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My AR 3/3a saga [a CSP group effort]


JKent

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Posted 27 January 2011 on the CSP For Sale forum:

"AR-3 Dark wood cabs are not torn up at all, but a square planter was placed atop one, and the veneer is starting to split. Woofs need a refoam, one of the mids seems to work, and maybe one of the tweeters. I'm half-deaf so it's tough to tell. Grilles are "cane" type material, and I didn't try to remove them when they put up a lot of resistance to being removed. Screw-in type AR badges are there. $75"

http://www.classicsp...?showtopic=6180

Picked these up from CSP member ToastedAlmond (George). SNs are 18051 and 21651.

Plan A: Convert these to AR3a. If there is 1 bad mid and 1 bad tweet, why not? Woofers are probably OK. The AR3 had cloth surrounds. But optimistically I'm hoping all the drivers are fine and it's just bad pots.

Popped the plastic grilles. One frame is broken but can be glued. Vinyl grille cloth is loose on the long sides of both. Numeral "3" brass logo is missing.

Here are the obvious problems:

Veneer on top of one speaker is separating and lifting at the seam. Guess I could force some glue in there.
The grille is woven vinyl, like the KLH Twenty-One radio. And like the 21, the material has pulled away from the frame.
There's a bash on the bottom FRONT corner of one. The corner can be repaired with John's epoxy & Mixol glop. The veneer will be reglued with hide glue.
Consistent with Tom & John's diagrams in the Library, the speakers have different crossovers. The earlier one has 2 coils; a 0.4uH and a 0.06uH. Pots are visibly corroded even on the outside

SN 18051

FG "blocks" total weight 42 Oz.

Wax block capacitor: 24uF/6uF #5201

tweet DCR 4.9

Mid DCR 2.4

Woof DCR 2.4

inductor ~0.4uH (marked "1")

inductor ~0.04 (marked "3")

The other speaker, obviously has been "worked" on. The kimpak was torn, FG not as neatly packed in. Excessive corroding on pots. Leads to the pots have been cut. Guess the pots were bypassed because they were not working.

SN 21651

FG "blocks" total weight 40 oz

wax block capacitor

tweet DCR open

Mid DCR 2.3

Woof DCR 2.3

inductor ~0.4mH (marked "1")

Plan B: Since all seems good except 1 tweeter, and AR3s seem to be gaining in value, rebuild these to original specs. I have a pair of AR2a's that I can cannibalize for the original tweeters.

Rebuild both crossovers with new Clarity caps, copying the earlier 2-inductor xo.
Substitute Janszen 0.05uH inductors for the 0.04.
Use Ohmite pots (after some experimenting, mounted them in small project boxes to keep the fiberglass out of the windings. One drawback: Too tight in there to try to replicate the correct white dot positions).
see this thread, post #6, 9 & 15 for more photos:

http://www.classicsp...?showtopic=6266

The 2a's, which are awaiting refurb, can be rebuilt with HiVi tweeters.

Finished one speaker, complete with new Johns Manville fiberglass (yes sir, yes sir, 3 bags full)*  About 27 0z. The corner bash is nearly invisible now that it's repaired, and the top veneer was reglued successfully. Hooked it up and listened. Sounds good. Maybe just a tad bass-heavy, so it could probably use a bit more FG stuffing. After a while I turned up the volume. Mid pot is about ¾ rotated. Then the trouble started: Some variation in output from the mid, then ragged sound and static. Drat! Tom Tyson has identified a possible source of this problem as the connection "arcing" over, causing the static. So the mid is not dead, but I doubt I can fix it. I already had to splice the leads, as shown in the AR3a Restoration Manual. Who dreamed up this nightmare? A ten pound midrange with tiny, hair-thin ALUMINUM leads connected to the outside of the cabinet?

So now it turns out the original description was right: a bad mid and a bad tweet. In the meantime, I reinstalled the tweeter "borrowed" from the 2a and listened to those. They sound beautiful! This is with absolutely no refurb. The caps are oil-filled mil-spec units. I didn't even touch the pots. The speakers have a rich, creamy sound that to my ears sounds way better than my carefully rebuilt 2ax's! These were a gift from CSP member Rob and I admit I never listened to them. Figured they "must" need new caps (no) and they "couldn't" sound as good as the newer, "improved" 2ax. I was wrong. Plus—they have beautiful lacquered mahogany cabinets and funky '50s-style grille cloth. These are keepers and should be left 100% original.

Plan C (aka Plan A redux): Roy C to the rescue (again). He has some very nice AR11 mids that are good replacements for the AR3a mids and work well in the 3. But now this won't be an authentic AR3 restoration, so it's back to converting the speakers to 3a's. Roy also provided a couple of AR#1 inductors and assorted other parts. John provided the #9 inductors, and both provided MUCH advice and long-distance hand-holding.

While waiting for the crossover parts to arrive from Roy, John and Parts Express, I rebuilt the one "finished" AR3, using the AR11 mid and HiVi tweeter.

see this thread for Roy's HiVi tweeter mod:

http://www.classicsp...?showtopic=6108

The crossover is still the rebuilt AR3, with Clarity Caps and Janszen inductor. Even playing just one speaker, in mono, it sounds GREAT. It will be interesting to see what happens when I build the 3a crossovers. I'll rebuild the other speaker as a 3a and do a comparison. My bias at this point is that the speaker with the 3a crossover will be better than the one with the 3 xo, but that remains to be seen.

Stay tuned.......

*edit: Actually, Roy and John have determined that about 20 oz or so is correct--not the original 28 oz.

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AR3 to 3a mod, Part Deux

Finally finished the other speaker. The 3a crossover is MUCH more complex than the 3, and as documented in this thread;

http://www.classicsp...?showtopic=5980 there were issues with the size and placement of the various components.

The new xo was built on a 7" square sheet of plywood. The caps are secured with cable ties as described in the AR3a restoration booklet. The inductors are mounted on brass machine screws, installed from the bottom of the plywood. Screws were epoxied in place and Lock-Tite was used on the nuts. Original color-coding of the wires was maintained.

Like the first speaker, I filled this with 3 bags of Johns Manville fiberglass (@ 9oz per bag). I really recommend replacing the old FG. The new stuff is not crumbly and it's much less itchy. I cut the batts into squares about 6"--a bit bigger than the blocks that were in there originally but easy to work with. At 27oz per speaker, they may be slightly under-damped. Will listen and see. I have 1 extra bag of FG just in case. Also replaced the crumbly old Kimpak with some "tulle" fabric.

Still to do: Some more Watco Oil on the cabinets, repair the 2nd speaker grille, install the badges. Oh yes..... rebuild the 1st speaker (again) so the two crossovers match.

First impression listening test:

So Now I have 2 speakers with original 12" drivers, AR11 mids and HiVi tweeters, but one has a rebuilt AR3 crossover and the other has an AR3a crossover. My bias is the 3a "should" sound better.

First of all, they both sound GREAT. A huge improvement over my 2ax's. Played some music in mono and rotated the balance back & forth to compare the 2 speakers. First shock: The one with the AR3 xo sounds better! Tried to figure out why. Is it the "better" big cap in the 3? Do fewer components in the signal path make for purer sound? Is the 3 a better design than the 3a?

Finally concluded the difference was simply one of volume. The 3a has more resistors, inductors and caps so I "assume" that's why it plays a tad lower at any given volume setting. This is a trick salesmen used to use (still use??) when trying to push a particular speaker. They'd set up an A/B comparison but with the demo rigged so the speaker they're pushing played a bit louder than the other. Subjectively it sounded "better".

So I'm still evaluating them but I'm sure I'll make them both "3a's". My understanding is the AR11 mid is identical to the original 3a and besides, it was such a PITA to build the 3a xo I'm not eager to take it out ;)

Here are a couple more photos. When the cabinets and grilles are finished I'll post pics of those.

Thanks to all CSP members who helped with this project!

Kent

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Hi Kent

I like your neatness and nice layout of your new crossover network but have you measure the value of the inductors and make sure they remain the same values after you put those bolts and nuts in the center of each one of them?

Minh Luong

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Hi Minh

Thanks and no--I didn't.

The inductors were matched before I put them in but I did not measure after. Think you missed where I mentioned that the #1 and #4 are mounted on solid brass machine screws. The #9 is fastened with a stainless steel wood screw.

Kent

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Hi Kent

I don't know if you have an extra inductor laying around handy? If you do then clip onto both leads and turn on the meter then slide the stainless steal and brass bolts and nuts and see if the inductance value change at all?

Minh Luong

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Almost finished

Here are a couple more photos.

The split and lifted top of the speaker on the left was repaired with hide glue. All's well there. Some of the scratches were deeper than I would want to risk sanding, so we'll call them "patina." ?

The speakers were lightly sanded, then the finish was evened out with Howard's Restor-a-finish, then several coats of Watco Danish Oil. Finally I applied some Minwax Antique Oil. I use it on the KLH radios but it's a little shiny for speakers, so it was lightly buffed with steel wool. Makes a nice soft finish.

The corner bash is on the bottom right front corner of the right speaker. Can't even see it. There's a close-up in post #1.

Can't say I'm a fan of the plastic speaker grilles. The one that's installed was broken. Fixed it with Plas-T-Pair, then glued the vinyl "fabric" on with Aleene's 7800. It works, but in some spots it bled through and looks a bit pinkish. Will use less on the next one.

The top of the grille frame is somewhat bowed--had not noticed before but probably caused by shrinkage of the vinyl. After snapping the top & bottom in the grooves, the fabric, which overhangs the frame a bit on both sides, was pushed into the grooves with a putty knife. 

I don't have the "3" numerals, but since these have been converted to 3a's I applied an "a" from a pair of AR-2a's.

Anyone know if the "a" logo was used on early 3a's?

Have been listening to these, with a whole variety of music, and they sound great. The speaker on the right still has a rebuilt AR3 crossover, and as soon as I get a round tuit I'll change that, so they're not entirely finished yet.

A bit of heresy: These sound a lot like my KLH Model Twelves (to me that's high praise but some AR3a fans may not see it that way). YMMV 

Kent

PS Also used Roy's woofer surround sealer after checking for return rate.

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I'm pretty sure that the earliest 3a's already had the rectangular badges and never used the "a" pin, but maybe Tom will have some other info on that.

That is correct. The 3a used the rectangular "AR-3a" brass logo with de-bossed red lettering for its entire product life. The early 2ax used the rectangular "AR" in one corner and the "a" in the other corner. The 3 used the AR logo and a brass "3" in the other corner. The "new" 2ax used the 3a-styled logo: brass rectangle with red de-bossed "AR-2ax" lettering.

Quiz tomorrow.

Steve F.

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On 4/2/2011 at 4:28 PM, DON said:

You did an outstanding job repairing the cabinets. If you have the time I'd love to hear and see (if possible) how you repaired the badly damaged corner. Thanks. Don

Thanks. I basically hammered all the bashed fibers back into place, then mixed up some epoxy and Mixol #22--a trick John O'Hanlon turned me on to, and described in my KLH Model Eight restoration guide in the CSP Library:

http://www.classicsp...h-model-eig.pdf

Another way to do it is to mix fine sawdust, from your sander's dust bag, with the epoxy. To tell the truth, I forget whether I used the Mixol or sawdust on the corner. Here's a photo of a small corner ding on one of the 3s filled with epoxy. I make a dam of masking tape, pour the epoxy. When cured I file down the epoxy repair to the level of the cabinet veneer, then sand lightly. Also attached is a "before" shot of some missing veneer. Sometimes I'll cut small pieces of veneer and glue them in place, but usually I use the brown epoxy--especially if it's on a back edge as shown.

Roy has mentioned the Mohawk brand epoxy "tootsie rolls". They are easy to work with and come in a variety of colors. More than one way to skin a cat.

http://www.woodfinishersstore.com/products/Mohawk-Epoxy-Putty-Stick.html

The split and lifted veneer was fun, too. I lifted what I could with xacto blades and dental picks, then forced hide glue under the veneer. In one spot the veneer was bubbled, so I split it with a razor blade, forced hide glue under, rolled it with a small rubber roller then wiped off excess, covered with wax paper, placed a flat piece of wood on top and plenty of weight on top of that. The hide glue was John's suggestion too.

Kent

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Thanks. I basically hammered all the bashed fibers back into place, then mixed up some epoxy and Mixol #22--a trick John O'Hanlon turned me on to, and described in my KLH Model Eight restoration guide in the CSP Library:

http://www.classicsp...h-model-eig.pdf

Another way to do it is to mix fine sawdust, from your sander's dust bag, with the epoxy. To tell the truth, I forget whether I used the Mixol or sawdust on the corner. Here's a photo of a small corner ding on one of the 3s filled with epoxy. I make a dam of masking tape, pour the epoxy. When cured I file down the epoxy repair to the level of the cabinet veneer, then sand lightly. Also attached is a "before" shot of some missing veneer. Sometimes I'll cut small pieces of veneer and glue them in place, but usually I use the brown epoxy--especially if it's on a back edge as shown.

Roy has mentioned the Mohawk brand epoxy "tootsie rolls". They are easy to work with and come in a variety of colors. More than one way to skin a cat.

http://www.woodfinishersstore.com/products/Mohawk-Epoxy-Putty-Stick.html

The split and lifted veneer was fun, too. I lifted what I could with xacto blades and dental picks, then forced hide glue under the veneer. In one spot the veneer was bubbled, so I split it with a razor blade, forced hide glue under, rolled it with a small rubber roller then wiped off excess, covered with wax paper, placed a flat piece of wood on top and plenty of weight on top of that. The hide glue was John's suggestion too.

Kent

Thanks for the information. I have a pair of ADS 810s that someone apparently left in a garage or storage area and one suffered some water damage on the bottom. They both had paint splatters and ink and water stains on top. I haven't repaired the veneer and may not go to great efforts since it's on the bottom. The paint splatters were easy to remove but time consuming. The ink and water stains were much harder. Some light sanding and judicious use of a well sharpened wood scraper got rid of the stains without removing the patina. These speakers probably cost close to $1000 when new! There should be an ASPCS.

I'm going to look up the materials you reference. I have other speakers and a couple of turntable bases that need repairing.

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