Here a description how to add DIY a Faraday / copper ring to a loudspeaker in order to reduce distortion and minimize inductivity of the voice coil.
First some information on how to remove a dust cap of a loudspeaker driver (detailed description follow the link) :
https://www.diyaudio.com/community/threads/how-to-remove-a-dustcap.397165/
First some information on how to remove a dust cap of a loudspeaker driver (detailed description follow the link) :
https://www.diyaudio.com/community/threads/how-to-remove-a-dustcap.397165/
After you have access to the pole piece you can add a copper ring or a 20 euro cent or 50 euro cent piece to the pole plate.
Copper ring added of appropriate size:
https://www.diyaudio.com/community/...-firing-speakers.121385/page-175#post-6707993
Read carefully how to use the glue for fixing ring or coin. Do not put too much glue as no glue is allowed to drop into the voice coil gap.
The small Euro coins of 10, 20, 50 cent contain copper so they can be used for this purpose
12cm driver with added 50 cent coin to the pole plate, I call it "50 cent trick":
https://www.diyaudio.com/community/...fication-to-current-drive.389985/post-7197710
https://www.diyaudio.com/community/threads/visaton-bg20-impressive-mod.408081/post-7576162
For who wonders about the alu foil on the paper cones -
My fullrange drivers get an aluminium sandwich cone DIY:
https://www.diyaudio.com/community/threads/how-to-make-a-loudspeaker-sandwich-cone.402917/
Copper ring added of appropriate size:
https://www.diyaudio.com/community/...-firing-speakers.121385/page-175#post-6707993
Read carefully how to use the glue for fixing ring or coin. Do not put too much glue as no glue is allowed to drop into the voice coil gap.
The small Euro coins of 10, 20, 50 cent contain copper so they can be used for this purpose
12cm driver with added 50 cent coin to the pole plate, I call it "50 cent trick":
https://www.diyaudio.com/community/...fication-to-current-drive.389985/post-7197710
https://www.diyaudio.com/community/threads/visaton-bg20-impressive-mod.408081/post-7576162
For who wonders about the alu foil on the paper cones -
My fullrange drivers get an aluminium sandwich cone DIY:
https://www.diyaudio.com/community/threads/how-to-make-a-loudspeaker-sandwich-cone.402917/
If you do this modification you can compare the effect by removing the dust cap of two identical drivers and listen to Mono music and use the balance knob of your pre amp to switch between the two drivers fastly. You just drop a copper ring without fixing it into one of both drivers on the pole plate.
25cm driver with "50 cent trick" :
https://www.diyaudio.com/community/...loudspeaker-sandwich-cone.402917/post-7495721
25cm driver with "50 cent trick" :
https://www.diyaudio.com/community/...loudspeaker-sandwich-cone.402917/post-7495721
If you want to transform your driver to a fullrange driver you can DIY add a full metal aluminum whizzer / double cone:
https://www.diyaudio.com/community/threads/how-to-make-a-whizzer-cone.398063/
You can also put back the original dust cap glued back into position if you only do a clean and wide cut out like in image 1 of this thread.
But here I prefered to add a double cone.
https://www.diyaudio.com/community/threads/how-to-make-a-whizzer-cone.398063/
You can also put back the original dust cap glued back into position if you only do a clean and wide cut out like in image 1 of this thread.
But here I prefered to add a double cone.
If you want to dive deep into this topic just read this
The Effect of Faraday Ring (Shorting Ring)
Usage on Voice Coil Impedance and Its
Benefits
http://www.diy-audio.narod.ru/litr/FaradayRingsVoiceCoilImpedance.pdf
The Effect of Faraday Ring (Shorting Ring)
Usage on Voice Coil Impedance and Its
Benefits
http://www.diy-audio.narod.ru/litr/FaradayRingsVoiceCoilImpedance.pdf
Great idea! Unfortunately, I don’t think any US or Canadian coins will work, they are mostly non-magnetic nickel. Unless non-magnetic nickel works as a faraday ring? I guess I could use copper pipe, end caps, or washers. Also, it’s easy to machine aluminum to the right size.
@Boden
I did once measurements and have them on some harddisk archived.
But now I have no working equipment for doing this.
If someone wants to try this mod feel free to post it here with measurements. Like impedance, THD and IMD for a given loudness with and without copper ring.
Maybe valuable to mention:
You can add several copper rings or coins for covering / shorting the full travel of the voice coil in one direction.
I found no possibility of adding a "full sleeve" shorting ring which would cover the voice coil travel into the other direction towards the magnet.
Maybe someone will have an idea for a mod without completely disassembling a driver what is not practical or economical.
I did once measurements and have them on some harddisk archived.
But now I have no working equipment for doing this.
If someone wants to try this mod feel free to post it here with measurements. Like impedance, THD and IMD for a given loudness with and without copper ring.
Maybe valuable to mention:
You can add several copper rings or coins for covering / shorting the full travel of the voice coil in one direction.
I found no possibility of adding a "full sleeve" shorting ring which would cover the voice coil travel into the other direction towards the magnet.
Maybe someone will have an idea for a mod without completely disassembling a driver what is not practical or economical.
example of a driver with removed dustcap and added farady ring.
There are three rings stacked so that all voice coil travel in one direction is covered up.
same driver now with copper
my collection of copper rings
There are three rings stacked so that all voice coil travel in one direction is covered up.
same driver now with copper
my collection of copper rings
It may brings some change. But not sure if it's improvement.
The design of Faraday ring isn't trivial. It's best to do with simulation and measurement to make sure its effect.
As mentioned by Lars Risbo somewhere, the improper implementation of Faraday ring may leads to position dependent shorting effect.
Which will not leads to better Le(x) linearity.
The design of Faraday ring isn't trivial. It's best to do with simulation and measurement to make sure its effect.
As mentioned by Lars Risbo somewhere, the improper implementation of Faraday ring may leads to position dependent shorting effect.
Which will not leads to better Le(x) linearity.
@yys310
you can dive deep into this thematic with post 5
https://www.diyaudio.com/community/...day-ring-to-a-loudspeaker.409852/post-7615912
from theory everything that brings coil inductivity down helps to minimize its movement dependend variation.
Its better to measure, thats true.
But
Once you heard the effect with a simple A / B test with one modified driver vs unmodified with a mono recording and balance knob of your pre amp, changing from left to right you learn to hear without measurement equipment.
You can even test that with an upright speaker not fixing the copper ring with glue. If you don't like it - remove it.
you can dive deep into this thematic with post 5
https://www.diyaudio.com/community/...day-ring-to-a-loudspeaker.409852/post-7615912
from theory everything that brings coil inductivity down helps to minimize its movement dependend variation.
Its better to measure, thats true.
But
Once you heard the effect with a simple A / B test with one modified driver vs unmodified with a mono recording and balance knob of your pre amp, changing from left to right you learn to hear without measurement equipment.
You can even test that with an upright speaker not fixing the copper ring with glue. If you don't like it - remove it.
Very good experimentation. Do you think perhaps a fully copper-plated T-yoke would be just as beneficial, or less than the simple add-on copper ring?
in the long and sophisticated paper on faraday rings I posted the author says that a full sleeve ring covering the complete travel to both sides is the optimum as I remember.
So my solution is what you can easily do diy on an existing driver:
faraday ring and if possible with some height covering the full travel in one direction lowers inductance and distortion.
Certainly most audible and effective is just one copper ring of 2 to 3 mm in height. Doubling was still measureable with small signals.
With signals using full cone travel and good measureing equipment you can see some more.
Easily was measureable the drop in impedance in the highs:
you could get down from 30 ohms at 20khz to 20 ohms and lowering in distortion was obviously already detected by listening to it.
And it was interesting to hear and learn about the difference in sound.
Less distortion always sounds "quieter" and less annoying.
For guys searching loudness, distortion reduction must not be desirable!
So my solution is what you can easily do diy on an existing driver:
faraday ring and if possible with some height covering the full travel in one direction lowers inductance and distortion.
Certainly most audible and effective is just one copper ring of 2 to 3 mm in height. Doubling was still measureable with small signals.
With signals using full cone travel and good measureing equipment you can see some more.
Easily was measureable the drop in impedance in the highs:
you could get down from 30 ohms at 20khz to 20 ohms and lowering in distortion was obviously already detected by listening to it.
And it was interesting to hear and learn about the difference in sound.
Less distortion always sounds "quieter" and less annoying.
For guys searching loudness, distortion reduction must not be desirable!
So If I machine down the pole-piece to fit a solid copper sleeve, I should make sure the Cu sleeve extends far enough down/back to cover the full length and stroke of the voice coil.
For the forward stroke, I already have solid alum 6061 phase plugs attached to the pole-piece/s, they should suffice, no?
For the forward stroke, I already have solid alum 6061 phase plugs attached to the pole-piece/s, they should suffice, no?
I do not know how to modify the pole piece itself with machine tools on an existing driver without damaging it.
Did you hear any difference in A/B test with and without alu phase plug?
Don't know if aluminium is the appropriate material for it. I would use copper.
With the driver facing up you can do impedance measurements (and other measurements) and listening test by removing and adding the copper ring / metal phase plug without glueing it in.
Did you hear any difference in A/B test with and without alu phase plug?
Don't know if aluminium is the appropriate material for it. I would use copper.
With the driver facing up you can do impedance measurements (and other measurements) and listening test by removing and adding the copper ring / metal phase plug without glueing it in.