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Discussion Starter #1
I've finally got around to getting a set of front speaker brackets and thinking about installing a stereo. I've heard reference to a problem with the magnet interfering with the operation of the gauges, specifically the tach. Anything I should know before I start buying stuff?
Thanks

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I've not heard of this before. Perhaps someone else has. There's quite a distance between the left speaker magnet and the dash cluster. Think there is a couple of inches of daylight between the edge of the speaker cone and the cluster. Seems to me that's far enough away to have no effect.
 

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Yes, this is a very real phenomenon. Magnetism will affect all the guages, not just the tach. This is why the factory original front driver's side speaker has a specially "turned" magnet. If you have one you'll know what I mean, don't have picture available. That's why you have to be careful with modern speaker with their big honkin' magnets! These have a much more powerful field surrounding them. If they rub or are simply too close, the instrument assembly, any ferromagnetic materials in the cluster or guage instruments themselves will be slowly magnetized affecting their operation.

SO...either have the factory correct speakers re-coned or find aftermarket speakers that will acommodate as much space as possible from the outer surface of the magnet base from the dash instrument housings.

[This message has been edited by Coppertop (edited 04-10-2002).]
 

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Discussion Starter #4
Thanks guys. Just by chance ,is there anything I could put under the speaker in the dash installation to stop the magnatizmo thingy you were refering to? Them gauges were expensive!!I hate to put speakers in the kick panels but.........
Thanks, Mark
 

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I ended up ditching the idea of speakers in the dash and putting them on the floor behind the seat. Granted, I have an El Camino and I don't know what the backseat of a Chevelle looks like, but maybe you could get speakers underneath the rear seat? I have a set of 6x9's in medium size boxes right on the floor. The sound is incredible! BTW, I couldn't find speakers that sounded good AND would fit into the dash. Plus, the dash cover traps so much sound! Something to consider if you're driving the car daily.

Good luck!
Ryan

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I would think you can put a plate between the magnet and teh gauges as a form of EMI shielding. Then take a wire from said plate to the chassis ground. I don't see how a "turned" magnet will help things C.T.? The field will propogate in all directions from the circumpherence of the magnet.

This is how ingition EMI is terminated in the hood so as not to affect radio reception.

They do sell "sealed magnet" speakers. used in TVs and home theater stuff. Put your cars sub next to your TV as watch it turn green.
fun stuff.

Just install it and see?

I ran an aftermakret 2 way speaker in my front two spaces and my sweep stuff never had any issues.

My current Autometer stuff runs mint, but it is likely good stuff internally.

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[This message has been edited by BB_Mike (edited 04-10-2002).]
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by Coppertop:
This is why the factory original front driver's side speaker has a specially "turned" magnet. If you have one you'll know what I mean, don't have picture available. That's why you have to be careful with modern speaker with their big honkin' magnets!<HR></BLOCKQUOTE>
Joe
I hate to be disagreable but you sure you aren't thinking of the 70 again? The 71/72 does not have a different speaker on the drivers side. The speakers are identical. Agreed about a large speaker magnet. It should be a concern. There is only about 3/8 of an inch from the bottom of the magnet to the headlight switch. Any bigger and you will hit it. There's not more than an inch between the magnet and the plastic dash bezel housing. Doubt you will find a 4 X 6 speaker with a bigger magnet than the factory ones. If you do, you will not be able to mount the speaker.
BTW
I like to cheat. Have a 72 parts car sitting outside with the pad off and the factory speakers still in it.
 

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Guys,

Mike, the "turned" magnet is to allow maximum distance from the closest point on the magnet from the dash cluster. Yeah, probably the best bet is get about 20 ga. steel plate, mount it to the firewall behind the dash so it is orientated between the speaker and and dash cluster--pretty darn crampped idea to install though!


John,

Yup, got a '70, but the speakers were replaced by my dad's mechanic years ago. Where did the speakers come from--a '71 or '72 parts car!!!
Still a turned magnet from what I can see...

I've got to post a pic.
 

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For what it’s worth- The factory tach movement is very sensitive 15 mili volts/ 500 RPM. Painting the pointer (needle) will throw off the calibration. It is possible that if a speaker with a large magnet were mounted close to the tach it could affect it. However the factory tach was designed for cheep mass production having only one active component on its circuit board. Accuracy is not one of its attributes.

As for the speakers- The 72 sweep dash got speaker part #7313151 on the right side and #7936221 on the left side. The Monte Carlo/SS dash got part #7936211 on the left side. The difference is the orientation of the magnet. The SS dash also has a different mounting bracket for the left side speaker. The 70 sweep dash got part #731314 on the left side the SS dash got part #7933176. Don’t have the part #s for 71. I tried to mount a sweep dash speaker on the left side of an SS dash and found that the speaker magnet and the amp gauge inst lamp holder tried to occupy the same space at the same time. The correct speaker with the offset magnet clears it.
 

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Elree/Joe
I stand corrected. I was looking at a sweeper dash.
*bummed*
4 months ago I spotted a 72 Monte where someone got to the gages ahead of me. Just learned I should have grapped the left speaker.
 

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Discussion Starter #11
Thanks alot guys ,I'm not gonna chance my
gauges. Looks like they will be goin in the kick panels.I've got an extra set anyway.
Thanks ,Mark
 

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I tuned my JCW replacement speaker on the driver side with a grinder! I have idiot lights tho not gages. The JCW speakers have a larger magnet than stock but by using the correct mounts(slightly modified) and by grinding one side of the magnet I made it fit pretty nicely.

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I can attest to the fact that painting the needle will throw the accuracy off. Spent a lot of time on a test bench trying to get a tach calibrated(after painting the needle). It is very sensitive. The needle will move just by tilting it a little either direction from vertical. Great info, I didn't know left and right speakers were different.
 
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