First; Thanks for this thread.
It can serve as a good handrule guide for capactor upgrades to B&O speakers in general - and of course there's
a reason for me saying this;

People who know me will also know, that I have the greatest respect for owners wanting to do their
best for their vintage B&O.
They will also know that I have a deep respect for people who want to do things themselves.
DIY'ers are slowly becoming extinct, I feel.

So rest assured that this post was made with the best of intentions;

During many years, I've been recap'ing B&O speakers. Hardly a week between.
Most owners wanted best value for money, others asked for high-end capacitors - even in Beovox 2702s... - and I duly obliged.
This provided me with a good chance to try out and evaluate different solutions in countless Beovox speaker models
but let's take the Beovox Penta as an example. It's a fairly high spec speaker, one where any differences and/or
upgrades would be clearly audible;
Most Penta owners wanted a simple upgrade; Replace old electrolytic capacitors with fresh electrolytics.
A few wanted an upgrade to foil capacitors - some of which quite expensive.
Based on experience with at least 20 pairs of Pentas, I must admit coming to the conclusion that I cannot tell
the difference from electrolytics to foil caps and neither can I measure any difference, even using the
best instrumentation available to me.
Foil caps don't dry out - that's true. Foil caps should in theory last forever where the old electrolytics seems
to have a lifespan of apprx 20-25 years and modern electrolytics possibly just a little more.
But to me this doesn't make it up for the much higher cost of the foil caps and the problems of fitting
them neatly to the filter boards.

As can be seen in your photo, the foil caps are typically much larger and bulkier than the electrolytics and fitting them
to the filter boards can be a problem. It typically ends up with these, fairly heavy, components hanging by their leads,
vibrating and more or less rattling along with the music, eventually breaking their solder joints and/or leads.
I've seen it many times and it's a shame, really.

Some so-called "audiophiles" seem to care very little for things like this, feeling comfort in merely knowing that the
capacitors fitted have the right golden markings and did cost a fortune.

I've seen filter boards filled with screw-mount fittings that, paired with the unavoidable vibrations, provide a huge
potential for bad connections and contacts, let alone the rattling these plastic things on cables provided themselves.

It's my general experience that no passive B&O speakers will benefit from using foil caps, at least for the
coming 25 years. - And in 25 years from now new caps or filtering methods will have been developed, I'm sure.
99,9% of the lift in sound quality comes from replacing the old electrolytic caps with new of the same type.
That's merely a matter of bringing back the original specs.
Anything above this is pure theory. That's not just my opinion but also my experience (repairing and restoring
B&O audio units since 1976).
Returning to the Penta example; For DIY'ers I once provided - per countless requests - both a standard electrolytic kit
and a somewhat more expensive foil kit.
A few owners first had the standard kit fitted and later decided to "upgrade" to foil but none of them could tell
the difference, even in a direct neck-to-neck test and I must admit; Neither could I.
For the same reason, the foil kit is no longer provided. It simply doesn't give value and/or meaning.
From reading your thread, I understand that you've come to the same conclusion.

Anyway, I take it that you will find ways to securely fix those large components sitting outside the board ? You should!
And those blue "chinese" plastic lead-twists are merely temporary connections, right? - Because they are bad! Bad! BAD!
 - particularly in vibrating environments like speakers and cars.

Last; For the odd surfer it's worth noting that the Beovox S60 came in different versions with slightly different filterboard
components.
If you are going to recap your Beovox S60s I suggest you check against your actual filterboards before ordering caps.
The list provided above is correct only for one version.

Martin

Even worse, I did some recaps on several Penta's and RL140's. From each pair, I recapped one and left the other with its original caps. To be honest, I could not hear any difference. I would have liked too but that's only in my imagination.

Thanks for your insight!  I soldered the wire junctions and then covered them with the plastic twist leads, mainly because it seemed cleaner than tape.  So the connections should be good, but I could see them rattling around if I didn't nest them well.  And yes, the size of the caps was quite a challenge.  Luckily, they fit next to the board and could be hot glued directly to the cabinet.  Now, the crossover would be quite a pain to remove, but I expect/hope that it will outlive the speaker itself.  Agreeing with you, since they sound the same to me, I would have just used new electrolytics to give the speakers another 25 years of life.  It would have been cheaper, easier, and probably outlasted my interest in the speakers.

Leslie, I must admit to have had the same experience a few times but in the far majority of cases even I
could tell a definite difference.
I have a feeling that the deterioration to the caps could depend on the conditions under which the
speakers lived, temperature, use etc. so some will be "farther gone" than others.

Anyway, I feel lucky to still be able to hear frequencies above 16KHz and able to tell a distortion of less than 1%.

Martin

As said, I did a few and was quite dissapointed about the result. Maybe I was "lucky" that the old caps were still in a good condition but was expecting a major difference.

I was hoping that the re-cap would make the bass fuller.  I still feel like they are lacking bass considering the size of the woofer, and might try putting another resistor in parallel with the left-most resistor in the first picture.  However that's just a total guess at where I might start tinkering.   If anybody who knows what they are doing has any suggestions, it would be much appreciated.  I'm not going to go too nuts about it because I'm just going to use them as secondary speakers or home theater rears.  Thanks!

Not unlike the Beovox S75, I feel the Beovox S60 is more of a "classical music" speaker, not particularly bass-rich.
If you are looking for a little more oomph and want to stay within the same range, I think you should be looking
for a pair of the M-speakers (M for Monitor).
Beovox M70, M75 or maybe even M100 have a little more "roughness" to them and it's my experience that they
are more suitable for "popmusic taste"-owners and especially the M100 for rock and disco.

It's rare to see a recap doing much to the bass-response, anyways.
It's typically the highs and mids that are affected by aging caps.

Martin

I notice a major difference to midrange vocal definiton after recapping my s75. My pair was victim of faulty assembly at B&O with a resistor placed on the square poly cap causing it to be partially melted quite badly. 

I used martins kit for the recap and they were dramatically better. I have noticed the S75 have very tight bass, but when they need to kick it out they can :)

i put expensive poly caps in my s45.2 and couldn't tell much of a difference between them and another pair with standard electro caps.

drew

Interesting. Of course I don't have Martin's experience, but have built and repaired speakers for 30 years (although I've been into B&O for only 5 years)...

Anyway, a cap change on my recently acquired M70s (with trumpet stands) have shown no difference in sound quality. If anything, I tried tin foil caps (a prestigious, costly French manufacture) on tweeters and found treble to be slightly recessed! 

The original 8 µF caps were in perfect order anyway!

I was wondering whether foil caps generally have higher ESR than electrolytics. 😕

Those expensive caps are just not worth the outlay investment in my view.

Dillen wrote:

Beovox M70 (...) have a little more "roughness" to them and it's my experience that they
are more suitable for "pop music taste"-

Martin, I find that M70s have less "roughness" than, for instance, MC120-2s. I've found my ideal B&O speakers I think.