Re: Garage Loudspeaker Lab
I was talking about TEF, not dual FFTs.
TEF has the greatest noise immunity by far of any measurement system (but I am not aware of all of them).
Several years ago I was in a Church doing some measurements.
We had just made a measurement and saved it. Just after that there was an industrial type shop vac (think LARGE) sucking out some water out of a floor pocket, within a few feet of the measurement mic and MUCH louder than the swept sine we were using.
So we decided to measure again with the noise on-just to see what the difference was. The two traces laid on top of each other. So the vacuum was not affecting the measurement at all.
That is the wonderful thing about the TEF-you don't have to have a quiet environment to measure in.
But that is ALSO the bad thing about the TEF. Because of its ability to "window out" other influences on the sound from the speaker-it does not always give you a good "correlation" to what you are hearing.
I do not use TEF for sound system alignments for that very reason. I prefer dual FFT-because it is more like what I am hearing and MUCH faster
But for loudspeaker measurements of performance, it is great and does things other systems can't.
It depends on "What am I here to do". and then choose the proper tool.
But as amazing as it is-I feel it will die within my lifetime. Truly sad 
