I have a new stereo to install on our boat and as far as I can tell, there hasn't been any speakers mounted for the cockpit in the past. I plan on installing a speakers on the bulheads and the bulkhead on the starboard side has my instruments already mounted. Will the magnet of the speaker on the starboard bulkhead affect the instruments. The picture shows our Datamarine depth and speed log (the two round instruments on the bottom) and our Simrad wind instrument (the square instrument on top closest to the companionway). I will take out the other square instrument (which is an old distance log and it is redundant) and install the speaker using the hole (it is round underneath the cover) which may need to be enlarged a bit. The bulkhead on the port side has nothing mounted on it so I will cut a new hole for the speaker. There is nothing behind it on the inside. Our only compass is mounted on the binnacle. Any worries? We don't have autopilot, yet.
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Magnet
Yes they will affect compass as far as 6 feet away. I still have a pair of brand new ones sitting in the garage. You need to get the magnetically shielded speakers. Unfortunately, most marine speakers as not made that way but there are exceptions. You got to look carefully. Bring a handheld compass with you when shopping. Alternately, you can bring them to a speaker shop and have a magnet of the same strength epoxy glued to the back. That's how computer speakers are made as they will affect the CRT monitor. Equal strength magnets are difficult to match but possible if you can find a good speaker shop. Unfortunately you can buy another pair and pry the magnets out for about the same price. I bought a pair of computer speakers and spray the paper cone with 303 fabric guard. It still working as I have a dodger and bimini to keep them out of the element.
Yes they will affect compass as far as 6 feet away. I still have a pair of brand new ones sitting in the garage. You need to get the magnetically shielded speakers. Unfortunately, most marine speakers as not made that way but there are exceptions. You got to look carefully. Bring a handheld compass with you when shopping. Alternately, you can bring them to a speaker shop and have a magnet of the same strength epoxy glued to the back. That's how computer speakers are made as they will affect the CRT monitor. Equal strength magnets are difficult to match but possible if you can find a good speaker shop. Unfortunately you can buy another pair and pry the magnets out for about the same price. I bought a pair of computer speakers and spray the paper cone with 303 fabric guard. It still working as I have a dodger and bimini to keep them out of the element.
Try Polks
I just upgraded my speakers last year to Polks. They're water proof so not problems with getting them wet from seawater or boat washing. I set them into the same location the original speakers were and the compass seems fine. Although they're within apx apx 4' of the compass it didn't swing when I moved them back and forth prior to installing. I had taken note of the reading prior to and after install and did not notice a difference. BTW the difference in sound is just awesome. I also replaced the cabin speakers with Polks and set a nice balance between the cockpit and salon and am very happy with the sound quality.
I just upgraded my speakers last year to Polks. They're water proof so not problems with getting them wet from seawater or boat washing. I set them into the same location the original speakers were and the compass seems fine. Although they're within apx apx 4' of the compass it didn't swing when I moved them back and forth prior to installing. I had taken note of the reading prior to and after install and did not notice a difference. BTW the difference in sound is just awesome. I also replaced the cabin speakers with Polks and set a nice balance between the cockpit and salon and am very happy with the sound quality.
I guess I should have been more clear ...
I'm only concerned about how the instruments may be affected. If you saw where we sail, you would laugh if you thought that the compass served any purpose.
Should I assume that the magnet has no impact on the depth, speed, or wind indicator?
I'm only concerned about how the instruments may be affected. If you saw where we sail, you would laugh if you thought that the compass served any purpose.
Should I assume that the magnet has no impact on the depth, speed, or wind indicator?
You're safe
Scott, that's funny. I didn't bother to look at your header and didn't realize you wouldn't need a compass. Don't worry about the speakers impacting the performance of anything other than the compass or your mood. Pop some big ole speakers in there and crank em up. Mike
Scott, that's funny. I didn't bother to look at your header and didn't realize you wouldn't need a compass. Don't worry about the speakers impacting the performance of anything other than the compass or your mood. Pop some big ole speakers in there and crank em up. Mike
Experiment w/ location
We experienced the same opportunity to replace two bulkhead mounted compasses and use the existing holes for speakers. The instrument manufacturer, Signet, said the analog wind direction instrument would be most suseptible to speaker magnetic interferance. We turned the instruments on and moved the speakers around to measure the range of the interferance. The speaker needed to be approx 18" away from the analolg wind instrument not to interfere. We were also advised to use SHIELDED wire for the speakers to further reduce speaker interferance. FWIW given a redo, since the stereo/speakers are on less than 5% of the time we sail, I wouldn't install cockpit speakers again.
We experienced the same opportunity to replace two bulkhead mounted compasses and use the existing holes for speakers. The instrument manufacturer, Signet, said the analog wind direction instrument would be most suseptible to speaker magnetic interferance. We turned the instruments on and moved the speakers around to measure the range of the interferance. The speaker needed to be approx 18" away from the analolg wind instrument not to interfere. We were also advised to use SHIELDED wire for the speakers to further reduce speaker interferance. FWIW given a redo, since the stereo/speakers are on less than 5% of the time we sail, I wouldn't install cockpit speakers again.
There's no way to shield a magnet
So it won't affect a compass. The Earth's magnetic field is very weak compared to a speaker's magnet, at close range. If you put the speaker in a ferrous metal box or add canceling magnets that will solve the crt interference problem. (who still uses crts?) But it will just create an even bigger distortion in the Earth's magnetic field at the compass because all that ferrous metal attracts magnetic field lines. Someone should make electrostatic speakers for boats.
So it won't affect a compass. The Earth's magnetic field is very weak compared to a speaker's magnet, at close range. If you put the speaker in a ferrous metal box or add canceling magnets that will solve the crt interference problem. (who still uses crts?) But it will just create an even bigger distortion in the Earth's magnetic field at the compass because all that ferrous metal attracts magnetic field lines. Someone should make electrostatic speakers for boats.
Bay sailor , Please don't tell thepilots that transported
magnetrons in aircraft during the 1960's. They came to us in wooden crates lined with soft steel sheets, And were checked with hand held magnetic compasses before they were approved for loading. There is no speaker that has a magnet as powerful as a magnetron magnet. They didn't ship those radar electron tubes all over the world by boats.
magnetrons in aircraft during the 1960's. They came to us in wooden crates lined with soft steel sheets, And were checked with hand held magnetic compasses before they were approved for loading. There is no speaker that has a magnet as powerful as a magnetron magnet. They didn't ship those radar electron tubes all over the world by boats.
Magnets are a lot stronger now
Today's NIB magnets are about 1,000 times stronger than the best Alnico magnets of 40 years ago. And I'm sure they didn't put those magnetrons and their shielding anywhere near the compass the pilot used while flying. The shielding contains the magnetron's magnetic field but it also distorts the Earth's field, resulting in compass errors. Try using a compass next to a car. You will have to be 20 feet away to get an accurate bearing. Inside the car it's a different story because the iron concentrates the Earth's magnetic field.
Today's NIB magnets are about 1,000 times stronger than the best Alnico magnets of 40 years ago. And I'm sure they didn't put those magnetrons and their shielding anywhere near the compass the pilot used while flying. The shielding contains the magnetron's magnetic field but it also distorts the Earth's field, resulting in compass errors. Try using a compass next to a car. You will have to be 20 feet away to get an accurate bearing. Inside the car it's a different story because the iron concentrates the Earth's magnetic field.
Compass and Speaker Hole concern for others
Compass concern: In my test with a Weems & Plath "Venus" and the hand-held remote for my loud hailer, the small handheld speaker/mic affected the compass card as far away as five feet and this is without having it electrically connected. The remote mic is an earlier version and not in the line anymore. For what it's worth, the remote mic magnet is physically much smaller than most any stereo speaker magnet. Since I couldn't get it far enough away from the compass to not affect it, it never got installed and is still sitting in the garage. W&P Venus (Amazon link): http://www.amazon.com/C-Plath-Venus-Compass-1-Degree/dp/B000KE1JOM Speaker Hole concern: For me, it is important to maintain as much watertight integrity of the boat as possible to prevent accidental swamping and sinking. Based on an experience several years ago with a 16ft daysailer which I swamped (on a lake) during a strong gust and a wind shift (it stayed floating due to flotation) I've had this concern. Also, I used to crew on a C&C 36 and one day when I wasn't crewing they got the spreaders in the water - similar situation with a gust and a wind shift but with a bigger boat. They were also flying a chute which made it difficult to dump the wind in a few seconds. Anyhow, the typical speaker installed in big holes in the cockpit would provide an easy passage for water to just blow through the cone and who knows what would happen next. Water weighs 62.4#/cu.ft. which is the same as saying the pressure on a speaker cone would be 62.4#/sq.ft. for every foot of depth of water (f.e., 2 feet = 124#/sq.ft, 3 feet = 186#/sq.ft., etc.). If one thinks about safety and whether their boat is a blue-water boat (used that term because of it's popular use), then they should think twice about the structural integrity of their cockpit and cutting big holes. This is something to think about.
Compass concern: In my test with a Weems & Plath "Venus" and the hand-held remote for my loud hailer, the small handheld speaker/mic affected the compass card as far away as five feet and this is without having it electrically connected. The remote mic is an earlier version and not in the line anymore. For what it's worth, the remote mic magnet is physically much smaller than most any stereo speaker magnet. Since I couldn't get it far enough away from the compass to not affect it, it never got installed and is still sitting in the garage. W&P Venus (Amazon link): http://www.amazon.com/C-Plath-Venus-Compass-1-Degree/dp/B000KE1JOM Speaker Hole concern: For me, it is important to maintain as much watertight integrity of the boat as possible to prevent accidental swamping and sinking. Based on an experience several years ago with a 16ft daysailer which I swamped (on a lake) during a strong gust and a wind shift (it stayed floating due to flotation) I've had this concern. Also, I used to crew on a C&C 36 and one day when I wasn't crewing they got the spreaders in the water - similar situation with a gust and a wind shift but with a bigger boat. They were also flying a chute which made it difficult to dump the wind in a few seconds. Anyhow, the typical speaker installed in big holes in the cockpit would provide an easy passage for water to just blow through the cone and who knows what would happen next. Water weighs 62.4#/cu.ft. which is the same as saying the pressure on a speaker cone would be 62.4#/sq.ft. for every foot of depth of water (f.e., 2 feet = 124#/sq.ft, 3 feet = 186#/sq.ft., etc.). If one thinks about safety and whether their boat is a blue-water boat (used that term because of it's popular use), then they should think twice about the structural integrity of their cockpit and cutting big holes. This is something to think about.
Do a test
Scott, I'd just do a quick test. Have someone hold the speakers where you'd like them and turn your instruments on. Move the speakers around to see of any of the instruments change. My guess is as long as the speakers are nowhere near the sending units you'll be fine. So if the speed paddle is located in the bottom of the hull and the wind sensor at the top of the mast you should be fine. Mike
Scott, I'd just do a quick test. Have someone hold the speakers where you'd like them and turn your instruments on. Move the speakers around to see of any of the instruments change. My guess is as long as the speakers are nowhere near the sending units you'll be fine. So if the speed paddle is located in the bottom of the hull and the wind sensor at the top of the mast you should be fine. Mike
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