7B Drivers

camaroguy

Hi Guys, this looks like just the forum I need to be a member of being that I have four pairs of Polk speakers. A pair of RTiA7's for my main system (in the middle of a Fortress Plus mod on those), a pair of 7C's for the living room, I even have a hidden pair of 6x9's in the back of my '68 Camaro show car and the topic of this post my 7B's that I bought 31 years ago. I recently got them back from the family member I gave them to many years ago and they need some help. I want to replace both tweeters because one has been replaced with some kind of a tweeter, so the first thing I need to know is what do I get? Second one of the mids has been replaced with one from Radio Shack so I want to replace both of those, I can get a pair of 6600X's would they work? And third I can also get a pair of 10'' passive radiators from the same seller, are they all the same? Sorry for the long first post but that's the way I am and Trey I'll get the Fortress Plus done in the next couple of weeks (been very busy), can't wait to hear them. Thanks for any info., camaroguy.

Nightfall

Somebody with more knowledge will chime in but I wouldn't replace the drivers with non stock ones unless 1) Polk made them as a replacement or 2) You do work on the crossovers to make them match the drivers you are putting in.

Look on the back of one of the OE Polk mid drivers you have left and it should tell you the model # Then you can either call Polk, make sure you tell them you're a member of club polk for a discount and free shipping, and order some new replacements or you can watch ebay. Be careful with Ebay. You could end up with frozen or magnet shifted drivers if the seller is either a liar, doesn't know what to look for before selling, or doesn't know how to properly pack and send your order.

As far as the tweeters, which one of these does your original Polk tweeter look like?

boston1450

MW6502 with sl2500 or sl2000 tweet i do believe. Welcome also

westmassguy

The woofers you need are the 4 ohm MW6502s. The Tweeters were most likely the SL2000s. The passive radiators were not all the same. The Monitor 10 uses a different one than the Monitor 7. The correct passive for the 7B or C is the SW101. The replacement tweeter for the SL2000 is the RDO-194-1. Unfortunately, Polk is out of stock until the end of October. They do have replacements for the MW6502s, or you can pick them up off eBay.

boston1450

westmassguy wrote: »

The woofers you need are the 4 ohm MW6502s. The Tweeters were most likely the SL2000s. The passive radiators were not all the same. The Monitor 10 uses a different one than the Monitor 7. The correct passive for the 7C is the SW101. The replacement tweeter for the SL2000 is the RDO-194-1. Unfortunately, Polk is out of stock until the end of October. They do have replacements for the MW6502s, or you can pick them up off eBay.

thanks for chiming in. I wasnt sure about the tweets. I knew some of the 7's had sl2500 & sl2000 without it looking up or picture

westmassguy

The Monitor 7 Model 2s or whatever they called them, had the SL2500s like the 10s and 5s for that matter. Their last hurrah. Around 1990

boston1450

Too many different models on the monitor series. Its crazy. But they are all nice speakers for sure

westmassguy

boston1450 wrote: »

Too many different models on the monitor series. Its crazy. But they are all nice speakers for sure

Agreed. You'd be hard pressed to find anything out there now, that's not made in China or north of a grand

camaroguy

Thanks guys, I'll get the correct mids from Polk and wait for the tweeters. I don't need them as I have plenty of speakers around the house, but I do want to fix them up as they were my first real speakers ( you know the ones that have removable grills) LOL. I'll also upgrade the crossover with new caps. like I did with the 7C's (big improvement). Thanks again, camaroguy.

jtgranby

7B' s should have peerless tweeter not any of the others.
Jim

westmassguy

jtgranby wrote: »

7B' s should have peerless tweeter not any of the others.
Jim

The original 7s had the Peerless, the As had either Peerless or SL1000. Bs had SL2000s

westmassguy

Just did some checking you may be correct, however I saw Bs with Sl2000s too

jtgranby

7c's had the sl2000 tweeter

doctor r

If they are early 7Bs then they should have the peerless tweeter. These do come up for sale occasionally. The replacement for the mid driver will be the mw6503 you can order a pair direct from Polk customer service (let them know you are a forum member). I bought my Monitor 7Bs new in 1980 and a few years ago did the crossover upgrades and changed to the 6503 drivers. If you cannot find a used peerless tweeter and decide to go with the Polk rdo model tweeter I believe it will require a change to both the cabinet and the crossover to accommodate the tweeter change. Others more familiar with this can give you more insight as this tweeter is the upgrade usually used in the later monitor series that started life with the original Polk tweeters.

SHOKDU

My 7b's have the peerless tweeter, so I presume they must be "early"?

westmassguy

Unfortunately, the schematics we have don't go back that far. You'll have to pull the crossover, and see what value caps were used, and perhaps measure the inductors. The 6503 is an 8 ohm driver. All the schematics show the 4 ohm 6502. If Peerless were indeed the original tweeters, you can look on eBay, just make sure they have the same model number on the back. Polk used Peerless made in Denmark and the US. Midwest Speaker sells a Peerless clone, that I'm told is very good.

camaroguy

Thanks guys, now that I look at the one tweeter that looks like a Polk tweeter I'm not so sure that it is. I checked my 7C's and they do indeed have the SL2000's, but the tweeter out of the 7B has no label just the ink stamped number 55144282, ink stamp showing it is 8 ohm, and a white MADE IN U.S.A. label. I do remember blowing a tweeter shortly after buying them, that may be a replacement tweeter the stereo store put in. Thanks for any help, camaroguy.

westmassguy

camaroguy, I know these have sentimental value, but if you have to replace both tweeters, both woofers, and both passive radiators, and still redo the crossovers, you might be better off just finding another pair of 7Cs.

camaroguy

Hi westmassguy, I don't need to replace the passive radiators. The seller with the 6600x's I was interested in had a pair he would take $25.00 for with the mids so I thought that would be a good deal (if they would work with the 7B's). As for fixing the 7B's, yes they do have sentimental value but since getting back into stereos about a year ago I'm also hooked on the DIY thing. So I look at them as another interesting project. As for the crossovers that is only about $25.00 for the capacitor kit like I bought for the 7C's. I just want to get the correct mids and tweeters. Thanks, camaroguy.

Easy Runnin

My 7Bs have peerless tweeters and 6500MW

camaroguy

Ok guys I think I'm set. I spoke to a tech from Polk and was told to get the tweeters from Midwest Speaker Repair (651-645-7385) part # MT4115 a direct replacement for the Peerless tweeters. As for the Mids. Polk has MW6502 in stock which the tech said were the correct mids for the 7B's. Now I just have to find a capacitor kit and I'll be good to go. Thanks, camaroguy.

doctor r

Make sure you look at the mid driver itself. The Monitor 7B started production with the MW6500 which would have a replacement of the MW6503. The crossovers are different since the 6500 and the 6503 are almost 8 ohm drivers and the 6502 is a 4 ohm driver. My 7Bs came with the peerless tweeter and the MW6500 mid drivers. The 6502 is listed as the standard replacement for the 7B but not actually true for all of them. You will find other references to this disparity on the forum.

Faustin

I bought a set of Peerless clones from Midwest Speaker to replace the original 7514 Peerless Denmark tweeters in my 10A's that I bought new in 1979. I am very happy with them. I bought 2 used Peerless tweeters and 1 was good and one was not working properly. So now I have one good 7514 Peerless and one that is working but does not sound as good. That all being said......the Midwest clones may be the way to go. I did find a pair of 4A bookshelf speakers that have the Peerless 5514 (made in the US) that work wonderful.

camaroguy

doctor r wrote: »

Make sure you look at the mid driver itself. The Monitor 7B started production with the MW6500 which would have a replacement of the MW6503. The crossovers are different since the 6500 and the 6503 are almost 8 ohm drivers and the 6502 is a 4 ohm driver. My 7Bs came with the peerless tweeter and the MW6500 mid drivers. The 6502 is listed as the standard replacement for the 7B but not actually true for all of them. You will find other references to this disparity on the forum.

Thanks for the info, only one of the mids is a Polk the other was replaced. The only markings I see are on the front surround, the word Polk and 180 degrees away SR 142/17. I doubt that's going to tell me which mid I have so what do I look for on the crossover? Thanks for any info., camaroguy.

westmassguy

Can you measure the Polk driver's DCR with a meter?

camaroguy

Hi westmassguy, to show what a novice I am I don't know what DCR is. I did measure the resistance across the two terminals and got 6.9 ohms. Great idea measuring the driver by the way, this is why I'm doing projects like this. Is DCR and a resistance reading from an ohm meter the same? Thanks, camaroguy.

westmassguy

That's an 8 ohm nominal driver. DCR means Direct Current Resistance. That's what most meters will read, DC resistance.
It also means, you need MW6500s or 6503s, not the 6502 that Polk has.

camaroguy

Thanks westmassguy, MW6503 it is. Polk has them in stock. You guys on here are real helpful, hopefully I'll be able to help someone out like you guys helped me. Thanks again, camaroguy.