Magnetic shielding

[Guido]

I'm planning to build a 4425 or maybe even better a 4435style 4425 hybrid (2x2214 ) as center for my HT.

The main prob is that as soon as I come only half close to my TV I feel like taken LSD. The colours get weird due to the magnetic field of the speakers.

OK for HF an older Alnico will work out fine. But the 2214??

Anybody any ideas to solve this?

Thanks!

[4313B]

Strategically placed Mu metal.

[Hofmannhp]

Originally posted by Giskard
Strategically placed Mu metal.

or....a lot cheeper with nearly the same efficiency (when 3mm thick and demagnetized) a steel plate screwed under the top plate.
Alternative is also a V2A plate (V2A is nonmagnetic)

HP

[4313B]

Yeah, why is that Mu metal so expensive anyway?

[Hofmannhp]

Originally posted by Giskard
Yeah, why is that Mu metal so expensive anyway?

in US it has to be called MI "magnetic impermeable", in germany MU "magnetisch undurchlässig"

thats an alloyed material of nickel/iron tempered with high temperature in a magnetic field till the cristal structure is aligned in one direction. Very often bonded with aluminium for better electrical conductivity. Prices I know here, are about 150,- € for 1m² or 10sq ft when 2.5mm thickness.

HP

[andresohc]

How do you screw a chunk of metal under the top plate (of the speaker driver right?) If you have done this, do you have a photo. I have experimented with magnetic shielding for years with little success (I havent bought MU metal though). Also do you know other names for V2A metal.

[Dieter]

Hi,

I've had a Klipsch ( sorry ) LaScala as a center speaker with the TV on top.

My solution was a 1 cm thick plate of iron between the top of LaScala and the TV, and everythig works fine.


Dieter

[speakerdave]

A couple of questions, Dieter. How much of a problem was it without the plate? And, how long have you been using this setup?

David

[Dieter]

Hello David,

without the plate many,many colours appeared on the TV-screen.

I have been using this setup for more than 4 years. When i replaced the Klipsch, all was right with the TV.

Dieter

[speakerdave]

And the plate has not become magnetized at all? I wonder if the degaussing loop that degausses the screen when it is turned on is also degaussing the plate.

David

[Hofmannhp]

Originally posted by andresohc
How do you screw a chunk of metal under the top plate (of the speaker driver right?) ...... Also do you know other names for V2A metal.

Hi andresohc,

I wanted to say that the shield has to be mounted under the top plate of the cabinet, not the driver. The effect of the shielding is better with some more distance between the magnet and the shield.
V2A = "stainless steel"

HP

[andresohc]

Hofmannhp , have you used plating on the side plates as well, if so how did you connect the sideplates with the top plate. I have tried this before and used foil tape (I think it was aluminum) from house ducting (but although the aluminum is electrically conductive I dont think it does anything for magnetic fields). I even tried one of those mylar balloons. Allright I might be touched, but we used mylar inside our very sensitive radio amplifiers in their dewars to cut down the noise levels. I didnt have any luck with any of this. My only solution was distance and positioning them off axis, below the axis of the tube, the most deflection occurred when the speakers were the same height as the speaker magnets.

[Michael]

We've had a 4311 centre sitting below a tube television in the past and we just lined the 18mm MDF that the tv was sitting on with 1mm lead. Not sure how much of an effect it had but there was no colouration due to the magnetic fields.

I'm having a bit of trouble now with a custom built dual 10" isobarik sub sitting under the desk the computer monitor is on. Theres no where I can move it but it only makes the monitor colourise a tiny bit along the botom where the blue XP startbar is.

Even this only happens on some occasions and I've tried the 1mm lead thing again (covering the top half of the top plates), but it makes little difference.

Maybe the 18" sub and 12" woofer to the right of the computer monitor balance it out a bit

[speakerdave]

Here's an earlier thread with a discussion on this topic.

http://audioheritage.csdco.com/vbull...light=magnetic

[Zilch]

End run: A new whiz-bang plasma or LCD HDTV monitor.

"Oh, shut UP!"

O.K., a custom built-in rear-projection setup, then....