Saving old vintage gear is a lot harder than people make it out to be.


I’ve been trying to save my Eosone rsf-600 speakers for a few months now. I noticed the highs were muffled & discovered that two electrolytic capacitors (16uf & 100uf) are used as some sort of shunt in the crossover design. I saw a Paul Mcgowan video (one of the dudes who designed the Eosones) where he makes a reasonable claim that electrolytics should be replaced by polypropylene due to the aging factor. That fixed a few problems; although, something seems off about the sound. Replacing old electrolytic capacitors is not as simple as putting in new polypropylene capacitors; there must have been some fine tuning with the orignal electrolytics in mind. The brand is made by tecate industries. Both are 50v 10± tolerance and they are both relatively small radial leads. There’s no point in buying an expensive tool to measure esr since the orignal caps must have changed in value. Are my Eosones screwed? Chat gpt has said to add resistors to poly caps but isn’t esr different for higher frequencies in electrolytics?

jmncbh

@jmncbh 

It is possible that something else is off in the crossovers or with the drivers themselves and replacing the caps is bringing the problem back into the spotlight.  Or possibly you got used to the way they were sounding and now the "repaired" sound is just different? 

Since these are bi-polar speakers, is it possible that the rear facing drivers were not working properly, and now they are?  If would definitely cause a change in the sound.  (Also keeping in mind that bi-polars need a lot of care and experimentation to get setup properly.)

So, are they screwed... probably not.  Are they worth working on and fixing?  I would say yes as long as the $$ are not too high.  Would I go changing the crossover design by adding additional resistors to the crossover, NO.  You could mess things up, and ChatGPT is not an Audio or Electrical Engineer.

And you can always send Paul McGowan an email at PS Audio, or post something in PS Audio's forum on there web site for his help.  He is usually willing to lend a hand when he can.

...just my 2 cents...

-Jeff

Thank you for the reply. What others could learn from me is that if you have speakers you love and they have electrolytic capacitors in the crossover: find a way to get proper measurements to find a suitable replacement. If you’re too late like me, then your speakers are never going to sound the same once the electrolytics start to age. Unless, the entire crossover is rebuilt. It’s the sad truth.

@jmncbh 

I wouldn't say that you need to get proper measurements to find a replacement.  I would think the point of replacing the parts is to try and fix the speakers, making them sound as close to orginal as possible? 

And I wouldn't say your are too late in process....In your case, assuming that everything else in the speaker (drivers and crossovers) is ok, changing to polypropylene caps is going to change the sound.  So maybe the thing to do is replace them with electrolytic caps of the same values.  Yes, different manufacturers of caps will still have an effect on the sound, but I would think not as much as a change in cap type.

I have repaired or rebuilt several sets of speakers in my past.  From old Polk Audio Monitors (10's and 5b's), to 2 sets of Definitive Tech 10's, a set of 8's and am now fixing blown tweeters on a set of 6's, replaced panels on Martin Logan electrostatics, repaired the crossovers on Magnepan MG12s, and two different sub-woofers.  Most of the time there was a change to the sound I had gotten used to, because there was something wrong with the speaker.  Thus the reason to repair/rebuild them.   (Except for the MG-12's, which I accidently sat on the remote and turned the volume to max and destroyed the crossover.  It was ugly..sparks and smoke....crying )

So don't loose heart.  Give the repairs a chance.  You may find that once you get used to the "fixed" sound, you might like it even more.

- Jeff

 

Thanks for the encouragement! I replaced electrolytic capacitors on my polk rt55's and loved the sound. I'm sure I'll be able to figure something out with the Eosones. I'm going to buy a number of electrolytic capacitors to find the best replacement for my tricky dipole speakers. 

@jmncbh 

The key is to take your time and be methodical about the process.  Don't make to many changes at once, don't get radical with anything (yet) and don't make any assumptions...test everything.  (Not getting any sound out of a speaker... make sure the cables are connected... and the amp is acutally plugged in... surprise oops...LOL)

And to the whole group... If anyone happens to have a schematic for the crossovers or know where he can get a copy, it would help.  I believe that Sandy Gross, who founded Definitive Technologies, was still at Polk at this point and may have been involved in the design of these dipoles.  If so, the rear drivers maybe crossed over at different points than the front drivers.  (As he did with some of the early models from Definitive.)

I replaced the new polypropylene capacitors with electrolytics that mimicked the old ones & the speakers sound amazing!