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Should I worry about EMI from a speaker?

Tall_Order

Tall_Order

Well Known Member
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I have a lightweight low-profile marine 6.5" speaker (for master caution, alerts, plus it sounds good when project is on ground power ;)) and am tin-bashing my custom side panels. Potentially this speaker can end up within a few inches of a couple electronic modules. I can't see anything regarding conventional safe distances online, but if anyone has experiences with this issue, I'd love to hear about them.
 
Tall_Order said:
I have a lightweight low-profile marine 6.5" speaker (for master caution, alerts, plus it sounds good when project is on ground power ;)) and am tin-bashing my custom side panels. Potentially this speaker can end up within a few inches of a couple electronic modules. I can't see anything regarding conventional distances online regarding typical safe distances but if anyone has experiences with this issue, I'd love to hear about them.
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I would be more worried about it making your old-school mechanical wind up wristwatch speed up. They don’t like magnetic fields!

6.5” sounds like that could be a very effective speaker :)
 
You're unlikely to end up with much electro-magnetic interference generated by the speaker from its operation but you're almost certainly going to have magnetic interference from the magnets in the speaker. If you have any kind of remote-mounted magnetometer in the same region it will upset the performance and give you erronous readings. I had to troubleshoot a very similar situation a couple of years ago when a speaker had been installed too close to a remote compass and it caused the heading display to favour North-South readings regardless of which direction the system was actually pointing.

Other sensors might be similarly affected. For example a fuel flow meter might not want to rotate freely or a magnetic reed switch might not activate at its normal threshold if a magnet is close by. I would be very cautious and maybe take note of systems performance with and without the speaker installed.

What are the other "electronic modules" you have mounted nearby? (I would consider "nearby" to mean anything within 18 - 24". For a magnetometer "nearby" could be within about 6 feet.)
 
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planenutz said:
You're unlikely to end up with much electro-magnetic interference generated by the speaker from its operation but you're almost certainly going to have magnetic interference from the magnets in the speaker.

What are the other "electronic modules" you have mounted nearby? (I would consider "nearby" to mean anything within 18 - 24". For a magnetomer "nearby" could be within about 6 feet.)
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Considering a low-sidewall location where the speaker would be within a few inches of the potentiomer/hall effect for the throttle-by-wire and a handful of breakers and switches. Next closest item would be the GPS about a foot above the top of the speaker. This speaker is less than a pound (the lightest "big speaker" I can find). My media player is android based so hopefully I will find an app that can do active noise cancelling one day?

There is another mounting spot that is far away from everything but less than ideal cubic feet behind the speaker. I just brought this up in an attempt to learn :D

I could be wrong, but magnetometers are often in one of the wings? If I read the rules correctly, with the way I'm planning the panel, I don't think I'll need a traditional standby compass; I'd rather have that weight be the speaker... :LOL:
 
Yes, magnetometers often end up in the wing or in the aft part of the fuselage however people put them in crazy places sometimes so you can never be sure.

There are other options out there that wouldn't require the big magnets associated with a speaker and my first choice would be audio via the headsets. In respect to the location and the other items you mention above, I would think the most likely issue would be with the GPS but it depends on which model you have. Really the only way to be certain the speaker is not influencing anything is to operate the aircraft without the speaker then install it and repeat the same tests. Carefully.

I have done a lot of EMI testing on engine control systems in my day-job and most EECU/FADEC systems are very well protected against radiated EMI. Magnets are a different ballgame though.
 
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planenutz said:
There are other options out there that wouldn't require the big magnets associated with a speaker and my first choice would be audio via the headsets.
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That depends if you think bass should be felt or heard :ROFLMAO:

But on a more serious note, points taken. Possibly of note is that a lot of big planes have the auto callouts and warnings that always come through a speaker (albeit they are prob smaller than this one)

I appreciate the comments and gotta love this forum when I post an idea and more often than not, an SME will chime in (y)

FWIW this is what I came up with yesterday out of 0.025" aluminum. Still a ways to go before I can test and know if the speaker will be a problem for sure. Worst case, I can put a decorative flux capacitor in the space for ambiance instead 🤓
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Are you really going to listen to this in flight? Seems like overkill, since C&W tones and such should be going through your AP to your headset, and the only real use for it will be listening to ATIS on the ground.

I put a small speaker under my panel thinking it'd be nice to listen to ATIS on the ground, and have almost *never* used it. I just use the first minute or so after start to let the engine warm up a bit and listen to ATIS in the ANR headsets :).
 
RV7A Flyer said:
Are you really going to listen to this in flight?
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No probably not, unless there is an Android ANR app, then maybe

Otherwise thanks for the input! 👍

Yes it could be replaced with a smaller speaker or no speaker: However I do see some value in being able to quickly tell if there's a headset issue or a radio issue.

Also in my case, working on a couple DIY avionics things I don't want to run through primary audio...
RV7A Flyer said:
Seems like overkill
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I have no comment 😆
 
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