I got given a couple of terrible, terrible looking- and sounding- speakers, and a pretty good power amp that has been in storage for a while, as a set. I haven’t started working on the amp yet, but it’s supposedly actually just fine. Yay!

But these speakers, goddamn. I mean look at this. This is already cleaned up. The other one is not better.


Already Cleaned. No, really.
By the way, if anybody knows how to get this goddamn horn off this tweeter driver? I’d like to know. Is there a trick? I took off the bolts and NOPE NOT MOVING. But it had to have been assembled in place, because you can’t fit it into the cabinet face otherwise. If it unscrews (after bolt removal) I don’t see how – I put a lot of force into it with a strap wrench and got nowhere.


HONK HONK
Honestly it’s like trying to fly the Constellation after the Doomsday Machine hit it. I got them wired up tho’ – it took some custom cabling and alligator clips, but I got them running. Limping along, anyway. But by that time I’d already discovered that despite their shitkicker exteriors, inside? All JBL pro gear. Really pretty high-end stuff. I don’t get it either.


If only we had some phasers…
Once I had them stable, I figured out the reason there was no high end was because hey, guess, what, neither of the tweeters were doing anything! The first one, I got back online by working around a bad connection. No idea how long that had been out. The second one…

The second one, I looked at, and tried to figure out what the hell they were doing with this weird circuit and this giant pot that like varied between 0 and 10 ohms maybe, and seemed to be in parallel with the speaker. Eventually I decided it was part of an inexplicably assymetrical Zobel circuit and realised that making it symmetrical would fix other problems too, so that’s fine, except…

…then I got the same circuit out of the now-working other speaker and discovered the one I’d been analysing had been misassembled since construction.

That’s as in at least 25 years. Probably 35 or so. SPEAKERS SURE DO SOUND DIFFERENT WHEN YOU ACTUALLY HOOK THE TWEETER UP, DON’T THEY? Or rather, hook it up so you haven’t filtered around it.

Which is what someone had done.

I am apparently the first to try to figure this out. I’m certainly the first to find it.

Honestly, I don’t even know what to say about that.

This post is part of a series on restoring these infamous vintage stage monitors. Spoiler: they made good, in the end.