"Special" Monitor 7? What should I do?

Ricardo

So I get ready to rebuild my Monitor 7B's; look at the schematics and buy the components I need; I also get a "like new" pair of MW6502's and a pair of Peerless tweeters.

Today I get the crosssover out (yes...I know...should have done that first) and it is different that the schematics that are in the sticky thread. Here's what I have:



Differences are:
1.-The 4.5 ohms resistor right after the fuse, in the schematics is a 2.0 ohms.
2.-The 2.7 ohms resistor is not in the schematics.
3.-The schematics and all other literature I've seen mention a MW6502 for all Monitor 7's. Mine has a MW6500.

I have no idea what the value of the inductors is, so I don't know if they are different from the ones in the schematics.

Everything looks original, so I'm pretty sure this is the way it came out of the Polk production line.

I guess I have some kind of intermediate model? The thing is that I have no idea of what the resistor values mean....so I'm asking the experts here for help.

-I am basically assuming that the MW6502 was a better fit for the M7, since that's what most of them came with. What should I do if I wanted to put the 6502's instead of the 6500's? (The 6502 is 4 ohms, while the 6500 is 8 ohms).
-What do the resistor values actually do? The tweeter is getting the positive signal through a 4.5 ohm resistor, vs a 2.0 ohm in "most" Monitor 7's; What is this doing?
-Why is the 2.7 ohm resistor added in the path to the MW6500? Anything to do with the impedance difference between the 6500 and the 6502?

-What's the purpose of the inductors? I don't know the values....should I just leave everything original? Any risk of damaging something if I decide to replicate the schematics with the 6502 and only one 2.0 ohm resistor....because the inductors might be different?

Appreciate any input.

BaggedLancer

Were the schematics you used for the monitor 7's with Peerless or SL2000/SL1000 or other variation?

i KNOW i read somewhere here that models with the Peerless tweeter had different crossover values because of that tweeter.

I wish I could back up that statement I just made but I have no idea where I saw them other than they were somewhere on here.

Oh and you aren't "Special", good try though.

Ricardo

BaggedLancer wrote: »

Were the schematics you used for the monitor 7's with Peerless or SL2000/SL1000 or other variation?

i KNOW i read somewhere here that models with the Peerless tweeter had different crossover values because of that tweeter.

I wish I could back up that statement I just made but I have no idea where I saw them other than they were somewhere on here.

Oh and you aren't "Special", good try though.

Just checked that the oldest M7 schematics in the sticky thread were approved in 1984; my 6500's are dated 1979, so I think that mine are just too old

I'm going to keep it original.....but I would still like to try how the 6502's sound; anyone knows what should I do if I wanted to swap an 8 ohm driver with a 4 ohm?

schwarcw

Ricardo wrote: »

Just checked that the oldest M7 schematics in the sticky thread were approved in 1984; my 6500's are dated 1979, so I think that mine are just too old

I'm going to keep it original.....but I would still like to try how the 6502's sound; anyone knows what should I do if I wanted to swap an 8 ohm driver with a 4 ohm?

Ricardo,

I suggest that you call/email Ken or Mark Suskind at Polk. They will give you the best advice. The rest of us will be guessing and maybe, give you bad advice. If I were to give you any advice it would be to build them they way they should be. Get the 6502 drivers, and the correct caps, resistors, etc. The only wildcard is the inductors. (PS, this could be bad advice:()

Now you have me wondering what is inside mine. I have the original Monitor 7's with the fuse in the back and Peerless tweeters.

Good luck! All of us Monitor 7 owners will be watching this thread, anxious to see what's going on here.

schwarcw

Here's a pic of mine:




This looks like the schematic that you posted.

schwarcw

And, I've got the 6500 driver. So, I've got just what you have.

Carl

danger boy

please post a picture of the front showing the drivers.. and the fuse(s) too on the back. thanks

dorokusai

Easy, look at the values on the Xover and replace them. I have yet to find someone who can hear the difference between a 6510 and 6511, for example, so don't lose sleep over it.

The Monitor series was all over the place in regards to spec's and parts that were actually used during manufacturing.

Ricardo

I kept them original. Drove to partsexpress this morning and got the right resistors. Sounding good.

schwarcw

Your thread now has me thinking, these speakers are over 28 years old. The capacitors are probably off value. The resistors are probably okay, but they were only 10% to begin with.

What did the replacement parts cost you Ricardo?

Ricardo

Total was $45, using Solen caps and Dayton audio grade resistors. I IMMEDIATELY could hear an improvemente in details/clarity......bass of course is expected to improve after break in.

mgsimmer

My Monitor 7bs also have MW6500 drivers with a 51981 datecode.

F1nut

10 year old thread.