Polk 7b Help

jakelm

Hi all
As some of you might know, I recently purchased a nice pair of Polk 7b's from ebay, but now I have some minor problems I hope some of you can help me with. I emailed Polk about these problems, but I was also hoping some of you vintage lovers might give me some advice. First I want to appologize if this has been covered before.

I recieve the package on time (for a change!!). I took off the grills and this is what I found

1. One of the 6.5" drivers (mw6500) was frozen solid.
2. A small pin hole in the center of both dome tweeters.

I have read that the old glue in the driver tends to freeze the speaker and the driver has to be replaced. Is this true?
I also own a pair of monitor 4's. What I did was take the 6.5" (mw6502) out of the 4's and put it in the 7b's. But, to me, the sound just isnt the same. I asked Polk if there was original replacements (mw6500 instead of newer models) and I'm waiting for thier reply. But if any of you guys and gals have any recomendations, please do tell.

Now as for the tweeters. The pin hole doesnt seem to effect the sound, but, I didnt noticed in the 5khz-10khz range there is minor distortion, even at low level playing. But not so noticable to the common ear. But I can hear it. Is this normal? Is the pin hole normal? The reason I ask if it is normal is because, the pin holes or absolutly identical in size and position on the dome. As if they were made that way.

Like I said before, I did email Polk with these issues in hope they would give some help, but if any of you have advise on what to do , I would appreciate it.

Jake

nadams

Your driver seized due to the magnet shifting during shipping, as you've already guessed. Common on the vintage Polks. I believe the MW6503's are still available. I just had to buy two for my SDA's.

The pin holes were done by hand by Polk to reduce distortion in the tweeters.

jakelm

Thanks Nadams. Let me ask you, is there any difference in the mw6500, mw6502, mw6503? Why am I hearing a difference between the 6500 and the 6502?

I also notice the fuses were blown when taking the speakers out of the packaging. What would cause the fuses to blow?

My dad owns 2 pairs of 7a's (stacked an they sound great). I assumed , just by looking at the design of the 7b's that they were identical speakers to the 7a's, just made in different years. Am I correct?

danger boy

you might want to find another 6502 driver on Ebay if Polk doesnt' carry a replacement for it. OR if Polk does carry the replacement.. you may want to buy two of them and replace the good one in the other speaker so they match.

the pin hole is normal. don't change out those tweeters unless they are bad.. if bad. replace with the same peerless tweeter.. used ones are on ebay all the time for little $

jakelm

I just bought 2 6503's from Polk. The ohms are closer to the 6500's than the 6502, (which I didnt know) thats why the sound was not the same. The customer service guy told me that even though my tweeters look the same as peerless they are not. Just to let some of you know.

jakelm

Thanks for all your help. Let me ask another question. I noticed alot of dust and dirt on the tweeters. Does this effect the sound quality? If so how do I clean them?

joelll

The dust and dirt on the tweeters won't affect them, as far as I know. The ones on my RTA-12's are more exposed (the same type tweeters are open-air top-mounted under a hat-like grille), and they work just fine.

jakelm

Ok all, I received my new mw6503's to replace my frozen mw6500 in my 7b's. Somethings not right!! Way too much midrange coming from them. Anyone else have this problem? Another thing, on the old monitor 7b's, is white pos and black neg or is white neg and black pos? On the old mw6500's there is no indication on which is which. I'm thinking this could be my midrange problem. Any suggestions???

joelll

Black is usually (but not always) negative, and white is usually (but not always) positive.

Try swapping the wires on one woofer to see if they're out of phase with each other. Occasionally even the best of factories use the wrong wire color, and they'll just swap the leads to fix the problem.

By the way, if the 6503's really don't work out, there may be a good speaker place that can repair the 6500 that's gone bad I'm assuming the cone is intact, but the voice-coil has frozen in place for some reason. And as always, keep your eyes out for what fleaBay might have on offer.

jakelm

Cs just emailed me that the black wire is positive. Thats the way I have it. We are trying to figure out the problem now. Every spec I read about the 7b's have the mw6502 as original. But I have the mw6500 as original. The mw6500 was put only in the begining 7b models right before the mw6502 was made. The mw6502 was used with the sl-1000 tweeter not the peerless tweeter I have now. The peerless tweeter I have is the original. It was put in also at the beggining 7b models before the sl-1000. So the original early configuration of the 7b's (the way I undertsand it) is just like the 7a's. The later 7b's were the transition of drivers from mw6500 ad peerless converted to mw6502 and sl-1000. The mw6502 has an ohm rating of 3.4 and the ohm rating of the mw6503 is 6.3. So anyone who is thinking of changing drivers , be ware of which ones you have. The large difference in ohm ratings will change the sound quality.