AR2-ax work

[klamsoss]

I'm in the process of getting things ready to move. This has motivated me to finally finish the work on a pair of AR 2-AX speakers that I got several years ago needing work on the crossovers.

I have the phenolic dome tweeters in these, the cabinets are in very good to excellent condition, and the woofers are currently sitting in the garage after I painted the sealant on the surrounds.

I'm wondering what a normal reading for DC resistance is across the tweeter. Im getting something on the order of 1.8-2 ohms with the tweeter out of circuit. Does that seem normal? I don't have any background with these speakers, really, so I'm not sure. Most other speakers I have worked on, individual drivers never had a resistance that low.

 

[klamsoss]

I found some info that the phenolic tweeters often do have a DC resistance of around 1.9 or 2 ohms when out of circuit, so I'm satisfied that these are at least not "open".

Anyone have suggestions on whether to reuse the rock wool that came out of these, or replace with some other fill material?

 

[gkimeng]

If it's really rock wool, replace it with fiberglass. If it's fiberglass, reuse it or if it looks grungy replace with new fiberglass.

These speakers won't perform as intended with poly filling.

 

[klamsoss]

If it's really rock wool, replace it with fiberglass. If it's fiberglass, reuse it or if it looks grungy replace with new fiberglass.

These speakers won't perform as intended with poly filling.

Thanks for the response. I need to go to home depot for boxes and tape, anyway. I assume any standard pink fiberglass insulation works? Or should I be trying to get a certain R value material?
Should I be trying to match the weight if the material I remove or....?

I've attached a couple photos of the material inside the speakers. I'm not sure how I would k ow the difference between rockwool and fiberglass.

 

[gkimeng]

Rock wool is usually grey and has obvious mineral particles in it (called "slubs"). It's actually pretty rare to find it, because it was only used for a brief period when the post-WWII home building and Cold War defense booms of the 1950s resulted in periodic shortages of fiberglass. By the time the 2ax came along in 1964 that was all over with.

 

[klamsoss]

I got R13 pink fiberglass. In various places I have seen that 20 oz. of fiberglass is the amount that works best for these speakers. I'll weigh the old crud that is in there and see if it's in the same ballpark. I know, though, that the density varies based on the R value, so I'm still interested to hear any thoughts on what would be the "correct" amount of fiberglass insulation to use.

 

[klamsoss]

Crossover work is done. Initially I was a little confused because I saw other threads where folks have resistors in their crossover network.
The pots weren't too bad. Some light sanding on the contacts and deoxit followed by faderlube has them reasonably smooth.

Now for some stuffing.
The woofers are curing in the garage. I suppose they'll be ready to go back in tomorrow. The stuff from vintage AR says give it overnight.

For folks who have done this speaker before (or other acoustic suspension speakers), is it better for me to drill new holes to re-mount the woofers? The existing holes may not offer enough purchase on the screw threads to compress the putty used to seal the basket in place. Eh?

 

[gkimeng]

You don't need to worry much about the R value, because you're measuring out the fiberglass by weight, not volume. Tear the roll apart into loose chunks about the size of your fist, which will tend to fluff them up, then put the entire 20 oz into the cabinet, making sure to get it into all the corners. You'll probably end up compressing it a bit in the process.

Be sure to wear gloves. I'm sensitive enough to the stuff that I use disposable tyvek coveralls, a mask and goggles to handle it.

If your woofer mounting flange doesn't have any breaks in the wood and the T-nuts are well seated, they should be ok. Scrape out as much of the old black putty as you can and either use vinyl rope caulk or foam weatherstripping to seal. Don't try to reuse any of the old putty.

 

[klamsoss]

You don't need to worry much about the R value, because you're measuring out the fiberglass by weight, not volume. Tear the roll apart into loose chunks about the size of your fist, which will tend to fluff them up, then put the entire 20 oz into the cabinet, making sure to get it into all the corners. You'll probably end up compressing it a bit in the process.

Be sure to wear gloves. I'm sensitive enough to the stuff that I use disposable tyvek coveralls, a mask and goggles to handle it.

If your woofer mounting flange doesn't have any breaks in the wood and the T-nuts are well seated, they should be ok. Scrape out as much of the old black putty as you can and either use vinyl rope caulk or foam weatherstripping to seal. Don't try to reuse any of the old putty.

I got some new putty with the AR resto kit that included the sealant for the woofers. I also have some thin foam I could use. Good idea. That will probably be easier than the replacement putty.

 

[klamsoss]

I have them all back together but it seems one of the midrange drivers (the mesh and white felt covered one) is not working. I know the pots are suspect on all of these, so I can't rule that out, but I'm suspecting that it's the driver itself.
It's a shame because what I do hear is quite good. Not as good as the KLH model six pairs that I've had, but not far off, and the sound has improved noticeably in just the first few minutes as things settle in. I suspect there will be some break in on these since they haven't been used for 20 years other than when I tested them at purchase, plus the Dayton audio caps do seem to "burn in" a little in my past experience. Anyway, I'm really enjoying the sound but wish that all drivers were working!!!

I'm somewhat inclined to eliminate the pots and the awkward double connector when I pull these open again. It seems unnecessary to have all of that going on when my Fisher has whatever tone control I could want (vis a vis R/L trebel and bass knobs). Any thoughts from the gallery?

I still need to make some new grilles for these since the originals are broken. What kind of grill cloth do folks like?