What is this phenomenon called?

I asked myself what this phenomenon was. After correcting the frequency response of my speakers with an inverse filter, I performed a slow sweep from 20 Hz to 20 kHz using a DSP with these filters on each speaker. The speakers are in good condition and identical. Only their positioning in the room varies. They are fixed to the wall with a mount and about 12 cm away from the wall. There is no interference with the subwoofer due to filters to eliminate crosstalk. The phenomenon in question emphasizes certain frequencies between 100 and 2000 Hz, different for each speaker, for example 105, 250, 400, 500, 700 Hz, up to 2, 3 or even 4 times normal intensity. The source seems to come from the speaker itself. At normal audio material listening, it bothers not really but I assume that if this phenomenon were corrected, the listening experience would improve. What exactly is going on here?

Wayne A. Pflughaupt said:

Sine waves can do strange things in a room, audibly-speaking. I expect that if you move even a foot or so in any direction when the “hot” frequencies are prominent, the apparent level will be reduced.

Regards,
Wayne

Click to expand...

Hi Wayne,

Exactly. One not having the proper audio equipment could verify with this online generator - https://onlinesound.net/tone-generator
E.g. at 800Hz here, every step you take, the SPL is diffferent: up, down, up, down
This can't be fixed by EQ. If I'm wrong, then this hasn't and will create enourmous distortion on introduce clipping at those frequencies. Hopefully, each speaker reacts differently. If they were perfectly in phase, that would be catastrophic.

Here is the response curve after the EQ. The amelioration is spectacular, aurally speaking, however it doesn't fix everything.