Polyplanar MA7500, re: magnetic resistance

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Tim McCarty

Question: Does anyone have any experience with the MA7500 box speakers mounted under stern rail seats? Does it affect compass/autopilot operation? Any insight would be greatly appreciated.
 
Dec 2, 2003
392
Catalina 350 Seattle
No Problems here

I've got 'em and haven't seen any affect on my compass or my St5000 below deck autohelm. I bought them from Dave's marine, with the navpod mountings, and paid quite a bit less than I had seen other places, particularly compared to what a dealer would charge new. link below. The only time I have seen an anomoly with my autopilot heading info was when I stored a metal air dehumifier on the matteress in the aft cabin. Couldn't figure out why the autopilot heading was so far off. Started looking for anything that I had done different and then spotted the air dryer box sitting where I normally wouldn't put it. Put it away (apparently away from the flux compass or something) and all was well. Good Luck Tim Brogan April IV C350 #68 Seattle
 
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Tim McCarty

Hey Tim, thanks for the tip on Dave's Marine

Shortly after I read your reply, I clicked on the link you provided and ordered a pair of speaker pods, and a pair of MA7500's (for the cabin). Dave's has the best pricing I've seen. The price on the Speaker Pods is outstanding when compared to a lot of other marine supply stores.
 
Jul 1, 1998
3,062
Hunter Legend 35 Poulsbo/Semiahmoo WA
Compass Safety

There are many reasons why some people say their compass isn't affected by some outside influence. Some of these can be because: 1. The compass on the boat isn't very sensitive. The typical OEM (Original Equipment Manufacturer) compass is CHEAP to begin with. The sensitivity of the typicall OEM compass isn't very good. 2. When the compass wears the gimball components degrade and the sensitivity degrades. 3. In the case of electrical/electronic items the magnetic flux varies not only with the distance from the unit but also with the amount of current going to the component. If one has a compass only for show then of course it doesn't matter but if you ever expect to REALLY use it then it should be at it's best. There's nothing worse than putzing around in pea soup with an unreliable compass. If you ever install a really good compass some of the magnetic items will be visible that weren't seen as a factor before. Some good web references: From the Ritchie web site at: http://www.ritchienavigation.com/service/compensation.html For checking the compass: http://www.andrewscompass.com/checkoff.html Note that Andrews also says to remove your compass during the off-season. One thing that this does is help to prevent the constant working of the gimballs.
 
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