Hello, I have seen many speakers / subwoofers ( low - medium power ) that have a " extra " magnet glued on the bottom , does it help ? why didnt they use double stacked magnets instead ? not just gluing another one on the bottom.
Will gluing a magnet on a ordinary speaker improve something ? like overall magnet strenght , more sensibility since the magnet is stronger ( stronger magnetic field ) ?
Here's what I mean.
Will gluing a magnet on a ordinary speaker improve something ? like overall magnet strenght , more sensibility since the magnet is stronger ( stronger magnetic field ) ?
Here's what I mean.
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The main use is for magnetic shielding (to protect old CRT monitors and TV's), but they also improve total magnet strength.
How does it shield , it is a magnet too . shielded speakers have that metal around the magnet like a can .
Opposite magnetic field (glued magnet is smaller).
Metal can is a second step in shielding residual magnetic field.
Metal can is a second step in shielding residual magnetic field.
The ceramic magnet will undo9ubtedly be a lot cheaper than a mu-metal can although the can is probably a much better shield. In the 90's, a friend purchased mu-metal shields for about $12 each. They fit a 5 inch diameter magnet as u7sually seen on high efficiency 5 inch drivers. In our case, it was a Focal 5K013L.
When I went to Jerry's house , he had such a speaker on top of a 21 inch table top television set. The speaker was less that 3 inches from the top of the CRT and had no effect on the electron beam. When the shield was removed, the beam was deflected when the Focal was less than 15 inches away.
My thanks to Sonce as I hadn't thought of reverse polarity shielding. I wondered why a larger magnet wasn't used if a stronger field was desired. I now wonder if the reverse magnetic shielding is as effective as the mu-metal can. Then, who places a speaker magnet within a few inches of a CRT not to mention who still uses a CRT television?
Extra "out of phase" magnet does 2 "good" things:
1) it focuses more of the main magnet in the gap area, where it matters most 🙂
2) "away"from the speaker, (think 8 inches away or more), it* substracts* from "outside" field so it reduces interference.
A win-win situation.
Besides, the ring ceramic magnet by itself, at bulk purchase prices, is cheaper than improving iron magnet parts.
1) it focuses more of the main magnet in the gap area, where it matters most 🙂
2) "away"from the speaker, (think 8 inches away or more), it* substracts* from "outside" field so it reduces interference.
A win-win situation.
Besides, the ring ceramic magnet by itself, at bulk purchase prices, is cheaper than improving iron magnet parts.
I have such a driver sitting nearby and have been wondering about this topic. Yes, mu-metal is expensive (I've been hoarding my piece for decades) but some speakers can do horrible damage to a CRT... which my bulk tape demagnetizer won't cure.
Is special magnet glue used or avoided?
B.
Is special magnet glue used or avoided?
B.
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OK, checked the web. My previously held belief is wrong. Turns out there is no special magnetic glue.
BTW, don't use the otherwise wonderful JB Weld epoxy with metal filler. Makes a mess when the metal filler migrates towards the magnet.
Ben
BTW, don't use the otherwise wonderful JB Weld epoxy with metal filler. Makes a mess when the metal filler migrates towards the magnet.
Ben
Now you've aroused my curiosity. Almost enough to make me want to try that myself. 🙂
Sent from my phone with Tapatalk. Please excuse any typpos.
Dear all,
please look to the picture of standard magnetic assembly
the value of speaker driver magnetic assembly is to focus magnetic field into air gap.
If you put another magnet into bottom iron plate of assembly, I think that it will not increase magnetic field in the air gap.
please look to the picture of standard magnetic assembly
the value of speaker driver magnetic assembly is to focus magnetic field into air gap.
If you put another magnet into bottom iron plate of assembly, I think that it will not increase magnetic field in the air gap.
Not really the same placement of magnet, but i experimented, and placing neo magnet around ferrite magnet easily change qes (and so qts) of a speaker. In the thread bellow, i managed to move from 0,39 to 0,27 qts...but the original or at least factory value was 0,27. It's a 4 layer voicecoil, with 7,5mm gap, so even with only 65mm diameter voicecoil it can yeld to even more concentrated magnetic field. If it were a 2 layer voicecoil, i can imagine it would have been harder to get this low. At some point, there is some saturation effect (that is desirable in fact) from what i i understood.
http://www.diyaudio.com/forums/subwoofers/284636-xtra-neo-magnet-qts-0-39-0-34-a.html
I'm still in process of moding it to have fun. Added venting to back piece, added bellow dustcap venting, ligthened glass fiber former, changed for 2 progressive spider, butyl surround, added 4 copper ring (1 inside pole venting, 1 on pole piece, 1 inside ferrite magnet hole, 1 on front piece). I have to make a glass fiber support for new spiders.
http://www.diyaudio.com/forums/subwoofers/284636-xtra-neo-magnet-qts-0-39-0-34-a.html
I'm still in process of moding it to have fun. Added venting to back piece, added bellow dustcap venting, ligthened glass fiber former, changed for 2 progressive spider, butyl surround, added 4 copper ring (1 inside pole venting, 1 on pole piece, 1 inside ferrite magnet hole, 1 on front piece). I have to make a glass fiber support for new spiders.
yes, if you put another magnets around original magnet with the same orientation you can increase magnetic field in the air gap. But look to the cut drawing of magnetic assembly. If you would like to use all power of added magnets around, you have to extend metal parts on the top and bottom. Then it depends on the metal part, what density of magnetic field can transfer.
Yes it will, but no so much as two stacked magnets between iron plates.
Primary function of glued magnet at the bottom plate is to decrease stray magnetic field - i.e. shielding.
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