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Rectilinear III Highboys


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  • 1 month later...

When I refurbished my Mini-IIIs, CSP member RoyC measured the values of the caps. He wrote:

"The large cap [XMC] measures 87 uf and the little one [XTC-M] may actually be 2uf, as they now measure 1.8uf.. It appears that DF is the same as an equivalent modern npe, so it is entirely possible they are still within spec. They appear in good physical condition, as the end seals are very tight with no signs of corrosion or damage. I doubt I would replace these caps unless I loved the speakers and was going to keep them forever, or if they were acting up in a way that pointed to the caps"

Here's the thread:


So it may be that the XMC is supposed to be ~87uF. I can tell you the Minis sounded good (I did replace the 2uF).

OTOH, there may be a schematic somewhere. A contributor to AK wrote "The other cap shows 60 UF which matches all the documentation that I can find." So maybe it's 60uF. My tech tells me electrolytic caps have a tolerance of -20%/+80%, so 60 to 87uF does not seem out of line.

But in this thread


the writer says he measured the XMC at 91 and 104. There is some technical discussion with arguments in favor of using a 100uF value.

Damn Rectilinear! Nice speakers, but why the secret cap values?? :angry:

Also found this: "Both speakers should have two caps: one is 2uF; the other is either 60uF or 100uF. The 60uF would be marked as such, the 100uF would probably be marked "xmc.""

That seems to be supported by this lengthy thread:


there's a photo of the xo, with one cap clearly marked "60". Read the whole thread though, apparently there were changes in drivers and cap values. There was a 100uF xo version and a 60uF version. You should be able to compare the appearance of your woofer and the xo to the ones over on AK and figure it out. I'm guessing you have the 100uF version (since the 60uF caps were apparently labeled).

I dunno if that helps. Maybe one of the Rectilinear fans here will have better info. You "could" use 60uF in one, use 60 + 40 paralleled in the other and compare how they sound. Madisound has Bennic NPEs in 100uF or experiment with 50, 10 & 40. For the 10uF vaue, you could use a 12uF NPE (close enough) or a 10uF Polypropylene "surplus" Cap (just 60 cents each). I'm betting on the 100uF value.

Good luck!


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  • 4 weeks later...

Hey, I just managed to find a pair of Highboys myself, one with tweeter and mid L-pads. I'm also considering recapping. What I've gathered from all the forums is a semi-agreement between 2 and 60 µF caps or 2 and 100 µF caps.

What I'm more concerned with though is that everyone has lined up behind the 2 µF capacitor. According to all of my calculators, 2 µF is a 10,000 Hz crossover, not 3000 as the literature states. Is this not a big discrepancy? ERSE's crossover calculator states that a 3000 Hz first order requires a 6.6 µF cap.

What are your guy's inputs on that?

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  • 2 weeks later...

I'm going to replace the capacitors in my Rectlinear III Highboys -- does anyone know the value of the capacitors? The only thing marked on the original capacitors is "XMC". They have a black plastic cover, and are 1" long and 5/8" diameter. Thanks.

The tweeter capacitors look to be 2 mfd.


There are several different pdf files in this link which give different versions of the crossover network. Good luck.

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