Polk Monitor 4: difference between series 1 and series 2

Zentish

Can anyone illuminate for me the difference between an M4a and an M4 with a "Monitor series 2" on the label? I ran across a single M4 series 2 for $10 and was considering grabbing it a spare for my existing 2 M4a's, but don't know if it matches. Anyone know?

Thanks!

skrol

A while back I started working on a document to catalog the vintage Polk Audio speakers. The attached document is the latest version and has some info on the different Monitor 4 variations.

Hope this helps,
Stan

StantonZ

This might help both of you: I have a pair of M4's with peerless tweets I purchased in 1981 (very sure about that). I believe these were the only version of Monitor 4 that had peerless tweets (and they still sound great after 30+ years).

Zentish

Agreed that all of these vintage Polks hold up well, physically and musically!

It appears that there are significant differences between the M4A's that I have and the M4 series 2. The tweeter,crossover points, and even the impedance are all different. I hadn't even realized that the M4a's are 4ohms which could explain some problems I ran into with my AVR's in the past when I was driving my M5B's (also 4ohms) as mains and the M4a's as my surrounds.

A single M4 series 2 doesn't match my existing M4a's so it would just take up space on my shelf.

Thanks for the help!

Polk&Beans

Monitor 4 Series 2-1990-$200... I had 2 pair of these and the driver specs are wrong in the PDF.

Corrected Specs...The rest sounds about right. The SL2500 was a 1" Tweeter...

Drivers:
1 - 3/4" Tweeter (SL1500) Poly Dome
1 - 6.5" Woofer (MW6502) Bi-Laminate

Dimensions: 14.25"H x 8.5"W x 7.5"D
Weight: 24 lbs/pair
Specifications
Frequency Response: 35Hz - 22kHz
-3dB Limits 53Hz and 20KHz
Impedence: 8 Ohms
Recommended Power: 20-100 watts per channel
Efficiency: 91 dB

Polk&Beans

P.S. They also had a VERY unique crossover.

Is was a 6db per octive, series crossover, not HP/LP circuits tied parallel, pretty much like the rest of the Polk XO's.
It had 1 shared air coil, 1 resistor and 2 caps, in a single series curcuit.
Series crossovers are more difficult to implement because of very difficult driver spec matching.
But the end result is everything is in-phase!

Oh Yeah, They also sounded great. Wish I would not have given them away now...

falcon65

Skrol, nice job with that list of vintage Polk speakers. I have a pair of Monitor 4s that I got back in 1985 or so. Used them first as stereo speakers for a TV system. Got the stereo signal from a VCR that had a stereo TV tuner. Ran the VCR signal into an old EICO Cortina amp (15 watts RMS/chan) to power the Polks. Way better sound that came out of the TV speakers. I never used my main amp (Adcom GFA 545 II) to power the Polks until recently when I took a pair of Thiel CS2s offline (I'm retired to a down sized home, the CS2s didn't fit the room anymore). I was never impressed with the sound of the Polks powered by the low power EICO amp, but it was good enough for the makeshift stereo TV system back then. I recently hooked up the Polks, sitting on a pair of very solid Bowers and Wilkins 24 inch stands, to the Adcom amp. I was stunned at how good they sounded. At the time I was auditioning a pair of B&W 585 S2 speakers at home and really didn't care for the somewhat distant diffuse sound especially in the midrange. I hooked up the Polks and was amazed how lively these 30 year old speakers were. More midrange clarity and much more detailed highs. Better dynamics, maybe the higher sensitivity is responsible for the lively sound The 585s have better bass. However, I came to realize that if the midrange is not right then its a deal killer for me. I'm now using them for music and stereo TV. By the way, the dealer honored the 30 day trial offer and gave me a full refund after returning the 585s. Lesson-don't buy a speaker before you can listen in your own home using your own equipment.