Imagine your left speaker is down 6db above 220hz and right stays flat, you play a bar choard at A 110 on a guitar that is panned hard left. Everything in that chord bellow 220 is hard left but everything above is now more in the middle and mixing with the vocals and drums which were set in the middle making things muddy. In reality we get dips and humps all over the frequency response and if they are not matched it spreads those sounds across the image and this can be quite bad. Play your A note and the fundamental is panned where you want it, the second harmonic is closer to center, the third is somewhere between those and everything else is more right, the sound is no longer isolated in the field where it should be. Now play your A an octave up (second harmonic of the previous A) and fundamental is closer to center, second is more left and so on, everything moves subtly. Apply that to an entire band playing with all of them blurred like this, the stereo image falls apart and we only get a vague impression
These examples are not exactly accurate to the real world, meant more to demonstrate the problem but we can hear it easily, this is a big part of why some speakers/headphones sound muddy and have poor deffinition. With more simple sources this is not much of an issue but as complexity increases the lack of matching becomes more noticeable.
In surround the rear speakers can be quite bad before issues arise since the shape of our ears and our head means we are not great at pinpointing the location of sounds behind us, we hear hard left and hard right behind us well but we have a dead spot between where things are not quite so clear. I would suspect some of the rear is also mixed into the fronts which would help, hard panning tends to be avoided as it does not sound natural. As I said, the surround stuff is a best guess on my part, I suspect I am in the ballpark but lack some of the nuances.
These examples are not exactly accurate to the real world, meant more to demonstrate the problem but we can hear it easily, this is a big part of why some speakers/headphones sound muddy and have poor deffinition. With more simple sources this is not much of an issue but as complexity increases the lack of matching becomes more noticeable.
In surround the rear speakers can be quite bad before issues arise since the shape of our ears and our head means we are not great at pinpointing the location of sounds behind us, we hear hard left and hard right behind us well but we have a dead spot between where things are not quite so clear. I would suspect some of the rear is also mixed into the fronts which would help, hard panning tends to be avoided as it does not sound natural. As I said, the surround stuff is a best guess on my part, I suspect I am in the ballpark but lack some of the nuances.