I bought my M70s new in '76. In the late 80s the tweeters were blown. A reputable shop replaced them with the closest thing available at the time since OEMs were not available. They were also bi-wired and resealed. Although a bit neglected cosmetically, they still sound good and get a lot of use in my #2 system. From my reading here and elsewhere I understand that at 32 years old they probably need to be re-capped and refoamed. For what ever reason, the foam isn't visibly cracked. Do I really need to replace it? So should I be concerned about the substitute tweeters when replacing the caps or just match the original caps? Should I restore the original internal wiring or just externally jumper them for standard wiring as they are now wired? Is there a list of the caps I'll need so I can order them ahead of time?
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M70s Recapping Questions
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Some older B&O speakers suffer from foam rot. Some models had rubber sounds on the woofers in which case it is not an issue, and some of those that have foam surropunds seem to mysteriously escape it when other speakers of the same age suffer.
If the speaker drivers all look and sound good then I would advise leaving well alone.
The recapping refererred to is replacing the electrolytic capacitors in the speaker crossovers which can start to fail after 20-30 years or so. The main noticeable symptom is the speakers sounding a little lifeless and dull. The requirements for this are a PM to Martin (Username Dillen on this forum) to enquire about the availability of a capacitor kit, a soldering iron and some solder. There are a couple of threads here that cover the process in more detail.
Simon
Edit: Just looked at the pictures and it looks like you have rubber surrounds so no re-foaming will be required.
Welcome to Beoworld.
Don't worry about foam rot - these have rubber surrounds so won't be a problem - ever! If you don't know the exact spec's of the thweeters then I would just replace the cap's as per original. I don't know of a list for the cap's but I would personally contact member Dillen (Martin) as he can supply you a full set for a very reasonable price.
Chris.
Recently I have decided to replace the caps in the crossovers in my Beovox M-100. After some difficulties I have found the original ones from Wicon. (I think the crossovers in your speakers have Wicon capacitors too). My speakers are 30 years old. When me and my friend began the recapping we have measured the most critical old capacitor from the plate. Its meaning occured in the allowed limits of 10 percents and my friend said that no reason to do the recapping🙂. I think you should stay all as is still the speakers sound good in your taste.
I didn't measure ESR. But probably I will do it if I get the special device. It's interesting for me too.
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