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Another AR-3a restoration


JKent

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I was asked to restore some AR-3a's. Turns out they still belong to the original owner who bought them from Sound Reproduction in East Orange NJ back in 1969 or 70. That's where I bought my 4x's at about the same time!

So my first thought is to adhere to the speaker doctor's oath of "first, do no harm." The cabinets and grilles are perfect! I'll clean the wood and oil them but nothing more is needed. The linen, although undamaged, shows its age so I'll install new linen from 123 Stitch.

These are early, with serial numbers in the 31,000 range, so they have the cloth-surround alnico woofers. I opened one today. The woofer is stamped Sep 17, 1969. Masonite on the surround and spider seem OK. The Kempac is intact but old, so I'll replace that with crinoline. The fiberglass is nasty, crumbly stuff. I put it in a bag and weighed it. Only 15 oz. Odd--it should be 28-30 oz and these "look" unmolested. I'll replace it with the correct amount of new, formaldehyde-free FG.

Pulled the wax bricks. The 150/50 measured 210 and 69uF. The 6 measured 7.8uF. I'll be using film caps as replacements.

All the drivers in this one work but there are lots of dead spots on the pots. I'll replace them with L-pads. Sort of undecided, for now, about what to do with the #7 inductor but there's lots of time to think about that and get input from others.

Photos will be posted when I have anything interesting.

-Kent

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Sounds like a really good project and I'll be interested to follow your efforts. Similarly, I'll be working on a pair of 3a's in the coming months with a friend of mine. This pair has great cabinets, grilles and badges. Have only conducted a brief cursory test/inspection, but all drivers are functional and pots are very crunchy and intermittent. These are consecutive serial numbers in the 461XX range and have the first generation ferrite-foam woofer (Fig A.2 in 3a restoration guide) and the brick-size double 50/150 cap. Probably next month we'll dig into these for a closer inspection, put together a parts list, and get to work. 

I'd be curious to know about the type of meter you're using for cap measurements, since I've never been fully comfortable with my meter for this application. Also, didn't the change in coil coincide with the change from alnico/cloth to ferrite/foam woofer? 

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Hey ra.ra

And I'll look forward to following your resto. 

To answer your questions, I had a cheap LCR meter and like you was not fully comfortable with it. I'm now using a B&K Precision 810C, which is very good for my purposes and less expensive than a Fluke. OTOH, it doesn't test inductance (L), which is sometimes helpful. Which brings us to your other question.

According to p. 17 in the restoration guide, yes. "In late 1969 or early 1970--probably at the introduction of the ceramic woofer--AR re-measured the 3a and increased the woofer inductor to 2.85mH (AR #9 coil)."  The guide says to either leave the #7, add a 1.0mH coil in series or replace the coil with a new 2.7uH (closest available off-the-shelf).

edit: That passage in the Guide is ambiguous at best. Fortunately we have Roy to set us straight. Latest word from him his there's no need to change the inductor with the alnico woofer. Good. Less work for me ?

Another bit of advice from Roy: the originals were over-damped at 28-30 oz. I'll use 20 oz. per speaker, which I think is 2 little bags of unfaced Johns-Manville FG.

Oh--one other thought about capacitance testing. It may be helpful to also test ESR. I have one of those dirt-cheap no-case LCR meters from ebay. Think they're under 10 bucks, shipped from China. They actually work and they test virtually everything: "Test ranges: Inductors, capacitors , diodes, dual diode , mos, transistor, SCR , the regulator, LED tube , ESR, Resistance, Adjustable potentiometer". You could spend a little more and get it on Amazon, with a case   https://www.amazon.com/Multifunction-transistor-Capacitor-Inductance-screwdriver/dp/B071Y5CHPK/ref=sr_1_20?gclid=Cj0KCQjwzunmBRDsARIsAGrt4mu6haKVP97dIgOgpmyVAD2H__8B8LraqC7qqIXNJoO-Y9RWMp9k4-AaAkq0EALw_wcB&hvadid=177795303352&hvdev=c&hvlocphy=9003579&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=10918808959811123088&hvtargid=kwd-309580207&hydadcr=25905_9903850&keywords=esr+tester&qid=1557840037&s=gateway&sr=8-20

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Quick update:

The original owner tells me these were never opened, but the 2nd one is also light on stuffing. No matter--I'll put in all new.

The big 150/50 brick measured 222/70. The 6 measured 7.76 uF.

The mid is fine but the tweeter, although working, is extremely weak. Time for a rebuild.

My PE order just arrived. Now the fun starts!

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On 5/14/2019 at 9:27 AM, JKent said:

Hey ra.ra

And I'll look forward to following your resto. 

To answer your questions, I had a cheap LCR meter and like you was not fully comfortable with it. I'm now using a B&K Precision 810C, which is very good for my purposes and less expensive than a Fluke. OTOH, it doesn't test inductance (L), which is sometimes helpful. Which brings us to your other question.

According to p. 17 in the restoration guide, yes. "In late 1969 or early 1970--probably at the introduction of the ceramic woofer--AR re-measured the 3a and increased the woofer inductor to 2.85mH (AR #9 coil)."  The guide says to either leave the #7, add a 1.0mH coil in series or replace the coil with a new 2.7uH (closest available off-the-shelf).

edit: That passage in the Guide is ambiguous at best. Fortunately we have Roy to set us straight. Latest word from him his there's no need to change the inductor with the alnico woofer. Good. Less work for me ?

Another bit of advice from Roy: the originals were over-damped at 28-30 oz. I'll use 20 oz. per speaker, which I think is 2 little bags of unfaced Johns-Manville FG.

Oh--one other thought about capacitance testing. It may be helpful to also test ESR. I have one of those dirt-cheap no-case LCR meters from ebay. Think they're under 10 bucks, shipped from China. They actually work and they test virtually everything: "Test ranges: Inductors, capacitors , diodes, dual diode , mos, transistor, SCR , the regulator, LED tube , ESR, Resistance, Adjustable potentiometer". You could spend a little more and get it on Amazon, with a case   https://www.amazon.com/Multifunction-transistor-Capacitor-Inductance-screwdriver/dp/B071Y5CHPK/ref=sr_1_20?gclid=Cj0KCQjwzunmBRDsARIsAGrt4mu6haKVP97dIgOgpmyVAD2H__8B8LraqC7qqIXNJoO-Y9RWMp9k4-AaAkq0EALw_wcB&hvadid=177795303352&hvdev=c&hvlocphy=9003579&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=10918808959811123088&hvtargid=kwd-309580207&hydadcr=25905_9903850&keywords=esr+tester&qid=1557840037&s=gateway&sr=8-20

I have never seen an original AR-3a cabinet with a #7 (1.88mh) coil when originally equipped with the later foam surround, ferrite magnet woofer, nor have I ever seen one with a #9 (2.85mh) coil when originally equipped with a cloth surround/alnico woofer. The #9 coil was used to compensate for the woofer change. There are probably quite a few 3a's in use today with later replacement foam surround/ferrite magnet woofers and #7 crossover coils, which is not a good combination. On the other hand, the alnico/cloth surround woofer can be used satisfactorily with either coil due to its smoother response.

A good rule of thumb is to replace the block caps, regardless of measurements.

Roy

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Finished one xo. I had forgotten how tight it is working inside that box but it’s all wired up. You can see the 3 original inductors across the top in this photo. Below those are the 6uF cap, Tweeter L-pad and Mid L-pad. Both have resistors installed per the AR-3a Restoration Guide. Then in the lower area are the 50+100uF bundle and the single 50uF cap. Some of the wires are new but I kept the original color coding.
On to the other one, probably tomorrow.

1st xo resized.jpg

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Finished the 2nd xo (2nd one always goes faster). Scraped gobs of duct seal off one woofer and cabinet. Cleaned the woofer flange with alcohol & Scotch Brite to prep it for PE foam gasket tape. Also soldered leads to woofer terminal tabs. Woofer will be easier to remove if needed.

2nd xo 1_edited-1.jpg

woofer_edited-1.jpg

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2 hours ago, JKent said:

Also soldered leads to woofer terminal tabs. Woofer will be easier to remove if needed.

Nice to see this detail - - and I agree with Larry - - a solid wire nut connection works fine for this purpose, and I've been re-building my speakers with this technique for the exact reason that JKent has already stated (future removal and access). Just be sure you put the Kimpac in before you connect the wire nuts. ;)

This 3a restoration project looks really good. Don't think I recall seeing you use Audyn caps before, but I know a speaker manufacturer in these parts that strongly advocates for this line of (red) Audyn caps. His opinion is that they offer excellent performance vs. cost value, and I'll probably be using this brand soon in some upcoming projects. 

On 5/14/2019 at 9:27 AM, JKent said:

I have one of those dirt-cheap no-case LCR meters from ebay.

Thanks for the meter info. That B&K meter looks pretty nice, and I've been thinking about trying one of those little cheapies, too, but I'm trying to find one that has a provision for wire leads with alligator clip.

On 5/15/2019 at 1:58 PM, RoyC said:

I have never seen an original AR-3a cabinet with a #7 (1.88mh) coil when originally equipped with the later foam surround, ferrite magnet woofer....

Thx Roy, I'll keep this in mind next time I poke my head into the pair I'll be working on. 

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Well, it all came together today. I put in the correct amount of stuffing: One 9 oz. bag of new pink fiberglass and 12 oz. of original crumbly yellow fg per cabinet. I put the pink in the top halves, which had been empty. These, oddly, had only about 14 oz. fg per box. The Restoration Guide says they originally had 28 oz. Roy said he and John did a lot of research on this issue and recommended 20 -24 oz. per. Also odd was that these had the later crumbly yellow fg which was not original to the 3a but Roy says is quite good. So I re-used it. Instead of Kimpac or crinoline, another great tip from Roy:  a single layer of low loft polyester batting from Walmart. It's great. Thin and acoustically transparent but it blocks all the nasty fg dust and it's basically the same as the poly speaker stuffing.

ra.ra: Those Audyn caps were a relative bargain. $26 for 100uF 400v 5% vs $33 for Dayton 100uF 250v 5%.

Re-installed the woofers and tweeters. Gave the woofers the 3-finger test and they came back a little faster than I would have liked so they got a coat of Roy's surround goo. For the dust caps, rather than waste the goo I mixed up some Aleene's Tacky Glue, a couple drops of water and a couple drops of Mixol #1 Black. Painted the baffles with the only black paint I had on hand: Gloss black Rustoleum. It's a little shiny but with the grilles on it will look great ?

An embarrassing confession (we're all friends here, right?). These speakers are so good they immediately revealed a mistake in my system's wiring. In my shop I have a speaker selector and #4 is a pair of speaker cables I use to test speakers. Never noticed a problem with lesser speakers but when I hooked up the 3a's, whoa! It was immediately obvious they were out of phase. A quick re-wire of the speaker selector and these babies were singing. Beautifully. They really sound wonderful. I'll be doing an A/B with my own 3a's and 91s but these sound perfect to me.

Not finished yet. Still have to re-cover the grilles with 18-count linen from 123 Stitch, re-glue one badge and apply a couple more coats of Watco oil. I did NO sanding on these. There are a couple of scratches on one speaker top and a few light scratches on both bottoms but nothing deep. I'm going to call it "patina" rather than take a sander to the veneer. It looks better in person than in the photo.

More pics to follow when they're totally finished.

batting copy.jpg

finished 3 copy.jpg

top scratches 3 copy.jpg

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Hi JKent, splendid work of "conservative restoration", from the photos we see that the tweeter is with the fabric dome, this is the solution proposed by Larry of V. AR?
What do you think about the sound of these tweeters and you were able to compare them with the original ones, if you can make a report, I think many of us would be interested in your evaluation !!

Giorgio.

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8 hours ago, Giorgio AR said:

Hi JKent, splendid work of "conservative restoration", from the photos we see that the tweeter is with the fabric dome, this is the solution proposed by Larry of V. AR?
What do you think about the sound of these tweeters and you were able to compare them with the original ones, if you can make a report, I think many of us would be interested in your evaluation !!

 

Thanks "eagle-eye" Giogio!

Yes, those are the tweeters sold by Vintage-AR. Our own RoyC builds them for V-AR. Roy has been a tremendous help on this project.

How do the tweeters sound? I did not compare them with the originals. One original was "OK" but the other was so weak I thought it was dead, so I sent them off to Roy. I do have my own AR-3a's but they have Hi-Vi tweeters so I can only compare to those (and will soon).

Initial impression of Roy's rebuilds: Excellent. They have a very strong output, so much that even with a 25 ohm resistor on the L-pad I have the level set at about half-way. The Mid level is about 3/4. I may fine-tune these settings. So with those settings, new caps, L-pads, resealed woofers these are extremely satisfying speakers. They are not placed ideally in my workshop but I played a variety of music ranging from Miles Davis to Bela Fleck to Beethoven to Fleetwood Mac. Bass was authoritative and solid, mids were clear with great sounding voices and the highs were crisp. I don't have all the audiophile babbel to describe them. They just sound good. They don't sound exactly like my 91s, which are theoretically just more modern 3a's, and I'm not sure which I prefer at this point but I'm leaning toward these 3a's at the moment.

-Kent

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3 hours ago, JKent said:

Thanks "eagle-eye" Giogio!

Yes, those are the tweeters sold by Vintage-AR. Our own RoyC builds them for V-AR. Roy has been a tremendous help on this project.

How do the tweeters sound? I did not compare them with the originals. One original was "OK" but the other was so weak I thought it was dead, so I sent them off to Roy. I do have my own AR-3a's but they have Hi-Vi tweeters so I can only compare to those (and will soon).

Initial impression of Roy's rebuilds: Excellent. They have a very strong output, so much that even with a 25 ohm resistor on the L-pad I have the level set at about half-way. The Mid level is about 3/4. I may fine-tune these settings. So with those settings, new caps, L-pads, resealed woofers these are extremely satisfying speakers. They are not placed ideally in my workshop but I played a variety of music ranging from Miles Davis to Bela Fleck to Beethoven to Fleetwood Mac. Bass was authoritative and solid, mids were clear with great sounding voices and the highs were crisp. I don't have all the audiophile babbel to describe them. They just sound good. They don't sound exactly like my 91s, which are theoretically just more modern 3a's, and I'm not sure which I prefer at this point but I'm leaning toward these 3a's at the moment.

-Kent

Kent, I work as a nurse and as such I am used to the observation and to the mental archive of the data collected (Tom Tyson is in my opinion the greatest observer and manages to catch all the details !!!).
Thank you for confirming what I saw and asked, I also appreciate your description on the sound of this pair of AR3a, clearly the speakers will need a proper break-in and use period to make a complete sound report and a comparison with your own AR91. I think you could even make the comparison with Hi-Vi tweeters, you have a rare opportunity to test two possible substitutes for the beloved paper dome tweeters!
Thank you

Giorgio

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Finished. I still want to spray the grilles with Scotch-Guard and do a comparison audition with my 3a's.

There's been some discussion of grilles and how to fasten them. I added a little linen pull-tab and all seemed good with just a friction fit but just to be safe I added 6 small pieces of Velcro.

finished7.JPG

finished14.JPG

finished15.JPG

finished17.JPG

finished18.JPG

finished21.JPG

finished12_edited-1.jpg

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Kent is a beautiful conservative restoration, even here there will be another twenty years of pleasant listening and pleasure of the sight of a splendid AR3a couple!

In my opinion, even without the grids, these speakers have a lot of charm, and this pair is very well finished aesthetically

Giorgio.

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On 5/25/2019 at 7:17 AM, lakecat said:

Look forward to hearing your thoughts on those tweeters.

My impression is the rebuilds are excellent and from a restoration point of view, a better choice than the Hi-Vis. I did some A/B listening, playing various music selections in mono and switching from one of these speakers and one of my own AR-3a's with the Hi-Vi tweeter. My 3a's started life as 3s. They have the same cloth-surround alnico woofers as these, AR-11 mids, the Hi-Vi tweets and home-built crossovers http://www.classicspeakerpages.net/IP.Board/index.php?/topic/6284-my-ar-33a-saga-a-csp-group-effort/&tab=comments#comment-87031

I heard no difference between the 2 speakers. I listened for "s" sounds on vocals and a variety of strings including classical and flamenco. I'll do some more listening, including some cymbals and snare drum brushes but I'd say the rebuilds and Hi-Vis are virtually interchangeable.

Of course these are septuagenarian ears. Maybe I should enlist a kid to help with the listening ?

Kent

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9 hours ago, JKent said:

My impression is the rebuilds are excellent and from a restoration point of view, a better choice than the Hi-Vis. I did some A/B listening, playing various music selections in mono and switching from one of these speakers and one of my own AR-3a's with the Hi-Vi tweeter. My 3a's started life as 3s. They have the same cloth-surround alnico woofers as these, AR-11 mids, the Hi-Vi tweets and home-built crossovers http://www.classicspeakerpages.net/IP.Board/index.php?/topic/6284-my-ar-33a-saga-a-csp-group-effort/&tab=comments#comment-87031

I heard no difference between the 2 speakers. I listened for "s" sounds on vocals and a variety of strings including classical and flamenco. I'll do some more listening, including some cymbals and snare drum brushes but I'd say the rebuilds and Hi-Vis are virtually interchangeable.

Of course these are septuagenarian ears. Maybe I should enlist a kid to help with the listening ?

Kent

Thanks for the testing and reply. I have a pair of Hi-Vi's in my original 3a's that Roy helped me with. The sound is superb and with being my keepers...not worried about resell value. But......I do keep a pair of 3a tweeters in storage....in case!...:)

The quality of the Hi-Vi's is a tribute to Roy for his testing and work on finding a reasonable cost alternative to the 3a tweeter when it wasn't repairable.

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On 5/31/2019 at 9:05 AM, lakecat said:

The quality of the Hi-Vi's is a tribute to Roy for his testing and work on finding a reasonable cost alternative to the 3a tweeter when it wasn't repairable.

Agreed. And now that I've listened to both the Hi-Vi and Roy's rebuild, with a variety of music, I can find no discernible difference.  I should mention that although I initially had these set at only about 1/2 I've since turned them up to over 3/4 volume. "Maybe" the Hi-Vi seemed slightly reticent but that can be explained (and corrected) by crossover modifications: The addition of the parallel .05mH inductor and the reduction of the 6uF tweeter cap to 3uF (Roy's latest thinking is to use a 5uF cap with the L-pads and skip the resistor) all have an effect on the sound. The refurbished 3a tweeter is a straight drop-in but I did use resistors on both the mid and hi L-pads on this restoration. Actually, on my 3a's I put a 6uF cap in series with the tweeter, effectively making the tweeter cap 3uF but also making it easily reversible. The lower value cap makes the Hi-Vi a bit more laid back. Other things that have an effect on the tweeter includes the wiring (like polarity or reversed). In other words, any very small differences that "may" be perceived between the Hi-Vi and the rebuild can be tweaked by altering the cap value, resistor, wiring and, of course, adjusting the level control. SO... I'm very glad I was able to put the rebuilds in Harry's 3a's. They sound great and look right. But I have no motivation to tear into my own 3a's to change the tweeters and crossovers. The pots and my preamp's tone controls afford all the adjustment I need.

-Kent

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