What is the maximum wpc power source (vintage receiver) can be connected to Polk Monitor 7?

sjduban

I have several vintage receivers (Yamaha CR820, Sansui G6000, Pioneer SX-750) and I want to run Polk Monitor 7s as primary speakers. Will the Monitor 7 accommodate the 65 to75 WPC range of these vintage receivers?

mhardy6647

Should be no problem if used responsibly. That's a roughly optimal power range by late 1970s standards for a loudspeaker like the Monitor 7... and on the low side of optimal by most modern lines of thought. A little common sense goes a long way.

What era of Monitor 7? Do they have one fuse (tweeter), two fuses (tweeter + system) or no external fuse (internal tweeter protection in the form of a "polyswitch" resettable fuse)?

I would further encourage you to make 100.000% sure the amplifier you choose is healthy before committing the loudpseakers to it. All three of those are direct coupled -- a driver or power transistor failure (among other things) could send the full DC supply voltage ("rail") to the loudspeaker (irrespective of output fuse or 'protection' devices in the receivers) and cook the drivers' voice coils very quickly (and, sadly, even if there are fuses in the loudspeakers).

PS Were I you... I'd go with the Yamaha, if it is in good working order (rehabilitated) and all else being equal. That era of Yamaha and the "Monitor Series" Polk loudspeakers go very well together (and, yes, I am very biased).

DSC_0241 by Mark Hardy, on Flickr

teekay0007

Hardy's out of control!

sjduban

mhardy, thank you for the info. My favorite set up at home is CR-820 with Monitor 5B. I enjoy the detail and separation. I have Polk 10s paired with Sansui G6000 and HPM100 paired with my Pioneer SX-1050, but my favorite listening room has the Yamaha Polk 5 combo. So sweet. I have desired to own Polk 7s for a long time, but they are hard to find, (for good reason). The set I picked up is a newer version with no fuse on the back. Would you recommend upgrading the tweeter with the RDO-194? Thank you again for the feedback!!

Gardenstater

Power recommendations varied greatly over the course of the Monitor 7 evolution.

My brochure I was given with my 7B's (Peerless Tweeter period) said that it was an 8ohm nom impedance and they recommended between 10 and 100 wpc. A later brochure (SL1000 tweeter period) says 8 ohms, 10 - 125wpc. A later still brochure for the 7C (SL2000 tweeter period) says 6 ohms nom. impedance and 20-150wpc. So the big jump came with the 7C with the lower nom impedance.

kevhed72

Pick the one that goes to 11 on the volume dial.

mhardy6647

I'll take that as a compliment.

Yeah -- I'm a little nonlinear when it comes to Yamaha hifi.
In terms of my 'real' hifi, I've moved on -- but I still have a deep and profound love (for lack of a better word) for the aesthetics & the sonics of many 'generations' of Yamaha audio equipment (right up to some of their present offerings).

Most of the big silver boxes in that photo are in good working order. None is known to
be non-functional... but, in full disclosure, I've never had the nerve to even plug in the CA-2010.

pitdogg2

Do it see the glow doc..

Gardenstater

@mhardy6647 Are all Direct Coupled amplifiers ticking time bombs and it's just a matter of chance and time whether or not the speakers will be destroyed? What should be done with an old 1979 vintage Crown D150 to help protect from this? I know about DC offset checks and replacing the electrolytic capacitors with new ones. Anything else?

mhardy6647

Are they ticking time bombs? Well, not necessarily, but there's certainly risk.
DC offset is, of course, key.
The biggest risk (IMO) is the failure of a driver or output transistor -- which could happen any time, but becomes more likely with age of the components. In theory, most "modern" (since the early/mid 1970s) transistor hifi equipment has some sort of output protection on board (if only a fuse) -- the old saying goes that a $1000 loudspeaker will often fail to protect a 30 cent fuse!

I'll defer comment on the D150 -- I saw a post today about the DC300 on another forum (ahem, ASR, ahem) asking about adding a fuse to protect speakers while the outputs stabilize after amp turn-on, so I am guessing that Crown wasn't too worried about their customers' loudspeakers (i.e., not worried enough to build some protection into the amps).

Back to the OP's question - I assume any old(er) Polk "monitor series" speaker with no fuse on the back has a Polyswitch on board. I'd suggest searching the forums here to see folks' opinions about them and strategies to work around them (so to speak). As to the tweeter -- yeah, prevailing wisdom would be to upgrade to the replacement if it's feasible for you (economically and in terms of availability).

HTH, as they say.

Gardenstater

Thank you. I was confused from reading info. about the Crown D150A Series II. Apparently that is Direct Coupled but I just read that the early one I am using is not DC, the D150 (no bloody A ). So I guess I don't have to worry 'bout that!

I did a little reading about DC amps and apparently they are usually protected with input capacitors. Also they may have fast acting DC sensing protection circuits that may trigger a relay to cut off the output.

Sorry to hijack. To the original poster, from what I have heard almost everyone is glad they upgraded to the RDO-194 from the SL2000. I guess it depends upon your hearing sensitivity to high frequencies but most people say they are too harsh for their tastes and lack smoothness.

dromunds

I concur with the above that the Yamaha CR-820 should be a sweet match with the 7’s. And yes you want to install the RD0-194 tweeters. Those vintage Yamaha receivers are really nice imho

Gardenstater

That receiver has a higher damping factor than my Technics SA500 Receiver that I ran my 7B's on in college (40 vs 24). Similar power ratings and distortion. I was never happy with the bass but only used 16awg lamp cord lol. Occasionally fuses would be blown from my tendency to push the vol a bit too high and there was probably some clipping involved or imminent.

sjduban

Thank you all. I pick up 7s next week and plan to upgrade tweeter to RDO-194 soon after.