Monitor 12 series 2 questions

[Deleted User]

Bought a super nice pair of M-12.2 a week or two ago and finally got some time to do some 'stock' listening. About 8 feet apart and 6 feet from side walls. Toed in a little at first. Didn't like it. Parallel with back wall mucho better. Parallel 12" off back wall even better. They sounded ok but needed help.

I'm a big believer in spikes so this was first mod. Anyone that doubts spikes needs to be **** slapped. Everything but the tweeters more livable.

Next added felt around tweeters. Tamed them down a little and now they're getting some focus and stage greatly improved.

Now my question. I have to do something to these tweets. I can't believe Mr.Polk didn't spend $6-8 to add notch filters to take the spike down. I've read the RDO198's are flatter and what I need. Do those now before crossovers so I can hear them with the Radio Shack caps and resistors so I can say it was $100 well spent? Or am I pissing up a flag pole so long as the xo is OEM?

And which mid-woofers are in these? One is a little tired that needs retired or at least re-coned.

Thank you.

westmassguy

There are two versions of the Monitor 12s. Both have the SL2500 Tweeters. Those tweeters do not have a spike around 12.5 KHz, like the SL2000s. The correct Silk Dome Replacement, is the RDO-198-1.
All 8 woofers should be MW6503s. Polk has replacements for them.

westmassguy

Normally I use a .5 ohm Mills, or .47 ohm Mundorf MOX. Unfortunately, the Monitor 12 is unique in that regard, you should not eliminate it, if it's there. If you look at the original and revised schematics, the RDE-090 Polyswitch and 4.2uf shunt cap were added. This, at a time when Polk had eliminated Polyswitches on pretty much everything else.
Best guess: the tweeters are driven hard in the Monitor 12s, and the Cap and Polyswitch are acting as a safety valve of sorts. When the current exceeds the Polyswitch's rating, it opens. This forces the signal through the shunt cap, which when added to the 12uf cap downstream, raises the crossover point. By raising the crossover point, you reduce voice coil movement, and theoretically prevent tweeter damage.
That's my story, and I'm sticking to it.

[Deleted User]

Thank you very much!

westmassguy

You're welcome

[Deleted User]

Is there a particular value resistor you always use to replace the PolySwitch with? Or should I measure DCR through it and use a resistor that matches it? Thx.