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AR3 restore


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Just confirmed that my dad's mahogany AR3's were located. They were working fine over 20 years ago. I will have shortly. Since they have not been active in over 20 years should I just open them up and assess assuming there will be damage to drivers and xover components OR should I power up and assess by listening? Also do I need an amp that drives 4 ohms or will an 8 ohm amp suffice to assess. Any pitfalls to opening up - I assume by removing woofer. 

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Welcome! I would download the the AR3a restore manual from this site. It is a great reference for working on the 3.

Good advice and ask as many  questions as you like. There are some really great experts here.


Edited by RickB
bad english
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Hey restodad. Welcome!

The AR-3s are very collectible speakers so you are right to be cautious. I would suggest that you hook them up to a 4-ohm rated amp and turn up the volume slowly. Crank the knobs on the back back-and-forth to loosen any corrosion and see if you get sound from the tweeters and mids. If they sound good, maybe leave them alone.

There are many challenges to working on these. Do be sure to download the 3a restoration manual but the first challenge will be just getting into the 3s. Some have plastic grille frames, some have fiberboard. Either can be easily broken but the plastic is probably worse. The grilles are tucked under grooves on the short sides while just the saran plastic grille material is tucked under the long sides. The grilles have to be bowed for removal and breakage may result. Fortunately the original grille material is still available if you need it.

Inside, the tweeters and mids are extremely heavy, with insanely thin, fragile aluminum leads. Don't touch them unless you are absolutely certain they are shot.

The woofer will probably need to be re-doped but that's one of the last steps. If you decide to re-cap them, that's probably a good idea. Yes--you get inside by removing the woofer which is sealed to the cabinet with Mortite putty that by now is as hard as concrete. Refer to the 3a resto guide for removal technique. The original cap is a big wax block you can leave in place and just wire in a 6uF and 24uF cap. Bear in mind there were FOUR versions of the AR-3 xo so there will be slight differences depending on the SN. If your speakers are SN C70229 or higher they will have AR-3a mids and you will need a 30uF cap in place of the 24uF. For earlier SNs, I don't know whether experts here recommend building the 3rd revision xo or just keeping it original but if your speakers are so far apart that the xo's are different I would make them match.

I believe old 12" drivers can be plagued by sagging spiders but have no experience with those. Keep us posted on your thinking and progress and surely others will chime in.


AR-3a restoration: http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

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  • 3 weeks later...

Nice grab!

Great advice so far, but I'll note that the woofer sealing putty should still be quite flexible. The key to removing the woofers is to dig out as much of the putty that squeezed out between the baskets and cabs. Use a plastic taping knife to dig it out. Use a large flat blade screw driver to pry the woofers loose. Use a metal putty knife to protect the cab edges when prying the woofer loose.

Put some card board or pieces of fabric on the cabinet face frame trim to protect the surfaces from the woofers once lifted out and flipped over. These woofers are quite heavy so be prepared.

Depending on how old these are, there's a possibility they will have oil can caps. Those are very good and are usually fine. I would not replace those. If they have the big wax block caps, then yes, a recap is in order.

I would not try these with an amp that is not 4 ohm rated.


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