DavidR Posted March 22, 2022 Report Share Posted March 22, 2022 Caution with some of those old oils. They could be askarel or a form of it. Askarel is a PCB oil. Quote Link to comment Share on other sites More sharing options...
RoyC Posted March 23, 2022 Report Share Posted March 23, 2022 8 hours ago, DavidR said: Caution with some of those old oils. They could be askarel or a form of it. Askarel is a PCB oil. Well, you could have told me that before I licked the foil! Seriously, I'm aware of the possibility. John O'Hanlon is a capacitor guru, and we had a number of discussions along these lines when we were putting together the 3a guide. He said there was greater chance of this type of oil in the early oil filled capacitor cans. I've attached some additional photos of a dissected block cap, as well as oil filled caps found in very early AR speakers. Roy Quote Link to comment Share on other sites More sharing options...
genek Posted March 23, 2022 Report Share Posted March 23, 2022 The cans are almost certain to be filled with some variety of PCB. PCBs weren't banned until 1979. BTW, solids and coatings that appear to be wax may also be PCBs. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 23, 2022 Report Share Posted March 23, 2022 15 hours ago, RoyC said: Well, you could have told me that before I licked the foil! But per the Old "Block" Caps thread, you did inhale! 😉 According to the Early Capacitor Manufacturing History thread, AR discontinued use of PCB caps several years before the AR-3a was introduced (but beware of early serial-numbered AR-3 speakers made through the mid-1960s). The wax-paper-impregnated caps that replaced them had an even lower ESR, and both were orders of magnitude less than that of NPE caps. These statements by @johnieo are most relevant to the questions I posed earlier (note that he inadvertently reversed the crossover frequency change, which decreased rather than increased). Quote These [NPE] ESR values are so high that it is obvious to me the speaker designer of the 1970s had to include that resistance in the calculation of the crossover frequency, and thus the legitimate concern when they are replaced with low ESR polypros. Quote --AR-3a: we observe that the ESR of paraffin caps was much lower than for NPEs and that the crossover frequency WAS affected--it increased from 525 Hz to 575 Hz from early to late models. He and @r_laski also provided some very interesting cap descriptions, measurements, observations, and recommendations here. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 23, 2022 Report Share Posted March 23, 2022 "Before" graph below. The green and orange traces are RMS averages of measurements on axis aimed between tweeter and midrange at 0.5m and 1.0m from the same position in my room. One of the pots on S/N 06064 works only near its maximum setting, so I set the other three the same for consistency. Both speakers are as they came from AR in the late 1960s except the pots in S/N 06052 and the midrange driver in S/N 06064 were replaced in the late 1980s. Digitized and SPL aligned at 400Hz for reference are the two curves posted in the AR-3a response curve thread. *Edit 2022-03-29: A 100Hz HPF was inadvertently engaged on the AVR channel used for these measurements hence the lack of bass extension.  Has anyone already modeled the AR-3a crossover in XSim?If not, are the FRD and ZMA files available for all three drivers? Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 23, 2022 Report Share Posted March 23, 2022 Here is 06052:  6μF capacitor:  50μF capacitor:  150μF capacitor:  Both potentiometers (of the type @RoyC described) work and the one I opened looked fine so I left them alone. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 24, 2022 Report Share Posted March 24, 2022 Here is 06064:  6μF capacitor:  50μF capacitor:  150μF capacitor:  The potentiometer that I was unable to adjust: After DeoxIT and emory cloth: The other pot looked (and mostly worked) fine so a little DeoxIT was all it needed. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 26, 2022 Report Share Posted March 26, 2022 As in my center channel project thread: *** WARNING! Images of crossovers with NPEs rather than MKPs below! Viewer discretion is advised! *** The new capacitor measurements for left and right were virtually identical so those below from one or the other are representative. High readings are typical as discussed in the Cap Value Accuracy thread. According to someone who posted a review of my Proster LCR meter, it measures capacitance using a 300Hz triangular 200mV pk to pk voltage waveform. I have found no such information on my TC1, which reads the same as the BM4070 for the larger caps, though for the small caps, it reads lower individually but higher when in parallel. Vloss sure looks better... 2.7μF + 3.3μF capacitors:  50μF capacitor:  150μF capacitor:  Reassembly:  Measurements and Impressions Before vs. after graph below. Again, the green and orange traces are RMS averages of measurements on axis aimed between tweeter and midrange at 0.5m and 1.0m from the same position in my room. All pots now work but I did my best to position them the same as before for consistency. Digitized and SPL aligned at 400Hz for reference are the two curves posted in the AR-3a response curve thread. *Edit 2022-03-29: A 100Hz HPF was inadvertently engaged on the AVR channel used for these measurements hence the lack of bass extension.  Any difference is too subtle for me to hear - they sound terrific! All that's left to do is apply cloth surround woofer sealant, which is on the way now that Vintage-AR has returned from vacation. I will measure before and after (with the AVR's HPF disabled this time) to see if there is a difference in output. This has been a fun project and I am very pleased with the outcome! Quote Link to comment Share on other sites More sharing options...
Brad1234 Posted March 26, 2022 Report Share Posted March 26, 2022 2 hours ago, bjmsam said: As in my center channel project thread: *** WARNING! Images of crossovers with NPEs rather than MKPs below! Viewer discretion is advised! *** The new capacitor measurements for left and right were virtually identical so those below are representative. High readings are typical as discussed in the Cap Value Accuracy thread. According to someone who posted a review of my Proster LCR meter, it measures capacitance using a 300Hz triangular 200mV pk to pk voltage waveform. I have found no such information on my TC1, which reads the same as the BM4070 for the larger caps, though for the small caps, it reads lower individually but higher when in parallel. Vloss sure looks better... 2.7μF + 3.3μF capacitors:  50μF capacitor:  150μF capacitor:  Reassembly:  Measurements and Impressions Before vs. after graph below. Again, the green and orange traces are RMS averages of measurements on axis aimed between tweeter and midrange at 0.5m and 1.0m from the same position. All pots now work but I did my best to position them the same as before for consistency. Digitized and SPL aligned at 400Hz for reference are the two curves posted in the AR-3a response curve thread.  Any difference is too subtle for me to hear - they sound terrific! All that's left to do is apply cloth surround woofer sealant, which is on the way now that Vintage-AR has returned from vacation. This has been a fun project and I am very pleased with the outcome! Nice job!  I have always wondered if the smaller, cheaper caps produce the same, or even better, sound than expensive ones?  I recapped the exact same model with the pricey metalized foil polypropylene caps (Jantzen) close to $200 and have been happy with it, but it was a big expense. My AR's are currently my favorite speaker, close behind are my JBL L100s. When I tested my old AR 3a brick caps, they were crazy off, I got 325 uF for the 150, so they were shot. I also doped my woofer surrounds and dust cap with the same Vintage AR sealant I bought back in Dec.  made them look shiny and beautiful!  Quote Link to comment Share on other sites More sharing options...
Dan Skye Posted March 27, 2022 Report Share Posted March 27, 2022 Looks great ! those are the early models with the damper on the woofer I could be wrong but these are probably I suspect  better than the more recent woofs without the rubber rings Quote Link to comment Share on other sites More sharing options...
Brad1234 Posted March 27, 2022 Report Share Posted March 27, 2022 57 minutes ago, Dan Skye said: Looks great ! those are the early models with the damper on the woofer I could be wrong but these are probably I suspect  better than the more recent woofs without the rubber rings I have not heard any other model, but these early model woofers produce some incredibly deep bass effortlessly. The size and weight of the magnet is also very impressive, they truly don't make woofers like this anymore.  I have a restoration question. Anyone have any advice on how to best restore/protect the paper labels attached to the backs of the cabinets on the AR 3a's?  I was thinking just carefully rubber cement the loose edges back down? Quote Link to comment Share on other sites More sharing options...
JKent Posted March 27, 2022 Report Share Posted March 27, 2022 4 hours ago, Brad1234 said: I was thinking just carefully rubber cement the loose edges back down? I would use Aleene's Tacky Glue. Have used on paper labels on speakers and old KLH radios. Easy to use, does the job, cleans up with water. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted March 31, 2022 Report Share Posted March 31, 2022 On 3/26/2022 at 7:52 PM, Brad1234 said: Nice job!  I have always wondered if the smaller, cheaper caps produce the same, or even better, sound than expensive ones?  I recapped the exact same model with the pricey metalized foil polypropylene caps (Jantzen) close to $200 and have been happy with it, but it was a big expense. My AR's are currently my favorite speaker, close behind are my JBL L100s. When I tested my old AR 3a brick caps, they were crazy off, I got 325 uF for the 150, so they were shot. I also doped my woofer surrounds and dust cap with the same Vintage AR sealant I bought back in Dec.  made them look shiny and beautiful! Thanks! Being happy is all that matters. 😉 Your speakers look great! My woofer surrounds (and dust caps) were bone dry and felt like fragile paper. Now they feel much more robust, and the cone returns much more slowly after being displaced. One coat seemed adequate.  Any difference in sound is too subtle for me to hear. Here is a graph of the woofer section measured on-axis in my room before and after sealing:  Since a 100Hz HPF was inadvertently engaged on the AVR channel used for the measurements I posted earlier comparing before/after capacitor replacement (inconsequential but annoying), here is a final graph of measurements on-axis in my room with everything done and dialed in:  The speakers are well aligned and not responsible for deviations from the red AR tech data trace as acoustic treatment of my room remains a work in progress... 🤔  Thanks again for the outstanding guide and support! Quote Link to comment Share on other sites More sharing options...
meta_noia_fot Posted June 11, 2022 Report Share Posted June 11, 2022 Just wanted to say a quick thank you to this community and the authors of the AR-3a restoration guide. I just restored a pair that had been bowdlerized with generic, 8-ohm woofers. I sourced proper replacements from Vintage_AR, replaced the caps, and sanded and varnished the veneers with Danish Oil. They're singing again and I couldn't be happier right now. I have pairs of AR-6s and AR-8s but these 3a's are a different beast. Incredible stuff. Quote Link to comment Share on other sites More sharing options...
genek Posted December 5, 2022 Report Share Posted December 5, 2022 The library link to the document is down. Here's a PDF. restoring-the-ar-3a-2.pdf Quote Link to comment Share on other sites More sharing options...
sWilly Posted December 6, 2022 Report Share Posted December 6, 2022 On 3/20/2022 at 6:18 PM, bjmsam said: Echoing feedback posted over the past fifteen years, the guide is terrific and most appreciated! I am preparing to dig into my pair which Dad bought new in the late 60s (serial numbers 06052 and 06064). I am comfortable with NPEs (recently employed with success in my center channel project)... ...but what are the early caps, exactly? The guide seems somewhat ambiguous on this point:  Also, the guide states: Since my woofers have cloth surrounds, the #7 inductor should not be replaced with a #9 coil, correct?  Sure glad I saw this - thank you! Perhaps the guide should be updated for those not poring over every post?  I'm restoring a 1968 pair of AR-3a's now and had many of the same questions. It looks like you went with modestly priced electrolytic capacitors. Are you happy with the results. Trying to decide between those and the more expensive Daytons or Jantzens right now. Quote Link to comment Share on other sites More sharing options...
Brad1234 Posted December 6, 2022 Report Share Posted December 6, 2022 1 hour ago, sWilly said: I'm restoring a 1968 pair of AR-3a's now and had many of the same questions. It looks like you went with modestly priced electrolytic capacitors. Are you happy with the results. Trying to decide between those and the more expensive Daytons or Jantzens right now. I recapped my AR 3a's with the Jantzen Crosscap foil capacitors and have not really been happy with them. i have done a ton of recap jobs with the Audyn Q4 caps and they sound really nice, loud and super clear to me. I am planning to recap my AR3a's again with Audyns and see if it brightens them up some. They are not cheap and I feel bad I already spent so much on the Jantzens only to have to do it all over again. Quote Link to comment Share on other sites More sharing options...
sWilly Posted December 6, 2022 Report Share Posted December 6, 2022 27 minutes ago, Brad1234 said: I recapped my AR 3a's with the Jantzen Crosscap foil capacitors and have not really been happy with them. i have done a ton of recap jobs with the Audyn Q4 caps and they sound really nice, loud and super clear to me. I am planning to recap my AR3a's again with Audyns and see if it brightens them up some. They are not cheap and I feel bad I already spent so much on the Jantzens only to have to do it all over again. Woops my fault, I meant to respond to bjmsam but it's good to get your take on the Jantzens. I think I'm going to try the Mundorf E-caps. If they don't work out it's not a huge loss. Quote Link to comment Share on other sites More sharing options...
DavidR Posted December 7, 2022 Report Share Posted December 7, 2022 6 hours ago, Brad1234 said: I recapped my AR 3a's with the Jantzen Crosscap foil capacitors and have not really been happy with them. i have done a ton of recap jobs with the Audyn Q4 caps and they sound really nice, loud and super clear to me. I am planning to recap my AR3a's again with Audyns and see if it brightens them up some. They are not cheap and I feel bad I already spent so much on the Jantzens only to have to do it all over again. How many hours do you have on the new Jantzen caps? Some caps can take 200 to 400 hours to 'settle in'. If I'm using film caps in a speaker project I will always 'run them in' prior to installation by playing an audio signal thru them. Quote Link to comment Share on other sites More sharing options...
bjmsam Posted December 7, 2022 Report Share Posted December 7, 2022 8 hours ago, sWilly said: I'm restoring a 1968 pair of AR-3a's now and had many of the same questions. It looks like you went with modestly priced electrolytic capacitors. Are you happy with the results. Trying to decide between those and the more expensive Daytons or Jantzens right now. Yes, I did (more info here), and yes, I am! Quote Link to comment Share on other sites More sharing options...
sWilly Posted December 7, 2022 Report Share Posted December 7, 2022 13 hours ago, bjmsam said: Yes, I did (more info here), and yes, I am! Thanks for the link. Looks like a cool project. I decided on the Mundorf E-cap's since the Solens (PartsExpress) seem to get mixed reviews. Glad to hear they worked out for you, though! Quote Link to comment Share on other sites More sharing options...
bjmsam Posted December 7, 2022 Report Share Posted December 7, 2022 On 12/7/2022 at 7:42 AM, sWilly said: Thanks for the link. Looks like a cool project. I decided on the Mundorf E-cap's since the Solens (PartsExpress) seem to get mixed reviews. Glad to hear they worked out for you, though! That's a fine choice. To be clear, I used M.D.L. NPEs for both my AR9C and my AR-3a projects, not Solens.  On 3/1/2022 at 8:04 AM, bjmsam said: I asked about use of NPE caps for shunts in the Capacitor upgrade in crossover - Is it audible? thread on ASR and the first reply includes, "Shunt vs. in-series doesn't have much impact as they are all effectively in the signal path" and "if you are recapping an old speaker, please be aware that the crossover designer may be expecting some series resistance to exist across some of the caps and there could be a negative impact if the replacement caps have no ESR even if they are better caps." Earlier in the thread, someone else stated, "Whenever I replaced electrolytics capacitors to film, speakers became overly bright, after some time I have to put back the original caps." 🤔 If your AR-3a speakers sound dull with new NPE caps, then rebuilding the 50+ year old tweeters (an option missing from page 11) might be more prudent than altering the xover with MKP (PP) caps to run them "hot" (see page 16). On 3/8/2022 at 5:05 PM, bjmsam said: Well, considering the shallow depth of my enclosure, the original AR design around NPE caps, and the analysis posted in such threads as Capacitor upgrade in crossover - Is it audible? ("according to these measurements a film capacitor does not make a better sound when used in the crossover compared to an electrolytic capacitor") and Cap Value Accuracy ("At this point my opinion on using new npe's has improved considerably, and I no longer believe the "high" measurement results to be one of questionable npe quality. I strongly suspect better npe's last much longer than they are given credit for in speaker forums."), I opted to see how the speaker measures and sounds with smaller NPEs before pursuing MKPs (easy enough to replace, so nothing but a few dollars to lose). All of the parts arrived today and I began laying out sections of the network. Exciting! *** WARNING! Images of crossovers with NPEs rather than MKPs below! Viewer discretion is advised! *** Example tolerance:  The goal of my AR-3a recap was to restore / maintain performance and protect drivers by ensuring that the xover operates as originally designed. When it comes to upgrading sound quality, I strive to prioritize investments that objectively make a measurable improvement, and in my experience, room treatment tends to offer the most significant return. Good luck! Quote Link to comment Share on other sites More sharing options...
Brad1234 Posted December 21, 2022 Report Share Posted December 21, 2022 Update on my previous post on this thread, I re-recapped my AR 3a's from the Jantzen Crosscaps to the Audyn Q4 caps and they sound like completely new speakers, so much louder and clearer with the Audyn caps!  There was something wrong with those Jantzen caps, I never really liked them from when I first installed them, and I have had them for about 9 months so they got well burned in with no improvement in sound.  I also have newly rebuilt tweeters and new potentiometers, so I suspected caps were the issue and took the plunge to recap them all over, so glad I did. I just wanted to share my experience with the Audyn and Jantzen caps to the group, I have had really good results with several recap jobs with the Audyn Q4 caps (red caps in photo). Quote Link to comment Share on other sites More sharing options...
MonteR Posted December 31, 2022 Report Share Posted December 31, 2022 On 12/12/2007 at 7:49 AM, administrator said: I think it's time we have a pinned topic for the "Restoring the AR-3a" document developed by six of our esteemed members - Roy Champagne, Ken Kantor, Minh Luong, John O’Hanlon, Bret Thiel, and Tom Tyson. The document is available here: http://www.classicspeakerpages.net/library...ring_the_ar-3a/ Per John's suggestion, I have put a counter on this page (available when I run statistics) so we can see how popular this document becomes. If you have feedback on the document and how it has impacted your restoration project, please reply to this thread. Mark Hello, I am a newbie and cannot seem to view the "Restoring the AR3a" document.  When I click on the link it just shows nothing.  What might I be doing wrong? Also, is there any section that has speakers for sale? Thank you, Quote Link to comment Share on other sites More sharing options...
bjmsam Posted December 31, 2022 Report Share Posted December 31, 2022 Welcome to the forum! Anyone logged in should be able to download the copy attached to this post (click the black arrow at right to view): On 12/5/2022 at 2:13 PM, genek said: The library link to the document is down. Here's a PDF.  The forum index includes this link: Quote For sale / Wanted Speakers for sale and wanted.  Quote Link to comment Share on other sites More sharing options...
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