Frozen drivers = trash?

Crashdot

I bought a pair of speakers that arrived with both drivers frozen (MW6502). From what I can tell in reading some threads, these cannot be repaired - is that correct?

Thanks

drumminman

That's what I've read too.

Mr. Bubbles

this depends on the reason for them being frozen. If it is magnet shift, they can sometimes be repaired but it's not real simple. If the voice coil is damaged it is my understanding that no parts are available for re-coning or repair.

nooshinjohn

Trash. IMHO your timw will be better spent getting or finding replacements than it would be messing around with attempting a repair.

transmaster

Cost more to have them fixed then to purchase new ones.

Mr. Bubbles

I have successfully repaired several with shifted magnets. It's not very complicated, but time consuming making a proper jig. Usually just the magnet and back plate/ pole piece shift. Since the pole piece must be centered in the hole in the front plate you simply make a jig to clamp around the whole assembly to center the magnet and the back plate with the front plate. the clamp not only aligns the parts but moves them into position as well so you don't have to fight the magnet. At the same time you should clamp from the front of the basket rim to the back of the back plate to pull everything together. If you can't do it yourself, you are much better buying replacement drivers. also as mentioned before. if the voice coils are damaged this does not do you any good. I just had some extra drivers and had gotten some out to trade with someone and dropped them. this shifted the magnets loose on some of them. Since i already had them and they were not in use, I figured it would be worth a try. It worked out pretty good. No rubbing and everything works great.

Toolfan66

I wouldn't waste my time, I would find another set of speakers and gut them for the spare parts before I tried spending the time doing that..

Oh wait I have done that..LOL!!!

Crashdot

What exactly happens? Is it the geometry of the speaker basket/spider that gets altered, or something to do with the magnetic field shifting? Sigh... these speakers were pristine before shipping, and out of the five or so sets of speakers I've bought, this is the only one that suffered this problem. The shipping company must have dropped them off of a building.

gdb

Crappy glue lets go and Hell Breaks Loose !

gdb

Here's what's worked for those who are "handy".

http://www.polkaudio.com/forums/showthread.php?79649-DIY-magnet-re-centering-info&highlight=repair+magnet

gdb

FWIW.....the glue and glue jobs are so crappy that it takes less than a mouse farting to dislodge the pole pieces/magnets. Colossal failure at quality control ! :frown:

nooshinjohn

gdb wrote: »

FWIW.....the glue and glue jobs are so crappy that it takes less than a mouse farting to dislodge the pole pieces/magnets. Colossal failure at quality control ! :frown:

Colossal failure???:question: Those drivers gave better than 25 years doing their job as designed, and only failed due to rough handling on the part of someone other than the good folks at Polk. That is a testament to how well engineered the SDA's are. They did not have CAD back then, and the adhesives they had to work with were far inferior to those of today. The quality of the SDA's are why we are here and why the company still supports 30 year old dpeakers by making new parts for them. Time to get a clue there gdb.:cool:

transmaster

I have a set of MW-6503's made April of 1988 in my Monitor 10B's I guess ignorance is indeed bliss in that I have never had the problem. As soon as I get over to Autozone I am going to pickup some JB Weldbond (JB-W) and anoint these originals so this never happens to them. I had to replace the pair in the other speaker, voice coils roasted, I bolstered them with JB-W before I installed them.

I have to agree with nooshinjohn adhesive technology was not as good, circa 1988 as it is today. I am just happy Polk Audio still has replacement drivers for an almost 25 year old set of speakers. I have a pair of 40 year old Warfedales W35 the 8 inch woofer in the right hand speaker was jack hammered to death by a new Onkyo receiver packing up. The driver demolished is a BIC-8950. Warfedale is still around, as is BIC but the speaker in question is long gone. They where both replaced with a NHT 8 inch driver where were as close as I could come to the original.

gdb

nooshinjohn wrote: »

Colossal failure???:question: Those drivers gave better than 25 years doing their job as designed, and only failed due to rough handling on the part of someone other than the good folks at Polk. That is a testament to how well engineered the SDA's are. They did not have CAD back then, and the adhesives they had to work with were far inferior to those of today. The quality of the SDA's are why we are here and why the company still supports 30 year old dpeakers by making new parts for them. Time to get a clue there gdb.:cool:

Piss off Noohie, I've been working with materials and adhesive in excess of 45 yrs. good thing other makers didn't have similar failures of their adhesives, like on a boat they produced AT F'in SEA !! You're the clueless, blinded fanboy character in this scenario,bucko

gdb

transmaster wrote: »

I have a set of MW-6503's made April of 1988 in my Monitor 10B's I guess ignorance is indeed bliss in that I have never had the problem. As soon as I get over to Autozone I am going to pickup some JB Weldbond (JB-W) and anoint these originals so this never happens to them. I had to replace the pair in the other speaker, voice coils roasted, I bolstered them with JB-W before I installed them.

I have to agree with nooshinjohn adhesive technology was not as good, circa 1988 as it is today. I am just happy Polk Audio still has replacement drivers for an almost 25 year old set of speakers. I have a pair of 40 year old Warfedales W35 the 8 inch woofer in the right hand speaker was jack hammered to death by a new Onkyo receiver packing up. The driver demolished is a BIC-8950. Warfedale is still around, as is BIC but the speaker in question is long gone. They where both replaced with a NHT 8 inch driver where were as close as I could come to the original.

Adhesives went to the lunar surface in.....wait for it........1969 ! Stop kidding yourselves, people! Polk, God love em, fell down on this one!

nooshinjohn

gdb wrote: »

Adhesives went to the lunar surface in.....wait for it........1969 ! Stop kidding yourselves, people! Polk, God love em, fell down on this one!

Yeah, I know because my dad was involved in developing them at a little company called 3M!. The tech for most of those adhesives are still classified and not available to the general public. Only in recent years have some of them become available, first for military application in programs such as the F-22 Raptor and other stealth aircraft. There has also been some use in the construction and repairs of naval vessels like submarines. The Auto industry has also been given liscense to use them (Audi and Jaguar) in aluminum monoque car bodies. These wonder adhesives would not have been available to Polk at the time the SDA's were made, and the special handling proceedures needed to use them on a factory floor would have required a completely new facility for OSHA reasons.

The stuff they used on the shuttle was among the nastiest odors I have ever smelled in my life. I knew it was not going to be a good day for my dad when he left for work in old faded jeans....

gdb

Did you guys witness the invention of the wheel too ???????????????

westmassguy

To the OP, I re-foam, re-edge, and recone drivers for a living. The jig mentioned is excellent, but if you're not handy, and don't have the materials on hand to make it, your better off just buying a replacement woofer. However, if you are handy, and don't mind doing a little cutting, there is a method I've used on several MW Series Polk Drivers. First, CAREFULLY cut the dust cap. Use a sharp exacto, scalpele, utility knife, etc. Start your cut about an 1/8" in from the edge of the cap, and gently cut almost all the way around. You should leave about 3/8" uncut, so the cap can be folded back. Or just cut it off completely, and get a new dust cap. Keep a vacuum handy, since you don't want any debris to fall down inside. Now look carefully inside. You'll see the pole piece in the center, surrounded by the voice coil former. Normally there's a tiny air gap between the pole and the former that is equal all the way around. With the magnet shifted, there will be a gap on one side, and no gap on the other. You'll need to find or make some shims. Old 35mm photo negatives are perfect, but any paper thin PLASTIC will do. DO NOT use paper or cardboard of any kind, as this can break-off or tear. You'll want to cut the shim about 1/2"- 3/4" wide, by 2" long. Cut two or three as you may need to build up the thickness. Now insert one shim in the large air gap, sliding it all the way till it bottoms out. If it feels loose, slide another shim down right on top of the other one. Now comes the fun part. On a flat surface, counter, etc., with the cone facing up and the magnet down, you're going to GENTLY tap the magnet from the side opposite where the shims are. I use a small sheetmetal hammer, but a claw hammer will work too. The hammer should be flat against the counter, and basically slid over to the magnet. You must hold the driver's frame steady while your doing this. Give it a couple taps, and check the gap. If the magnet shifted back, there should be a gap on the side opposite the shims now. If not, try again, with a little more force. If done correctly, the magnet will have shifted enough to safely remove the shims, and the voice coil will now travel freely. It may take several tries, and you may overshoot, and have the shims wedged too tight, or the magnet shifted, but off to one side. Keep at it. I've had some that re-centered on the 1st tap, while others took numerous tries, and I ended up feeling like a golpher missing a 2' putt 20 times in a row. Remember, it's a ceramic magnet, so it may chip a little when the hammer strikes it. If all goes well, and the cone moves freely with no rubbing, you can carefully reglue the old dust cap, or buy a new one. Give it a shot, the driver is toast now anyway, nothing to loose, but lot's to gain if successful.
If all was successful, use epoxy or JBWeld to secure the magnet in place.

transmaster

I have a couple of MW-6503’s with fried voice coils, with replacements available from Polk there is no point in having the originals rebuilt. So I decided to see just how much force it took to seize up the voice coil. All it took was a very light tap, about enough to start a small finishing nail to dislodge the magnet enough to seize the voice coil. When I took the magnet assembly completely apart I could see not much, of whatever the adhesive used, was applied. With this knowledge over the weekend I am going to give the original pair MW-6503 drivers (dated April 1988) in the other 10B the Weld Bond Treatment.

There have been observations here about adhesives going to the moon. This is of course true. But most of these advanced adhesives were not generally available in the late 1980’s and if available where too expensive, too technically difficult to use, or both. I was in a Navy Anti-Submarine squadron in the early 1970’s and we had some really heavy duty stuff used in the repair of bird strikes on the P3 Orion’s we had. We had tech reps from 3M around all of the time helping us out.

gdb

Horse **** ! Epoxy was developed in 1927 !!! It's been holding things like boats and airplanes together (without fail) EVER SINCE ! You people are likening the early eighties to the dark friggin ages ! They weren't. Simple....crap glue + crap application = crap adhesion/service span. Ever had a dental crown "glued" into the benign and welcoming enviroment..... the inside of your mouth presents ??? Get real folks !!:rolleyes:

transmaster

gdb wrote: »

Horse **** ! Epoxy was developed in 1927 !!! It's been holding things like boats and airplanes together (without fail) EVER SINCE ! You people are likening the early eighties to the dark friggin ages ! They weren't. Simple....crap glue + crap application = crap adhesion/service span. Ever had a dental crown "glued" into the benign and welcoming enviroment..... the inside of your mouth presents ??? Get real folks !!:rolleyes:

It wasn't epoxy, but an aviation grade Cyanoacrylate adhesive, Oh and by the way I was around in the 1950's.

nooshinjohn

At least he knows how to use Wikipedia.

Mr. Bubbles

gdb wrote: »

Horse **** ! Epoxy was developed in 1927 !!! It's been holding things like boats and airplanes together (without fail) EVER SINCE ! You people are likening the early eighties to the dark friggin ages ! They weren't. Simple....crap glue + crap application = crap adhesion/service span. Ever had a dental crown "glued" into the benign and welcoming enviroment..... the inside of your mouth presents ??? Get real folks !!:rolleyes:

Man that northbound mule must have passed a little gas. You seem angry!:evil: Anyway I agree with both sides of the coin here to some extent. I agree with you completely that This is a weak point in the Polk design that could have easily been improved. I mean aside from the boats, planes, subs, etc that I know nothing about, there are many speakers around from much farther back in time that do not experience this issue; Glue or no glue, its not the only method of holding a magnet and back-plate on. There are other areas in the Polk models that i own that i feel could have been improved as well.

However, as I say many times it is all about trade offs when you look at it from a manufacturers viewpoint. Polk obviously built some damn good product or we would not be listening to it so many years later. That doesn't mean that it couldn't have been better, but the engineers, developers, manufacturing personnel, marketing, etc all had a hand in the final product to some varying extents. There were not only performance and durability to consider but also aesthetics and cost along with other factors.

There are many things that can be done and some that could have been done then to make these even better, but Polk made them fit the bill they needed them to fit and did what i consider to be a damn good job. I also agree that there are areas that i believe I would have changed would I have been involved in the design, but I wasn't and can't be sure since I wasn't there dealing with all of the factors they had to deal with.

Just ragging you about the mule and giving my OPINION to all that may read this.

Mr. Bubbles

Holy crap now I know how you guys were chuckling at me when i got angry on here before.

Since wicki was mentioned I looked there. (le t me state that i personally know little about adhesives other than they stick stuff together, some better than others) The invented/ development dates for epoxy is actually given as 1936 though research started in 27 and cyanoacrylates were developed in 1942. Either one was developed way before these speakers and if super glue will hold that man up in the air by his hard hat, I would think it would hold a speaker magnet on. he was kicking pretty hard. ( some of you may not remember that commercial.

transmaster

Since wicki was mentioned I looked there. (le t me state that i personally know little about adhesives other than they stick stuff together, some better than others) The invented/ development dates for epoxy is actually given as 1936 though research started in 27 and cyanoacrylates were developed in 1942. Either one was developed way before these speakers and if super glue will hold that man up in the air by his hard hat, I would think it would hold a speaker magnet on. he was kicking pretty hard. ( some of you may not remember that commercial.[/QUOTE]

Let me tell you a story about ?super glue?. I was in VX-1 an experimental anti-submarine squadron which at the time (1972) was in Naval Air Station, Key Largo, Florida, Trying out new things was what we did adhesives where just one of those areas. We had a Seaman who was up on a wing repairing yet another bird strike on a leading edge. He started to slip and got a hand in some of glue he had just applied. It glued his hand down to the wing. That was bad enough but it was late in the afternoon everyone was gone, and the PO that was supposed to be watching him decided to go off to drink at a local bar. The Seaman?s struggling to get loose caused him fell off the wing and was found the next morning hanging by that hand unconscious. He had the necessary safety harness on but the safery rope was just a couple of feet longer then he was hanging. They had to cut out the section of wing surface he was glued to, and medevac'ed him out, never to return. The CO got totally mid-evil on that PO, the Chief running that department, the butter bar running the section, and the Officer in charge of the maintenance division. I mean we are talking Viking berserker arrrgh! Here.

Sea

westmassguy wrote: »

To the OP, I re-foam, re-edge, and recone drivers for a living. The jig mentioned is excellent, but if you're not handy, and don't have the materials on hand to make it, your better off just buying a replacement woofer. However, if you are handy, and don't mind doing a little cutting, there is a method I've used on several MW Series Polk Drivers. First, CAREFULLY cut the dust cap. Use a sharp exacto, scalpele, utility knife, etc. Start your cut about an 1/8" in from the edge of the cap, and gently cut almost all the way around. You should leave about 3/8" uncut, so the cap can be folded back. Or just cut it off completely, and get a new dust cap. Keep a vacuum handy, since you don't want any debris to fall down inside. Now look carefully inside. You'll see the pole piece in the center, surrounded by the voice coil former. Normally there's a tiny air gap between the pole and the former that is equal all the way around. With the magnet shifted, there will be a gap on one side, and no gap on the other. You'll need to find or make some shims. Old 35mm photo negatives are perfect, but any paper thin PLASTIC will do. DO NOT use paper or cardboard of any kind, as this can break-off or tear. You'll want to cut the shim about 1/2"- 3/4" wide, by 2" long. Cut two or three as you may need to build up the thickness. Now insert one shim in the large air gap, sliding it all the way till it bottoms out. If it feels loose, slide another shim down right on top of the other one. Now comes the fun part. On a flat surface, counter, etc., with the cone facing up and the magnet down, you're going to GENTLY tap the magnet from the side opposite where the shims are. I use a small sheetmetal hammer, but a claw hammer will work too. The hammer should be flat against the counter, and basically slid over to the magnet. You must hold the driver's frame steady while your doing this. Give it a couple taps, and check the gap. If the magnet shifted back, there should be a gap on the side opposite the shims now. If not, try again, with a little more force. If done correctly, the magnet will have shifted enough to safely remove the shims, and the voice coil will now travel freely. It may take several tries, and you may overshoot, and have the shims wedged too tight, or the magnet shifted, but off to one side. Keep at it. I've had some that re-centered on the 1st tap, while others took numerous tries, and I ended up feeling like a golpher missing a 2' putt 20 times in a row. Remember, it's a ceramic magnet, so it may chip a little when the hammer strikes it. If all goes well, and the cone moves freely with no rubbing, you can carefully reglue the old dust cap, or buy a new one. Give it a shot, the driver is toast now anyway, nothing to loose, but lot's to gain if successful.
If all was successful, use epoxy or JBWeld to secure the magnet in place.

I know this is an old post but it worked for me. I had already bought a new one but I though I would give this a shot. Thanks for the post.

westmassguy

Sea wrote: »

I know this is an old post but it worked for me. I had already bought a new one but I though I would give this a shot. Thanks for the post.

Sometimes it works, sometimes not.

Sea

It was a definite trial and error to get it pretty well centered. Scarred the magnet pretty badly but it works.

Schurkey

gdb wrote: »

Here's what's worked for those who are "handy".

http://www.polkaudio.com/forums/showthread.php?79649-DIY-magnet-re-centering-info&highlight=repair+magnet

This one's better--includes photos, and a great video of how drivers are manufactured:
www.polkaudio.com/forums/showthread.php?135716-Let-s-Try-to-Fix-a-MW6511-Damaged-in-Shipping

JesseS

Pardon the silly question, but how can one tell by listening whether a driver magnet has seized or shifted? My 10b Monitors sound pretty great, but they are all original, and sometimes I would swear there’s less oomph from the left. With the two drivers mounted side by side in each speaker, I’m not confident that I would hear if one were not firing properly, unless the effect is more dramatic? Likewise, maybe what I think sounds great isn’t everything it should be, without a reference for comparison. Thanks folks!

pitdogg2

Yea I would think you would. They can sound scratchy, loss of bass and when you push in evenly around the center dust cap it will feel like sand paper or not move at all.