Bucking Magnet Source?

[Biff Byford]

I'm about to go bonkers trying to find appropriately sized bucking magnets for my Sony Xplod XS-GF1320 car stereo speakers.

(Bucking magnets, a.k.a. cancellation magnets, are glued to the back of speaker magnets to prevent interference with monitors. This lets you mount unshielded speakers fairly close to a monitor without adverse effect. Or so I've read -- ask me again when I have the right magnets in my hot little hand ... )

(Also, I learned you have to be really careful when you say the 'bucking' part at Radio Shack.)

At any rate, the magnets on my speakers are 70mm in diameter and about 20mm thick. Supposedly, you need magnets about 1/2 to 2/3 the size of your speaker magnets. Assuming that 'size' means dimensions and not weight, that would mean the magnets should be 35mm to 50 mm in diameter.

Problem is, the only magnets I can find start at 60mm in diameter:

http://www.partsexpress.com/pe/showdetl.cfm?DID=7&PartNumber=329-208

However, they're shaped like a donut (with a center cutout), so there's actually less area than a solid 60mm magnet.

I guess what it comes down to is that I need help determining which of the following is true:

1) The overall DIAMETER of the bucking magnet in relation to the speaker magnet the important part. If so, the 60mm bucking magnet, at 85% of the 70mm speaker magnet, is too large. In this case, I'm SOL because I haven't been able to locate any smaller bucking magnets.

-OR-

2) The overall AREA of the bucking magnet in relation to the speaker magnet is the important part. If so, the 60mm bucking magnet with a 35mm hole in the center, at 52% of the 70mm speaker magnet, is within the acceptable range.

-OR-

3) The overall VOLUME of the bucking magnet in relation to the speaker magnet is the important part. If so, the 60mm bucking magnet with a 35mm hole and a 10mm depth, at 25% of the 70mm x 20mm speaker magnet, is too small. In this case, there are larger magnets for sale from the same supplier, so it'd be easy to determine the right size.

I'm assuming it's #3, because ultimately you'd want to balance the overall power of the bucking magnet to that of the speaker magnet, and I'd assume a thicker magnet is more powerful. Can you help verify?

Thanks!

[itismejs]

*ucking magnets...not a bad idea.....when to people wear them comewithin 1 foot of each other.......

[Darkstalker]

Dual layer COPPER shielding that is attached to a hard ground will work.

[Darkstalker]

*ucking magnets...not a bad idea.....when to people wear them comewithin 1 foot of each other.......

Yes, but think about who would use such things, and that would prove why that is a bad idea  

[Darkstalker]

Basically, to make a magnetic shield, you want something permiable.  The dual layer aspect is just like dual pane windows, and the connection to ground is just ESD preventative measures.

You could use iron since it's permiable as well, but it is a lot harder to work with.

It's very kiddie-level in it's explanation, but here's a good link to see the effects of a shield:

http://www.exploratorium.edu/snacks/magshield/

edit: Since we're talking small speaker magnets, I'm thinking a dual layer shield is a bit overkill.  Probably best to shield the CRT though since it is the main thing you're trying to protect, then you don't have to worry about messing with the speakers.

[spystyle]

After scouring Google I found this :
http://www.clothedandy.com/Voight%20Pipes/shielding.html

looks like it's in keeping with the BYOAC way ($5 @ Home Depot)

Can you dig it?
Craig

[Darkstalker]

Nice find!  Never thought of using duct piping..

But yes, when I say ground, I mean to either the ground prong in an electrical socket, or a metal pipe running into the ground (NOT your CP's common ground!).  Since most cabs have a surge protector, I figure you can "adapt" a PC power cable to get a nice earth ground source inside a cab.  Just remove the hot and return prongs on the male plug side.

Again, this is more or less just to be on the safe since there are electro-magnetic fields involved.

[itismejs]

*ucking magnets...not a bad idea.....when to people wear them comewithin 1 foot of each other.......

Yes, but think about who would use such things, and that would prove why that is a bad idea  

Dont worry...you will have to have proof to buy a positive or negitive magnet.....or they will repel