Guest wsjoe Posted March 18, 2004 Report Share Posted March 18, 2004 I have a pair or ar-2a's in good external condition. I wired the speakers to my amp and I am not getting much from the tweeter. I tried turning the pots and they are not smooth, a little screechy. I managed to open the front grill with a hair dryer by melting the glue on the fabric. I unscrewed the mids but did not pull them out. There was insulation and afraid to damage them.My questions is where exactly is located the crossover? How can I service the pots? Deoxit? Is it a good idea to replace the caps? Are they electrolytics? Do you purchase from Digikey like the Panasonics?thank youAll I want to do is hear the good sound it did when it was new and prime of its era. Link to comment Share on other sites More sharing options...
ar_pro Posted March 18, 2004 Report Share Posted March 18, 2004 It's likely that your original level controls are not making proper contact, and need to be cleaned. They and the crossover can be accessed by removing the woofer & insulation. Take a photo of the connections (or make a nice drawing) so that you can re-attach everything properly. Many here feel that the original Acoustic Research crossover components are *not* prone to failure (I tend to agree), and that keeping up-to-spec original parts in place is the way to go. Link to comment Share on other sites More sharing options...
Guest dogmeninreno Posted March 19, 2004 Report Share Posted March 19, 2004 >I have a pair or ar-2a's in good external condition. I wired>the speakers to my amp and I am not getting much from the>tweeter. I tried turning the pots and they are not smooth, a>little screechy. I managed to open the front grill with a>hair dryer by melting the glue on the fabric. I unscrewed the>mids but did not pull them out. There was insulation and>afraid to damage them.>>My questions is where exactly is located the crossover? How>can I service the pots? Deoxit? Is it a good idea to replace>the caps? Are they electrolytics? Do you purchase from>Digikey like the Panasonics?>>thank you>>All I want to do is hear the good sound it did when it was new>and prime of its era.Are the tweeters audible after turning the pots on the back? If so I agree with AR Pro that a cleaning and lubricating is in order. I seldom see the crossovers in need of service...Dale Link to comment Share on other sites More sharing options...
r_laski Posted March 19, 2004 Report Share Posted March 19, 2004 >>My questions is where exactly is located the crossover?<<As ar pro stated, to access the crossover you must remove the woofer and the fiberglass stuffing inside the cabinet. The crossover is mounted to the back where the binding posts and attenuation pots are – they are part of the crossover. >>How can I service the pots? Deoxit?<< There are numerous threads on this forum that deal with this subject. I recommend you use the search feature and search the word “pots.” I did, and found several threads you will find interesting and informative and answer the questions you have. >>Is it a good idea to replace the caps? Are they electrolytics?<<>>>>Many here feel that the original Acoustic Research crossover components are *not* prone to failure (I tend to agree), and that keeping up-to-spec original parts in place is the way to go.<<<<Although I have done some AR crossover repair / restoring recently, I agree it is not necessary to replace all the capacitors in every AR speaker ever built. However, I found it well documented that electrolytic capacitors degrade over time and eventually go out of tolerance and worst case, they “leak” (electrically not literally).Unfortunately, to test whether a capacitor is “up-to-spec,” you have to remove it from the crossover. You cannot measure its capacitance while it is connected to other components. This is not an easy task when you have to de-solder the leads off connectors shared with other capacitors, resistors, inductors, and speaker wires.I tested the capacitors from the four AR-11s I recently repaired/restored:Cap rating (assume 10% tolerance) / cap meter readings of all four caps listed lowest to highest -- notes10uF / 9.95 / 10.74 / 15.99 / 18.50-18.94 -- cap 3 is out, cap 4 readings fluctuate and is out40uF / 39.7 / 42.6 / 47.2 / 53.1-53.8 -- cap3 is out, cap 4 readings fluctuate and is out120uF / 119.1 / 128.7 / 130.4 / 132.4 -- cap 4 is out5 out of 12 caps are out of spec. I’d also like to point out that pairing 2 caps with widely different readings will also affect the sonic balance between the two speakers. For example, pairing the 119.1 and 130.4 caps together is not a good matching of capacitors, even though both are within tolerance. Additionally, all four 15 Ohm resistors and some of the others had cooked away the hot melt glue used to hold them to the crossover board. I replaced all the caps and resistors.I tested the capacitors from one of the AR-90s I’m working on. I’m leaving the other one “stock” for now as a control while I conduct listening tests on different replacement caps.Cap rating (assume 10% tolerance) / cap meter reading4uF / 4.13 good6uF / 6.47 good8uF / 8.85 out (slightly, but out)24uF / 28.5 out30uF / 48.5 out (yes 48.5, its not a typo)40uF / 44.2 out (slightly, but out, this one also fluctuates)80uF / 92.8 out350uF / 395 out6 of 8 cap are out of spec.I also tested the midrange and tweeter caps in a pair of LSTs. These were all Sprague electrolytics and appear to be replacements. One crossover had a single 40uF for the midrange the other crossover had a pair of 20uF caps paralleled. The single 40uF cap was out of spec (45uF).While my sample size is small compared to the “universe of all AR speakers ever built,” I believe it provides empirical evidence that testing capacitors 20 years old or older, particular electrolytic capacitors, is at least worth considering. Replace capacitors that are out of spec, but also pay attention to the variation in capacitance between the capacitors in both speakers.<< Do you purchase from Digikey like the Panasonics?<<I use North Creek capacitors whenever possible – when the budget allows. They are relatively expensive, but IMHO so superior to anything else I’ve tried, they’re worth the extra price. Solen & Axon (made by same company) are also good caps.Rich Link to comment Share on other sites More sharing options...
Guest wsjoe Posted March 21, 2004 Report Share Posted March 21, 2004 Thank you for all your replies.I have noticed that if I pull on the pots as I rotate I can get the tweeters to sound but it is intermittent as I turn on the pot. I really think that the pot has gotten dirty because the tweeter comes on about 1/3 during the full turn of the pot. And like I said, screechy.I attempted to open the woofer and even after unscrewing all 6 screws, I could not remove the woofer. There was a black sticky gummy stuff all around the woofer and it is holding the woofer tightly. Any idea on how to get it out? Should I remove all that black stuff out? Pry them to the side?Thank you again. Link to comment Share on other sites More sharing options...
Guest russwollman Posted March 21, 2004 Report Share Posted March 21, 2004 The black stuff that seals the woofer to the baffle is very sticky. The stuff retains its sealing ability for a long time and you can likely reuse it.The woofer has to be pried up from the baffle. A little pry bar (Stanley makes a great one) carefully applied under the outer edge of the woofer will do the trick. But place another piece of wood, or thick sheet metal, under the fulcrum point of your pry bar and the baffle, so you don't damage the edge of the baffle as you pry. Move slowly and carefully. The woofer will come out even though it may seem eternally mounted!If you want to replace the level controls, you can contact Larry Lagace, ljlagace@aol.com, who offers a good replacement.I notice on a pair of 2ax's that the tweeter output—the small black dome "supertweeter"—is subtle, barely noticeable unless I put my ear right up to it. I'm not familiar with the 2a drivers so I don't know if this observation applies to your speakers. Link to comment Share on other sites More sharing options...
Rlowe Posted March 21, 2004 Report Share Posted March 21, 2004 Rich,>I tested the capacitors from one of the AR-90s I’m working on.>I’m leaving the other one “stock” for now as a control while I>conduct listening tests on different replacement caps.I am interested to hear about the results from the AR90s you are currently testing. Would you be able to describe the capacitance test you used, indicating what equipment? And indicate what recordings you are using as the listening test.Richard Link to comment Share on other sites More sharing options...
ar_pro Posted March 21, 2004 Report Share Posted March 21, 2004 Once the screws have been removed, use a flat-bladed screwdriver to carefully lift under the edge of the woofer's frame...the woofer will come out easily, once you have it started and can get your fingers under the frame. Be careful not to poke the cone, or tear any wires. The black gummy stuff is used to make a tight seal, and will need to be replaced when you're ready to re-seat the woofer. Again, be sure to document *all* of the connections before removing anything. Link to comment Share on other sites More sharing options...
r_laski Posted March 23, 2004 Report Share Posted March 23, 2004 Richard, I will answer this in a different thread started by rrcrain about rebuilding AR90 crossovers. I don’t want to garbage up this thread about AR-2a’s. My intent for posting what I did was an attempt to bring to light that some capacitors installed in AR speakers do degrade. The only way to know if you have “good” or “bad” capacitors is to test them. I am in the process of final assembly of the AR-90 crossovers and want to listen to both with "new" crossovers in them before I answer your questions about testing and results.Rich Link to comment Share on other sites More sharing options...
Guest mainstay Posted March 24, 2004 Report Share Posted March 24, 2004 >Unfortunately, to test whether a capacitor is “up-to-spec,”>you have to remove it from the crossover. You cannot measure>its capacitance while it is connected to other components.>This is not an easy task when you have to de-solder the leads>off connectors shared with other capacitors, resistors,>inductors, and speaker wires.I'm somewhat of a newbie and didn't know this. My quick question is why can't you test caps while in circuit? Link to comment Share on other sites More sharing options...
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