I understand how single layer/wound voice coils work, where the positive lead is at one end of the coil and the negative is at the other, but how do double wound coils work where both leads terminate at the top? See photos below for what I mean by double and single wound. On the double wound, wouldn't the electrical charge take the shortest route and not even charge the layers below the two leads since it would just go straight to the negative lead? What am I missing/not understanding?
Single wound:
Double wound:
Single wound:
An externally hosted image should be here but it was not working when we last tested it.
Double wound:
Two identical windings, as far as I know, which can simply be wired together (depending on their impedance, series or parallel, not sure) but giving you some special options.
An opportunity to create an excellent sub-woofer with mixed bass (by simply putting L and R into the respective windings). You would make the sub-woofer of your dreams, needing just one, provided your cross-over was not too far north of 120 Hz and steep (trust me on that... 50 yrs experience).
Or motional feedback.
Ben
An opportunity to create an excellent sub-woofer with mixed bass (by simply putting L and R into the respective windings). You would make the sub-woofer of your dreams, needing just one, provided your cross-over was not too far north of 120 Hz and steep (trust me on that... 50 yrs experience).
Or motional feedback.
Ben
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Think about triple wound. Or the windings in a transformer. Now look up the right hand rule. It is the turn direction that produces the magnetic field. So winding down and back does give more turns to produce a magnetic field. Of course if you wound one set clockwise and the other counter then you would cancel (mostly.)
Hi simon7k
Usually one has a double layer coil even with just one winding, this allows both ends to be at the cone side of the coil.
A double coil would normally be either two parallel wires or an inner and outer winding, the later producing a slightly higher Rdc as it is slightly longer.
If you work through the relationships for a figure of merit, it turns out it’s the flux density and the volume of space to put the conductor that matter here, it doesn’t matter if you divide that volume up into lots of turns of fine wire or a few turns of heavy wire, it’s the volume of conductor in the gap.
The choice of what gage wire is based on what Rdc you need.
If you leave one coil un-driven, it will be a velocity transducer for the cone with the Voltage being proportional to velocity…… Wait a moment for thoughts of a closed loop woofer using that start to surface... The sort of a problem is there is also some signal picked up through transformer coupling from the driven coil which contaminates the Velocity / Voltage with drive signal.
Anyway, hope this helps some,
Best,
Tom Danley
Usually one has a double layer coil even with just one winding, this allows both ends to be at the cone side of the coil.
A double coil would normally be either two parallel wires or an inner and outer winding, the later producing a slightly higher Rdc as it is slightly longer.
If you work through the relationships for a figure of merit, it turns out it’s the flux density and the volume of space to put the conductor that matter here, it doesn’t matter if you divide that volume up into lots of turns of fine wire or a few turns of heavy wire, it’s the volume of conductor in the gap.
The choice of what gage wire is based on what Rdc you need.
If you leave one coil un-driven, it will be a velocity transducer for the cone with the Voltage being proportional to velocity…… Wait a moment for thoughts of a closed loop woofer using that start to surface... The sort of a problem is there is also some signal picked up through transformer coupling from the driven coil which contaminates the Velocity / Voltage with drive signal.
Anyway, hope this helps some,
Best,
Tom Danley
So it doesn't matter where the two connections end, only that they maintain the same winding direction? I didn't know the right hand rule applied to E&M as well. I'd only ever used it for torque. Pretty cool! Thanks for explaining!
So now that I know this is the case, why does it work that way? I still don't understand how ending both wires up top results in a stronger magnet. The way I see it right now (which I assume is wrong, so please help me understand) is that the electricity would take the shortest path and go straight from the positive to negative leads, thus never traveling through the rest of the winds. Does there need to be a layer of insulation between each layer of winds?
So now that I know this is the case, why does it work that way? I still don't understand how ending both wires up top results in a stronger magnet. The way I see it right now (which I assume is wrong, so please help me understand) is that the electricity would take the shortest path and go straight from the positive to negative leads, thus never traveling through the rest of the winds. Does there need to be a layer of insulation between each layer of winds?
Frosteh,
The wire used for a voice-coil is always insulated, there is no short circuit going on there, just a continuous winding of an insulated magnetic wire. There is more than one way to make a multilayer voice-coil and many reasons to do that. As said above it is the number of windings and the length of the magnetic gap that is important. This is called the B/L ratio and it has to do with the length of wire in the gap. Some dual wound voice-coils are done one on top of the other and others are with a winding on the inside and outside of the former for heat dissipation reasons. The voice-coil former is typically an insulator unless it is aluminum, a terrible former material, and this allows the inner and outer coils to transfer more heat to the magnetic motor steel. Typically a double wound voice-coils is done because it is an 8ohm coil and it takes a longer wire to achieve that impedance. Most 4ohm coils would end up being a single layer unless it is an extremely short length coil. You have to also look at whether you are talking about round wire or flat wound wire which is typically not double wound as it is hard to change direction with a flat wire and it is much wider and would entail a very wide gap which would loose the advantage of the flat wire. One reason that a 4ohm voice-coil is often used over an 8ohm voice-coil is because it will typically have 1/2 the weight of the 8ohm coil and this decreased mass increases the efficiency of the loudspeaker. I could go on but this is the basic idea.
Steven
The wire used for a voice-coil is always insulated, there is no short circuit going on there, just a continuous winding of an insulated magnetic wire. There is more than one way to make a multilayer voice-coil and many reasons to do that. As said above it is the number of windings and the length of the magnetic gap that is important. This is called the B/L ratio and it has to do with the length of wire in the gap. Some dual wound voice-coils are done one on top of the other and others are with a winding on the inside and outside of the former for heat dissipation reasons. The voice-coil former is typically an insulator unless it is aluminum, a terrible former material, and this allows the inner and outer coils to transfer more heat to the magnetic motor steel. Typically a double wound voice-coils is done because it is an 8ohm coil and it takes a longer wire to achieve that impedance. Most 4ohm coils would end up being a single layer unless it is an extremely short length coil. You have to also look at whether you are talking about round wire or flat wound wire which is typically not double wound as it is hard to change direction with a flat wire and it is much wider and would entail a very wide gap which would loose the advantage of the flat wire. One reason that a 4ohm voice-coil is often used over an 8ohm voice-coil is because it will typically have 1/2 the weight of the 8ohm coil and this decreased mass increases the efficiency of the loudspeaker. I could go on but this is the basic idea.
Steven
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Hi,
Dual voice coils and dual layer are not the same thing, though
a dual wound voice coil has to be at least a dual layer coil.
Single drivers are 1,2,3 or 4 layer, dual drivers 2 or 4 layer.
A nice example is the edgewound formerless single layer
ribbon voicecoil used in genuine Audax 10mm tweeters,
the cheapo knock offs use a former and multilayer coil.
Madisound Speaker Store
rgds, sreten.
Dual voice coils and dual layer are not the same thing, though
a dual wound voice coil has to be at least a dual layer coil.
Single drivers are 1,2,3 or 4 layer, dual drivers 2 or 4 layer.
A nice example is the edgewound formerless single layer
ribbon voicecoil used in genuine Audax 10mm tweeters,
the cheapo knock offs use a former and multilayer coil.
Madisound Speaker Store
rgds, sreten.
sreten,
I guess I wasn't paying that much attention to the dual voice coil as he seemed to miss the point that either way the wire would be insulated. Yes you can go to four layer voiceccoils but the efficiency is going to be a tradeoff with the increase in gap width to make room for the stacked voicecoils.
I guess I wasn't paying that much attention to the dual voice coil as he seemed to miss the point that either way the wire would be insulated. Yes you can go to four layer voiceccoils but the efficiency is going to be a tradeoff with the increase in gap width to make room for the stacked voicecoils.
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