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Old 6th October 2008, 07:58 PM   #1
PKNJ is offline PKNJ  United States
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Default Crossover Cap Help

I've had a pair of kef 104aB speakers since 1980. After many years away, I needed to restore them. I replaced one open circuit T27 Tweeter, but there are still sound quality issues. I've been told to replace all the caps in the crossover, which I'd be happy to do.

My problem is deciding which type. I've got a schematic, and know the values. But even PartsExpress offers a bewildering array of types. Given a limited budget, what are good, but affordable, caps in the following values?

0.6 uF
3.3 uF
5.0 uF
10 uF

Thanks for any advice, I'll be having many more questions!
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Old 6th October 2008, 08:28 PM   #2
DcibeL is offline DcibeL  Canada
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Cheap MKP (metallized polypropylene) type such as Bennic or Solen Fast Cap (Dayton brand if ordering from PE) will offer the best bang for your buck.

If the current crossover uses standard bipolar electrolytics, you'll find that the MKP caps will be significantly larger, in which case you can have the leads hanging off-board, and fasten them down to something with epoxy, to prevent vibrations in the speaker from breaking the solder joints.
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Old 7th October 2008, 01:37 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Click the image to open in full size.

TBH using bipolar electrolytics will be more accurate to the original,
save you considerable mounting problems and end up a lot cheaper.

/sreten.
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Old 7th October 2008, 04:28 PM   #4
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For around the same price I have found that Jantzen Cross Caps sound better than Daytons or Solens. Did an A/B comparison with a couple of different speakers just to be sure.
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Old 7th October 2008, 05:56 PM   #5
PKNJ is offline PKNJ  United States
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Thanks to all. As a noob, it's nice to get a reality check.

Sreten: That crossover looks familiar! I appreciate the advice on Non Polar Electrolytics. I thought they all were polar, and was confused at the two "+" signs.

This does sound like an opportunity to see if i can hear the differences between cap types. Should be a fun experiment.

Thanks to all.
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Old 7th October 2008, 06:25 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

You will be able to hear the differences between the capacitor types.

See the comments on mods here :

http://www.mhennessy3.f9.co.uk/rogers/ls7.htm

Better is not always "best" in a well balanced design.

Note that electrolytics do degrade over time, around 15/20 years or
so apparently before you need to worry about it, and that replacing
the electrolytics with like for like will also likely make a difference.

If you do put larger capacitors on the board make sure it will still
go back through the back panel hole. It looks quite tight to me.

/sreten.

P.S. all electrolytics are polar. Non-polar electrolytics are basically
two polar capacitors in series with reversed polarity, = the 2 +'s.
(And the double indents on the LS7 caps + Dayton np elcaps.)
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