Finally working on the AR-3. Pics and usual dumb questions.

[Reel Man]

I've had these for 10 years now ( https://audiokarma.org/forums/index.php?threads/ar-3-score-advice-sought.448012/,) but found a pair of 3a's that were in worse shape, that I worked on first, as there wasn't a challenge removing the woofers on them. Those speakers, along with other gear, burned me out on fixing up this old stuff, but I did buy some stuff for the 3's in 2017 (jeez. 5 years ago), l-pads, resistors, and the caps I thought I needed. I was motivated last winter to work on these, but that sealant dissuaded me; I decided to wait until summer, when I could put them on the sun porch to soften the sealant, and it worked. My informal date code guessing of 1964/1965 assembly was pretty close, I found this stamp of the assembler. I also found that the pot wipers were Shot, and the caps I ordered were mostly incorrect. I apparently need a 6uf and 24uf cap, and that's it. I did manage to find the AR-3 specific wiring diagram from this site by googling it. My initial question is if a 25uf cap is close enough, or should I get a 20uf and a 4uf and tie them together. https://www.daytonaudio.com/product/226/dmpc-25-25uf-250v-polypropylene-capacitor

[Reel Man]

Some "Glamour" shots. They appear to be lacquered Mahogany.  I'm really motivated to hear the mids and tweeters work on these, as I haven't yet. I've read that they generally need restored at this point, but a squeak from them would be an improvement.

[GD70]

Those 3s look great!
Combine the 20 & 4uf caps. I’m a firm believer in matching cap values as it was designed. 
The bigger issue will be the mids output. It’s well known the white sealer around the base of the mid dome has hardened over the last 50 plus years, greatly reducing output. Roy rebuilds the mids and I have to say the difference is amazing. Tweeters usually hold up fairly well. 
Glenn

[Reel Man]

Good to know that I might not have to get the tweeters done. Any suggestions for touching up the scratches? I'd like to keep the original finish, if possible. My other pair have some patina. I have a friend with a wood shop, so I have that option. Might as well test the mids and tweeters first for function, though.

[JKent]

13 hours ago, GD70 said:

Combine the 20 & 4uf caps.

I agree. The 25uF would be fine and certainly within tolerance but if you can build up the exact value, why not?

I don't know about those phenolic dome tweeters. Any that I've seen have been rather tired and often the domes pop off the foam blobs. I do agree regarding the mids so if you contact Roy about having them rebuilt I'd suggest asking him about the tweets.

You can replace the pots with L-pads as described in the AR-3a restoration booklet. They work well and will last far longer than cleaned-up AE pots. If you want new heavy-duty pots send me a PM.

Love the mahogany! I had some 2a's in that finish. I'd suggest stripping them. Try lacquer thinner--it can be time consuming but effective. Follow with block sanding. You may find those scratches disappear. If any are deep you can steam them out with a damp cloth and steam iron. Then spray with Minwax Gloss spray lacquer. Do it outside. It dries very fast and you can re-coat after 10-20 minutes. Do at least 4 coats, the more the better. You can block sand with very fine sandpaper if there are any runs but let it dry over night before doing that. After the final coat wait at least a day then buff it out with a white Scotch Guard pad for a softer look, or leave it glossy if you prefer.

Kent

[Reel Man]

So you do think they are Mahogany? I wasn't sure I would recognize Cherry, but the wood looks like the Gibson guitar(s) I've owned over the years. I also thought the hard finish was factory, but did they do that? I bought L-pads 5 years ago, with resistors, as these pots felt terrible, and didn't work a bit( I just recently stumbled on a thread on here about your heavy-duty pots). I was going to use this picture below as a wiring template, with the appropriate caps for an earlier design/serial.

[Reel Man]

I also share your pessimism on the tweeters, which is one of the reasons these have sat - tweeter resto, Mid resto, and the cabs. Snowballed pretty quick. One has some water damage, but on the bottom, and it didn't affect the acoustic seal, surprisingly. I'll have to look up testing the speakers with a meter, before I send them for restoration.

[Reel Man]

Incidentally, I used the 3a guide for these speakers. I need cloth, and maybe a new tweeter, or a repair. I've been playing with them with a more appropriate amp.

 

[Reel Man]

I have Dayton audio polypropylene caps in a shopping cart, and noticed in the 3a guide about using resistors on these caps. They're cheap enough, but what should I use for the 24uf(combined) caps? I doubt my ears will be able to tell, but might as well order them,anyway.

[JKent]

17 minutes ago, Reel Man said:

I have Dayton audio polypropylene caps in a shopping cart, and noticed in the 3a guide about using resistors on these caps. They're cheap enough, but what should I use for the 24uf(combined) caps? I doubt my ears will be able to tell, but might as well order them,anyway.

Personally I wouldn't bother but Roy "wrote the book" so let's see what he says.  If I were doing it I'd use ~0.27 ohm, 20W but I didn't add resistors when I did mine and I think if you search through pictures of others' 3a's you'll find no one else did either.

Kent

[RoyC]

4 hours ago, JKent said:

Personally I wouldn't bother but Roy "wrote the book" so let's see what he says.  If I were doing it I'd use ~0.27 ohm, 20W but I didn't add resistors when I did mine and I think if you search through pictures of others' 3a's you'll find no one else did either.

Kent

For the record, I lobbied not to include this minutiae in the 3a restoration guide. In practice, there is no reason to use the resistors. The level controls and ancient drivers are much more influential than the additional fixed resistor. If you really want them to behave "authentically", use electrolytic capacitors. For the simple AR-3 crossover I would just use the Daytons you have chosen

Regarding the tweeters, they seldom suffer the same type of degradation as the mids. If the output seems OK, and the dome is not protruding from the voice coil gap ("popped dome" issue), I wouldn't be too concerned. Sometimes the foam suspension "blobs" and/or the clear rubbery material around the tweeter dome needs to be refreshed. The tweeters can always be dealt with after everything else is completed.

Roy

[Reel Man]

Good to know. I did order the resistors for the 6uf , as they were $3, but wasn't likely to use them, as I doubt my ears would notice. It will also make for a cleaner install. My short term plans are cab repair, installing the L-pad/wiring harness/caps, and making a silcone-rubber gasket to test on the woofer. I just want to hear sound from the mids and tweeters, even if not ideal. I plan to send the mids out for restoration, then use proper woofer sealant if the gasket doesn't seal (I already have it).

[GD70]

After you have the mids rebuilt, recap the crossovers, and replace the pots, and are loving their sound, then move onto the cabs.

The one pictured sure took a beating from moisture. How far do you plan to go on the resto? 
 

[Reel Man]

I dunno, I keep mentally flip-flopping about the finish. It makes sense to have it done when I have the speaker seals broken, and the mids being worked on; not that much extra work to remove the tweeters at that point. I'll have to get a quote from my woodworking friend, as I just won't have the ambition to do that work myself. I checked your 1960 AR-3 post on AK again. What kind of putty did you use on the corner? It looks darker than what I'm familiar with. The moisture damage didn't affect the acoustic seal, surprisingly enough, though I'm going to inspect the inside corner there to verify the condition. My caps came in, so I have some options to play with this weekend.

[Reel Man]

An update. Worked on the water-damaged cab over the week - gluing the pieces that had fallen off, and gluing and puttying the corners, which ended up taking a few tries. Not especially pretty, but being in the back, and at the bottom, it isn't very noticeable. I got some new speaker terminal screws from work, and some new star-washers, as the originals were rusty. It looks like nice weather for the next week, so I'm not sure when I'll get the pots and caps in and wired; I definitely plan to work on these during Thanksgiving break.

[Reel Man]

More tinkering. We've had exceptional weather this fall, even on weekends, so I haven't had much time with these. I did get the L-pads and a new terminal mounted, but found it frustrating to solder inside the cabinet, and the Dayton caps take up a lot of room. It's apparent to me now that the electronics were a sub-assembly built outside separately,then mounted on that pressed cardboard material(not sure what it's called), then stapled/glued into the cabinet. I'm electing to do something similar. I removed the wax capacitor block, and turned the choke, and am experimenting with the layout of the new caps.

[Reel Man]

The AR3-a restoration post mentions using an Ohmmeter to check the mid and high drivers; 3.5 ohms. Does this apply to the 3's drivers as well?

[RoyC]

2 hours ago, Reel Man said:

The AR3-a restoration post mentions using an Ohmmeter to check the mid and high drivers; 3.5 ohms. Does this apply to the 3's drivers as well?

No, The AR-3 tweeter and mid have much lower dcr. The tweeter is just under 2 ohms, and the mid is closer to 2.5 ohms.

Roy

[Reel Man]

More tinkering. I can probably lower the caps for a straighter shot at the pots; I'll do that for the next one. I didn't have my good strippers and crimper, so I stopped here. Anybody contemplating this for their speakers, I would recommend a 24uf 400v Solen cap, (which I didn't think to google first), I went to Dayton audio first. One cap is easier than two. 16ohm pots would also clean up the wiring, as the resistors make it trickier to solder.

[Aadams]

30 minutes ago, Reel Man said:

16ohm pots would also clean up the wiring, as the resistors make it trickier to solder.

New 16 ohm pots are available.   For the resistors you can use long wire leads from the lpad and also the resistor if you choose.

 

[Reel Man]

Yes, I'm aware of that now (16 ohm pots). I ordered the L-pads in 2017. I plan to have the mids serviced, but have to verify they function - ohming it got very jumpy readings. Not splurging on 16 ohm pots gives me more cash for speaker servicing/issues. I'll have at least one speaker ready to test during Thanksgiving break.

[Reel Man]

Arghh.....now I remember why I took a break from this. Looks like the mid is toast in this one, however the tweeter seems fine(see link). No sound out of the mid, and I can't get it to ohm, it goes bananas. I was thinking the pots were why this was parked, it might have been the mid. I'll pop it out, and start packing the fiberglass, and fitting the woofer. 

 

https://youtu.be/JkFs3WcOXSo

[JKent]

RoyC may be able to fix the mid. 

[RoyC]

43 minutes ago, JKent said:

RoyC may be able to fix the mid. 

Hi Kent,

I actually have been restoring many AR-3 mids these days. Even when they are functional they often have compromised output due to dome suspension issues.

I see you are back in the pot business!

Roy

[Reel Man]

Yeah, I planned on sending the mids to Roy anyways for servicing; hopefully, the other one is just low on output. On a related note, does anybody fix AR-3a mids and tweeters? Pretty sure a tweeter is out on my 3a; I have to ohm it soon. Also, how hot will the resistors get? Do I need to be concerned about them being too close to the masonite?