Altec 421 dust cap replacement

I have refoamed at least 14 speakers and what I used to melt the glue was isopropyl. The purest is used to get water out of gasoline, get it at the auto parts store. Q-tips will work but I found the best way to apply it was with a dropper. You can control it very easily with the squeeze bulb and if you decant a bit into the bottle the dropper came with ( I use washed out bottles from herbal tinctures) you can keep down the amount of water it will absorb from humidity. 100% isopropyl will quickly dilute itself after it is opened to the air so if you get the pure stuff keep it tightly sealed and use a separate small bottle for the glue melting.
There isn't much flexing going on at the dust cap and you might be able to get away with Elmers, but the glue used for speakers will work for sure.
The dust cap is just that, it keeps tiny rocks from getting into your voice coil and doing damage. You want a good seal.
421s have metal dust caps if I remember correctly, it will be easy to do. After you get the old one off there will be a trace of glue left to guide you to getting it back on exactly where it needs to go. If that monster is still in the cabinet, lay the whole thing on its back, you want to do this with the cone pointing up. Leave it over night to dry.
Have fun,
 
With Q-tips you can get the dosage much more carefully IMHO. A dropper works too but the rubber and the acetone aren't a good combination in the long run. If the glue dissolves with alcohol, you can ofcourse use that, it's probably then even the better choice. A lot of types of glue aren't much impressed from alcohol though, that's why I suggested acetone.
 
With Q-tips you can get the dosage much more carefully IMHO. A dropper works too but the rubber and the acetone aren't a good combination in the long run. If the glue dissolves with alcohol, you can ofcourse use that, it's probably then even the better choice. A lot of types of glue aren't much impressed from alcohol though, that's why I suggested acetone.

Yes I would agree acetone my be a bit too much in long run.
Thanks for the help

Cheers
Ed
 
Isn't that pretty much what it if I have 421lf in it now?
I pick up two old rental cabinets that have 421lf drivers.
I have 805b horns to use with them, and want to do cabinet mods and bracing. Seems a lot of folks don't like the 421 and preference 416 or 515. Figure I can try this first before braking the bank on other drivers.
 
There's no fluid in any original Altec speakers. No idea about the computer versions.
If you look at the back of the speaker you'll see that the magnet is vented on both the 15" and 16" frames. Tape will be sufficient to block the air from passing through.
The easiest thing to do is get an exacto knife and cut the foil dust cap off and glue the 416 style cap on. Alternatively, you can get an non vented cap and glue it over the foil cap.

The 16" 421s can also be reconed with 416 cones. They will measure quite close to 416-8Cs.
 
Seems a lot of folks don't like the 421 and preference 416 or 515.
The 421 is an industrial driver. It handles more power and is more suited for PA work. The 515 and 416 are preferred in home use.
Doesn't the 421 have silicone damping fluid around the dust cap to cone joint?
Not a soft material like the surround goo, it's harder. It maybe difficult to remove the entire cap as the tinsel leads enter the cone outside the cap and removing it might damage them.