Crossover Gurus: rehab advice for mangled Monitor 4s?
I recently came into possession of a pair of old Monitor 4s, the kind with a Peerless Tweeter, MW6500, and a binding cup with a fuse and posts instead of the spring clips used in later 4s. To say that they've seen better days is an epic understatement. When I first hooked them up I got very weak sound from the tweeters and nothing at all from the MWs. One MW had a shifted magnet and was frozen, but the other appeared fine. But in making that diagnosis, I discovered a much bigger issue. At some point someone "modded" the crossovers and just butchered them.
The problem is that these are older (1982) than the earliest schematics available here, and the crossovers don't look like anything I've ever seen before. There are no resistors at all, just two inductors and a 5.8uF cap. Based on the condition of the hot glue, it looks like these components are all original, but obviously some of the electrical connections have been changed. The leads to the fuse were cut, but I have no way of knowing if there were other parts that were removed. Interestingly, the 5.8uF cap has one leg crimped into the terminal for the negative lead. I've never seen anything like this in any other Polk crossover, but it appears to be original and untouched by the modder. Same thing with one of the small inductor leads but in the positive terminal. That at least looks a bit more normal.
I've included a picture of the crossover (warning: some viewers may find this image disturbing :eek:) and my attempt at a schematic of the crossover as it's currently assembled (pardon my limited skills in this area). I'm hoping one of the guys who actually understands crossovers could take a look and see if this beast looks like something that could actually work as a crossover. If not, would anyone be willing to hazard a guess as to what the original crossover might have looked like so I could try to get them into some kind of working condition?
At this point, I'm thinking these things are beyond repair (the cabinet that contained the frozed MW is shot also), but I'd like to figure out if the tweeters and unfrozen MW6500 are still viable. Any help would be greatly appreciated... even if it only ends up being an academic exercise. Thanks, as always!
Monitor 4a Crossover Pics (as requested)
Sorry for the delay in posting these, I was caught up in work stuff for the last couple of days and couldn't break free...
Just my opinion, these (my) speakers seem to be on-par with my other vintage Polk's in terms of tweeter performance and bass response... in fact. I would rate the Peerless tweeter equal to or higher than the RDO-194's I've swapped into my Monitor 5's and 5jr+'s. I'm listening to them now back-to-back playing "The Nine Worlds" by Achillea. Bass response is also very good in my opinion for a bookshelf speaker.
Anyway, here are the pics as you requested. It didn't appear that these speakers were ever touched or modded in any way from original....