Do passive X-overs go bad over time?

I have a pair of JL audio components in my truck powered by a Fosgate 250x2.  The speakers are over 5 years old and I've found when playing my music loud there is a "compression" effect on my upper frequencies.  It's like your adjusting the trebble all the way down.  Now if I turn it down a little you can hear the upper frequencies come back.  I've changed the amp thinking it was that (Pioneer Premier 250x2) and it did the same thing.

Speakers will generally wear out - especially when played at high volume - long before crossovers.  But yes, it is possible a capacitor in your crossover has a higher DCR (or ESR) than it should due to age.  If this was your problem the effect is unlikely to change with volume level, though.  Much more likely the problem is your head unit or your amp is clipping, or the speaker is simply being over-driven from too much power.Support the12volt.com

It might also be your ears. They do that. It's one of several things that fall into a phenomena known as "threshold shift", and it's an indicator that you should turn it down. Ask me how I know. -daveThis is not a sig. This is a duck. Quack.

Well I'm sure it's not my ears as I run a board connected to a system documented at 129db Always sounds good!  Now back to my truck.  I believe the speakers are ~175watts ea. and have been in the truck as long as the other components.  When everything was new, this didn't happen.  It's easy to reproduce and to experiance (other people have)  I can turn up the volume and 30-55sec later it sounds like I'm moving the sliders down on the Eq starting with the highest frequencies and working my way down.  When it finally settles out it sounds like there is no 1k and above .  As soon as I turn down the volume, you start hearing the return of the lost ambiance.  Also my Sony ES MDX-8500 (I believe) is hooked up completely passive. The internal amp has NEVER been used as I've always had seperate amps hooked up for front, rear, and sub channels. Thanks

Opps, Yes both front channels do this at the same time.

Try this.  Swap the RCA connections on your front and rear channels but leave the speaker connections alone.  If the problem moves to the rear it is your head unit.  If it stays in the front, it's either the amp or the speakers.  If it stays, try swapping the speaker connections AND the RCAs (swap the front channel amp and rear channel amp.)  If it moves, it's the amp, if it stays, it's in the speakers - or crossovers.Support the12volt.com