Thoughts on replacing caps in 30 year old speakers

To clarify: I have upgraded KEF's, Magnepans and Quad ESL's, not Thiels. But if you like their sound, why not? 

When I upgrade to film and foil, I expect increased clarity and decreased harshness. I have found that polypropylene is rounded, polystyrene is very slightly rounded, teflon is slightly edgy. I would never replace old metallized with new metallized. I get good results with MIT Multicap f&f. YMMD

Speaking about Thiel CS7 I have one set since 1997. I changed twice the fragile tweeters in these last long years. Last month again one of my tweeters started to give some "ssshhhhh" on piano and voice recordings. I contacted Thiel Audio for replacing it but they don't have any spare parts because Scan Speak closed production of this driver.
Someone of you can help me in some way to try to recover my old but wonderful sounding CS7s? Thanks!

Hey @fd60 Take your questions to DIYAudio in the multi-way forum. Take a picture of the driver, if it's marked as a SS driver the part number will be on it, otherwise maybe contact Thiel and ask what they were using.

you'll find lots of speaker builders and repair experts in that forum.

Best,


Erik

My point to asking Thiel is to see if you can find either a used or NOS replacement diaphram or driver. If it's a standard SS part then it would looking for it by the standard part number will give you more options to search for, but if it truly was a Thiel-only part then you're going to have to find a used or NOS replacement for the Thiel.

If I remember correctly,  this speaker uses mostly the higher voltage Solen Polypropylene caps, The 400 to 630v parts are pretty decent. If someone brought these to me to do, I would first recommend changing the series caps in the upper midrange and next the series cap in the tweeter and lastly the series caps in the lower midrange.... If your replacements are good enough,  you'll hear these changes in a positive manor.  I'm really not sure that changing anything else will make a marked difference.  These crossovers have some fairly extensive compensation circuitry,  but I really believe that you'll spend a ton to replace these comp parts with minimal if any improvement. (as long as the compensation parts are polyprop and 250v or higher) 
I hope this helps, Tim