audio/speaker issues

i have a set of logitech z-680 speakers and just today i noticed that the subwoofer isn't hitting the lower bass notes like it should.

i noticed it when listening to a few songs that have hard bass hits. i thought, hmm, maybe the sub level is just way low or the volume is too quiet. i cranked both and still, it failed to hit them like i have heard it do before.

i have a few ummm, i guess competition bass tester mp3 tracks where they just go down and down and down. with these tracks i verified that at one specific point, it loses about 75% of it's punch. the higher-frequency bass notes are fine and powerful, but at one point, the loss is very noticeable.

i've checked: power (multiple outlets), all connections and all settings/levels (on the unit itself and in winamp).

any ideas? is the sub going down? i put my ear up the speaker and listened for any signs of it being blown and heard none. it's not crackling or sounding "maxed out," its just waaay quieter than it should be at certain frequencies.

any help or suggestions/ideas appreciated. thanks.

It might be the fact that mp3 is a lossy format and very low frequencies are stripped away to save space.

try playing a proper cd and see if there is a big difference.

they played normally before. something has changed and i'm trying to figure out what and why. it's a huge difference at one point. they did not act that way before on the same mp3s.