Boston Acoustics A100 cross-over components?

[Sgt. Mortar]

Hi all,
I just acquired a mint pair of series 1 BA A100's that have been refoamed. They're in great shape, but I haven't listened to them yet.
Curious about the cross-overs because I want to at least re-cap them since they're from 1981. I don't care about the coil.

My dilemma is that I'm getting conflicting info on the specs for the two caps. Everyone agrees about the 20uF one, but I keep seeing where the other is a 4.7uF cap.
Mine are 8uF's and 20uF's.
These don't look to be re-capped as they're both the same manufacturer and the glue is untouched. They both sure look original. It does look like a woofer was replaced though, which was with the same BA part but a year earlier than the other.

I can't find find 20uF replacements that are non-polarized\bi-polar. I could probably put two 10uF caps together in parallel to get the 20uF spec, but I'd like to avoid that. I can find the 8's (100V) but if they're supposed to be 4.7's, I'll get those instead. They're on back order at Parts Express for a couple weeks.

Which value is correct? I want good sound that can handle heavy rock (and some Steely Dan) unless the audio response is supposed to be better with 8uF caps?
Thanks!

 

[StimpyWan]

Those Unicon capacitors were very good, made in Japan quality electrolytic caps. An open, airy capacitor, with great dynamics. They were still good in my AR58S speakers, so I'd listen first before replacing. As to the values, I'd replace like-for-like, as many manufacturers back then often had undocumented updates.

Good luck...!

 

[Sgt. Mortar]

Those Unicon capacitors were very good, made in Japan quality electrolytic caps. An open, airy capacitor, with great dynamics. They were still good in my AR58S speakers, so I'd listen first before replacing. As to the values, I'd replace like-for-like, as many manufacturers back then often had undocumented updates.

Good luck...!

Thanks StimpyWan. (Love the Blue Ridge )

That makes sense...maybe these are a unicorn revision. Going to power them up tonight and have a listen.

 

[onanysunday]

Have a listen -anything off this list (closest to 8uF & 20uF) would be a big upgrade and sonic improvement even if the originals were not dried out and still perfectly in-spec some 41 years later mainly due to the difference in electrical characteristics between 'lytics and polypropylene providing a much more accurate, uncolored sound. Specifically, pay attention to bass response with the 'lytics. Over time, it gets loose, boomy and flabby with reduced transient response and the rest of the sound becomes more blended together than it can otherwise sound using better materials that don't "age out" with reduced performance as time goes by. If you don't believe it, try recapping one speaker with MKP, then listen to both speakers at the same time to see which one sounds better.

A100 Crossover Caps

 

[Sgt. Mortar]

Have a listen -anything off this list (closest to 8uF & 20uF) would be a big upgrade and sonic improvement even if the originals were not dried out and still perfectly in-spec some 41 years later mainly due to the difference in electrical characteristics between 'lytics and polypropylene providing a much more accurate, uncolored sound. Specifically, pay attention to bass response with the 'lytics. Over time, it gets loose, boomy and flabby with reduced transient response and the rest of the sound becomes more blended together than it can otherwise sound using better materials that don't "age out" with reduced performance as time goes by. If you don't believe it, try recapping one speaker with MKP, then listen to both speakers at the same time to see which one sounds better.

A100 Crossover Caps

Awesome ... Thank you

 

[onanysunday]

Everyone has a different perspective -that's just mine. I don't like to rain on anyone's parade but don't think an old general-purpose 'lytic has better 'tone' than polypropylene or that it's just a matter of personal preference. I think it goes beyond that. Film sounds better, consistently -especially when dealing with polypropylene, polystyrene, pps and especially teflon. I suppose someone can still say they prefer a 'lytic, -I just personally haven't found that to be the case, unless you're comparing something like an AudioNote Kaisei BP 'lytic or UES Muse BP 'lytic (or similar) to a kemet R82 polyester cap. The best sounding 'lytic can still sound better than the worst sounding film cap (in my opinion). Your mileage may vary. Good luck to you. Just my $0.02.

 

[StimpyWan]

Have a listen -anything off this list (closest to 8uF & 20uF) would be a big upgrade and sonic improvement even if the originals were not dried out and still perfectly in-spec some 41 years later mainly due to the difference in electrical characteristics between 'lytics and polypropylene providing a much more accurate, uncolored sound. Specifically, pay attention to bass response with the 'lytics. Over time, it gets loose, boomy and flabby with reduced transient response and the rest of the sound becomes more blended together than it can otherwise sound using better materials that don't "age out" with reduced performance as time goes by. If you don't believe it, try recapping one speaker with MKP, then listen to both speakers at the same time to see which one sounds better.

A100 Crossover Caps

Nothing wrong with upgrading to film. But, I had to step up to ClarityCap CSA's to improve on the Unicon caps in my AR's. The Unicon's were very decent sounding NPE's, which surprised me. Now, I usually use Mundorf film caps in most of my speaker projects. I like their airy, open tone. They definitely offer a transparency that I don't hear from other brands I've tried.

 

[homebrew]

Also, the resistor should be replaced with this one:

Dayton Audio DPR10-1.5 1.5 Ohm 10 Watt Precision 1% Audio Grade Resistor

Dayton Audio DPR10-1.5 1.5 Ohm 10 Watt Precision 1% Audio Grade ResistorDayton Audio's Precision Series Audio Grade resistors are designed specifically for use in high-end, no compromise crossover networks. The nickel-chromium winding, a high thermal conductivity ceramic core, welded...

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