I recently stumbled upon a pair of Aurasound MR-12.4 subwoofers on eBay, new in box, for $300 including shipping. A fantastic price, I thought, for the NS12-794-4A's flamboyantly dressed twin.
I bought them, received them, and as promised, they were new in box. Unfortunately, all was not well with the subs.
Their coils were rubbing.
I removed the magnets and found that the plating on the neodymium magnets was bubbled on one, and bubbled/flaking on the other. I was able to remove the bad plating, but this left me with two problems:
1.) The magnets are neodymium/iron alloy. Without the plating, they will corrode/rust over time.
2.) The voice coil in one driver was scratched in several places by the flaking plating, resulting in shorting. Its coil reads 2.6 ohms instead of 3.5.
The seller was excellent about this, refunded me my money, and let me keep the subs. Needless to say, I want to try to repair them. So, I was hoping to do a little brainstorming with you all.
My initial ideas are to:
1.) Coat the exposed sides of the magnets with a high-heat primer, or maybe even a dielectric varnish to take care of any possible corrosion.
2.) Gently sand away the scratches on the damaged voice coil, and recoat it with varnish.
Anyone have any thoughts, concerns, or ideas? What would you try?
I bought them, received them, and as promised, they were new in box. Unfortunately, all was not well with the subs.
Their coils were rubbing.
I removed the magnets and found that the plating on the neodymium magnets was bubbled on one, and bubbled/flaking on the other. I was able to remove the bad plating, but this left me with two problems:
1.) The magnets are neodymium/iron alloy. Without the plating, they will corrode/rust over time.
2.) The voice coil in one driver was scratched in several places by the flaking plating, resulting in shorting. Its coil reads 2.6 ohms instead of 3.5.
The seller was excellent about this, refunded me my money, and let me keep the subs. Needless to say, I want to try to repair them. So, I was hoping to do a little brainstorming with you all.
My initial ideas are to:
1.) Coat the exposed sides of the magnets with a high-heat primer, or maybe even a dielectric varnish to take care of any possible corrosion.
2.) Gently sand away the scratches on the damaged voice coil, and recoat it with varnish.
Anyone have any thoughts, concerns, or ideas? What would you try?
How concerned do you think I should be about power handling if I sand the coil?
To avoid any issues, i was considering first trying to work apart the scratched areas of the windings that are making contact using the blunt side of a fine X-acto knife (and a magnifying glass so I can see. Haha!). But I have doubts about how effective that will be, and I may end up damaging it more.
They are shunted you need new coils (note: I don't have experience)
I bet you have a place (local) you can use for new ones ir recones.
If you make them yourself you need to measure all dimensions for specifications of new ones.
I bet you have a place (local) you can use for new ones ir recones.
If you make them yourself you need to measure all dimensions for specifications of new ones.
@hurrication : It was a lost cause, for me, anyway. The plating hadn't failed, the magnets had. Under the plating was a layer of magnet that was basically dust.
I tried repairing them anyway (peeled off the plating and coated the magnets with transformer varnish). But the gashes in the voice coil were too deep for me to sand away. So I sold the pair to someone who hoped to do better.
@maxolini : the seller was unaware of the issue, but issued a full refund and let me keep the subs when he was made aware.
I tried repairing them anyway (peeled off the plating and coated the magnets with transformer varnish). But the gashes in the voice coil were too deep for me to sand away. So I sold the pair to someone who hoped to do better.
@maxolini : the seller was unaware of the issue, but issued a full refund and let me keep the subs when he was made aware.
