Cockpit speakers - safe compass distance?

[ohana]

Hi all,

In my SO 439, there are factory fitted cockpit speaker locations on either side, probably circa 500mm or so from each compass. I am looking at upgrading these to likely fusion speakers, but checking on line, the recommended safe compass distance (depending on the speaker type) is given as around 2000mm - 3000mm. 

Like many on here, I use plotters etc to navigate and do not (if I am honest) use my compasses very much, if at all. However, I dont feel happy in just ignoring this safe compass advice and possibly compromising the compass settings. Neither do I want to go to the expense of a professional compass adjuster to compensate for the speakers.

Am I alone here - what have others done in these circumstances? Is the safe compass distance given by speaker manufacturers too conservative? 

[Zanshin]

Optimally, Jeanneau will have "swung the compass" after installation but I have never seen variation cards on a boat. The big permanent speaker magnet might affect the reading if too close, and you might see 10-20 swings when Tchaikovsky's 1812 cannons go off

Realistically, the fluxgate compass on the autopilot/chartplotter is the primary compass on the boat and needs to be free of magnetic clutter. The cockpit ones are used (at least on my boat) when hand-steering at night. In the latter case I'm not necessarily steering to a course but holding a course steady.

So I'd feel comfortable replacing speakers with ones of similar magnet size.

[ohana]

Thanks - however Im not sure I have the same confidence as you that Jeanneau would have swung the compasses!!

[Zanshin]

I don't think that Jeanneau did. But you've been living with, and navigating with, those speakers and their induced deviation for a couple of years already - so it's a known evil and shouldn't get worse when replacing with identically sized magnets at the same distance

[Charlie-Bravo]

You could investigate the distance the speakers will effect a compass by experiment with your hand bearing compass at a variety of distances, being a smaller compass and probably not as well damped as a binnacle compass   it may well be affected to a greater degree (small play on words) 

CB

[Charlie-Bravo]

The suggestion of the 1812 cannon effect is valid, but could also be reproduced by Ace of Spades by Motörhead, the continual bombardment of the noise may give more time to see the deviation produced by the speakers at full throttle.
Probably best to experiment at quite a distance from a marina berth.

CB