SL3 Xover capacitors - worth changing?

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JohnA

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Hi guys,

I've been investigating if it is worth changing any of the capacitors in my 20-year old SL3s.

Xovers are of the late type:

SL3 Xover.jpg

I don't want to be changing things that don't need changing, but I want to be sure that I'm not losing high frequency performance because of ageing electrolytic caps

After studying a diagram kindly provided by another member here, I am focusing on these three fellows:

3 caps.jpg


I understand that the lower one (small black 330uF 100v) is the woofer low pass, the one above it (30uF 250v) is polyprop for panel high pass, same as the larger white thingie (Wesco).
I'm not sure about this one, according to the diagram it is a 33uF 100v polyester cap, yet it doesn't show any capacitance figures on the label (says 33mm 5% 30 -200)

My question is:
Do any of these elements warrant pre-emptive replacement, or are they best left alone?
The two top ones don't even look like electrolytic caps, so do they really degrade normally as to be worth sourcing replacements?

Cheers,

John
 
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Spike

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My ReQuests are 25 years old, and I was contemplating this same question recently as I was about to open up my speakers in order to replace the panels. A few of my trusted HW engineering friends stated the same opinion:
"As these XO caps run at no voltage and no heat, there would be no deterioration in the electrolytics, and the polypropylene versions never deteriorate. If you trusted Martin Logan enough to buy their speakers, I wouldn't selectively mistrust Martin Logan on their choices of caps. No need to pre-emptively replace the caps. Capacitors don’t just ‘break’ because they are 25 years old and neither do resistors."

During the process to purchase the replacement panels, I asked ML about the caps and here's Brian's reply:
"We only really recommend replacing when something does not work. We can sell new power supplies if they are needed.
However, if your electronics/power supplies are still working fine, then they should not need to be replaced."


I replaced my panels a couple of days ago, and left the caps alone.
 

JohnA

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True, what voltages and heat are these exposed to.
They are not power supply caps from a power amp.

I.e. if it ain't broken, don't fix it eh

Thanks for the sanity check!
 

Lightloopy

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If those are 20 yo panels, then they need to go. You will be amazed. That is a phenomenal speaker. Get the panels while you can. Not sure what your options are in London though.
 

JohnA

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I have washed the panels once (with soft water) and I hoover them every now and then.

I can use REW, can I tell easily if the panels are underperforming?
 

Robert D

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I have washed the panels once (with soft water) and I hoover them every now and then.

I can use REW, can I tell easily if the panels are underperforming?
The big thing that tipped me off was how high the gain had to be on my Marantz. Audyssey had to set it up near the max of around + 13. Now with the new panels, it is set at - 1.5.

So loss in volume is huge.
 

Zwick

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Martin Logan gave me new panels on my Quests within the first year of ownership because I heard a noise that I now believe could have been remedied by vacuuming the panel. Glad I kept the original matched set of panels.
 

Mirolab

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I'm facing a similar situation.... I am currently awaiting new panels for my SL3's, and once i have them apart, I will likely replace that 330uF electrolytic cap. At 20 years old, it has likely drifted from its intended value. As for the others, I'll wait for the new panels to break-in, and maybe replace the one feeding the panel with a modern, high end cap. But I know just because it's more expensive doesn't mean it'll sound better in a given system. I've upgraded caps before, only to put the originals back in because they simply sounded right.
 

JohnA

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The big thing that tipped me off was how high the gain had to be on my Marantz. Audyssey had to set it up near the max of around + 13. Now with the new panels, it is set at - 1.5.

So loss in volume is huge.
Is that 14.5db difference?o_O
 

Robert D

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Is that 14.5db difference?o_O
Yes. I was really pushing the Aragon amp hard. I thought maybe that was normal since everyone always says how hard electrostats are to drive. The Prodigy speakers were my first. I should have replaced the panels immediately. They still sounded good with the DSP on.

The Aragon is still going strong now.
 
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