Speakers with exposed voice coil... do they have a name ?

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The voice coil of a speaker is positioned inside its very narrow magnetic gap so it cannot be seen. If the voice coil is exposed then the speaker will not work.
To see an exposed voice coil you can buy a speaker re-cone kit that has it exposed because it is without the magnet parts.

Maybe you are talking about the "spider" in a speaker that positions its voice coil in the magnetic gap while allowing it to move up and down the magnet.
 

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Sorry I have never seen a speaker with an exposed voice coil. Thay all have paper caps or cones over them.
Do you mean something like this;


Can we as what its for?
 
Thanks.
Modern speakers with toroidal magnets are like you describe. Older ones from the sixties as in the picture, are built different, as the ones on the link.
The one on the picture has a foil glued to the side openings to prevent dust reaching the coil, which is completely exposed by removing the foil. Perhaps they are named 'old alnico' type. Will find one, take a picture and post when I can.

Edited, added:
The coil is exposed by the magnet area, not on top by the cone/spider.
Resourcing to a patent drawing as the picture may take too long:

(Magnifiable)----> https://patentimages.storage.googleapis.com/pages/US3134057-0.png
Being 1 the cylindrical Alnico magnet
2 and 3 polepieces,
4 the gap, 7 the coil, 9 the 'spider'

The coil/bobbin is exposed, visible, you can see it moving while operating..
 
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You cannot see the voice coil of a speaker:
1) The cone blocks a view from the top.
2) The magnet structure blocks a view from the sides or bottom.

I have Alnico and Ferrite magnet speakers and neither type has a foil dust cover.
 

Ok I see now. I remember seeing some old radio speakers with foil dust covers on either side of the magnet assembly.
Alnico is really the magnet type but seems to be linked with this kind of speakers.
They are vintage and not been made for years but I did find some;
http://www.ultraelectronicactive.com/elx/Vintage-Speakers-RAW.html
I have never seen any newer speakers made like this.
Maybe someone somewhere makes new replacments.
They all seem to be really low power.
If you don't mind me asking why you want this old style speaker.
 
Let's wait until the OP responds to what/why?

Some of the pics of speakers he had could be 30 or 40 ohms. High impedances were popular in car tube radios.
 
I have never seen a speaker with an electromagnet instead of a real magnet but I remember seeing those hot glass things that glowed.
 
Thanks.
4pyros:
Yes, you got it ! You remember seeing those. They are not electrodynamic, am not after those; they have a permanent magnet made of Aluminium - Nickel - Cobalt alloy. Am after a 3-4 inch one, perhaps used in fifties tabletop tube radios. My '61, '62 Cadillacs have them. Am after one as will have to work submerged in a fluid and will not do the 'piston hydrolock' behavior.
Cannot drill 'pressure relief' ports on a modern one as metal shavings would be stuck all over the guts into the bobbin.

Your link shows a slightly newer type of 'Alnicos' without the foil, a dust ring added as dust shield , as in halfway of arrow '12' in
Magnifiable ----> http://patentimages.storage.googleapis.com/pages/US2925541-0.png
 
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Externet said:
Cone stays. Unharmed by inert silicone oil.
Click to expand...
Ok. But why does the coil need to be exposed? Can't you just perforate the foil/dust-seal, so that hydrostatic pressure is equalised on the two sides of the cone/diaphragm?
 
There is several ways being evaluated.
Just bought this ----> **broken link removed**

Will see how they behave...
 
Alnico's loose their magnetism over time so your new one ought to sound better, or at least louder.
 
The cheap foreign transducers have no impedance. Instead they have independance. Beware.
 
I have about 30 old speakers from the 60s from old TVs, old stereos, old real to real tape recorder, old record players. Not sure I have any that small but I will go look.

OK, smallest thing I have is a 6"x9" speaker.
 
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My first pc was made by Compaq in 1994 and had a 486DX2/32 processor (32MHz). I soon replaced the plugged-in processor with a 486DX4/100 (100MHz) that had bits of the soon to be released Pentium processor. The dial-up modem was very slow.
Anyway, the pc was inside the case of its small CRT monitor with a CD/DVD player and two little 2" x 1" speakers. The speakers were in ported bass-reflex enclosures and sounded pretty good. My son blew up a speaker with feedback and it was replaced by warranty. The tiny speakers in cells phones, tablets and laptops sound awful.
 
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