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Do electrolytics values stay constant ?
Do electrolytics values stay constant ?
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Old 20th September 2019, 07:25 PM   #21
Galu is offline Galu  Scotland
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Quote:
Originally Posted by Xoc1 View Post
I found that some of the old Elcap electrolytic capacitors in the KEF held their values but had quite a high ESR value, while others were massively dried out and not doing much at all.
Hi!

Yes, those nasty Elcaps should always be replaced as a matter of course, as they do not age well!
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Old 20th September 2019, 07:56 PM   #22
Galu is offline Galu  Scotland
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The electrolytics on your crossover board certainly look in good physical condition!

Alcaps are good quality NP electrolytics and should have a long operating life.

The non-polar electrolytic capacitors in a loudspeaker crossover do not become as hot as polar electrolytics might do in an amplifier. Consequently, the damp electrolyte does not dry up as fast, which helps ensure a long working life.

If the wire lead outs still remain perfectly sealed then the Alcaps are likely to be well within spec.
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Old 21st September 2019, 07:33 AM   #23
lolilol1975 is offline lolilol1975
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Ah, that should sound like good news but to my ears it sounds like bad news, as that means it's likely there may be not much improvement.
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Old 21st September 2019, 09:04 AM   #24
waxx is online now waxx  Belgium
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in my experience (and i did rebuild quiet a few crossovers), you stay with the original plan (replace elco's with elco's of the same values, including the ESR) or you redesign the crossover with new parts from start on measuring the speakers and often following the same effect (order and slope) of the originals. What you do depends on the situation. But just replace an elco with an film cap or so is asking for problems.

In this case i would order the replacement kit (wich is a good one) and keep it original. But when i redid the crossover of my Goodman Mezzo SL set, i started from scratch, also because in one speaker the inductor was damaged and not useable anymore and i did not have the schematic.
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Old 21st September 2019, 10:50 AM   #25
lolilol1975 is offline lolilol1975
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Quote:
Originally Posted by Galu View Post
The electrolytics on your crossover board certainly look in good physical condition!

Alcaps are good quality NP electrolytics and should have a long operating life.

The non-polar electrolytic capacitors in a loudspeaker crossover do not become as hot as polar electrolytics might do in an amplifier. Consequently, the damp electrolyte does not dry up as fast, which helps ensure a long working life.

If the wire lead outs still remain perfectly sealed then the Alcaps are likely to be well within spec.
I sent the photo to the guy at Falcon Acoustics and he told me that the KEF caps were made in the 1980s so for him these are original caps. So there is that.
I'm still waiting for the little gadget that measures ESR and my set of replacement caps, and I guess I'll start to do some soldering work.

Also, I have to say that I've replaced a pair of dodgy interconnects between preamp and amp and the sound has improved a LOT !

Last edited by lolilol1975; 21st September 2019 at 10:52 AM.
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Old 21st September 2019, 02:52 PM   #26
Galu is offline Galu  Scotland
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Originally Posted by lolilol1975 View Post
Also, I have to say that I've replaced a pair of dodgy interconnects between preamp and amp and the sound has improved a LOT !
That's very open of you to say so. Always a good idea to check the connections before suspecting the equipment!

Your speakers are bound to sound even better after you have fondly fettled them.

At the very least, by recapping your vintage speakers, you will have staked a claim in their ownership and can be sure that they are giving of their best.
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Old 25th September 2019, 01:31 PM   #27
Mark Tillotson is offline Mark Tillotson
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Select-on-test for electrolytics is bogus, they are fundamentally imprecise components
and drift loads.
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Old 25th September 2019, 02:47 PM   #28
Galu is offline Galu  Scotland
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Quote:
Originally Posted by Mark Tillotson View Post
Select-on-test for electrolytics is bogus, they are fundamentally imprecise components and drift loads.
Mark is absolutely correct and it may be worthwhile, in the context of this thread, to elaborate on his statement.

Despite all their advantages, wet electrolyte capacitors are subject to slow deterioration caused by gradual evaporation of the electrolyte inside.

Their ESR increases over time and their capacitance decreases.

Film capacitors do not suffer from these ageing problems and, if I were designing a loudspeaker crossover network from scratch, my choice would certainly be to use more reliable film capacitors wherever possible.
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Old 26th September 2019, 12:13 AM   #29
trobbins is offline trobbins  Australia
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Is there an elephant still in the room - the drivers themselves!
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Old 26th September 2019, 12:22 AM   #30
Galu is offline Galu  Scotland
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Falcon Acoustics is knowledgeable about the KEF drivers and has chosen the components in the replacement capacitor kit to match the original capacitors as closely as is possible.
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