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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
georgehifi's avatar
georgehifi
10,312 posts
 
I agree with the crossover problem. There is a power resistor in series with the tweeter. If it is failing, the resistance rises with temperature and the signal voltage is converted to heat instead of music.
It wouldn’t cause this explanation, just muted high frequencies, he would still have all the bass and midrange.
" will exhibit significantly lower volume (down to almost no volume)"

Try another amp first, as these Extremas are put together like a Swiss watch, it would be a shame to break/damage all the seals to find out they’re fine.

Cheers George
gs5556
1,213 posts
 
I hear you, George, but it happens with two amps. I guess the way to be certain is to repeat the failure mode, turn off both amps and immediately measure the resistance across both speaker's terminals and compare. If one is way higher than the other then it's the resistor. If both are the same it's something else. (The only other thing to check is to swap cables at the speaker terminals instead of the amps to rule out a flaky cable connection).
wcheng2 OP
39 posts
 
How would I measure resistance across the speaker terminals?
georgehifi's avatar
georgehifi
10,312 posts
 
Yes you got two sets, one for the bass and one for the tweeter.
The tweeter pair should measure open circuit because of the cap in series .
The bass will measure what ever the resistor is in series, (does anyone know what that is?) . https://ibb.co/BNtQdtJ



One of the speakers periodically will exhibit significantly lower volume (down to almost no volume) in the middle of a listening session.
BTW: you haven’t said what’s actually happening, is there nothing from the tweeter or nothing from the mid-bass or very little from the tweeter or very little from the mid-bass
Cheers George
mijostyn's avatar
mijostyn
8,223 posts
 
wcheng2, You need a volt /ohm meter. You can get one cheap.
  https://www.amazon.com/AstroAI-Digital-Multimeter-Voltage-Tester/dp/B01ISAMUA6/ref=sr_1_4?crid=25A5L2Z8KUDEW&keywords=volt+ohm+meter&qid=1571097024&sprefix=volt+o%2Caps%2C160&sr=8-4
There is a short in that speaker. Again, if they are still under warranty let the dealer deal with it. If not you are on your own. You have the good speaker for comparison. Good luck,

Mike
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