Does anyone out there have experience in shielding compasses from the magnets in speakers? I have a place to put the speakers that is ideal but close to the compasses. I've even purchased shielded speakers but they have the same effect as the unshielded. Thanx
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Speakers and compass
I found installing speakers with a permanent magnet anywhere on my boat will effect my compass. My speakers are about 8' away from my compass, and I imagine the change in magnetic footprint of my boat could be compensated for with compass adjustment, but as soon as you turn them on everything changes. I use my compass as a reference for holding course determined by my GPS now. Mark Major 86H23 Lesismor
I found installing speakers with a permanent magnet anywhere on my boat will effect my compass. My speakers are about 8' away from my compass, and I imagine the change in magnetic footprint of my boat could be compensated for with compass adjustment, but as soon as you turn them on everything changes. I use my compass as a reference for holding course determined by my GPS now. Mark Major 86H23 Lesismor
Speakers and Compasses
Cliff, Mark's right. I kept mine about 3 to 4 feet away and there is an effect. The other thing to watch out for is your autopilot. We have an ST3000 cockpit mounted control panel with built in fluxgate compass. It used to be 2 feet away from the speakers and when the stereo came on the boat started to wander all over the place! I changed the CD, but the boat still didn't like it!
Moved the control panel a few feet further away to a better place, anyway, and it's fine now. Most autopilots have remote fluxgate compasses wired to the control panels, so may not bother your installation. Stu
Cliff, Mark's right. I kept mine about 3 to 4 feet away and there is an effect. The other thing to watch out for is your autopilot. We have an ST3000 cockpit mounted control panel with built in fluxgate compass. It used to be 2 feet away from the speakers and when the stereo came on the boat started to wander all over the place! I changed the CD, but the boat still didn't like it!
Moved the control panel a few feet further away to a better place, anyway, and it's fine now. Most autopilots have remote fluxgate compasses wired to the control panels, so may not bother your installation. Stu
Rap? No Way!
Arrgh matey. No, it was Quito Rhymer from the BVIs. Maybe the boat was trying to head there. I have Cane Garden Bay on my GPS, it's only 3,250 nm, bearing 123! Then I changed to "Christian Island" by Gordon Lightfoot, tried Harry Belafonte, the whole works. *5 Stu
Arrgh matey. No, it was Quito Rhymer from the BVIs. Maybe the boat was trying to head there. I have Cane Garden Bay on my GPS, it's only 3,250 nm, bearing 123! Then I changed to "Christian Island" by Gordon Lightfoot, tried Harry Belafonte, the whole works. *5 Stu
Cliff, curious as to what brand speakers you use
I've read that some Poly Planer speakers are supposed to not affect compass
I've read that some Poly Planer speakers are supposed to not affect compass
Mark, I'm puzzled...
... by your statement "but as soon as you turn them on everything changes." You don't turn speaker magnets "on" - they are always on. If the magnets were the problem the interference with the ompass would be constant. Your amp should not be putting a dc current through the speakers. Sounds more like stray fields from a wire carrying dc current too close to the compasss. Derek Destiny - Pearson 422
... by your statement "but as soon as you turn them on everything changes." You don't turn speaker magnets "on" - they are always on. If the magnets were the problem the interference with the ompass would be constant. Your amp should not be putting a dc current through the speakers. Sounds more like stray fields from a wire carrying dc current too close to the compasss. Derek Destiny - Pearson 422
Derek
Permanent magnet speakers operate by using DC current, creating an opposing magnetic field at varying frequencies to produce sound. Turning them on introduces the opposing magnetic field, and raising the volume increases the strength of that field, so my observation is that compass deviation is directly effected as a factor of speaker volume. There are speakers made that use opposing electromagnetic fields for the same effect, but they still create a field when turned on. The only "practical" way I can think of to dampen the effect of magnetic field is with iron around the speaker, including a heavy iron grill in front of the cone (keeping in mind any iron brought aboard changes the magnetic footprint of the boat, and compass adjustment will still have to be made). One could also devise a dynamic deqaussing system, I suppose, but at this point taking guitar and voice lessons sounds much easier, eliminating the problem entirely. I'm niether engineer nor musician, and not much of a sailor, so I use my GPS with my compass as a reference while getting blown around, jammin'. So far I've made it back. Mark Major 86H23 Lesismor
Permanent magnet speakers operate by using DC current, creating an opposing magnetic field at varying frequencies to produce sound. Turning them on introduces the opposing magnetic field, and raising the volume increases the strength of that field, so my observation is that compass deviation is directly effected as a factor of speaker volume. There are speakers made that use opposing electromagnetic fields for the same effect, but they still create a field when turned on. The only "practical" way I can think of to dampen the effect of magnetic field is with iron around the speaker, including a heavy iron grill in front of the cone (keeping in mind any iron brought aboard changes the magnetic footprint of the boat, and compass adjustment will still have to be made). One could also devise a dynamic deqaussing system, I suppose, but at this point taking guitar and voice lessons sounds much easier, eliminating the problem entirely. I'm niether engineer nor musician, and not much of a sailor, so I use my GPS with my compass as a reference while getting blown around, jammin'. So far I've made it back. Mark Major 86H23 Lesismor
Mark, with all due respect....
... what you say is simply not true. Speakers work through a Lorentz Force interaction between the static magnetic field in the gap (established by the permanent magnet) and the alternating (ac) current in the voice-coil, - not dc - and this current will have zero effect on nearby compass direction. The electrical signal will impose miniscule cyclic variations on the local magnetic field at the acoustic frequency, but this field would at best create a tiny-tiny vibratory force on the compass needle. The mass of the needle and the damping of the compass fluid will prevent any observable response of the needle at these frequencies - 10 Hz and up. Your amps should NOT pass any dc current through the speakers - that would cause an offset of the cone which could cause all sorts of distortion on the output. Happy to provide a full mathematical analysis if you wish - this stuff is my bread and butter. Regards, Derek Destiny - Pearson 422
... what you say is simply not true. Speakers work through a Lorentz Force interaction between the static magnetic field in the gap (established by the permanent magnet) and the alternating (ac) current in the voice-coil, - not dc - and this current will have zero effect on nearby compass direction. The electrical signal will impose miniscule cyclic variations on the local magnetic field at the acoustic frequency, but this field would at best create a tiny-tiny vibratory force on the compass needle. The mass of the needle and the damping of the compass fluid will prevent any observable response of the needle at these frequencies - 10 Hz and up. Your amps should NOT pass any dc current through the speakers - that would cause an offset of the cone which could cause all sorts of distortion on the output. Happy to provide a full mathematical analysis if you wish - this stuff is my bread and butter. Regards, Derek Destiny - Pearson 422
And Fred, it's guys like YOU
that keep newbies like me reading these boards every day! You, Rick Dinon, John Farnsworth, Henk Meuzelaar, and of course Phil and Peggy and all the other "regulars" and "irregulars" (?)*yks on these boards. You all have made this winter "tolerable" for me. I'm a newbie "rag hauler" (ex "Stinkpotter"), bought my first sailboat (h456) at the Fall Annapolis boat show and like many of you I'm just waiting for the warmer weather!!! Thank you to all of you who share your thoughts, opinions, and humor! Keep doing what you do =) Regards, -Jim- s/v Forever
that keep newbies like me reading these boards every day! You, Rick Dinon, John Farnsworth, Henk Meuzelaar, and of course Phil and Peggy and all the other "regulars" and "irregulars" (?)*yks on these boards. You all have made this winter "tolerable" for me. I'm a newbie "rag hauler" (ex "Stinkpotter"), bought my first sailboat (h456) at the Fall Annapolis boat show and like many of you I'm just waiting for the warmer weather!!! Thank you to all of you who share your thoughts, opinions, and humor! Keep doing what you do =) Regards, -Jim- s/v Forever
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Jim S, Speaking of raghaulers and stinkpotters, music and the Annapolis show, did you pick up an Eastport Oyster Boys CD while you were there?
Jim S, Speaking of raghaulers and stinkpotters, music and the Annapolis show, did you pick up an Eastport Oyster Boys CD while you were there?
Hey Fred, while we are forming...
... a mutual admiration society, let me congratulate you on your rebuild project. After having a love-hate relationship with a H34 for 18 years, I truly am amazed at your efforts. Tawhiri was a great family cruising boat, but so many of the construction details drove me nuts. You have addressed almost all of them in your project. Way to go... For everybody else: if you haven't already done so, take a look at Fred's web site (related link) to see the wonders that he has done with his H34 that was "hurt" by a hurricane while stored aground.
... a mutual admiration society, let me congratulate you on your rebuild project. After having a love-hate relationship with a H34 for 18 years, I truly am amazed at your efforts. Tawhiri was a great family cruising boat, but so many of the construction details drove me nuts. You have addressed almost all of them in your project. Way to go... For everybody else: if you haven't already done so, take a look at Fred's web site (related link) to see the wonders that he has done with his H34 that was "hurt" by a hurricane while stored aground.
Well,,, What can I say guys? My wife and I thank
you all, so much. We can't stop smiling. Thank you again,,,,oh, OK!
you all, so much. We can't stop smiling. Thank you again,,,,oh, OK
!Derek, well shut my mouth!
And thanks for setting me straight and correcting my mis-information; like I said I'm no engineer, only observed these things on my boat. You have me curious, though, and the formulas would be useful to me here, and in other ways...Ok, I could go back to school, but since you offered, I'd appreciate it. My boat is on a trailer in my back yard, and tomorrow I will check what I thought I observed, for I have a problem with compass deviation I attribute to my audio system and I think you're the man to help. Thanks. Mark
And thanks for setting me straight and correcting my mis-information; like I said I'm no engineer, only observed these things on my boat. You have me curious, though, and the formulas would be useful to me here, and in other ways...Ok, I could go back to school, but since you offered, I'd appreciate it. My boat is on a trailer in my back yard, and tomorrow I will check what I thought I observed, for I have a problem with compass deviation I attribute to my audio system and I think you're the man to help. Thanks. Mark
Speaker brand....
Tom I changed to Poly Planer for the shielding they advertised. Worked just like the unshielded I had tried previously. Cliff
Tom I changed to Poly Planer for the shielding they advertised. Worked just like the unshielded I had tried previously. Cliff
Thanx everyone
Thanx everyone I found out more than I ever wanted to know about speakers and magnets but such is the power of this group. Keeps me reading. Final solution was to move the speakers around the corner in the cockpit to the port and starboard side. Diagonally it's about 14 inches away but no affect(or is it effect, I can never remember) on the compasses. Additional benefit is there is right channel music in the quarter birth and left channel in the head. Oh well......... Cliff
Thanx everyone I found out more than I ever wanted to know about speakers and magnets but such is the power of this group. Keeps me reading. Final solution was to move the speakers around the corner in the cockpit to the port and starboard side. Diagonally it's about 14 inches away but no affect(or is it effect, I can never remember) on the compasses. Additional benefit is there is right channel music in the quarter birth and left channel in the head. Oh well......... Cliff
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