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Old 30th October 2018
  #18
Lives for gear
 

Quote:
Originally Posted by ReDRuMx View Post
BTW, perhaps I'm misunderstanding you but...

1. If the distance between the ears is 15 cm, that doesn't mean that the sound from one speaker reaches one ear "15 cm earlier" than the other ear, because it is arriving at an angle. The delay will be shorter.

2. Same sound reaching one ear later than the other (say 0.5 ms) will not result in a perceived dip at the "expected" 1 kHz. Your brain is smarter than a microphone. Try it with headphones.

This is why it is usually suggested to measure each speaker individually, and not worry that much about their sum at one MONO location for high frequencies.
Yup, I agree! I think we're on the same page.

I has hoping to achieve the most pithy assessment of what's going on in a stereo monitor situation; hence my trepidation about getting into this topic at all. I guess I can't cover all the implications in so few words. Here are some more words.

The speaker measurements in the OP's test are being done with a microphone at a single point in 3D space. I was clear about that in my append. That single mic has the effect of summing the contribution of the two speakers at a single point. Moving the single microphone just a little (like the 2-inches I mentioned) does in fact change the measured response. To me, it's daunting that such a small movement can create such differing results.

I alluded (not so clearly, sorry) to the "Two-Ear Problem". (It's not an official term, but TEP sounds kinda cool as an acronym.) With the TEP, we're catching two speaker sources at two different points in 3D space. It won't be the same 'dip' in each ear because the arrival of the indirect sound in each ear is different. The 3D position of the ears has a fixed offset between them, but each ear is having a different experience.

The wetware signal processing in our brain does a marvelous job of real-time calculation of relative strength, timing offsets, reflection interpretation, and EQ. I am always blown away by the joy of riding in my convertible through a wooded area. The fact that the 3D space of the bird calls occurring above, in front, in back, left/right, and at widely varying of distances can be readily ascertained in a moving vehicle is a fantastic testament to how good the system is.

The analysis gets to be a rather different problem at longer wavelengths as the speaker itself starts putting out a more widely dispersed signal, and the room interactions are both more dramatic and harder to absorb/control. I'm running for the hills before this discussion drifts in to the world of bass in a room.

Last edited by MediaGary; 30th October 2018 at 02:30 PM.. Reason: typo