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Polk Audio Monitor 10 A Frosting like on basket and magnet

S

speks

New Member
Hi guys, first time posting here,

So recently i buy from a guy this speakers, they sound pretty good, not distortion what so ever.

I started to investigate on this speakers, when a new about the common problem of the shifting magnets, 3 of the 4 mid drivers produce a scratching sound when i push in with just one finger on the outside of the cone, if I push in with two or more fingers evenly no scratching sound is produced.

So i decided to take out the driver and this is how it is, woth a frosting like pouder in the metal plate that sandwiches de agnet, i actually ended up taking both of them, and they are the same.

Once in my home i realice the speakers wherer like "gunky", i clean them up and theres no signs of watter damage on the cabinets.

Is this toxic? Hoy can I tell if the magnet have shift or misaligned?

Can i fix it?

Last questions, this speakers have the peerlees twitter, when I was testing them i felt ear out of the twitter, they have the hole in the center, just wantend to know if this is normal?

Thanks in advace for all the help.

IMG_20221009_233106

IMG_20221009_233106

  • Media owner speks
  • Date added

IMG_20221009_233030

IMG_20221009_233030

  • Media owner speks
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I have no idea what that is on your mid-driver, but I do know it is not normal.

You must apply even pressure on the cone to test. Pushing with one finger will always result in a scratching sound.

The hole in the tweeter dome is supposed to be there. Leave it alone.
 
If the frosty residue is cadmium oxide, then it could be toxic, and I would handle it carefully. I am not sure if oxidation stabilizes cadmium so that it is not toxic. A lot of steel speaker baskets (frames) and chasses plated this way were prone to this problem. I remove that kind of residue with a damp cloth while wearing rubber gloves. Better safe than sorry.
 
Might be zinc oxide? Thought cadmium oxide was more yellow in color. With way clean carefully with CLR or similar product. Don't drown the driver.
 
Thanks for the help, I'm gonna clean them with a lot of careful, i remove also the twitter and it was full of white dust, like alooot, probably Zinc oxide.

I remove also the drivers from the other speaker and they where fine, o frost powder, o oxidation.

I'm going to clean them with white vinegar, then I will apply sewing machine oil to prevent more corrosion.

Any idea if i should remove the dust cup and check the voice coil? If is full of this stuff, how should i remove it?

Thanks.
 
Bigyank said:
Might be zinc oxide? Thought cadmium oxide was more yellow in color. With way clean carefully with CLR or similar product. Don't drown the driver.
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I agree. More likely zinc oxide. I dought very much that it's cadmium.
Just wipe it off. And while you have the midbass drivers out. Run several beads of epoxy around the magnets. Above the ring magnet, and below where it's attached hed to the basket. Its just good insurance against magnet shift.
If your going ro press down on the cone to see if it's rubbing, use a finger on each side. As F1 nut said, 1 finger will make it rub. I wouldn't add oil, but if you do, epoxy the magnets first. If that oil seeps into the old brittle magnet glue, the magnet could shift maybe? A good bump and the magnets can shift on these old Polk speakers.
 
I have a table radio speaker that has a slightly yellow-orange tinged color of plating on its stamped frame. Would that be cadmium?
 
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