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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
 
(mine came from Stereophile, your doesn’t say, except diy)

Which ever xover it has, the OP has to say to us.
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
Only then can this problem be sorted before dismantling the speaker.


https://www.hifisentralen.no/forumet/attachments/diy-og-utvikling-ha-yttalere-forsterkere-etc/228418...
If it does have this xover then the mid/bass unit should be what the voice coil is of that driver my guess around 4ohms).
And the tweeter should be around 7.5ohms (because of the 2 x paralleled 15ohm series resistors and the almost short of the inductor)
Cheers George
imhififan's avatar
imhififan
2,205 posts
 
George,

From the Stereophile review:

A first-order crossover can be achieved, not with a series capacitor but with a single inductor, this connected in parallel with the tweeter. The parallel inductor connection terminates the high-frequency driver well, helping to control its natural fundamental resonance. For the inductor to give a defined filter characteristic, however, there must be a series impedance; in the case of the Extrema, a resistor (fig.B). This resistor/inductor combination appears wired across the speaker input terminals; it will dissipate power over the speaker’s entire frequency range, mainly according to the resistor value.

image: https://www.stereophile.com/images/archivesart/sfefigB.jpg

Fig.B Conventional first-order high-pass crossover filter (top) vs "Sine-Cap" filter (bottom).

In the case of the Extrema, the series resistor for the treble section is typically 20 ohms. This provides the required source impedance for the crossover inductor, and also correctly attenuates the treble unit by the required 4dB or so. Yet with the Extrema’s nominal 8 ohm drivers, the total system impedance does not fall below a 4 ohm minimum—it is nominally a 5 ohm-rated design.


Read more at https://www.stereophile.com/standloudspeakers/915/index.html#C1tSeYjx17owvP01.99
Maybe OP should disconnect the jumper and test the treble section and mid/woofer section separately.
georgehifi's avatar
georgehifi
10,312 posts
 
Maybe OP should disconnect the jumper and test the treble section and mid/woofer section separately


Agreed but first maybe the op wcheng2 OP should let us know,
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
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