Is it too bright or is it high resolution?

Damaged drivers
bad connections
electronics...

I think the question might be a bit too broad.

One must wonder if a "to bright" presentation may be the result of harmonic distortion. Whether this is an amplifier issue a preamplifier issue or the interplay between the electronics and speakers. I am certain that we all want all of the details without undue brightness.

Trace amounts of higher ordered harmonics cause brightness as the ear converts distortion into tonality. It also uses the higher ordered harmonics to gauge sound pressure (rather than fundamental tones) and so is more sensitive to them than modern test equipment.

Bright is a bad thing. Its a coloration.

Detailed is a good thing.

Quite often the two are found together. This gives detail a bad name!

Its possible to be extremely detailed and yet quite relaxed. Brightness is often not an actual frequency response error; instead its often caused by distortion (particularly in solid state and digital but can manifest from tubes and analog easily enough) which the ear converts into tonality.

By adding brightness, this can cause a system to temporarily seem more detailed. But in time it will be seen for what it is- a coloration, and not a very pleasant one.

This is just another way of restating what Spencer posted above.