Cockpit speakers and safe compass distance

[West Coast]

Hi all,

In my Jeanneau SO 439, there are factory fitted cockpit speakers on either side at the aft end of the cockpit, outboard of the steering positions. I guess this is fairly typical of many AWBs, with either speaker probably circa 500mm or so from each compass. The original speakers are failing, so I am checking into replacements. However, a typical replacement speaker has a 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 helm 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?

 

[Dellquay13]

The original speakers may be magnetically shielded, why not try to source the original brand and check their specs and continued availability?

 

[lustyd]

I don’t think my cockpit has anywhere 3m from the compass, and that’s a 36’ so realistically people must be fitting them closer than that!

 

[Refueler]

Fit and then do a check ... make a note of Deviation on example each 10 degree course ...

No need to adjust even with big errors as long as you know what they are. For Tiller or Wheel pilot - they don't care ... when you set pilot - it stays on that whatever it is ... even if you have plotter connected to pilot - its Off Course error it uses - not actual compass heading.

I have two compass on my 38 that read about 10 deg different to each other ... because previous owner mounted the Garmin MFD right underneath the stbd one ... which ones correct ? Neither !! Have I checked error against bearings etc. ? Not yet ... will do later .. when I remember.

 

[LittleSister]

The Vikings seemed to manage without cockpit speakers.

(And compasses, come to that.)

On several boats (all much smaller than the OP's) I've never been able to have the various instruments, displays, transducers, plotter, etc. their recommended safe distance from the compass. I haven't had a problem yet, but then I don't expect my compass to be accurate to the last degree. (I suspect, too, manufacturers err well on the cautious side in their specs on such things.)

Perhaps use a pocket compass to get a seat-of-pants check on of potential speaker purchases, either in-store or during 14 day return period on mail order?

| would like to think that certain types of music and speech would create more magnetic disturbance - thrash metal and fascist rally speeches to be avoided, while easy-listening and BBC Book at Bedtime would be OK.

 

[Refueler]

The Vikings seemed to manage without cockpit speakers.

(And compasses, come to that.)

On several boats (all much smaller than the OP's) I've never been able to have the various instruments, displays, transducers, plotter, etc. their recommended safe distance from the compass. I haven't had a problem yet, but then I don't expect my compass to be accurate to the last degree. (I suspect, too, manufacturers err well on the cautious side in their specs on such things.)

Perhaps use a pocket compass to get a seat-of-pants check on of potential speaker purchases, either in-store or during 14 day return period on mail order?

| would like to think that certain types of music and speech would create more magnetic disturbance - thrash metal and fascist rally speeches to be avoided, while easy-listening and BBC Book at Bedtime would be OK.

Do they still have "Listen with Mother" ????

 

[Boathook]

A lot of items giveca safe compass distance and quite often i suspect manufactures are covering themselves. If buying from a shop I would do the same as littlesister or if buying on line try and get the same make, etc.

 

[thinwater]

I would consider the distance to the autopilot compass.

 

[Refueler]

I would consider the distance to the autopilot compass.

Technically yes - but in practice the Autopilot will just reference whatever it is 'heading' to steer to ... unless the magnetics are so strong as to prevent AP doing its job ...

IMHO - its far less important than the actual compasses used to navigate with.

 

[ithet]

With speakers most of their mass is in the magnets. If the gross weight of the new speakers is similar to the old ones, then the power of their magnets (hence affect on compass) should be similar.

 

[Martin_J]

Wouldn't it just be easier to replace with non-magnetic speakers? Then you'd not really need to worry so much...

Something like.



Or

 

[Martin_J]

As Dellquay mentions... The above are probably just magnetically shielded, or at least designed so that any magnetic field is kept close to the coil.

Even some of the strong neodymium magnets are very very strong on their face, but the magnetic field diminishes rapidly with distance.

 

[thinwater]

IMO, it would be better to blank off the spaces , or just leave the grills in place, and not have speakers in the cockpit.

Sound really carries over the water, and a lesson most of us learned, at least by college is that no one else wants to hear your tunes. This rule holds no matter what your taste in music and no matter how strongly you feel that other will enjoy it. They won't.

Speakers in the cabin are fine. If you need to listen to something on watch (a bad idea IMO), since hearing is one of the senses you are supposed to use), that's what ear buds are for.

But this is off-topic. As for magnetic deviation, I agree that unless quite close it will make no practical difference. But check it with a hand compass. There is one in your smart phone.

 

[Refueler]

IMO, it would be better to blank off the spaces , or just leave the grills in place, and not have speakers in the cockpit.

Sound really carries over the water, and a lesson most of us learned, at least by college is that no one else wants to hear your tunes. This rule holds no matter what your taste in music and no matter how strongly you feel that other will enjoy it. They won't.

Speakers in the cabin are fine. If you need to listen to something on watch (a bad idea IMO), since hearing is one of the senses you are supposed to use), that's what ear buds are for.

But this is off-topic. As for magnetic deviation, I agree that unless quite close it will make no practical difference. But check it with a hand compass. There is one in your smart phone.

Have to agree with you about sound ... I have speakers that I can plug into the system if music etc reqd outside cabin ... as in a party or whatever.

But little confused by this : "As for magnetic deviation, I agree that unless quite close it will make no practical difference."

That all depends on whether you are a long distance sailor or coast hugger ..

I made a point earlier that if the magnetic force of the speakers is strong enough - it could stop the autopilot or steering compass from swinging freely. But if its just causing deviation that could be significantly large ... do well to try to quantify and tabulate.
Simplest way of course is to stand hanging off transom with a handheld and compare readings with Autopilot and Steering compasses .. noting on each heading ... then apply Variation etc. to arrive at boats deviation per unit. Its not the best - but its usually good enough for yottie tables. But please empty pockets of mobile phone .. keys .. car remote ... take off your watch ... etc.

 

[West Coast]

Thanks all for the comments. Will experiment with HH compass and Who knew non magnetic speakers were available?!

 

[thinwater]

... But little confused by this : "As for magnetic deviation, I agree that unless quite close it will make no practical difference."

That all depends on whether you are a long distance sailor or coast hugger ....

Actually, it all depends on whether the sailor uses the compass or not. In this day, 90% of sailors navigate chart plotter and ATNs, and maybe they use a steering compass at night. For this practice, so long as it is steady, minor deviation does not matter.

I learned to navigate before GPS, so I actually agree with everything you said. I ran a lot of DR plots out of sight of land. I adjusted the compass very carefully. I've also been messed up by a tool left near the compass! More recently, I was scraping on something in the cockpit of my F-24 while underway, and became confused when the boat kept changing course. Well, I using a metal scraper near the tiller pilot! With each stroke, the course changed! I felt a little silly, but also meant there was no actual problem, other than me.

Also, something that was not mentioned in the thread with that with electrical/magnetic interference, the compass deviation can also change when the gear is turned on. Sometimes just turning on nav lights moves the compass. But that is another topic.

 

[William_H]

As said I really doubt that the "non magnetic " speakers have no magnet in them. The only alternative to magnetic speaker is piezo electric as sometimes usedd in ear buds. I have not heard of that in speakers. A typical speaker has a powerful magnet but the field is enclosed ina very tight circuit with only a gap of a millimeter or so. I would suspect that this is part of Non magnetic claim. So OP has had speakers mounted for a long time no problem. He should compare magnetic field with a hand compass of the old speakers with any new option. I think the "speaker safe compass distance quoted would be very conservative. ol'will

 

[Dellquay13]

As said I really doubt that the "non magnetic " speakers have no magnet in them. The only alternative to magnetic speaker is piezo electric as sometimes usedd in ear buds. I have not heard of that in speakers. A typical speaker has a powerful magnet but the field is enclosed ina very tight circuit with only a gap of a millimeter or so. I would suspect that this is part of Non magnetic claim. So OP has had speakers mounted for a long time no problem. He should compare magnetic field with a hand compass of the old speakers with any new option. I think the "speaker safe compass distance quoted would be very conservative. ol'will

Normal speakers have pretty powerful magnets at the back, enough to firmly stick a screwdriver, and the occasional Stilson wrench on. I use the magnet from an old 12” guitar speaker stuck below a steel tray to keep nuts and bolts safe when working on my van engine.

Shielded speakers have enclosed magnets which reduces the magnetic field around them. They were very commonly used in tv surround sound systems and desktop computers in the days of cathode ray tubes when the magnets in unshielded speaker cabinets would cause rainbow effects on nearby screens.
That’s the Audio Visual technician in me mansplaining. Sorry.