Center speaker magnet affecting in-dash tachometer on 69 rr

[jacsin69rr]

Am having an issue with the in-dash tachometer on my 69 RR being affected by the pull of the magnet on the front speaker. It causes the tachometer to read 3500-4000 RPM. To verify this, I removed the tach and the needle went back to 0. Any information out there on what can be used to block the magnetic pull on the tach, which is located next to the radio/speaker on the panel?

 

[HT413]

They make magnetic shield material for just this purpose. I don't have a link but google I'm sure it'll come up. Propwash (wil) used it if I recall, send him a PM.

 

[Photon440]

Do you have a monster speaker in there or the stock one?

 

[Propwash]

Yup,

Had the same issue. 2 aftermarket Polk speakers for the center and the tach rev'd right up. Installed a product called MuMetal. Worked like a champ. For the life of me I can't find the receipt from where exactly I got it, but below is a ebay link showing the stuff. Comes in an array of different sizes/thicknesses. Don't think mine is any thicker than .010 combined. You can also buy speakers with magnet shields on them. Good luck!

http://www.ebay.com/itm/Ultraperm-80-Metal-Shield-MuMetal-Mu-Metal-Sheet-Audio-/160613440162

 

[jacsin69rr]

4X10 stock

 

[Roscoethug]

I fixed it for $0. Aftermarket dash tach has no shielding. It's in a plastic case. My Big *** JBL speakers are center mounted under the dash. Tach read 2000 RPM with battery disconnected because of magnetic interference from the speakers. I cut up a soup can (must be ferrous metal i.e. attracted to a magnet. Lead, aluminum, etc. won't work) with a Dremel to get a 1" wide curved strip of metal. Slit it to clear the wires of the tach and secured it to the barrel of the tach with two sided tape. Before and after pictures below.

 

[Richard Cranium]

Do you have a monster speaker in there or the stock one?

 

[Roscoethug]

2 JBL 4" mounted side by side on a piece of 1/4" plexiglass. Radio is from '69 Plymouth with updated guts. 40 Watts. All speakers were rescued from an Infinity in the scrapyard.