dtafil Posted July 29, 2018 Report Share Posted July 29, 2018 Hi All - It's been a while, but I always remembered the constructive suggestions and recommendations from an AR5 restoration I shared on this forum a couple years back, so I wanted to start this new one to help anyone else that's interested, as well as get some pointers from others. I just picked up a set of AR3a's that looked identical; cabinets are in pretty solid shape (and heavy as heck, lol). Seller had picked them up as part of a larger estate auction with some other vintage gear, so no past history was known. Prior to my purchase, I took the grills off (seller had apparently not done so), and was surprised to find they came off rather easily; they had both been velcro'ed down (I was expecting glue). One speaker has a front wired tweeter (only), the mid is wired from the rear. The other speaker has a different, rear-wired tweeter, same as the mid. The woofers appeared different, both with foam surrounds. Some very low music, and careful adjustment of the rear rheostats got both the older (?), front wired tweeter and mid working (the woofer is fine) on speaker one. The second, newer (?) speaker's mid and woofer was working (this is the one from 1974, according to the only available paperwork on the back of that cabinet), but no luck on the rear-wired tweeter. The Hi pot felt a bit crunchy, so thinking it could be that, or something in the crossover. In any event, I'm rather OCD about having things perfectly matching... curious what I have here, apart from the common Walnut cabinets, grills, and mid range drivers. My plan is to get the woofers out this week (I'll add some pictures of the model numbers on the back of them), order a refoam kit, as well as get some pictures of the crossovers (hoping they're the same, but we'll see). I used Dayton caps on the 5a's, thinking of trying something different on these; suggestions most welcome. Question to the AR3a gurus... any initial thoughts about what exactly these are? Simply 2 speakers simply a revision or two apart? Go with a rear mounted tweeter as well for speaker one and replace/match up on one of the woofers? I'm in no rush, just wanting to share my progress and do these speakers justice like my earlier 5a restoration. Thanks guys! Dave Link to comment Share on other sites More sharing options...
genek Posted July 30, 2018 Report Share Posted July 30, 2018 The speaker on the right is one of the late models turned out after AR's move to Norwood, MA. It's distinguished by the MDF construction and back-wired mid and hi drivers. Link to comment Share on other sites More sharing options...
dtafil Posted July 30, 2018 Author Report Share Posted July 30, 2018 Thanks for that, very helpful. Perhaps I'll wait on these, and see if I can turn up a matching orphan for one or the other... will update this thread as I make any progress. If it's allowed, and any other folks have leads on a potential match for one or the other, please feel free to reach out. Would love to restore a pair of these in unison. Link to comment Share on other sites More sharing options...
JKent Posted July 30, 2018 Report Share Posted July 30, 2018 Hey dtafil Nice find. You can find info on all of the drivers at the end of the restoration guide: http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/ -Kent Link to comment Share on other sites More sharing options...
ar_pro Posted July 30, 2018 Report Share Posted July 30, 2018 They're not that far apart...you could easily restore both as a pair. If you do open them up, please take lots of photos, especially if you note any differences. Is that mildew on the woofer cone of the left speaker? Link to comment Share on other sites More sharing options...
DavidR Posted July 30, 2018 Report Share Posted July 30, 2018 I had mildew on my 91 woofer cones (even on top of the vc magnet) and found cotton balls dampened (not soaked/wet) with rubbing alcohol worked well at removing it and dried fast. Link to comment Share on other sites More sharing options...
Stimpy Posted July 30, 2018 Report Share Posted July 30, 2018 There's been recent threads here at CSP, and at Audio Karma, discussing using spray dye to 'paint' a discolored cone. I guess one uses an air spray gun? The results are pretty impressive. Link to comment Share on other sites More sharing options...
dtafil Posted July 31, 2018 Author Report Share Posted July 31, 2018 You guys are a bad influence, lol. I already started pulling these apart... some good news, and lots of pictures. Pic 1: Both woofers, from underneath. Woofer "A" had a 200003 label on it, woofer "B" had none (nothing in the liner (forgot the name of that fabric) or the fiberglass either). Pic 2: Both woofers from the top after a thorough cleanup. No mildew... maybe some North Carolina pollen though. Looking much better. Cones measured 8.5" end to end; inner baskets were roughly 9.75" end to end. Pics 3 & 4: Both woofers measured right at 2.7 ohms. No worries there, correct? 4 ohm speaker. Will need to order the correct surrounds... any recommendations for that auction site or someone that stocks the proper 5/8" diameter roll? Continuing on the next post for the crossovers/rheostats... Link to comment Share on other sites More sharing options...
dtafil Posted July 31, 2018 Author Report Share Posted July 31, 2018 OK, onto the crossovers. Pics' 1 & 2: They appear to be identical! I'm happy about that. I noticed one of the rheostats has that wonderful green buildup. All of them will be coming out for a vinegar and salt bath, deoxit/dremel, and fader lube after that. I'll be checking out some caps tomorrow and placing an order on Wednesday or so. Any comments welcome on what you've observed. I used Dayton's for my AR5's a couple of years back, might be nice to try something new. These will primary be driven by a 150-220 watt/channel Marantz/Pioneer reciever for some classic Jazz and some good old R&R. Link to comment Share on other sites More sharing options...
lARrybody Posted July 31, 2018 Report Share Posted July 31, 2018 I too have a mismatched pair of AR3a's. This is my middle pair of three that I have. I did mention them here once but never elaborated on what they are.. Looking at yours reminds me of these. The speaker on the left has a serial number of 87147, about 9000 before your identified speaker except my midrange is front wired. I am thinking it is from around 1974. The speaker on the right is missing it serial number label, but by the A2 woofer (with the longer tinsel leads) puts it around 1970 right after the discontinuation of the alanco (cloth surround) woofers. If you look closely there are some slight cosmetic differences in the front baffles. Your other speaker with both upper drivers rear wired has to be late production and reminds me of the AR3a improved model. Believe it or not they are not really that far apart. The newer speaker woofer threw me for a second, but it is just because it has different dust cap, probably added when it was refoamed. Rick Cobb has the correct surrounds you will want to use. I am currently getting ready to work on my recently acquired third pair of AR3a's with cloth surround woofers. They came from the original purchaser and are Immaculate. Never touched, grills still glued on. I had purchased Dayton polys for the big caps,but started having second thoughts. Today I received these matched Mundorf E-caps and still debating which way to go. Opinions? Good luck on restoring your AR3a's. You definitely are at the right place for advice and opinions on whatever may come up with the process of getting them road worthy. Link to comment Share on other sites More sharing options...
DavidR Posted July 31, 2018 Report Share Posted July 31, 2018 2 hours ago, dtafil said: Both woofers measured right at 2.7 ohms. No worries there, correct? 4 ohm speaker. Typically measure 2.6 DCR Link to comment Share on other sites More sharing options...
genek Posted July 31, 2018 Report Share Posted July 31, 2018 Sprague Compulytic caps don't need to be replaced if they don't show signs of damage. Link to comment Share on other sites More sharing options...
Aadams Posted July 31, 2018 Report Share Posted July 31, 2018 4 hours ago, genek said: Sprague Compulytic caps don't need to be replaced if they don't show signs of damage. 0 There is a lot of experience on this forum that supports the above statement. Below is a post, from the highly respected Carlspeak, regarding Spragues as a result of his cap testing across many brands of old caps. You would more certainly get a better return on your investment with a tweeter rebuild. IMO Adams Forum Moderator Administrators 0 2,183 posts Gender:Male Location:North Central Connecticut Report post Posted January 20, 2012 Vintage but GOOD caps. Yes, there are some. Over some years of doing restorations and subsequent cap testing, I have found the AR Compulytic caps made by Sprague have stood the test of time. So now, when I retore an AR with these caps, I simply leave 'em in there. Below are tests done on the 150 uF 50 V and 50 uF 50V Compulytics found in some later AR3a's accompanied by tests run with the same calibration on ERSE 100V NPE caps of equivalent uF values. The 150 uF Compulytic cap that's wired in parallel with the 11 inch 3a woofer creates a 2nd order electrical rolloff. I estimate it operating passband to be in the 10 to 800 hz range. Here we see the range of uF to be 156 to 142, well within the10% tolerance printed on the cap. ESR is 2.1 ohms to 58 miliohms. The ERSE 150 uF cap's test showed similar results. However, the ERSE cap had a brader range of phase angle over the entire test range. The 50 uF Compulytic cap is an important cap for the midrange because it's wired in series with the midrange driver that operates from about 300 hz to over 5000 hz. It's uF range over that hz range was only 52.3 to 50.4 uF; quite impressive. ESR was .40 ohms to 19 miliohms. The ESR 50 uF cap performed similarly. The bottome line: Compulytics don't need to be changed out. OTOH, the Chicago Industrial caps, as was shown in a previous post should be replaced. Link to comment Share on other sites More sharing options...
dtafil Posted July 31, 2018 Author Report Share Posted July 31, 2018 28 minutes ago, Aadams said: 4 hours ago, genek said: Sprague Compulytic caps don't need to be replaced if they don't show signs of damage. 0 There is a lot of experience on this forum that supports the above statement. Below is a post, from the highly respected Carlspeak, regarding Spragues as a result of his cap testing across many brands of old caps. These are interesting comments to me, with some research to back them up. What I may do (as I need to pull the rheostats anyway) is to hook up my ESR meter to the caps (taking them out of circuit first) and see how mine are doing. If the Sprague caps are within 10% of the uF values, I'd probably leave them for now as well. Thanks for those pointers guys! Link to comment Share on other sites More sharing options...
dtafil Posted August 2, 2018 Author Report Share Posted August 2, 2018 Got all 4 rheostats disassembled and cleaned out today... also checked the 6 uF Sprague caps for the tweeters... one was spot on at 5.99 uF, the other a bit higher at 6.68 uF. Going to leave them both alone for now. The rear-wired tweeter tested open; wasn't the rheostat or cap. If anyone has a spare, AR3a rear-mounted tweeter for sale, please let me know... the hunt is on. I'd like to stay original for now. The second speaker's mid and tweeter are working fine; waiting on woofer surrounds for both. Will post up some new pictures tomorrow. Link to comment Share on other sites More sharing options...
JKent Posted August 2, 2018 Report Share Posted August 2, 2018 Those tweeters are old and tired. You can either replace them both with the popular Hi-Vi tweets or, if you must have originals, send both to CSP member chris1this1 to be rebuild. You could send just the dead one but then you'd have one freshly rebuilt tweet and one on its last legs and they won't match. -Kent Link to comment Share on other sites More sharing options...
dtafil Posted August 2, 2018 Author Report Share Posted August 2, 2018 12 hours ago, JKent said: Those tweeters are old and tired. You can either replace them both with the popular Hi-Vi tweets or, if you must have originals, send both to CSP member chris1this1 to be rebuild. You could send just the dead one but then you'd have one freshly rebuilt tweet and one on its last legs and they won't match. -Kent Thanks Kent. I do see others have done the Hi-Vi replacement with very good results, so I may do that as well. Initially, I'm reaching out to Chris. For my next Parts-Express order, I may just grab a pair of the Hi-Vi and inductors and see which setup I like more... I'd like to hear both I think. Link to comment Share on other sites More sharing options...
dtafil Posted August 2, 2018 Author Report Share Posted August 2, 2018 Some additional pics of the Sprague tweeter caps and a before & almost after of a rheostat... in case no ones seen that before ? Link to comment Share on other sites More sharing options...
JKent Posted August 2, 2018 Report Share Posted August 2, 2018 Outstanding clean-up job on the pot. That wiper on the left looks different. Is it original? Link to comment Share on other sites More sharing options...
dtafil Posted August 2, 2018 Author Report Share Posted August 2, 2018 1 hour ago, JKent said: Outstanding clean-up job on the pot. That wiper on the left looks different. Is it original? Thanks. The wiper on the left is indeed original - I found the ones under the wipers were a bit nicer to being with across all 4 rheostats. Got 'em back in the cabinets already :-) Link to comment Share on other sites More sharing options...
ra.ra Posted August 2, 2018 Report Share Posted August 2, 2018 2 minutes ago, dtafil said: The wiper on the left is indeed original - I found the ones under the wipers were a bit nicer Great photo documentation, dtafil. Just to clarify, do each of these pots have the thin double wipers - - one with contact nub and one with flat surface? Your pic of corroded pot seems to suggest this, but it is difficult to confirm. I once ran into this type of double wiper on original A-P pots in vintage AR speakers, but those speakers dated from 1964 or 65. On your (left) woofer, you can see that someone had used the wrong size foam replacement as evidenced by the radial splice seam at 10:00. Keep up the good work on your project - - - they're gonna turn out great. Link to comment Share on other sites More sharing options...
dtafil Posted August 2, 2018 Author Report Share Posted August 2, 2018 1 minute ago, ra.ra said: Great photo documentation, dtafil. Just to clarify, do each of these pots have the thin double wipers - - one with contact nub and one with flat surface? Your pic of corroded pot seems to suggest this, but it is difficult to confirm. I once ran into this type of double wiper on original A-P pots in vintage AR speakers, but those speakers dated from 1964 or 65. On your (left) woofer, you can see that someone had used the wrong size foam replacement as evidenced by the radial splice seam at 10:00. Keep up the good work on your project - - - they're gonna turn out great. Hi there - Yes, double contact wipers on all 4 rheostats. The one(s) with the upper & lower nubs were in the upper position. And yes, that one woofer "refoam" job looks like it was done with a glue gun and I noticed that splice as well. Industrious perhaps, but not my standards, lol. Link to comment Share on other sites More sharing options...
lakecat Posted August 3, 2018 Report Share Posted August 3, 2018 I have found the double wipers on the later serial numbered 3a's I have done. I like them. Link to comment Share on other sites More sharing options...
RoyC Posted August 3, 2018 Report Share Posted August 3, 2018 13 hours ago, lakecat said: I have found the double wipers on the later serial numbered 3a's I have done. I like them. Agreed, Jeff....the pots shown in dtafil's photos began being used sometime in the mid 70's . They had reinforced wipers, metal shafts (as opposed to the previous red or black plastic), and seem to be a bit more resistant to corrosion. Roy Link to comment Share on other sites More sharing options...
ra.ra Posted August 4, 2018 Report Share Posted August 4, 2018 8 hours ago, RoyC said: ....the pots shown in dtafil's photos began being used sometime in the mid 70's . Thx, Roy, I had mistakenly thought that these pots found in a pair of AR-4's (circa 1964±) were part of the original cabinet assembly. Link to comment Share on other sites More sharing options...
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