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Kef 105/4 crossover recap

 
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Rosco
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Joined: 11 Jul 2018
Posts: 2

PostPosted: Sat Jul 14, 2018 2:33 pm    Post subject: Kef 105/4 crossover recap Reply with quote

Hi Guys Newbie here with a question about capacitor values. My crossover is a sp1129 with alcap capacitors but when I contacted Falcon Acoustics they were out of stock on some values. I requested a quote from Solen and they sent me the replacement list with slightly different mfd values. my understanding is the voltage values don't really matter as long as they are greater than the expected voltage.
My question is how will the slightly different values affect the overall sound and imaging?
Thank if you can help Ross
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speakerguru
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Joined: 18 Nov 2005
Posts: 1011
Location: Green Hut, Tovil

PostPosted: Tue Jul 17, 2018 12:28 pm    Post subject: Reply with quote

KEF (Electronics Ltd.) crossover components in the 70-90s era were sorted and matched in +/-1% bands. If you want to retain the design intent balance and integration of the originals, you will have to do the same.

You can use multiple capacitors in parallel to get to within 1% of the required value, assuming you knew the original values (which are not necessarily what is written on the case).

A very rough rule of thumb is that a 10% deviation in component value will give a 1dB difference in s.p.l. in the band over which it has any influence.
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Rosco
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Joined: 11 Jul 2018
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PostPosted: Fri Jul 20, 2018 4:03 pm    Post subject: Reply with quote

Hi Thanks for your reply! One other question that I have is some of the Caps are marked"LL" example.. 3.3mfd 50v LL. What is LL and does it make a difference? Again thanks for for your help!
Ross
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audiolabtower
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Joined: 06 Jan 2009
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PostPosted: Fri Jul 20, 2018 6:51 pm    Post subject: Reply with quote

Low Loss electrolytics are used in places where high internal resistance may be troublesome. Very generally speaking used for high crossovers around 3kHz where the ear is very sensitive or series caps to the mid unit.
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speakerguru
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Joined: 18 Nov 2005
Posts: 1011
Location: Green Hut, Tovil

PostPosted: Sun Jul 22, 2018 10:02 pm    Post subject: Reply with quote

LL stands for low loss. Electrolytic capacitors have internal losses which take the form of a series resistor in the equivalent circuit of the capacitor. This equivalent series resistance (e.s.r.) may be spec'ed. Alternatively the capacitor dissipation factor, D, may be given instead. The two are related by a simple formula. See https://www.illinoiscapacitor.com/pdf/Papers/impendance_dissipation_factor_ESR.pdf for example
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