the mic which is presumably designed to deal with wind effects.
Anyway, next time I do some measuring I'll see what the MMM procedure can bring.