No Magnetic Influence Loudspeakers

Some loud speakers are designed and described as having magnetic shielding which can localise the magnetic field. You do not have normal speakers that have no internal magnetic field. The amount of influence then will be somewhat less on the referred speakers but not necessarily none.
good luck olewill
 
Even the shielding used will distort the magnetic field around it by not being free space but some magnetizable material.

I think William was saying - all normal speakers rely on a strong magnetic field in a gap which the coil moves in. There will always be some field out of the front of a speaker where the magnetic poles are.

There are non-magnetic based piezoelectric and electrostatic speakers made but these are either generally used as e.g. tweeters and echo sounder transducers, or very expensive electrostatic dust and fly extractors.

Put the speakers at a greater distance from the Autohelm, or get creative and build speaker horns into the lockers to keep the drive units away from the autopilot, but the sound coming from near it.
 
the magnetic field from speakers falls away pretty quickly and at 1m the earth's magnetic field will be much stronger. That said, as 4thought suggests, try to get them as far away as practicable from the compass and at a minimum 1m.
 
A couple of weeks ago I was fiting a 'waterproof' speaker in the cockpit of a Contessa 32 and found that I had to mount it at the rear of the cockpit.

I was quite surprised to find that it was deflecting the magnetic compases when it was any nearer than 5 feet from them.

Iain
 
You will also find that you may have no deflection on one heading or relative position of speaker to compass - but will have on another as the lines of flux add, interfere or subtract from the natural lines. So just because you find a position that seems to be OK - you may find your deviation card is now 'out'.
 
Wey Hey no .... I want my Led Zeppellin to be HEARD by all !! /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

It's not unknown when I do small river partys to carry domestic speakers on deck of my boat ! Surprising how many others then join in with the revelry !
 
I suppose they could be electrostatic speakers but it doesnt say on the site. The only way yopu can tell whether they will affect your compass is to buy them and use them.
 
Thank for that.

THe problem is not the compass, but the Autohelm - I had to rip out the ones i had as the speakers sent it allover the place...
 
Autopilots are driven by an electronic compass, which should be:
a) placed as far as possible from any interference, and
b) calibrated to compensate them, anyhow.
Given these conditions, no speaker on earth should be able to send the pilot "all over the place"...
 
I had 2 autopilots:
One a very old Autohelm 1000 with a separate control head on a bit of wire - It worked fine, until it died...
The other one is an old Navico TP something or other.. All in one unit: When the Autohelm died I stared using the Navico after a gap of a few years. In the mean time I had fitted some speakers on the inside of the transom in the cockpit right next to the tiller.
Navico would only hold some headings, on others it would drift off to one side until I turned it off.
I ripped out the speakers and all worked fine again.
Now I have the wiring and 2 empty grills, but no speakers... So I was looking for some that did not have a magnet field.

Andrew
 
Aha, I see. I wasn't aware of these all in one units.
In this case, I'd suggest to use a proper pilot instead, if I didn't expect you to tell me to bugger off... /forums/images/graemlins/grin.gif
 
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