Thoughts on replacing caps in 30 year old speakers

Why not.  Projects are fun and you derive satisfaction from hearing the distinct improvement.  Would not go nuts with Mundorf and Jorma internal wiring, but within reason it's a good idea.

Sure, there's always room for improvement in any commercial design, but keep the old parts in case you don't like the sound.  It will sound different, not necessarily better.

I think you'll be surprised and very pleased.  However, Theil made some bitchin' difficult and complex cross-overs, so good quality stuff will be
expensive just due to the parts count since a single good big cap can run $80 or more, so...

Around 40 caps per speaker . Solen . Could just redo with solen . Biggest cap priced out around $10 . Have zero experience with speaker building , can the solens be easily improved upon ? With the costs being reasonable ?

From my reading it is the electrolytic caps which deteriorate with time and change value.  If your crossover contains any of those they will be the candidates for replacement.

"Upgrading" any other caps will more likely be a matter of taste.  As rcprince suggested, it may not necessarily be better than what the speaker designer chose.

I like the idea of replacing with new version of same caps - remember too that you are used to the sound with the old caps and have sort of adjusted your listening to them...

There is a capacitor review on humblehomadehifi.com that you may find interesting.  He tested a bunch of them and wrote his impression.  I thought about replacing the capacitors in my Infinity Renaissance 90 speakers a few years back but never seemed to have the ambition or time.  Evidently Infinity tested each capacitor installed and if it wasn't up to spec they would add, delete or change until it read proper.  Two of the same crossovers may have different capacitors in them.  I figured there was more of a chance of me messing it up that fixing anything.
Good luck , John

there is a lengthy and interesting discussion of this by Alan Shaw on the Harbeth users group web page

Shaw is the owner/designer of Harbeth 

That harbeth forum is one i had read . what was the final thought on the polyropylene caps lifetime ?

it's a long, complicated response.  Harbeth's do not need new caps, other speakers might...I think that was his conclusion

you need to know a lot about your speakers caps...

Stolen makes four basic grades of cap, in ascending order: metallized polypropylene (black), tin foil and polypropylene film (white), metallized teflon (blue), and tin foil and teflon film (green). They sound very different.

Metallized poly is the least expensive of the audiophile grades. It sounds relatively smeared. Tin film and foil is a big improvement in clarity, but this may not suit your system as a whole. I find that teflon adds a slight edge, which may make your system unlistenably sharp, or much more life-like, or something in between. As ever, YMMD.

In critical applications I divide the critical value into 3: 1/3 Solen teflon f&f, 2/3 styrene. This gives me a slight edge from the teflon, and a slight rounding from the styrene, for a pleasingly neutral sound. Unfortunately Solen does not sell styrene.

Not only would I do it, I have done it. As you can infer.

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

I recap'd my 30 year old Magnat ribbon 5's with mundorf caps and while the tone stayed pretty true, the improvements across the board were very noticeable.

Well worth it

If it ain't broke, don't fix it!

I recently recapped a pair of Thiels along with an internal wire change..I say absolutely do it..I havent met a speaker yet that didnt improve on a recap !