Forst thing is to put a known signal into the speakers, say from a CD recorder to isolate a possible mixer or other source being marginal.

If the sound is still bad, verify that your volume settings are reasonable.

DO NOT crank the gain on these speakers full and then throttle the signal to them as that cause poor signal-to-noise ratio.

If you have driven these speakers very hard (these are only INTENDED for lower level monitoring within the engineer's booth), you MAY have damaged the speakers. It htat case, repair will be necessary.

Try to determine if the lows or highs or both are bad sounding.