Additional test tonight and might be one of the CX100 which might have some issues but waiting for additional pair of CX100; so let's see if the treble issue disappears. And doubled up on the Cona speakers as well; so going try out one Cona per channel 🙂

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Lawrence, checked and both of the CX100 has the foam rings around the tweeters. But, I did also get hold of an additional pair of CX100 were the treble was balanced so guess that the crossover filter is due for overhaul which would would involve replacing the poly-capacitor in the speakers which is easy enough. Currently now just reading up (Audio Circle: link) if there are any potential other improvements which can be done for the CX100 speakers itself but now now I'm sticking to new caps poly-caps (another rabbit hole one can dive into: ) but a lot can be said whether one should jump in or not here is another thread, diyAudio:

Those links are a laugh. 
They discuss Beovox CX100 - right?
They seriously discuss replacing 20cm leads with super high-grade antimagnetic copper, that has been left out on the moonlight for at
least five consecutive hours every night for a week a secret place in northern Equador in order to be completely neutralized and spook-free.
It must only be bent in right-going curves as seen in the direction of the current they carry.
Never left.

Seriously - DON'T listen to any of this audiophoolery!
You will never hear any difference - and neither do they, though some may actually believe they do. For some it's placebo and for others merely a matter of sounding smart and clever.
They forgot to add the most important thing, - that glueing a photo of Einstein underneath each speaker makes a huge difference to the experience - relatively speaking of course.

Seriously:
The original internal wiring is adequate for Beovox CX100.
And you should only fit expensive gold-plated caps coming in small boxes lined in black velvet, if you think it will make you sleep better at night.
The speakers won't care one bit and they won't sound any "better", more "dynamic", "open", "linear, "detailed", "sterile" or whatever fine words audiophools like to shed out.
The boxes velvet linings won't add to anything and the gold-plating will be out of view once the cap is fitted.

Replace the capacitor (there is just one in each cabinet) with a fresh electrolytic with specs as near the original as possible (when the original was new, that is). That's what the speakers and filter circuits were constructed for (and film caps were in fact available, when CX100 was produced, so they
were not decided against because of cost savings or unavailability).

For Beovox CX100 any good quality electrolytic with correct capacitance and suitable voltage rating will be fine, really.
For the larger speaker models, parameteres like tolerances, equivalent series resistance etc. - and for things handling power perhaps even dissipation factor, begins to play a role.
Lacking exact matching specs from any of the quality suppliers on the market, I actually had capacitors designed and custom manufactured to match the original specs as close as possible. They are in the Beoparts-shop.
Primarily manufactured for use with the larger and more "serious" speaker models, but why not use them for the smaller bookshelf models, now it's possible.

They come in a plain and very downplayed, yet discrete, zipper bag.
But, sorry, - they are not particularly expensive.  😂

Martin

Hi Martin, I agree with you, and which I wrote rabbit hole since I started of just reading a bit on the topic and the more I read them the more I enjoyed the nonsense argument for using copper/silver wires which has been wrapped with cotton.... And also, Yes the first link did discuss the CX100 but the other didn't but was used as rabbit hole examples. But, clearly shows that there are people taking deep dive into this and this go on and on; let's not get started on speakers cables which mitigates the 'snake skin' effect 😁