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New AR3a find and restoration thread


dtafil
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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

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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.

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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

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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...

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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.

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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.

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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.

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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.

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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?

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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.

 

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4 hours ago, genek said:

Sprague Compulytic caps don't need to be replaced if they don't show signs of damage.

 

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  • 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

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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.

 

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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!

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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.

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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

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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.

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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 :-)

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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.

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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.

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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

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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. 

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