AR3a Guidance/Advice

[ADVENTAGIOUS]

Well this is my second post but so much more exciting than the first. I just acquired a very nice pair of AR3a's from the original owner. From pictures in "Restoring the AR-3a" guide that I downloaded it appears that mine are early ones from the late 60's. One of them has a serial # that you will see in the pics. There is hardly a scratch on the cabinets. My intentions are to replace the pots, add new speaker connectors, add new caps for the mid and high drivers, buy new badges (mine are missing) and lustfully listen to some beautiful sounds. I am concerned though with the damping pads on the cones as they are split around their inside circumference. I noticed this on several other members woofers but it didn't look as serious as mine. Since the publishing of the "Restoring the AR-3a-2007" guide are there any changes, suggestions, things learned from experience that I can implement on mine. I have been reading many of the posts and it gets a little overwhelming and...confusing. From the outside, everything looks great (except for the damping pads), the pots are quite bad and grab when you try to turn them slowly. I have not tried to listen to them yet with the pots in this condition for fear of creating a problem. I guess I could jumper the pots to check the rest out.......just a little nervous right now. I am fortunate to own a pair of the OLA Advents, a pair of Small Advents, a pair of AR7's, and pair of KLH17's and now a pair of these legends. Please have a look at my photos. Any advice you can offer would be greatly appreciated.

I found these Ohmite pots on the web today and am hoping that these are the ones that have been recommended on other posts...

http://www.alliedelec.com/search/productde...spx?SKU=2964220

[JKent]

If you want the Ohmites, check out this thread or send me a PM

http://www.classicspeakerpages.net/IP.Boar...9&hl=ohmite

Kent

[RoyC]

Well this is my second post but so much more exciting than the first. I just acquired a very nice pair of AR3a's from the original owner. From pictures in "Restoring the AR-3a" guide that I downloaded it appears that mine are early ones from the late 60's. One of them has a serial # that you will see in the pics. There is hardly a scratch on the cabinets. My intentions are to replace the pots, add new speaker connectors, add new caps for the mid and high drivers, buy new badges (mine are missing) and lustfully listen to some beautiful sounds. I am concerned though with the damping pads on the cones as they are split around their inside circumference.

ADVENTAGIOUS,

They look like nice specimens! Other than some sources for materials, and experimentation with replacement tweeters for the aging originals (see attached pics), there is really nothing new to report. BTW, if you are going for new badges from Vintage AR, you may want to contact him soon. He told me he is down to a few pairs of original 3a badges, and his reproductions (which I always thought were excellent) will be plastic going forward.

I would not worry about the damping pads on the woofers. They look quite acceptable.

What are your plans for the "speaker connectors"?

Attached are a few pics of a 3a restoration I finished yesterday, sporting replacement tweeters for the missing originals.

Roy

[Carlspeak]

I think Larry's already run out of the metal 3a badges. I received to pair last week and they're plastic.

[JKent]

Carlspeak said:

I think Larry's already run out of the metal 3a badges. I received to pair last week and they're plastic.

I'm looking into having some made but won't know until next week if it can be done. In the meantime, I do have some reproductions of the small square ones (found on the 4x, turntable, etc) and larger square ones (found on some 2ax's & ?). They are similar to Larry's but cheaper. I also have some nice repro KLH badges. Eventually these will be listed in the For Sale section but I'm waiting to see if the heavy engraved brass plates (3a, 2ax, 7 etc) are doable. Stay tuned.....

Kent

[tysontom]

Well this is my second post but so much more exciting than the first. I just acquired a very nice pair of AR3a's from the original owner. From pictures in "Restoring the AR-3a" guide that I downloaded it appears that mine are early ones from the late 60's. One of them has a serial # that you will see in the pics. There is hardly a scratch on the cabinets. My intentions are to replace the pots, add new speaker connectors, add new caps for the mid and high drivers, buy new badges (mine are missing) and lustfully listen to some beautiful sounds. I am concerned though with the damping pads on the cones as they are split around their inside circumference. I noticed this on several other members woofers but it didn't look as serious as mine. Since the publishing of the "Restoring the AR-3a-2007" guide are there any changes, suggestions, things learned from experience that I can implement on mine. I have been reading many of the posts and it gets a little overwhelming and...confusing. From the outside, everything looks great (except for the damping pads), the pots are quite bad and grab when you try to turn them slowly. I have not tried to listen to them yet with the pots in this condition for fear of creating a problem. I guess I could jumper the pots to check the rest out.......just a little nervous right now. I am fortunate to own a pair of the OLA Advents, a pair of Small Advents, a pair of AR7's, and pair of KLH17's and now a pair of these legends. Please have a look at my photos. Any advice you can offer would be greatly appreciated.

I found these Ohmite pots on the web today and am hoping that these are the ones that have been recommended on other posts...

http://www.alliedelec.com/search/productde...spx?SKU=2964220

ADVENTAGIOUS,

You have a very nice, original pair of AR-3a speakers, and it is likely they were manufactured in the fall or winter of 1967, shortly after the AR-3a was officially introduced to the public. The speakers appear to be finished in Cherry -- possibly Oiled Teak -- both of which are fairly rare finishes, as most were finished in Oiled Walnut. I can't tell for sure on the finish, so please post some additional images of the cabinets (downgrade your camera's resolution setting to "Medium" to avoid such large files) would be great.

The splits on the damping rings on the #3700 AR-3-type woofer are completely normal; don't worry about it, but don't remove the damping rings or alter them in any way. The woofer shown in your picture has never been removed from the cabinet. While the woofers are still mounted in the cabinet, take your fingers around the outside of the dust cap and gently push in the woofer cone inward about 1/4-inch, hold for a second and then release quickly. Note how fast the cone returns to the center or "normal" position. If the cone bounces back instantly, you might need to add some of Roy's cloth-surround treatment; if the woofer return slowly, as if in a viscous fluid, then they are fine, and you don't need to touch them. By the way, the midrange driver shown in that one picture is original; the tweeter shown is the later "back-wired" factory-replacement unit, which is fine. Send pictures of the other speaker if you can, as well as shots of the cabinet.

I would suggest that you not retrofit the level controls unless the ones you have are oxidized or corroded beyond repair. You should clean the original ones first, and then give it a try. Usually, a Dremel Tool works great to refurbish the controls, and they can usually be made to resume normal operation. There is also no absolute guarantee that the crossover capacitors are bad, but most on the forum would recommend changing them -- that's your option.

Beyond that, those speakers look great, and you are quite lucky to find a pair in this condition and this early in production!

--Tom Tyson

[danajohnhill]

Advantageous,

I'd like to echo some of Tom and Roy's advice. The splits in your woofer's rings look exactly like those on my own, and mine perform perfectly. Also, he's spot on about your woofer's seals. That was the first thing I noticed in your picture. I have a pair of 1969 AR3as (the date of production on yours will be stamped in ink on the back of the woofer), and mine needed re-sealing. I used Permatex and it worked great. Also, don't be so quick to replace your potentiometers. If you have a one-owner pair (like I do), and that owner took decent care of the speakers, you may find that you have only a moderate amount of green crud to clean off the inside of the pots. A Dremel tool with a wire brush attachment will clean them up in a matter of seconds and cost you no money. Others can give you advice on the best caps to buy.

It looks like you have a later tweeter, and someone has added Velcro to hold on the grill, but that's actually pretty handy. I had to pry my grills off the cabinets, since the forty-year-old glue still held tight.

The AR3a restoration guide is a masterpiece you owe it to yourself to print and keep handy during your project. And, if it helps at all, you can browse my gallery of AR3a photos I took last January during my project. I was lucky to receive a set of 100% original 3as in immaculate condition, with the badges and all, and I took many close-up photos of parts before and after clean-up.

http://www.flickr.com/photos/danajohnhill/...57623145435801/

Dana John Hill

[ADVENTAGIOUS]

Thanks for all the advice. I still haven't opened them up yet.....nervous as h*ll. Will do the cone test before I do that for the surround sealing suggestion. I did order new Ohmite pots......just in case. Should I go ahead and recap the x-over...could you please recommend brand etc. I only want to open these up one time if that is possible. I will post progress. File sizes will be much smaller this time.

[JKent]

Thanks for all the advice. I still haven't opened them up yet.....nervous as h*ll. Will do the cone test before I do that for the surround sealing suggestion. I did order new Ohmite pots......just in case. Should I go ahead and recap the x-over...could you please recommend brand etc. I only want to open these up one time if that is possible. I will post progress. File sizes will be much smaller this time.

Recommend the brand? Boy, are you opening a can of worms!

Seriously, look at the restoration booklet, page 16. The 6uF is a no-brainer. Use a film cap. Carli 6uF caps from Madisound are just $1.50. Many people like Solens--they are $3.65.

For the 50uF, you can get Solens for 16.60 each, or use non-polarized electrolytics aka NPEs (Madisound has Bennic for 1.70 each)

The 150uF is big and expensive. Solens are 40.70 each, the NPEs are 3.70 each. Big difference. And the Solens are 62mm x 82mm--that's about 2 1/2" x 3 1/4". Big suckers.

Remember, the speakers originally had NPE caps, not expensive film caps. The big advantage to the film caps is that they will last forever, while the electrolytics will last 15 - 20 years.

So consider your budget and your future plans. NPEs are good enough. Film caps are very nice. And you can mix them. No need to stick to one brand or one type. You could use Carli 6uF, Solen 50uF and Bennic 150uF (just as an example).

SOME golden-ear listeners report that some caps sound better than others. If you have golden ears and deep pockets you can get some very big, fancy capacitors.

So: You should replace the old caps but ANY new caps will be an improvement.

Good luck

Kent

[danajohnhill]

In keeping with what JKent said, I should mention that when I did my AR-3a restoration this year, I installed inexpensive caps. I am aware that I'll have to replace them down the road, but that's no biggie to me. My speakers sound outstanding no matter.

I completely understand your feeling nervous. I was totally green when I got my speakers six months ago. They had NEVER been opened up before, and I had never even learned to read a schematic. With the advice here, and a little from a coworker, I managed to get by, and learned to understand the schematic perfectly by the end. I did all the work myself, and, after one hiccup, my speakers came out perfect. They have, without exaggeration, changed my life.

Give yourself a weekend, have your computer handy, the AR-3a restoration guide ever-ready, and the required tools, and you'll be fine.

[ADVENTAGIOUS]

Well I finally opened one up. It took the best part of 2 hours to get the woofer out of the cabinet. I used a small curved utility knife and a pick to get as much sealant as I could from around the speaker before attempting to pry up on the metal frame. I also made a tool from a piece of metal roof flashing to cut through the sealant around the circumference (about 3/16") underneath the edge of the speaker frame. I wanted to remove (break) as much of the adhesive factor of sealant before I started prying up on the woofer. Next time I think I will try a dental scaling tool to get underneath the outer edge and see how that works compared to my tool. The paint lid opener was fine for prying but I'm going to make another tool to get more leverage for the second one..........I don't want to leave any marks on the plywood. I did order Ohmite pots from Kent just in case the originals are unsalvageable.....received them yesterday...thanks Kent! I would like to consider testing the caps (ESR) before new ones are ordered. Any inputs on that?

Forgot to mention that the previous owners called and said they found the owner's manuals for them so we made a quick trip to pick them up. There were also some other docs including AR Stylus info that I will scan and post later.

Today I opened one of the pots (couldn’t wait). Actually it didn’t look too bad. I filled up a plastic DeOxit cap with vinegar and salt (recommended from another post) and dipped the pot into the bath for a couple of hours. (I didn’t want to cut any wires at this time). Well after a couple of hours the corrosion disappeared but also the same portion of plating that was covering the copper. Was this a No No with the brine???! Someone suggested that applying dielectric grease will prevent any future corrosion ......Any inputs on that? I haven’t touched the other 3 yet. Should I just go ahead and install the new pots?

Some photos attached for a look. Thanks for all inputs.

[genek]

Today I opened one of the pots (couldn’t wait). Actually it didn’t look too bad. I filled up a plastic DeOxit cap with vinegar and salt (recommended from another post) and dipped the pot into the bath for a couple of hours. (I didn’t want to cut any wires at this time). Well after a couple of hours the corrosion disappeared but also the same portion of plating that was covering the copper.

Those parts are not plated copper, they're solid brass. Brass is an alloy of copper and zinc, and as the alloy oxidized and pitted over the years, copper and zinc were leached out of the brass at different rates. The salmon/pink surfaces you see now are a thin layer of copper left behind when zinc was eaten away. You could grind through it to expose new brass, but there's no point in it. Just reassemble the pot and coat the moving parts with dielectric grease to help retard future oxidation.

[JKent]

Nice photos. We love pictures. They're still a bit large tho.

If you read the 3a restoration booklet, p. 16 "Replace Capacitors?" you'll see the answer is "YES!" Those wax caps are old and most certainly out of spec.

The pots are your choice: You have new Ohmites now and they are heavier-duty than the originals. OTOH, the originals are fine--just need a little buffing and some dielectric as Gene said. And you'll need some kind of shield to keep fiberglass fibers out of the windings. As I mentioned, I think cheap little plastic storage containers (Zip-Loc?) should work fine.

btw--those speakers look beautiful! They were obviously well cared for (how many people still have the literature for their 40-year-old speakers?) Tom pointed out they are early, with rare finishes and in great condition. What a score!

For those reasons, you may want to keep them as original as possible, so maybe keep the A-P pots. But originality is NOT desirable when it comes to caps that are w-a-y past their life expectancy.

Speaking of original condition--I would NOT replace the binding posts. They are simple but work fine. Just crimp ring terminals to your speaker wires and tighten the knurled nuts--you will have a secure and original connection.

No word yet on the reproduction logo plates but hope to know within a week or so.

Congratulations, and good luck. Keep us posted!

Kent

[JKent]

Bad news on the logo plates. My engraver guy can't make the original thick brass. Sorry.

I do have The square brass-color logo plates that were used on early 2a, 2ax etc. Also smaller ones for 4x, turntable etc. And some KLH and Advent repros. Will put together an ad for the FS section one of these days.

Kent

[ADVENTAGIOUS]

Well I decided to dump the original pots. I tried cleaning the 2nd one and the wiper just looked to pitted for my liking so I'm not going to waste any more time on them. Besides, I had already acquired 4 Ohmite pots from Kent just in case. I have been spending a bit of time on this thread (Ohmite Pot Covers) to see what I could do to protect those new pots. In the meantime too, I acquired Solen PP caps for the high and mids and a Bennic 150 uf for the low from MS. The Bennic looks a little inadequete for my liking, it is quite small although the spec is correct. So, I started to remove hardware today to start fitting of the new pots and thought I might as well check the cap values (my new cap tester...yay!!) and here is what I found; the 50uf measured 64, the 6uf measured 6.56 and the 150uf measured 165. All appreared a lot closer than I expected. The new ones were bang on!! My question is...can I still use the original big one (150uf) and just replace the mid and high caps? Doing the math, the big one is 10% out of spec. I don't think I want to use the Bennic and new big ones are at this moment too expensive for me. By the way, I had to double up on the 3uf caps (thumbnail) as the 6uf were out of stock.

[Mexicomike]

Replace all the caps. There is no reason to fool around with leaving any of the originals in the circuit. I thought my 3As sounded fine with the original caps but when I recapped one of them and A/Bd the two speakers, there was an obvious difference in clarity and realism. Cap testers do not simulate the load in the circuit and therefore, especially with an old cap, what the meter says the capacitance is and what actually happens in the circuit can be quite different.

I would retain the original pots. The pitting wont hurt anything and if you use dielectric grease, as others have advised, they will work perfectly with no issue at all. Same is true of the speaker connectors - also as others have advised, leave them as is and put an appropriate connector on the speaker cable.

After all that it's just a matter of hooking up a good amp and off you go!

[ADVENTAGIOUS]

So Mexicomike, you think those little Bennics will do the job. Compared to the originals they look wimpy. Specwise, they should I guess. I did read something on another thread somewhere here that said not to worry too much about the woofer cap but definitley replace the mid and tweet.

[Carlspeak]

The Bennic NPE's may look 'wimpy' compared to the original caps but they are a very good cap. I have measured the Bennics and found them to measure quite flat at their spec'd uF and phase is flat across the freq. spectrum from 10 to 20 kHz.

The 150 uF cap is only a few $ and worth it while you have the speaker's innards exposed.

IIRC, the drill is twist the ends of the 50 and 150 together and connect the blue wire there. Then connect the black to the other end of the 150 and the green with to the other end of the 50. Solder and you're done.

[JKent]

On 3/24/2011 at 12:37 PM, ADVENTAGIOUS said:

I acquired Solen PP caps for the high and mids and a Bennic 150 uf for the low from MS. The Bennic looks a little inadequete for my liking, it is quite small although the spec is correct.

No worries. Check page 16 of the restoration manual. NPEs are fine--that's what was used originally and they may sound better to some because the ESR is similar to the originals. OTOH if you want them to last forever, use film caps. Problem is, they're big! The Daytons are probably the most compact and lowest price but they are still big and expensive. And you'll have to parallel them. Here is a shot of my newly-constructed 3a xo being test fit in the cabinet. I used 100uF + 50uF Daytons but if you go that route three 50s, stacked in a pyramid may work better.

btw--I took your advice and drilled a 1" hole in the plastic pot enclosure. Hole faces downward and is covered with fiberglass screen.
Kent

edit: Coil #9 is too close to #4. See post #29. Coil was moved.

[Mexicomike]

No worries. Check page 16 of the restoration manual. NPEs are fine--that's what was used originally and they may sound better to some because the ESR is similar to the originals. OTOH if you want them to last forever, use film caps. Problem is, they're big! The Daytons are probably the most compact and lowest price but they are still big and expensive. And you'll have to parallel them. Here is a shot of my newly-constructed 3a xo being test fit in the cabinet. I used 100uF + 50uF Daytons but if you go that route three 50s, stacked in a pyramid may work better.

btw--I took your advice and drilled a 1" hole in the plastic pot enclosure. Hole faces downward and is covered with fiberglass screen.

Kent

[Mexicomike]

Just curious, what is the purpose of the pair of wire-wound resistors? Their are (were) none in my AR3As which had all the original Xover parts/caps in place when I disassembled them.

[ADVENTAGIOUS]

Mexicomike, did you post a reply?

[Carlspeak]

Just curious, what is the purpose of the pair of wire-wound resistors? Their are (were) none in my AR3As which had all the original Xover parts/caps in place when I disassembled them.

I'll jump in here and answer for Kent. They are 1 ohm resistors he put in there to simulate the apparent ESR (equivalent series resistance) of the old caps. I think that might be a bit high. Pete Basel (Advent guru) recommends 0.23 to 0.3 ohm resistors be put in series with film caps replacing vintage caps. The purpose of adding the resistors is to minimize a possible dramatic apparent shift in the high freq. sound that might be objectionable.

I've recently measured an AR-6 10 uF paper/wax cap of the same type used on AR3a (6 uF). The ESR was about 0.33 ohms at 1.1 kHz (typical measurment freq.) and 0.283 ohms at 1460 hz around the crossover point where the cap takes over. The ESR drops from there to 0.143 ohms at 20 kHz.

[ADVENTAGIOUS]

Kent, do you want to do mine? Nice work!!!!! Did you build the Xover outside the box on a piece of plywood and then secure it inside? Are those the series resistors for the PP caps? Lots of questions eh?

[Carlspeak]

Kent, do you want to do mine? Nice work!!!!! Did you build the Xover outside the box on a piece of plywood and then secure it inside? Are those the series resistors for the PP caps? Lots of questions eh?

Try reading my post just above your last one.