Monitor Series M10 And M10 Series 2? Do I have a mismatched set?

Both appear to be the Series 2.

The left driver in the left speaker has either been removed for some reason and reinstalled or replaced because it is upside down.

RDO-198 tweeter is the upgrade but I really think you need to check inside, to solve the mystery of the labels and serial #'s.

It's possible that there may be ferrofluid (?) that is in need of replacement in those SL2500s but upgrading the tweeters would be the way to go.

The drivers are all MW6503, so no worries there.

The black marker...who knows, maybe the wrong date stamp.

The crossovers are the same. The single big yellow mylar is a 12uF. Polk used two caps, a yellow and a blue to obtain the 12uF value for the other crossover. It's a common practice when one doesn't have the exact value on hand.

I think the earlier mid 1990 speaker was in that transitionary period where they were still using up leftover parts from the 10B. Yes even labels!!! That's the way they flew lol. The other one is about a year later and is mid 1991 when they had used up all the 10B parts. That one MW6503 with the 1992 date was probably a replacement MW by a previous owner.

That big yellow mylar capacitor had *better* be 16uF (not 12). I don't think that it is proper what they did in your newer speaker where they paralleled a mylar cap with a polarized electrolytic (?) for the tweeter. That electrolytic may be out of spec/past its prime and could possibly be responsible for the harshness you are hearing....who knows? Probably they should have used a mylar for the one paralleled with the 2.7 Ohm resistor as well but at least they did that with both of them.

With your older transitionary PCB I believe I see where they jumpered out the polyswitch and also I see some concerning brown discoloration on the PCB around the 2.7 Ohm tweeter resistor which could be a sign of overheating.

The tweeter inductors definitely look to be different sizes in the two crossovers so I have to wonder if they are the same DC resistances and inductances.

Just my 2c.

kjsnfl wrote: »

Gardenstater, thank you! This is a fun dive. This is info I thought I'd never find!

I like the idea of adding Mundorf or Jantzen caps. I noticed the brown stuff as well, maybe a new crossover would be nice.

Do you like any specific brand or series of capacitors for this speaker?

I think those 2 brands are supposed to be fantastic but pretty darn expensive. I only have experience (great) with the Sonicaps but they have gotten pretty pricey. I'd check out the prices on those ones you mentioned but I'd seriously consider Claritycap CSA. I'd also check out all the corresponding inductors and make sure that the DCR is the same or close, even if I didn't have an inductance meter (I don't).

In the 10B for the MW inductor they had a 1.55mH and they went to 1.75mH, 18awg for the Series 2 so I would *hope* that is what you have in both speakers. They also went from 0.4mH in the tweeter inductor to 0.22mH, 22awg in the Series 2.