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AR18 cap value


Guest stackowax

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Guest stackowax

Does anybody know what the correct capacitor value is for AR18 (serial numbers 15889/90). The value printed on the current caps is 6uf. But they measure around 10.7uf. The owner's manual for the ADD series on this website puts the crossover frequency for AR18 at 2000 hz. Assuming an 8 ohm impedance for the driver, a 2000 hz xover point would require a capacitor of around 10uf, at least according to the calculator provided on this page: http://www.bcae1.com/passxovr.htm.

I am not sure if the tweeter is an 8 ohm driver. And I know nothing about xover design, but I'm guessing it is more complicated then plugging a few values into a calculator. In any event, can anybody say for sure what the correct capacitor value should be?

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HI

I'm no expert on this but I believe cap values increase as the cap goes bad. I think your best bet is to go with the value printed on the cap. Maybe someone who is an expert will chime in.

Use film caps. Carlis are a good value:

http://www.madisound.com/catalog/product_i...products_id=166

Many people like Solen

http://www.madisound.com/catalog/product_i...products_id=756

or Dayton

http://www.parts-express.com/pe/pshowdetl....tNumber=027-427

Or you can go hog-wild:

http://www.parts-express.com/pe/showdetl.c...tnumber=027-732

or totally insane:

http://www.madisound.com/catalog/product_i...roducts_id=8374

:)

good luck

Kent

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Does anybody know what the correct capacitor value is for AR18 (serial numbers 15889/90). The value printed on the current caps is 6uf.

The AR-18 used a 6-uF cap, the AR-18b, 5-uF and the AR-18bx, 4 uF. If yours is an 18 then it looks like you have a Callins NPE wih black PVC casing and red PVC (hot poured) end filler plugs. The end caps did not make a good hermetic seal because insertion of the capacitor body left electrolyte residue on the inside of the PVC tube. The increased value of the bad capacitor will allow added energy in the band below the desired crossover to pass and potentially damage tweeter at high volumes.

Scrap all caps of that style - dont waste time making measurements; they have all gone bad by now. A new NPE will last quite some years; a new polyproplyene or Mylar will outlast your grandchildren.

cheers

John

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Guest stackowax
If yours is an 18 then it looks like you have a Callins NPE wih black PVC casing and red PVC (hot poured) end filler plugs. The end caps did not make a good hermetic seal because insertion of the capacitor body left electrolyte residue on the inside of the PVC tube. The increased value of the bad capacitor will allow added energy in the band below the desired crossover to pass and potentially damage tweeter at high volumes.

Thanks John. You have described the caps perfectly--as can be seen here:

post-102878-1229843848.jpg

And here's an image showing the value (6 uf) written on the cap itself:

post-102878-1229844038.jpg

I guess it is unlikely that replacement tweeters for the 18s would still be available?

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Thanks John. You have described the caps perfectly--as can be seen here:

I guess it is unlikely that replacement tweeters for the 18s would still be available?

1068, the number imprinted on your capacitor, is the EIA (Electronics Industry Association) manufacturer's number for Callins.

AR-18 tweets do come up on Ebay from time to time. The original AR-18 and the AR-18-s used AR tweeter # 200014-3, the AR-18-b used AR tweeter #200034-0. Others who know this speaker say the tweeter used in the AR-18-b was essentially identical to the 200014-3. If purchasing, have the seller show you an image of the driver's backside with part number. Do not purchase a tweeter from the AR-18-bx or -bxi series; they were a totally different animal using low quality tweeters that were not manfuactured by AR. As well, their crossover frequency was increased from 2000 to 3200 Hz.

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