genek Posted January 3, 2021 Report Share Posted January 3, 2021 Try the grain filler on the worst surface and see how that looks. It may not be necessary to pick at every little trace. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 3, 2021 Author Report Share Posted January 3, 2021 I you had not yet touched it I would say leave it but you are in deep now. I was already planning to check the crossover because the former owner had already removed the pots out of the system.. I had already found a scheme on this forum of the crossover so I can redo it. I think most here would advise you to replace the 4 with a new film cap. Is it a problem if I take a 3.9uf film cap? they are more easy to get.. Can you maybe advise me in where to get the parallel coil for the HIVI tweeter? Quote Link to comment Share on other sites More sharing options...
Aadams Posted January 3, 2021 Report Share Posted January 3, 2021 34 minutes ago, Luxman said: Can you maybe advise me in where to get the parallel coil for the HIVI tweeter? Same place you get your tweeters and Lpads? 34 minutes ago, Luxman said: Is it a problem if I take a 3.9uf film cap? they are more easy to get.. It is 3% off spec but probably close enough. Quote Link to comment Share on other sites More sharing options...
JKent Posted January 3, 2021 Report Share Posted January 3, 2021 3.9uF is fine. Acceptable tolerance for capacitors is -20% to +80%. Modern caps tend to be spot on or certainly well within 5%. Thinking regarding the parallel resistor seems to change over the years but I believe it is not necessary. You can adjust the tweeter's output with the L-pad. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted January 4, 2021 Report Share Posted January 4, 2021 "Acceptable tolerance for capacitors is -20% to +80%"...? That seems too broad of an acceptable tolerance. A tweeter or midrange capacitor at +80% could lead to damage of a driver. Happily, many modern electrolytic capacitors are sold with a -/+10% tolerance, even tighter. Most poly caps are -/+5% or tighter. Even Parts Express sells the inexpensive Dayton -/+1% film capacitors. The Mundorf caps I use are -/+3%. On removing paint, I've had good luck with Citri-Strip Gel Stripper. Rub it on, let it sit, and wipe it away. It does a great job on removing paint and lacquer. I also have a pair of AR-5s to restore. So, I'll follow this thread for ideas. Quote Link to comment Share on other sites More sharing options...
JKent Posted January 4, 2021 Report Share Posted January 4, 2021 Yeah—I’m just sayin don’t get hung up on small differences. I’d discard a cap that was 80% off but certainly anything that’s within 5% or so is perfectly fine. So a 3.9uF can be used for a 4.0 without giving it a second thought. But -20%/+80% is within spec for electrolytic capacitors. Quote Link to comment Share on other sites More sharing options...
AR surround Posted January 4, 2021 Report Share Posted January 4, 2021 16 hours ago, JKent said: 3.9uF is fine. Acceptable tolerance for capacitors is -20% to +80%. Modern caps tend to be spot on or certainly well within 5%. Thinking regarding the parallel resistor seems to change over the years but I believe it is not necessary. You can adjust the tweeter's output with the L-pad. 8 hours ago, JKent said: Yeah—I’m just sayin don’t get hung up on small differences. I’d discard a cap that was 80% off but certainly anything that’s within 5% or so is perfectly fine. So a 3.9uF can be used for a 4.0 without giving it a second thought. But -20%/+80% is within spec for electrolytic capacitors. Carl, may he rest in peace, told me that capacitors needed to be +/-15 order to produce a noticeable difference audio wise. I've used that figure as a benchmark, but it's moot because I replace all the caps when recapping speakers since I'm in there anyway. Quote Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2021 Report Share Posted January 4, 2021 "Acceptable tolerance for capacitors is -20% to +80%" Very low quality crossover capacitors can have a stated tolerance of +/-20%, but +80% is not even a thing in the world of speakers. Would the 24uf midrange cap used in the AR-5 be acceptable at 43uf, or its woofer 72uf cap be acceptable at 130uf (+80%)? Nope...Those caps would be considered shot in any universe, and would never have exhibited those numbers when new unless they were defective. Even the old Industrial Condenser block caps used in AR's would have been within 20%...and the very oldest oil filled caps of the 50's and early 60's typically measure within 5%. 20%+/- (never +80%) can be found in cheaper speakers of the old days, but 10% was more common in better speakers (like AR). Attached are photos of an AR-5 Sprague 24uf capacitor manufactured in 1974, and a relatively new Erse 150uf npe cap (ie "modern," and not of highest quality). Both measure within 10%. Although I personally believe paying more for "matched 1%" film caps is a waste of money, any modern cap with a stated tolerance of 5% to 10% of the required spec is the prudent way to go. Roy Quote Link to comment Share on other sites More sharing options...
JKent Posted January 4, 2021 Report Share Posted January 4, 2021 OK! I don't want to be banished to the Kitchen!! 😉 I was trying to make a point and maybe engaged in a bit of hyperbole. My point was; don't get hung up a a few picofarads. A 3.9uF is a perfectly fine replacement for a 4.0uF. There are caps and then there are caps. As Roy points out, speaker caps are a different animal. +80% IS (was?) the tolerance for some common electrolytics. I've seen it printed on caps I've removed from vintage amps and I've discussed it with my technician friend. Also see this web page: https://www.electronics-tutorials.ws/capacitor/cap_3.html And there are letter codes for various tolerances. Code Z is for -20/+80%. I don't want to belabor the point--just let you know I wasn't hallucinating 😄 But of course we want our crossover caps to be spot on. As an example, I just finished a crossover that called for 16uF caps. I had a bag of cheap Carli 15uF 10% caps and decided to test them and see if any were 16uF. Closest I found was just under 15.5. Quote Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2021 Report Share Posted January 4, 2021 1 hour ago, JKent said: OK! I don't want to be banished to the Kitchen!! 😉 I was trying to make a point and maybe engaged in a bit of hyperbole. My point was; don't get hung up a a few picofarads. A 3.9uF is a perfectly fine replacement for a 4.0uF. Kent, I think you are confusing microfarads with picofarads. Microfarads are huge in comparison (1 microfarad=1000000 picofarads). You're correct, a few picofarads will not make a difference but a few microfarads can, especially in a discussion regarding a 4uf (microfarad) capacitor. I only responded because a +80% tolerance is so absurd, and I felt it could be confusing to people who know very little about speaker capacitor replacement, and are just looking for information. The article you linked which mentioned "+80%" has to do with the characteristics/behavior of tiny polarized capacitors (measured in fractions of picofarads) used in active electronic circuits. Speakers in our discussions all have non-polarized capacitors used in passive circuits. Really big apples and microscopic oranges. 🙃 Roy Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 After a week a new report on this topic. work has been going on. last couple of days I have been searching for a scheme and pictures of the crossover. I also ordered a couple of new capacitors, managed to find the original 4uf types. I guess they will be here within a week. today I have placed the sprague capacitors back, rebuilt the crossover and placed the old pots. Tested the speakers and everything works however the cleaned pots do not quite work like they should, when turning there are parts that do not work perfect but for now it's okay, I was planning to replace them anyway.. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 Last week I also made a new front for one of the two cabinets. Luckily I had the original masonite fronts. All that's missing is the logo, but that comes later.. The cloth I bought online, I also used it before for my AR 4xa's. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 Just accidently placed the wrong picture of the crossover. this was the old situation. Here is the new one.. Quote Link to comment Share on other sites More sharing options...
Aadams Posted January 9, 2021 Report Share Posted January 9, 2021 14 minutes ago, Luxman said: Here is the new one.. Luxman Are you sure this is the correct photo? Those 4mfs are not Sprague Compulytics but ICCs. Had you shown this image earlier you would have definitely been advised to put in new 4mf caps. Adams Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 One of the woofers ready to be refoamed. Foam will probably be delivered next monday. This is the least of my problems🙂, done dozens of these jobs already. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 You mean the 4uf right from the pots? this indeed is the old one. Has to be changed. A new one (4uf MKP) is on it's way. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 9, 2021 Author Report Share Posted January 9, 2021 Also been looking at he tweeters. One of the two is working. The working one has already been replaced once.. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 17, 2021 Author Report Share Posted January 17, 2021 This week I have refoamed the woofers, worked out fine.. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 17, 2021 Author Report Share Posted January 17, 2021 When the glue was dry I placed the woofers in the cabinets and used a couple of wharfedale tweeters to test if everything works. At the moment there's no dampening in them yet because Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 17, 2021 Author Report Share Posted January 17, 2021 😊because I did not receive the 4uf caps yet. Also the old pots which I cleaned are in there at the moment and I'm not sure if I'm willing to keep them. For now actually they work fine.. Quote Link to comment Share on other sites More sharing options...
Luxman Posted January 17, 2021 Author Report Share Posted January 17, 2021 The cabinets stil have the rat-look but technically everything works fine. The pots work fine and after testing they sound amazingly good. Even with these test- tweeters. When the new caps are in I'm planning to place the original working tweeter and after that I will order the new HiVi tweeters to finish the project. In a couple of months the cabinets will be finished. I already have a new liquid cleaner which should do the job. Quote Link to comment Share on other sites More sharing options...
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