New (to me) Monitor 7

notmydecision

Hi all -

Have lurked for some time as I have a set of Monitor 4 in my garage, but just got into an earlier set of Monitor 7 yesterday ($80). No model or serial on one cabinet and no fuse, the other is 7-26764 and has a fuse. Otherwise appear identical with what I'm assuming is the Peerless tweeter.

Woofer is seized on unit with model number. Looking into repairing which I've found resources on. However, would it be easier to simply replace both drivers? What is my best replacement option in 2024/5?

Gardenstater

That's strange. The early ones with silver basket midwoofers definitely had fuses. That other one is probably a 1979 one where they were re-using old labels but it would be a 7B. You can do a saved search on eBay for MW6500 and see if there are any currently available as well. My 1979 #19XXX ones that I am the original owner of, had the same labels on back that just said "7" but the shipping boxes were stamped 7B. I guess they were very frugal at Polk.

DeRod

The crossover without the fuse isn’t the original one for those speakers.

Can you take out the crossovers and check the dates ? The crossover with the label and the fuse looks like it is the original one.

Gardenstater

At some point they changed the mold for the terminal/crossover cup. The earlier ones had a smoother surface and you can see that in your pictures. I have some spare 7B crossovers that are "7B 52577" and "7B 52578" that are the textured finish. Yours may be from a 7C which could be a problem because it would not be the correct crossover for the Peerless + MW6500. It would be for the SL1000/SL2000 + MW6502.

You definitely should remove that crossover and post photos.

DeRod

Can’t really tell on the one without the fuse till you remove it and check.

It might not even be a monitor 7 crossover

notmydecision

Crossover dated 1985 is from the unit without a fuse.

I pulled the MW6502 from my Monitor 4s to replace the drivers - will that be problematic?

Gardenstater

notmydecision wrote: »

Crossover dated 1985 is from the unit without a fuse.

I pulled the MW6502 from my Monitor 4s to replace the drivers - will that be problematic?

Yeah that's a 7C crossover with a polyswitch and it is for the SL1000 or SL2000 combined with MW6502, not Peerless combined with anything (either MW6500 or MW6502)

Those MW6502 are not compatible with either of those crossovers and the Peerless.

This is the crossover you should have in the errant speaker. You might be able to figure out how to modify the one you have to look like this with a little ingenuity. If you do away with the fuse I'd put a 4.7Ohm resistor instead of the 4.5 Ohm. Some early 7A actually did have a 4.7 Ohm with the fuse but I'm guessing at some point Polk changed it to 4.5 Ohm.

notmydecision

Sounds like my best bet is to repair these MW6500 and find a 7B crossover?

Will these work?

https://www.ebay.com/itm/225063893194?chn=ps&mkevt=1&mkcid=28&google_free_listing_action=view_item&srsltid=AfmBOoqWlqGre3vkSQ8m_eokdis-6Js8Fuz_CiCKWgT1afA03wYkCyNHWKk&gQT=1

Gardenstater

That's probably an early 7A crossover when they had dual fuses. You could probably use those. I'm assuming that is a 34uF electrolytic because I can't see the value. It could be that the 4.7 was needed vs the 4.5 to balance for the second fuse.

Personally I'd prefer not to have any fuses if I had trustworthy and ample amplification. I think you could jumper them out and delete them if you wanted.

notmydecision

I'm probably gonna grab them and sort the rest out later.

DeRod

https://www.ebay.com/itm/125832638118?

Those are correct ones

DeRod

Look at those ☝️ they are the same date as yours and almost the same numbers

notmydecision

I saw! I just ordered them. That's a crazy coincidence.

DeRod

Bro that's a one in a million! I guess that means it was meant to be that you restore those awesome speakers!

You might as well replace the capacitors and resistors since you already have everything taken apart.
Also you could go ahead and install hurricane nuts since your pulling the bad driver out.

Post some pics when you get the new crossovers.

DeRod

o yeh and the one good driver you got JB weld the maganet ASAP

notmydecision

Above and below magnet as shown? I'll do it with my 6502 while they're out of the cabinet as well. I got the regular steel reinforced epoxy.

DeRod

Yes exactly. Above and below the magnet.

I wrap the basket in plastic wrap and use masking tape on the edges of the magnet to keep everything clean. With my finger I smear a nice smooth bead along the top and bottoms edges of the magnet.

pitdogg2

Popsicle/craft sticks are your friend.

Toolfan66

IMO, I would do away with the fuse blocks, take them off completely and plug the holes.

if you're going to keep them, clean the contacts really good, and get some quality fuses..

shvd285

Great choice