AR-3a Refoam

[Guest]

I am in the process of refoaming a pair or AR-3a

woofers. The woofers have a masonite? ring around

the basket about 1/4 inch or so in height. Do I remove

the ring or keep the ring and apply the foam onto the ring?

I would be interested in hearing from someone who has done

this before. Thanks

juliankowa

[Guest]

I refoamed the AR-3a with the ring in place and now I can see

why the ring was on the basket in the first place. If the ring

were removed than the cone and spider would sit too low in the

assembly. I refoamed without removing the dustcap and I can say

that everything seems in proper alignment. Of course this is

not my first refoam work as I have done at least 25 sets of

speakers over the past few years, but it was my first AR-3a

and I have previously fixed a pair of older AR-3 speakers. I also am in the process of replacing all the capacitors on the

AR-3a speakers.

[Guest]

Interesting stuff.....

If its pretty easy to refoam these - I wouldnt mind having a go.

I bought a pair of 94's from a garage sale for US$150 and a pair of 38's from another garage sale on the weekend for US$20.

Where can I get some foam surrounds for these?

The local Hifi shop will do them and do a full test for US$40 per speaker....not sure if I should go that route though....If I do - maybe they should replace the caps as well....heard this can make quite a difference.

[Guest rickcee]

Hi In general - if you have no experience and you want some assurance of quality job (therse were once high q. speakers ) I'd suggest prof. job - I tried to do the surrounds on my Mom's Ar spks - the kit I bought didn't fit (1/2 or even 3/4 " too big ) and result not great. For what - $15. ea over cost of the kits ? Of course if the object is really learning to do . . . anyway Rick

[Guest]

This AR woofer is its own unique size, really an 11" instead of a 12" as AR lists it, so refoaming them naturally take a special size surround. Some DIY foam kit vendors get their surrounds from "far east" suppliers, and they don't make this odd piece. There is one US manufacturer who has the correct dies to make this surround [that's it], and we have a batch run every so often just to keep a good supply on hand. If the die set ever got damaged it probably wouldn't get replaced.

We are working on having exact reproduction cones made for this woofer. New factory replacements are very good quality, but expensive enough that it would be worthwhile to completely rebuild the old frames if proper parts can be had. Existing 3rd party cones just don't sound right, they're too light and the resonance is too high. You get better efficiency but loose low bass output. No exact ETA on the new repro cones, maybe mid summer.

These 11's are a bit more tricky to refoam than other AR drivers, but as long as you take you time and work carefully they can be done. The top spacer ring must be kept in place, otherwise the cone will ride too low in the frame. If it comes off while you are cleaning the woofer, it is easily put back on with epoxy or a proper solvent based speaker adhesive. This almost never happens on the stamped frame woofers, but is common on the older cast frame version.

Things to check out for before refoaming an old set of 11" woofers or buying used: #1 problem is with collapsed spiders. This usually has more to do with wear than age, as I see just as many 80's vintage woofers with this problem as late 60's models. To really be worth refoaming, the spider should be equally "springy' in both directions, relatively flat across and not too "sunk in" in the center. When the spider gets worn out and collapses, the voice coil is bottomed out in the bore at its resting position. With no rear travel available, the coil easily smacks the back plate even at moderate volumes, leading to voice coil damage. Overall sound is degraded as well [low volume, distorted sound].

Issue #2, bent/creased formers on those woofers with paper voice coil formers. Most are aluminum, but some "middle aged" AR 11" woofers [usually square magnet] were built with paper formers [not good]. These have considerably lower power handling than the metal former versions [think insulator vs. heatsink], and are easily damaged if the woofer is ever over-driven and the coil smacks bottom. The aluminum formers will usually flex and survive a mild "impact", the paper usually creases or collapses in the gap between the neck of the cone and the start of the coil windings [weak point]. If damage is minor the cone may be tilted and hard to center but still work OK. If severe the damaged area can bind in the gap, or the cone may be tilted too much to be centered.

[Guest]

Hello audio-friend:

Please advice, if you know, where can I get rubber sorrounds kit for a pair of AR3a woofers?

Thank you very much

JotaM

josembenite@hotmail.com

>I refoamed the AR-3a with the ring in place and now I can

>see

>why the ring was on the basket in the first place. If the

>ring

>were removed than the cone and spider would sit too low in

>the

>assembly. I refoamed without removing the dustcap and I can

>say

>that everything seems in proper alignment. Of course this is

>not my first refoam work as I have done at least 25 sets of

>speakers over the past few years, but it was my first AR-3a

>and I have previously fixed a pair of older AR-3 speakers. I

>also am in the process of replacing all the capacitors on

>the

>AR-3a speakers.

[tysontom]

"This AR woofer is its own unique size, really an 11" instead of a 12" as AR lists it."

With all due respect -- and this comes up periodically -- the speaker is measured in conventional wisdom by its frame size, not by the cone & surround size. You can call it what you want to, but the AR-3a, AR-11, etc., all have a 12-inch woofer. The AR-2ax, AR-5, etc., all have a ten-inch woofer. However, the one exception was the original Alnico AR-2 and AR-2a 6-bolt cast-frame woofer: its frame did measure 11 inches.

"We are working on having exact reproduction cones made for this woofer."

This is a great idea. While you are at it, you should also try to get the skiver (surround) to match the original, as well. Most the replacment surrounds I have been able to find have a 1/2-inch cross section vs. the 3/4-inch on the original.

"Things to check out for before refoaming an old set of 11" woofers or buying used: #1 problem is with collapsed spiders. This usually has more to do with wear than age, as I see just as many 80's vintage woofers with this problem as late 60's models."

I wasn't aware that collapsed spiders was a problem particularly with the ferrite woofer; it was a common problem with AR-1/AR-3 Alnico woofers and some early, highly-compliant AR-3a ferrite woofers. The collapsed spider syndrome can be caused by several things, but mostly from someone leaving one of the early AR speakers face-down or face-up for long periods. The weight of the cone will push the cone towards the back plate and will stretch the spider. A collapsed spider will definitely cause the speaker to introduce more distortion.

"Issue #2, bent/creased formers on those woofers with paper voice coil formers. Most are aluminum, but some "middle aged" AR 11" woofers were built with paper formers . These have considerably lower power handling than the metal former versions , and are easily damaged if the woofer is ever over-driven and the coil smacks bottom."

I learn something everyday. However, every 12-inch AR ferrite-magnet, stamped-frame woofer (starting with the late-1968 production-run AR-3a) I have ever seen had a nomex (paper-like) voice-coil former; I have never seen an aluminum former on the 12-incher. Every 12-inch Alnico cast-aluminum frame woofer had a bronz voice-coil former, and I know there is no exception to this. I've cut open dozens of all vintages of these woofers through the years, and none had paper, and I have never seen or heard of aluminum formers. Exceptions to this might be the much-later, Japanese-built replacement units. Advent, on the other hand, did use the aluminum former.

--Tom Tyson