Monitor 11 needs help

motorcityguy

Earlier this week I scored a pair of (early?) Monitor 11's. I have a lot of vintage Polks (7's, 10's, RTA12, SDA2) but have never seen or owned a set of 11's. They're apparently pretty uncommon, at least around here. Based on Jesse's positive comments about this model, I'm very excited to have them, and look forward to getting them operating properly.

Here's the situation. As purchased, they are Franken-Polks: The prior owner replaced the original tweeters with some garbage parts that don't even fit! (See picture.) But they play, and all 4 mid-woofers seem to work (and match). The cabinets and grilles are dirty but actually in pretty good shape. I took a peek inside and was pleased to see the crossovers and wiring look intact, original, and unmolested. So I think the prognosis is good. I just need to replace the tweeters, clean them up, and glue the magnets. But I do have a number of questions, so I'm hoping that Jesse and others will weigh-in with comments.

1. I think the correct original tweeters would have been Peerless? I have seen pictures of Monitor 11's with both Peerless and later (SL2000?) tweeters. But the non-Peerless versions look to have have a 10" PR. In contrast, mine have 12" PR, like the ones Jesse had, so I am assuming they are early and had Peerless tweets? (Not sure if it is an indication of the tweeter type, but the speakers do have an external tweeter fuse, like early Monitor 10's. See picture.)

2. The wooden frame for the grilles is quite weird, but obviously original. It has an odd shape cut-out over the tweeter that looks like it would impede sound. (See picture.) What's up with this? Also, is this odd shape a clue as to which type of tweeter the speakers originally had?

3. Are these supposed to be specific LEFT and RIGHT speakers? Again, referring to Jesse's M11 description, I think the one of the mids in each speaker operates differently than the other, making the speakers different for LEFT and RIGHT channels. Mine have original serial number tags, but they do not have any markings for "LEFT" or "RIGHT". How do I tell which is which?

4. Inside the cabinets, there is both foam, and the typical white "fiberfill" stuffing that I'm used to seeing in my other Polks. All of this stuff has fallen to the bottom of the cabinets, so I'm not sure where it's supposed to go. Can someone provide some direction on where the foam and fiberfill material is supposed to go? A picture or sketch would be most helpful!

Thanks, in advance, for any information/help/advice anyone can provide!

Gardenstater

I'll get it rolling before your thread disappears again. I was starting to reply when it vanished.

Re 1) The cutouts in your cabinets are clearly for either the Peerless or the SL1000, which Polk replaced the Peerless with sometime around 84 (?). The cutout for the SL2000 would be completely different. The change most likely did not accompany any crossover tweaks but I'm not sure on this. What is the date on your crossovers and your MW's? That serial # certainly looks early in the series but I do not know how many were made. Edit to add - I see that somebody butchered your tweeter cutouts and you are going to have trouble getting the new gasket to seal unless you do some work with some wood filler first.

Very interesting speakers and maybe (?) the best of the Monitor line.

I don't see a proper schematic, just the PCB layouts:

https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18779.pdf
https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18780.pdf

Gardenstater

Re 3) I believe that the MW that has the blue and white wires and the reduced bandwidth signal would be the outer driver. See if it is on the L side of one speaker and on the R side of the other, to make sure you have proper mirror imaged pairs. Just going by memory I believe I read in another thread that the foam would be up behind that outer driver with the blue and white wires.

Gardenstater

Aug 1982 advertisement. They called it "RTA 11", not Monitor 11. Definitely shows a Peerless tweeter and states mirror imaged pairs (not that there was any doubt)

Gardenstater

Audio Oct 1982 (It was a 1 year wonder because it doesn't appear in 1983 or 1984)

Gardenstater

Audio Aug 1982

Gardenstater

This is the link to manual for yours. I now see some pics of ones with SL2000's and non-planar passive radiator. I guess once again it shows that Audio Magazine Buyer's Guides are not always 100% reliable. No doubt you've got the good one!

https://polksda.com/pdfs/Model11Manual.pdf

Gardenstater

I think after the 12" planar passive radiator/MW6600/Peerless tweeter RTA 11, the one with the SL2000 was referred to as Monitor 11 but they strangely never seemed to advertise it or show it in any of their lineup photos as far as I've been able to tell. Here's a Monitor Manual that doesn't show it in the photo lineup but does have it listed. Ha ha they must've been smoking weed because they show a photo of the RTA 12C in the photo spread but don't list it in the detailed specs section but do show the Monitor 11 there. Ya can't make this stuff up :

https://polksda.com/pdfs/MonitorReferenceManual.pdf


Alright that's enough of tracking down this strange bird. I've always been curious though. Enjoy.

Gardenstater

OK I had to keep looking. No entry for an RTA 11 or Monitor 11 in Audio 1985, but then lo and behold, in Audio Oct. 1986 there it is. So it appears that the RTA 11 was brought out in 1982 and then discontinued and then brought out in a slightly different front baffle driver spacing (noticeable in pictures where the drivers in the RTA 11 are much tighter together) and appearance of cabinet with different drivers in 1986 and was then called Monitor 11A for $800/pr ? It could happen (Judy Tenuda voice). Next year in Oct 1987 Audio it was gone but they had the RTA 11t which as we know is the tower speaker.

pitdogg2

T was for tower.

F1nut

Yours are the original Monitor 11 with the Peerless tweeter. The sheet of acoustic foam goes just under the inside mid-driver. You should be able to see glue/foam residue inside the cabinet where it was attached. The poly fill goes under both mids with none behind the PR.

The butterfly cutout on the grill was likely for dispersion.

motorcityguy

F1nut wrote: »

Yours are the original Monitor 11 with the Peerless tweeter. The sheet of acoustic foam goes just under the inside mid-driver. You should be able to see glue/foam residue inside the cabinet where it was attached. The poly fill goes under both mids with none behind the PR. The butterfly cutout on the grill was likely for dispersion.

Thanks, Jesse! I'll look for the witness marks on the foam and cabinet to help determine where it was originally located. Hopefully that will be obvious, once I pull out all the drivers so I can see inside more clearly.

Btw, when you refer to the foam being on the "inside" mid-driver, is that my clue for figuring which speaker is left/right? Or is there another way to tell?

I think I have some Peerless tweets in my stash that I can install, now that I know they are correct. Can you comment on correct polarity for the white/black tweeter wires on Monitor 11? I know that some Polks, like my RTA 12, have backwards polarity due to the way the crossover is mechanized. (With the originals gone, I have nothing to reference.)

Thanks,
Greg

Gardenstater

Not Jesse here. Blue/White wires are the outer drivers as per the PCB layouts I gave the links to. Apparently I remembered wrong and the foam goes behind (and under?) the inner drivers. That makes sense actually now that I think about it. More important to control the backwave reflections from the driver receiving the full midrange signals, in addition to the bass.

They also do specify that the "Tweeter Out" is Black and therefore the "Tweeter Grnd." must be the white.

The manual says that the speakers are marked on the back L and R. Must've worn off or fell off of yours.

motorcityguy

Gardenstater wrote: »

...What is the date on your crossovers and your MW's? ... I see that somebody butchered your tweeter cutouts and you are going to have trouble getting the new gasket to seal unless you do some work with some wood filler first.

George,
Thanks for the response and all the information. Regarding the MW's and x-overs, I don't know the dates yet, as I've not pulled the x-overs and mids out of the cabinets yet. However, I will be doing so soon. And yes, the serial numbers are very low (4-digit). I notice that Jesse's pair also has a similarly low 4-digit serial number.

Regarding the butchering... Actually (and fortunately) there is only very minimal cabinet material that was removed for the Frankenstein tweeter, and it's (fortunately) not near the mounting holes, nor does it extend beyond the footprint of a Peerless tweeter. I intend to repair it using wood epoxy, which should be durable and unnoticeable, once the new tweeter is installed. Btw, the other speaker has a different Frankenstein tweeter which fits even worse, but had no cabinet hacking. :-)

Gardenstater

That's a good deal. The Peerless gasket doesn't have very much material above and below the dome anyways. As long as you have 1/4" or so you should be find I'd say.

motorcityguy

Gardenstater wrote: »

...Blue/White wires are the outer drivers as per the PCB layouts I gave the links to....
...the foam goes behind (and under?) the inner drivers...
...the "Tweeter Out" is Black and therefore the "Tweeter Grnd." must be the white.

George,
Thanks for the additional clarification. I'll look for evidence of foam on the inners (as also confirmed by Jesse) and verify the "blue/white" wires are on the outers. That should hopefully nail down which is left/right. I'll be sure to mark the cabinets "left/right" for the future! Thanks!

Gardenstater

You're welcome and good luck. I have been wondering about this mysterious model for a while now and why it is so rare. I think I may have found out why if the Audio Buyer's Guides are correct regarding the 4 year hiatus or so between the two different versions and each one only being made for a year or so. That would make sense.

motorcityguy

Gardenstater wrote: »

Aug 1982 advertisement. They called it "RTA 11", not Monitor 11. Definitely shows a Peerless tweeter and states mirror imaged pairs (not that there was any doubt)

Hey George,
The ones in the ad are definitely the ones I have, including the funny cut-out in the speaker grille. I've not pulled out the drivers yet, but with a small mirror, I confirmed the mids are MW6600 and the PRs are 12". I'll report the driver dates as soon as I pull them out.

Sure seems confusing that they are referred to as RTA11, and (later) Monitor 11.

F1nut

Also called the Model 11 by some. Foam goes under not behind the driver.

Gardenstater

Hey Greg.

Good news. I think this schematic in the archives is actually mislabeled as "rta11t orig" but it seems to be your schematic for your RTA 11 !! It is dated "circa 1983" which is pretty darn close and the RTA 11t is totally different and would be circa 1986 or 1987. Earliest adv I've seen is June 1982 and the PCB layouts are March 1982. This is the missing schematic. Verifies that tweeter isn't reversed polarity I'd say because they don't indicate anything to suggest that. There is something missing or cut off
on the right side of the sketch though.....aaaargh......always something lol.

motorcityguy wrote: »

Sure seems confusing that they are referred to as RTA11, and (later) Monitor 11.

Yeah it is confusing and I had fun reading through some old threads where people argued about that and the tug of war was amusing to say the least. It is also rather odd that there doesn't appear to be any schematic for the later variant called Monitor 11 (circa 1986) with the SL2000 tweeter in our archives. Maybe the only thing they changed is the tweeter, MW's, and the Passive?? Speculation at this point. Another thing that is odd is that 4 years later the price basically stayed the same at $800/pr.

https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18706.pdf