Rich W Posted September 1, 2007 Report Share Posted September 1, 2007 Earlier this week, I had the incredibly good fortune to acquire a pair of AR-3a's from a local thrift store for the unbelievable price of $15. Since the grills were cemented in place, I didn't even bother to visually check things "under the hood" at the store - I was just so excited at the prospect of having a pair of these speakers to restore, regardless of what it would take to "get them up to speed". Upon checking them out back at home, there are some obvious issues but I can honestly say I'm not disappointed.Some of you may remember my post from a few months back where I lamented having sold my 3a's back in the 70's:http://www.classicspeakerpages.net/dc/dcbo...5&mesg_id=12925 Needless to say, getting my hands on another pair of these speakers was a real windfall . . . I'm a happy camper! Here's a rundown of what I found:- Serial numbers are 35270 and 35724. One cabinet had the mid-period version of the 3a woofer, with the circular dampening disc. The other cabinet contained an AR factory replacement woofer, part number 1210003-0 as described in the 1986 AR parts catalog (however, there's a 'B' suffix after the stamped part number on my woofer). Both woofers are in need of a refoam. - All drivers are operational, with the exception of one midrange. I tested it by sending it direct signal (by-passing the pots and caps entirely). It is dead beyond question.- Pots are intermittent and will need a good cleaning.- The oiled walnut cabinets are in very good condition, with the exception of one top that's pretty scratched up. It's responded well to some sanding with 400 grit, however. Grills are dirty, with corroded logo plates, and will need replacing.- Both units contain the older style wax capacitors: a 6 uF. Industrial Condenser Corp., and a box unit, strapped to the back of wall of the interior containing the 50 uF and 150 uF capacitors. The caps in the first unit I disassembled are badly out of spec: 14, 210 and 370 uF. respectively! These wild values would certainly explain why one of the midrange drivers is blown.I've made some assumptions on how I plan to proceed with the restoration, and of course, a few questions. - According to Tom Tyson, all the AR 11" these woofers are close enough in performance to have a negligible effect on the sound, once they've been refoamed. So I'm not planning on replacing either one. I have a refoam kit on order from Larry Ligace of Vintage-AR.- I'll plan on scouring eBay to find a replacement midrange driver.- Cabinets will be sanded down and oiled with Danish Oil or boiled linseed.- Now comes the question which I know I will open a can of worms: Cap replacement. I've done some searches on this subject here on the forum, and have noted a wide divergence of opinions. My goal is to stay as close to the original designer's intentions as possible. Any final "tweaking" in sound I plan to do with a one-third octave equalizer. Since these are wax and/or oil-based capacitors and are no longer available, from purely "closest match" standpoint, am I better off with NPE's or poly's? From my own experience (and I realize they are very different animals), I was very pleased with the performance of a pair of AR-7's and AR-18's after recapping with Solens. However, a pair of recapped AR-18S's did not fare as well, as they sounded too bright after the recap. I do not know if the speakers were intrinsically brighter than the older two pairs (I did not listen to them before the recap), or that the Solen's "didn't agree with them".Incidentally, I could not find the .47 ohm wire-wound resistor indicated on the AR-3A schematic. Is it enclosed in the box with the dual caps?I know there'll probably be more questions as I proceed. Any advice is greatly appreciated! I want to thank the contributors to this forum for providing such a treasure trove of information and practical advice.Best Regards,Rich W Link to comment Share on other sites More sharing options...
Rich W Posted September 1, 2007 Author Report Share Posted September 1, 2007 After posting my message, I did some additional searches on cap replacement (this forum has so much valuable info!). Based on research by John O'Hanlon http://www.classicspeakerpages.net/dc/dcbo...1&mesg_id=4281& wax caps have an "extremely low ESR". Since most poly caps have low ESR's as well, all else being equal, shouldn't a poly cap, with their intrinsically low ESR be an ideal replacement for a wax cap? Don't differences in ESR's only become an issue when attempting to find an ideal replacement for NPE caps, which have higher ESR's? Am I oversimplifying? Rich W Link to comment Share on other sites More sharing options...
johnieo Posted September 1, 2007 Report Share Posted September 1, 2007 >- Serial numbers are 35270 and 35724. One cabinet had the>mid-period version of the 3a woofer, with the circular>dampening disc. The other cabinet contained an AR factory>replacement woofer, part number 1210003-0 as described in the>1986 AR parts catalog (however, there's a 'B' suffix after the>stamped part number on my woofer). Both woofers are in need of>a refoam. Hello Rich: Nice work! Glad to see that someone with interest found these first.Could you post a photo of the earlier woofer? sn 35270? Is it a cloth-surround, alnico woofer with a heavy damping ring? If so, it could be recoated with a latex compound rather than being destroyed by refoaming. If the data I have been collecting are accurate, AR switched to the ceramic magnet, foam surround woofer between 38,xxx and 39,xxx, although it may have been replaced if damaged. Also, would it be possible for you to weigh the fiberglass insulation and see if it contains 28-30 ounces, or has been reduced to 20 ounces by that serial number. I'll guess your speakers were manufacured in February, 1970. Likely by then the #7 woofer coil had been changed to a #9. If your alnico is in good shape, you might consider an alternative approach -- purchasing a mate on eBay and selling the foam-surround woofer. >- Both units contain the older style wax capacitors: a 6 uF.>Industrial Condenser Corp., and a box unit, strapped to the>back of wall of the interior containing the 50 uF and 150 uF>capacitors. The caps in the first unit I disassembled are>badly out of spec: 14, 210 and 370 uF. respectively! These>wild values would certainly explain why one of the midrange>drivers is blown.Obviously you should replace the caps. Two viable options: a) audio grade non-polar electrolytic capacitors, or polypropylene caps with very small resistances (.25 to .47 Ohms) in series. Most folk claim that they sound the same. My personal choice to avoid electrolytic caps is purely for reasons of long-term reliability and not because polyproplene caps are "botique." Capacitors are called "passive" components, but an electrolytic is anything but; its a chemical reactor in a small can.>I was very pleased with the>performance of a pair of AR-7's and AR-18's after recapping>with Solens. However, a pair of recapped AR-18S's did not fare>as well, as they sounded too bright after the recap. I do not>know if the speakers were intrinsically brighter than the>older two pairs (I did not listen to them before the recap),>or that the Solen's "didn't agree with them".The 18s is supposed to be almost the same as the 18. You might try putting a 0.25-Ohm resistor in series with the tweeter caps and listening again.>Incidentally, I could not find the .47 ohm wire-wound resistor>indicated on the AR-3A schematic. Is it enclosed in the box>with the dual caps?In that era, the resistor was a piece of Nichrome wire. Look for a loop of shiny "bare wire" connected between two tie points.Keep us posted!Cheers, Link to comment Share on other sites More sharing options...
Rich W Posted September 1, 2007 Author Report Share Posted September 1, 2007 John,Thanks for the info. The older woofer definitely had a foam surround, as I've already removed the crumbly fossilized remains in preparation for a refoam. The residual glue on the cone was so tenacious that I had to resort to a highly toxic heavy-bodied paint remover to get it off - and with multiple applications. From the woofer's appearance, I can't imagine that it ever had a cloth surround in an earlier incarnation, the type of which I'm familar with from my KLH Model 5's. As you suggest, it's possible that it is a replacement for an original cloth surround woofer. Will post photos in the next few days anyway. I'll also get the weight fiberglass stuffing once I get access to a high resolution scale.It's so strange that I would quote a post of yours just seconds before you posted your own response to my original post! In any case, I don't understand the need for additional resistance if the original wax caps indeed have a low ESR (as your research states), as do the Solen poly caps.Best Regards,Rich Link to comment Share on other sites More sharing options...
johnieo Posted September 1, 2007 Report Share Posted September 1, 2007 Although I have measured low ESR on some of those old ones, it is no where near as low as in a polypropylene. Roy C has done lots of listening tests and concluded that the added fraction Ohm seems to replicate the ESR of the non-polarized electrolytics used in most of the AR-3a units. My musician listeners here agree.Cheers,John Link to comment Share on other sites More sharing options...
RoyC Posted September 1, 2007 Report Share Posted September 1, 2007 Rich,Does your woofer with the damping ring look like the June '70 ceramic magnet specimen in the attached photo? If so, you may have one of the rare transitional woofers...what appears to be a hybrid between the alnico magnet, cloth surround version and later ceramic magnet, foam surround version.Roy Link to comment Share on other sites More sharing options...
Rich W Posted September 1, 2007 Author Report Share Posted September 1, 2007 Roy,That was the exact appearance of the woofer before I removed the foam, down to the "nasty to remove" glue and the splits radiating from the center of the dampening ring.Nice to know that I may have a "rarity" in the evolution of the AR-3a.Best Regards,Rich Link to comment Share on other sites More sharing options...
Rich W Posted September 1, 2007 Author Report Share Posted September 1, 2007 John,The cabinet contained 20 oz. of fiberglass. The woofer is identical to the one depicted in Roy's post.Best Regards,Rich Link to comment Share on other sites More sharing options...
Rich W Posted September 3, 2007 Author Report Share Posted September 3, 2007 Both cabinets contain the infamous #7 coil. They'll be ugraded to #9 as part of my restoration.Rich W Link to comment Share on other sites More sharing options...
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