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Upcoming AR3a project


fran604g

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A friend of mine called me last week, telling me he found a pair of AR3a's at an estate sale for $10 and would I like them? He said he Google'd them and saw they were selling on eBay for hundreds of dollars. I told him I didn't know anything about them and value would depend on the typical problems associated with the old surrounds, xovers, etc.

I came over here and did a quick search and called him back.

I asked him if he was intending on flipping the 3a's and if he was, I'd help him check them out and get them fixed up, or point him in the right direction to parts them out, or whatever. He said, "NO, you can have them if you want them, I just thought of you, because you're the only audiophile that I know." I almost pissed my pants, that's the first time anyone ever called me that. He told me to come over and take a look when I got a chance.

A week later, I finally got over to his place to check them out, he had the grills off and told me that I was right about the surrounds being junk. I asked him what he wanted for them, and wound up giving him $20 for them.

They're not mint, but they're in nice enough condition that I think they're the perfect speakers to do a complete restoration on. I think I will team them up with my ADCOM GFA-555 or my TAD60, as I've read that they like a lot of power to perform optimally.

Preliminary inspection has indicated to me that the one, SN 3A 04125, has been worked on. The tweeter and midrange are newer models, it seems, with internal wiring that has been brought out through the front baffle via 2 drilled holes with no seal.

The second unit, SN 45696, appears to be completely original.

Both units obviously need new foam surrounds, but both look like identical woofers to me with the masonite ring.

I looked around here, but didn't see any particular foam surround kits I should buy for them, but I did see that I should use 5/8" bead foam, is this correct?

I hope to get your thoughts from you folks, as I have zero knowledge of this speaker system...for now ;)

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Edited by fran604g
Added photos to replace broken links 3-13-2019
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Great find! Great friend!

Many of us use kits from M Sound. Very complete kits, correct for your speakers, and good email support.

http://www.ebay.com/itm/AR-3-AR-3a-reFoam-Kit-11-Woofers-Repair-Foam-Kit-/330517316989?pt=US_Amplifier_Parts_Components&hash=item4cf45e057d

Good luck.

Kent

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Yup, Kent is right. John at M Sound is the guy to get the surrounds from. Great guy.

I assume you found the AR 3a restoration guide by now. If not go to the library and down load it. It's here: http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

Good luck with your 3a's. I got a set late last year and rebuilt them......to this day I'm still amazed with the sound of them.

I'll be curious to hear from some of the experts here with their take on the different mid and tweets.

John

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Well, I just battery tested the drivers and they all work, except one tweeter. I checked for continuity and it is broken somewhere. I checked and resoldered the outside exposed connection and it is good, so maybe the vc is damaged. I will take it out of the cabinet and investigate further soon.

I don't have a decent DMM so I can't check DCR at the moment.

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Yes, the one on the right has been retrofitted with newer back-wired drivers dating from the mid-1970's. They appear to be the correct replacements, so if the drivers are working and wired correctly you shouldn't need to do anything but seal around the holes in the cabinet.

5/8" roll is correct for the foam.

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Yup, Kent is right. John at M Sound is the guy to get the surrounds from. Great guy.

I assume you found the AR 3a restoration guide by now. If not go to the library and down load it. It's here: http://www.classicsp...ring_the_ar-3a/

Good luck with your 3a's. I got a set late last year and rebuilt them......to this day I'm still amazed with the sound of them.

I'll be curious to hear from some of the experts here with their take on the different mid and tweets.

John

Thanks John, yes I saw the restoration guide and downloaded it before I went to look at the speakers. It is invaluable, for sure. I can't wait to fire these babies up for the first time. I love my KLH 6's and I've read that some people think they're comparable.

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Yes, the one on the right has been retrofitted with newer back-wired drivers dating from the mid-1970's. They appear to be the correct replacements, so if the drivers are working and wired correctly you shouldn't need to do anything but seal around the holes in the cabinet.

5/8" roll is correct for the foam.

That's good to hear, thanks genek

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Well, I decided to take a closer look at the speaker with the open tweeter. With my magnifying work light and a pair of tweezers, I was able to very carefully remove the tape that was on both leads going to the terminal strip.

After I pulled the bottom piece of tape that held the positive lead in place, I realized it wasn't connected to the VC lead. The wire had appeared to be disconnected from the bottom of the dome where I assumed the end of the wire had been going through the silicone where it was internally connected to the VC.

I was very wrong about the attachment point! I couldn't see the actual VC lead until after I took some macro photos!

Tweeterwiringmacropicwithtext-1.jpg

Tweeter wiring macro pic with text (Large).JPG

Edited by fran604g
Added image to replace broken link 3-13-2019
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Not yet, my DMM died and I need to buy a new one. I did a 1.5V AA battery test and it works! :) YAYAYAYAY to say the least.

I am absolutely going to reattach the wire, it's just that I need to think very carefully about how I am going to do the reattachment; all aluminum tools for instance, and a much higher magnification worklight and/or optics.

But, I don't really know how I'm going to actually fuse the copper wire to the VC lead, it looks like it's aluminum, so I'll need some advice with that. Somewhere I saw an article on reconnecting broken wires, but I can't remember where, probably it was here.

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I just realized that I have the polarity switched on my above picture. According to the sketch I found in the repair document, the right side of the tweeter is NEGATIVE. When I get time, I will correct that mistake, sorry ;)

Edit: Tweeter lead picture diagram fixed.

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I managed to solder it! Very carefully, of course. I have 1.5 ohms at the terminal. I see it should be between 2.3-3.5 ohms. I don't understand what could be wrong. Can someone give me advice?

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Edited by fran604g
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Good morning folks,

Today I will be ordering the surrounds for the 2 woofers.

This morning, I measured the tweeter I repaired yesterday and got ~3ohms. I then measured the midrange driver and got 2.9ohms. So I guess I'm in the ballpark with both of these drivers, but I really need to buy a new DMM that I can trust. This one is a cheapy Cen-tech that actually came with my TAD-60 amp for biasing the output tubes. I checked the 2 in the other cabinet and got ~3.8ohms on both of them. It looks like everything is going to work out with the drivers, at least.

When I remove the woofs to refoam, I'll check the crossover network and go from there as needed.

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This morning, I measured the tweeter I repaired yesterday and got ~3ohms. I then measured the midrange driver and got 2.9ohms. So I guess I'm in the ballpark with both of these drivers, but I really need to buy a new DMM that I can trust.

When I remove the woofs to refoam, I'll check the crossover network and go from there as needed.

Nice job of reconnecting the leads...

Make sure your solder joint is not touching the bare metal surface around the tweeter dome. A partial short circuit could be the reason for your low readings. If so, you may have resolved the issue when you re-taped everything.

Roy

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Thanks Roy, for your insight.

I actually think that's what happened. I wasn't thinking yesterday because I was so excited to see my very scary and nerve wracking solder job actually work out! When I put the tape on later, I was very careful to make sure the VC wire was as centered in the urethane as I could manage, also. Too exciting!

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Fantastic pics in this post, and kudos for being able to salvage this ailing tweeter - - - you get an A+ in Soldering on your summer report card! These teeny delicate wires for these external (electrical tape) connections always make me very hesitant to remove these drivers - - after the 40 year-old black tape begins to lose its adhesive qualities, the entire connection tends to seem so fragile it is almost begging to fail even if you just take the grille cloths off too frequently. I certainly don't know what went into the decision-making design of these drivers originally, but I've always felt these little external wiring solutions were somewhat antithetical to the rest of the classic AR product (non-acoustical) design objectives - - - clear and simple, robust, and maintainable.

Since some of these front wired drivers were eventually replaced with rear-wired versions, I often wonder why that was not the original solution from the get-go? This leads to my curiosity with this particular speaker restoration project - - - when original front-wired drivers are replaced with rear-wired drivers (see AR-3a on right), why isn't the external terminal bypassed altogether and replaced with wiring direct from the crossover components to the driver's rear terminals, thereby eliminating not one, but two, penetrations of the baffleboard?

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Since some of these front wired drivers were eventually replaced with rear-wired versions, I often wonder why that was not the original solution from the get-go? This leads to my curiosity with this particular speaker restoration project - - - when original front-wired drivers are replaced with rear-wired drivers (see AR-3a on right), why isn't the external terminal bypassed altogether and replaced with wiring direct from the crossover components to the driver's rear terminals, thereby eliminating not one, but two, penetrations of the baffleboard?

I agree. Here's one of my AR-3's. converted to 3a with new Hi-Vi tweeters and AR-11 mids, both rear-wired. I really hate those front-wired drivers (on the Allisons, too).

Kent

post-101828-0-99585300-1346724086_thumb.

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I certainly don't know what went into the decision-making design of these drivers originally, but I've always felt these little external wiring solutions were somewhat antithetical to the rest of the classic AR product (non-acoustical) design objectives - - - clear and simple, robust, and maintainable.

The 3a era dome drivers were actually very friendly compared to the earlier AR-3/2a domes equipped with aluminum leads. It is extremely unlikely fran604g would have been able to accomplish the same repair on one of those buggers.

AR didn't move to rear wired dome tweeters and mids until the mid 70's. Given the cabinet grilles were glued on with lots of hot glue to that point, AR probably didn't expect anyone else would be doing repairs, much less discussing this issue 40 years later. :)

Roy

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Fantastic pics in this post, and kudos for being able to salvage this ailing tweeter - - - you get an A+ in Soldering on your summer report card! These teeny delicate wires for these external (electrical tape) connections always make me very hesitant to remove these drivers - - after the 40 year-old black tape begins to lose its adhesive qualities, the entire connection tends to seem so fragile it is almost begging to fail even if you just take the grille cloths off too frequently. I certainly don't know what went into the decision-making design of these drivers originally, but I've always felt these little external wiring solutions were somewhat antithetical to the rest of the classic AR product (non-acoustical) design objectives - - - clear and simple, robust, and maintainable.

Since some of these front wired drivers were eventually replaced with rear-wired versions, I often wonder why that was not the original solution from the get-go? This leads to my curiosity with this particular speaker restoration project - - - when original front-wired drivers are replaced with rear-wired drivers (see AR-3a on right), why isn't the external terminal bypassed altogether and replaced with wiring direct from the crossover components to the driver's rear terminals, thereby eliminating not one, but two, penetrations of the baffleboard?

This is a point of contention for me with my project in particular. I have thought very seriously about swapping the high and mid range drivers, changing the crossovers and pots and keep the original components as relics. I am going to do the resto first, and if I'm not 100% satisfied with the sound, I will consider doing that more seriously. I am kind of an "all original" enthusiast, though, so I doubt I will actually swap things out. I still may try to match the original unit to the "upgraded" however, but it remains to be seen if that is really necessary.

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AR didn't move to rear wired dome tweeters and mids until the mid 70's. Given the cabinet grilles were glued on with lots of hot glue to that point, AR probably didn't expect anyone else would be doing repairs, much less discussing this issue 40 years later. :)

Roy

It is pretty amazing that we are still enjoying these classics. I feel very fortunate to be a small part of that bygone era and the philosophy that made it possible.

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