Even so, recording loudspeakers is not an easy task because you need a lot of experience how to do it.
1. The microphones used may differ more than +-10 dB 20-20000 Hz. This gonna colour the sound and its very audible. Are your microphones of a very high quality and do they have a frequency response +-1 dB in the audible area ?
2. The microphones should be nearer the loudspeaker than the critical distance in the room - ie less than 1 metre. And yes - you can only record one loudspeaker , because otherwise you gonna have comb effects. In this youtube video - the recording is done in the wrong way and are therefore of no value at all. Its wortheless.
3. Putting the microphones at listening position gives very false results - what you really are recording is only the room response - not the loudspeakers direct sound because you are way outside of the critical distance. This gives results of no value. A lot of recording amateurs dont know anything about this.
After 5 ms soundtravel and more, ( 1,7 metres distance and longer ) the ear/brain starts to select sounds and the mic take up all sound. You cant trust measurements in this case because of the precedence effect. The mic and brain are VERY different.
Read more about critical distance here :
Critical distance - Wikipedia
en.wikipedia.org
I’m not saying it’s a perfect system, just better than most crap out there.
Btw typical domestic rooms don’t have a reveberant field or a critical distance in the academic sense. They’re too small to form a reverb field.
Sure the response will always be better closer to the speaker but there will never be a portion of the room where loudness is equal in that portion (beyond the critical distance).