Help with Sonus Faber Extrema issue


I have a pair of Sonus Faber Extremas hooked up to a pair of Parasound JC1 monoblocks.  One of the speakers periodically will exhibit signicantly lower volume (down to almost no volume) in the middle of a listening session.  It seems to occur when during more dynamic passages and also when the amps have been on for a while.  If I turn everything off for a few minutes, the problem usually goes away.  I reversed the speaker cables at the speakers and the same speaker still exhibited the issue, so the issue is with the speaker.  What could cause this problem?  Could it be a bad connection somewhere in the speaker?  Could it be that crossover parts need to be changed due to age?
wcheng2
Winston, the amp could still be the problem...if you are still connected to the same mono bloc..If not, then I would definitely suspect the x-over. Probably one of the x-over parts is getting hot and is therefore acting up. Once it cools, you are temporarily ok.
The age factor that you mention is the culprit. 
BTW, thought you had sold the SF's...great speaker BTW!
wcheng, it might be the speaker tripping the amps overheat safety shut off. Disconnect the speaker cables from the speakers and check the resistance of each speaker with a meter. They should be very close to the same. In order to trip the amp the speaker's impedance would have to go below 2 ohms. A short anywhere in the speaker could do this and you should be able to see it with a meter. If that speaker reads low then check each driver independently then the cross over. If they are still under warranty let the dealer deal with it. 

Awesome combination btw, JC1’s and Extremas, best Esotar dynamic tweeter with the high bias setting on the JC1 should sound absolutely maaaaaaaagic!!!

Hope it’s not the speaker. See if you can try another amp, before pulling the speakers apart.

There is nothing to the xover to really do what your saying, the inductor across the mid/bass unit either works or doesn’t the resistor the same, can’t really go semi faulty, and the cap on the tweeter would knock out the highs if open.
http://www.stereophile.com/images/archivesart/sfefigB.jpg

Cheers George