AR2ax tweeter terminal post trouble

[dd123]

I finally got my first pair of AR's -- early version 2ax's! They need work so I pulled the woofer on one. Painting the house can wait, right? I bypassed the corroded pots by attaching temporary jumper wires so I could check out the mid and tweeter. The tweeter's output was noticeably less than the midrange's. I disconnected the tweeter from the cap and pot, and attached a meter to the underside of the tweeter terminal posts, I found that the resistance reading bounces all over the place when I wiggle the top of one of the spring loaded posts. When all is well it reads 1.8 ohms. Has this happened to anyone else with this tweeter version (see photo)? More importantly, what do I do about it? That thin little tweeter wire makes me a bit gun shy.

And now for the true confession. While inspecting the wire and terminal post, I started unwinding the excess wire that was wrapped around the top of the post and naturally it broke off. So now I'm thinking there might not be enough wire to do whatever needs to be done for a good connection. Ugh! How is the wire supposed to attach to the post?

Is that thin tweeter wire insulated? Can other wire be soldered to it by someone with five thumbs if I need to make it longer? Can I learn to keep my hands off of this stuff until I get input from folks who know what's up?!!! OK, I'll stop talking now.

[RoyC]

The tweeter's output was noticeably less than the midrange's. I disconnected the tweeter from the cap and pot, and attached a meter to the underside of the tweeter terminal posts, I found that the resistance reading bounces all over the place when I wiggle the top of one of the spring loaded posts. When all is well it reads 1.8 ohms. Has this happened to anyone else with this tweeter version (see photo)? More importantly, what do I do about it? That thin little tweeter wire makes me a bit gun shy.

And now for the true confession. While inspecting the wire and terminal post, I started unwinding the excess wire that was wrapped around the top of the post and naturally it broke off. So now I'm thinking there might not be enough wire to do whatever needs to be done for a good connection. Ugh! How is the wire supposed to attach to the post?

Is that thin tweeter wire insulated? Can other wire be soldered to it by someone with five thumbs if I need to make it longer? Can I learn to keep my hands off of this stuff until I get input from folks who know what's up?!!! OK, I'll stop talking now.

It is normal for the tweeter's output in this model to be noticeably less than that of the midrange. The tweeters are operating only at very high frequencies. The 1.8 ohm reading is also normal for the tweeter in your version of the 2ax.

Now for the bad news....The tweeter leads each consist of a thin strand of uninsulated aluminum wire, and, as you found out, are extremely fragile. Soldering the aluminum wire is very difficult and cannot be accomplished with conventional solder. Some forum members have had success with very small crimp connectors. Others have mentioned conductive glue.

Roy

[oldguide]

The crimp method can work, but you will have to search to find crimp connectors that small. RS does have them. This only works if you have some wire to work with, because if you don't, you really only get one chance at it. The issue here is that the RS crimps are about an inch long, so you need some space to work with.

One note: the aluminum wire on many of the speakers has a coating/oxidation on it that will need to be gently removed. I use 400 grit sandpaper. Just as with a copper wire, when it is shiny you will know you have eliminated the coating. One way I found to do this safely is to GENTLY "anchor" the end of the wire nearest the speaker cone with a small pair of needlenose pliers.

A second method that has worked for me when there is enough wire is to take some stranded number 22 wire and unbraid it. Best is silver stranded wire like the marine wire recommended in the manual. After unbraiding, you should have a bunch of tiny wires sticking out. If they are not pretinned you can try to CAREFULLY tin these individually as you will be using some of them to attach to the aluminum wire.

Cut them off so you have a pile of tiny unbraided wires. Take one of the wires and slowly snake it around the aluminum wire. Do this with another of the copper strands. The idea is to have the copper strands making contact with the aluminum as much as possible. In essence they should be like a braid around the aluminum. Once you have made the braid solder the connection. The braid will hold the copper to the aluminum and the solder will make the joint solid.

I have not tried method number three, but the tip came from someone who works in refrigeration where they have to solder copper to aluminum. Apparently the product of choice is something called J.W. Harris Alsolder 500 aluminum solder. The problem is the stuff is sold to refrigeration contractors in large amounts. I called Harris to see if I could locate a source and they gave me three local sources which I will check out and see if perhaps this is the best solution. No one has it online.

Number four is a product called JB Weld. You can find it at most big box home supply stores or auto supply places. You just want aluminum JB Weld. It works like epoxy in that you mix two tubes of compound to make a glue. Remember before you do this to clean the aluminum wire and to braid together the copper wire you will be connecting to it. JB Weld is nonconductive, so you need to be sure to get good contact between the copper and aluminum. Unlike soldering once you put the JB Weld on that's it, so if your connection is not good for some reason, you can only cut the wires and start over.

If I had to rank them I would say crimp is #1, followed by braiding, JB Weld and Harris--only because I have not tried it.

Good luck.

[dd123]

Really good stuff, thanks Roy and oldguide. It was a real let down when I heard the relative quietness of the tweeter -- I've been wanting affordable ARs for a while -- so I'm glad that it may be normal. Next step is to check the other one.

I'm really leaning toward crimping (even though I'd like to keep them original) due to all I've heard/read about trying to solder aluminum wire, especially one little strand.

I made a temporary fix by rotating the terminal post so the hole is closer to the wire stub, and straightening the wire. I gently scraped off the coating with a razor blade. It just reaches and should be OK until I find crimps or the courage to solder. Now the tweeter measures 1.4 ohms...go figure.

[dd123]

The lower output of the tweeter makes me wonder why AR bothered making it adjustable with a pot. I would think most folks run it wide open?

[oldguide]

If it just reaches, you might want to use the strand method or very small gauge (24 or higher) solid copper to hold it in place. Then try soldering to the copper to keep everything solid.

Definitely don't use the glue method with so little wire to contact, because once the glue has hardened you would then have to cut the wire if you needed to troubleshoot.

Good luck.

[oldguide]

DUMB! DUMB! I have a tendency to lapse into AR3 mode, so disregard my last email in which for some reason i was focusing on AR3 connectors and not yours.

Anyway, the proverbial light bulb lit and I think I have a quick an dirty--and easy to implement--answer for you. Use conductive foil tape. They sell this at electronics stores, but for your purposes there is a cheap--and perhaps no cost--alternative. If you have even an inch or two of coax TV cable you can spare, most of them have a conductive foil winding around them. Just cut the outer insulation, strip away the braiding (if any) and then unwrap the foil. Try wrapping this around the stub of wire that barely fits to help stabilize the connection. The foil is thin enough that it wraps easily.

I checked to see if this would work using two sections of #14 wire (something I have lots of around) and the foil served just like a crimp connection Perhaps this might be a solution to our long-standing short wire problem as it would allow connecting aluminum and copper. See if it works for you.

Roy, what do you think?

Good luck.

[RoyC]

Roy, what do you think?

I say get some aluminum roofing nails, and nail the suckers to the surface of the cabinet!

I'm not sure foil would be tight enough in the long term, or if oxidation would become an issue...but it is probably worthy of experimentation.

Of course, what "works" for someone may not always be the best solution if re-sale is a concern.

dd123: AR originally referred to their dome tweeters as "super tweeters"...meaning they operate only at very high frequencies. Listening to these drivers separately from the rest of the system will not sound like much. In fact, folks with high frequency hearing loss may not hear anything at all.

The 2ax midrange was used as a tweeter in the similar 2-way, AR-2x. Although the AR-2x tweeter is called a "midrange" in the 2ax, the 2ax crossover does not attenuate the high frequency response of this driver at all. It simply runs in parallel with the (super) tweeter, which augments this driver's high frequency response. The 2ax design is actually more like a 2-way system with the tweeter providing "some" assistance to the reproduction (and, more importantly, dispersion) of high frequencies. The overall reticent nature of the high frequency response of the early ARs (like it or not) is part of their "warm" tonal character or "voicing". The tweeter level controls were more useful in a day when recording and playback (radio, records, and tape) limitations produced unpleasant high frequency artifacts.

Roy

[oldguide]

You nailed that one!

[dd123]

Hey, watch the cracks about hearing loss

More good stuff for my gray matter. I love learning about all this. Thanks to you both. I've got to get a move on ordering replacement caps and probably pots -- the corrosion is so bad that part of the rotating contacts are eaten away. Maybe I'll just bypass the tweeter pot. Any recommendations for parts?

I'd also be interested in your thoughts on AR3 or 3a compared to 2ax. Are the 3 and 3a true 3-way speakers where the tweeter produces more? Do they sound lots better than the 2ax to your ears?

[RoyC]

Hey, watch the cracks about hearing loss

More good stuff for my gray matter. I love learning about all this. Thanks to you both. I've got to get a move on ordering replacement caps and probably pots -- the corrosion is so bad that part of the rotating contacts are eaten away. Maybe I'll just bypass the tweeter pot. Any recommendations for parts?

I'd also be interested in your thoughts on AR3 or 3a compared to 2ax. Are the 3 and 3a true 3-way speakers where the tweeter produces more? Do they sound lots better than the 2ax to your ears?

If you bypass the pots, you should maintain 15 to 16 ohms in parallel with the tweeter. Cutting the wire (which goes up to the tweeter) attached to the "B" terminal of the pot, and re-connecting it to the #1 terminal will accomplish this. I have extra pot parts (and roofing nails ). PM me if I can be of assistance.

The dome tweeters of the AR-3, 3a, and 5 are all implemented in the same way as the 2ax, but the crossovers serving their dome mids are more sophisticated, providing some midrange driver attenuation at higher frequencies. In answer to your question, however, the tweeters will sound pretty much the same when isolated from the rest of these systems, and do not "produce more" than the 2ax tweeter. The 2ax, 3, 3a, and 5 all have very similar high frequency characteristics as well as a similar overall sonic character. Wider dispersion resulting from the dome mids, and the bass response of the classic 12" AR woofer in the 3 and 3a are the most obvious differences.

Roy