will a magnetic USB plug mess with a bluetooth speaker? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2018, 01:50:40 pm
content: I bought a magnetic USB plug and its pretty nice for some gadgets and a cell phone, but I am wondering if its possible it can interfere with bluetooth speakers.I tried it on one speaker (a fairly beefy one) and I don't notice any difference. But I do have some smaller ones and I was wondering if it could effect them, I don't have them here for testing though (it will be a while) and I can get a good deal on the cables where I am right now and its not going to be a hassle with quality.Also, is there any particular music or tones that would make any kind of effect of a magnet near the speaker be more noticeable for testing? I assume you would need alot of field to mess with the coil but with all the crazy audio stuff people do I began to wonder.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 17, 2018, 02:01:32 pm
content: It is virtually inconceivable to think of any phenomenon or mechanism where a magnetic connector could interfere with radio waves (Bluetooth, etc.) At least in modern consumer gear.And while speakers work with a magnetic field, while the magnetic field of those connectors is rather strong, it i also quite small and the magnetic field drops off rapidly (a few mm) So natural separation between the magnetic connector and the magnetic transducer (speaker) is more than adequate to eliminate any practical interference.

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2018, 02:04:10 pm
content: yea I know it won't mess with the antenna its just that blue tooth is pretty compact for a speaker.I think it could technically mess with filter inductor networks and tuned coils a bit but I doubt it since the blue tooth is a digital signal anyway and it gets decoded.how big a magnet would you need to make an audible quality decrease? from the electromechanic part of the speaker.I am gonna test it but I was thinking about that too, if I put a big magnet on the base of one of the wireless speakers so I can stick it to a car hood or something. I am not putting weak attached anything on a car anymore since I managed to make a function generator fall/roll/bounce down like 150 feet of steep road hill (quite a few stories) one morning because I forgot about it.

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 17, 2018, 02:51:05 pm
content: If the shielding is not in place there might be an influence. But not from the magnet but from the un-shielded gap of these connectors. A normal USB plug maintain a closed shielding. While this magnetic things might not maintain the shielding at the connecting place this is could be different. But as the gap is rather small the risk of influence the Bluetooth connection is low. USB can in fact influence Bluetooth links as the USB 3.0 signal rate on the cable is rather close to Bluetooth and WLAN. Especially if the cable shielding is weak.About your question if there's some special tone or music: Remember Bluetooth is digital. So there's a coding on the Bluetooth link, even the audio will be compressed. So either it works or not. Thenotmight be intermittent dropouts or reduced range. You'll notice that easily. It's not like old analog links you can hear some hiss or other noises in the background. Still if you want to use Bluetooth on stage: Use something more reliable.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 17, 2018, 02:55:09 pm
content: The only practical problems with magnetic speakers was not on the speakers, but on the speaker's effect on OTHER things. For example you can still see monitor speakers advertised as "magnetically shielded". But that was back a decade ago when we were using CRT monitors and the speaker magnetic field could distort the screen image because it deflects the electron beam. But the only way it could affect the electron beam from a distance of several inches is because the electron beam had virtually zero mass and was easily deflected.It is virtually impossible for you to play with any magnets that have a strong enough field to actually affect a conventional speaker. The magnetic field strength drops off so rapidly it is of no practical consequence.We have seen some signal inductors that used permanent magnets for particular applications, but the magnet had to be physically touching the inductor core. The magnetic field from a few mm or inches away will have no practical effect.When you start playing with magnetic fields like they use in the Large Hadron Collider, get back to us. Otherwise don''t worry about it.

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2018, 03:04:28 pm
content: Quote from: Twoflower on December 17, 2018, 02:51:05 pmnah I meant if you got a really powerful magnet that can actually effect the movement of the speaker enough to be perceptible would that be more noticeable with particular tones or music?and yea the shield connection sucks on it, you don't get a over lap anymore its just bearly touching as far as I can tell

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 17, 2018, 04:13:03 pm
content: Quote from: coppercone2 on December 17, 2018, 03:04:28 pmNO.QuotePlease tell us what are the symptoms of your "barely touching" shielding?I suspect you are imagining things that aren't there.

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2018, 04:16:12 pm
content: i don't have a problem with it I told you in the opening post I can't see a difference. I am just saying its technically worse since there is no insertion but just a face seal.I am also curious about what the distortion would sound like if you had a powerful enough magnet to mess with it (even if its a super conducing DC magnet).

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 17, 2018, 05:27:05 pm
content: IF you could get a strong enough DC magnetic field close enough to a speaker. If it was in the SAME polarity (to ADD to the speaker's magnetic field) then it might make the speaker slightly louder (probably not audible).And if it were the OPPOSITE polarity (to REDUCE the speaker's magnetic field), it might make the speaker slightly quieter (probably not audible).But an external magnetic field THAT STRONG would not be good for YOU. Note how careful they are about having magnetic objects in the same room as an MRI machine. And that is just extremely SHORT bursts of magnetic field.

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 17, 2018, 05:58:00 pm
content: Adding/substracting fields to an existing field isn't that easy. Most likely the field will be uneven and cause the voice coil to move not in the expected direction. It can cause that the voice coil collides with the yoke of the speaker magnet.According to the Wikipedia: The strong field in a MRT is a static field. And it is active all time as the energy is stored in supra conducting magnets. Weaker MRTs use even permanent magnets. An additional RF field is applied but that's not that strong. This one is pulsed and needed to generate the de-orientation of the atoms. The returning of the orientation of the atoms is measured.Trivia: Because of eddy-currents in the nerve cells magnetic fields cause human bodies needs to be transported slowly into MRTs with more than 3T magnetic flux. Otherwise it can cause unpleasant feelings.

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2018, 09:03:52 pm
content: I want to see a gutted speaker inserted close to a strong magnet to see how it behaves.