Hi Kindhornman,
I understand it is difficult to Judge on these info. But there are more topics I opened on this project. Everytime a peace of it in different forums. Why? So nobody exactly knows how it just works
. I have already a working system with ferro... (yes ferro is expensive but the only way to go). I am going to work with a phaseplug for the reason you mention (pressure) The first system is made of 4 neo's but they are also not cheap that's why i try to make it with 2. (commercializing is an option i consider IF it works like I want)
It wil not be cheap. It need a second dc circuit to drive the EM suspension. The Em suspension is ready in most aspects and lineair till 25khz (compensation of distortion and in phase). You are also correct that the cones are not 100% round (I have bought some for testing and these are not 100% round) Solution: If you see the simple picture i posted you see that there is a edge of 10mm on the outerdiameter it wil prevent the cone from flexing. I have made my own mold and with a mixture of carbon fibre and kevlar it is possible to make it 99.9% round.
The ferro is strong enough to hold the whole cone (already tested)
The most mechanical problems are solved but the electrical like distortion and small thiel parameters there is a lot of work to do.
I calculate the cost of it. around the 150bucks/st is my target to manufacture. + the price of the dc circuit (want to work with a chargable battery) so you have the choice with battery if it is loaded (no noise) or with the supply if the battery is empty (a very little noise). The difference in noise a have to test. for now i work with a battery.
regards
I understand it is difficult to Judge on these info. But there are more topics I opened on this project. Everytime a peace of it in different forums. Why? So nobody exactly knows how it just works
. I have already a working system with ferro... (yes ferro is expensive but the only way to go). I am going to work with a phaseplug for the reason you mention (pressure) The first system is made of 4 neo's but they are also not cheap that's why i try to make it with 2. (commercializing is an option i consider IF it works like I want)It wil not be cheap. It need a second dc circuit to drive the EM suspension. The Em suspension is ready in most aspects and lineair till 25khz (compensation of distortion and in phase). You are also correct that the cones are not 100% round (I have bought some for testing and these are not 100% round) Solution: If you see the simple picture i posted you see that there is a edge of 10mm on the outerdiameter it wil prevent the cone from flexing. I have made my own mold and with a mixture of carbon fibre and kevlar it is possible to make it 99.9% round.
The ferro is strong enough to hold the whole cone (already tested)
The most mechanical problems are solved but the electrical like distortion and small thiel parameters there is a lot of work to do.
I calculate the cost of it. around the 150bucks/st is my target to manufacture. + the price of the dc circuit (want to work with a chargable battery) so you have the choice with battery if it is loaded (no noise) or with the supply if the battery is empty (a very little noise). The difference in noise a have to test. for now i work with a battery.
regards
Not needed if you balance the magnetic circuit to cancel the flux modulation. An over/under circuit will not be balanced inherently like DCD, but it should be possible.
You could use ribbon wire voice coil. Choose the wire thickness to produce the DCR you want. And better efficiency too.
Best wishes
David
Jef,
When you input the information into Femm did you do the drawing in the program or did you import the drawing from another program? I have the program and want to do some analysis with it but haven't used that program before. I have my drawing in a cad program and it would be real easy if I can just import what I have already done.
Dave,
If the flat wire is contained in the gap, short coil & long gap the flat wire will have no effect on efficiency. Now if you are talking copper clad aluminum wire it will weigh less and that can be a bonus if you need the decrease in moving mass. It would be effective in a short gap with an equal or long coil.
When you input the information into Femm did you do the drawing in the program or did you import the drawing from another program? I have the program and want to do some analysis with it but haven't used that program before. I have my drawing in a cad program and it would be real easy if I can just import what I have already done.
Dave,
If the flat wire is contained in the gap, short coil & long gap the flat wire will have no effect on efficiency. Now if you are talking copper clad aluminum wire it will weigh less and that can be a bonus if you need the decrease in moving mass. It would be effective in a short gap with an equal or long coil.
If we keep the coil external dimensions and number of turns constant then flat wire can lower resistance because it fills the space better. Efficiency is a function of (BL)^2/R. Lower resistance = better efficiency for short or extended coil.
There should be small improvement in thermal properties too. with the replacement of epoxy/enamel (or air) with conductor.
Maybe Speakerdave has some data on this?
Best wishes
David
I think you cannot import it from a cad program like autocad. I put the X-Y coördinates in autocad on each corner. The middle section of your motor is the 0 point. Then you put the coördinates back in femm with "tab" function.
The easyest way to start is to open an example of a speaker motor (is within FEMM already) Then erase only the "motor" not the boundry. And redraw your schematic. If you have questions please ask... you guys also helped me alot.
@ Dave
The problem with rectangular wire is to find it in small amounts. In copper i found it but in alu it is very hard to find. I used 0.15mm copper wire but maybe 0.20alu would just enough for decent values. I have to calculate that. In other words it's to find the right balance. thx for the info.
rgds
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I dont understand how you will achieve linearity with uneven ratios.
If the upper voicecoil has shorter excursion than lower, either it will have a hard time to return the moving mass once the upper voicecoil leaves the gap or it will limit the lower voicecoil excursion.
What parameter is linear to 25Khz?
also if i understood correctly do you plan to energize the upper voicecoil with a battery? Not sure how it can work as a suspension in this case, it will only cause on offset. I thought it will be shorted or driven like Dave Zan suggested with JBL's Differential Drive.
@ Hentai
In first place the upper voicecoil i won't use. It is only for centering and to achieve a higher and flatter flux density in the lower gap. If I have to use it, the height of the upper voicecoil wil be higher then the one on the bottom so it is even in excursion. (i'm trying to avoid that too much mass i think)
One thing is the inductance of the suspension coil (or EMK) it wil be compensated with a current driven power supply. When the inductance raises the voltage wil also raise to maintain the same current (force)
"also if i understood correctly do you plan to energize the upper voicecoil with a battery? Not sure how it can work as a suspension in this case, it will only cause on offset. I thought it will be shorted or driven like Dave Zan suggested with JBL's Differential Drive."
No, everything is at the lower gap. Oke if you take a normal coil it would like you said give a offset but it isn't a normal coil ;-) it isn't also a coil above and under the gap (this is far from lineair in the zero position) I can tell but not public. If I don't get te desired results I will tell all about it with pleasure I hope you understand.
In first place the upper voicecoil i won't use. It is only for centering and to achieve a higher and flatter flux density in the lower gap. If I have to use it, the height of the upper voicecoil wil be higher then the one on the bottom so it is even in excursion. (i'm trying to avoid that too much mass i think)
One thing is the inductance of the suspension coil (or EMK) it wil be compensated with a current driven power supply. When the inductance raises the voltage wil also raise to maintain the same current (force)
"also if i understood correctly do you plan to energize the upper voicecoil with a battery? Not sure how it can work as a suspension in this case, it will only cause on offset. I thought it will be shorted or driven like Dave Zan suggested with JBL's Differential Drive."
No, everything is at the lower gap. Oke if you take a normal coil it would like you said give a offset but it isn't a normal coil ;-) it isn't also a coil above and under the gap (this is far from lineair in the zero position) I can tell but not public. If I don't get te desired results I will tell all about it with pleasure I hope you understand.
There are a few contract voice coil companies that may supply.
Or try Oxinal wire company (USA) or Heraeus in Europe.
Probably supply a small amount if you say it's for a prototype.
Best wishes
David
Jet,
Thank you for the reply on Femm. I will look for the loudspeaker example and see how easy it is to change the parameters. If I have a question I will contact you and ask for your help as you do seem to have a handle on the input of the drawing. I understand Dave saying to saturate the pole piece to limit the magnetic flux modulation, but I think he is missing the effect of the back EMF of the movement of the voicecoil and this is one of the functions of the shorting ring if used correctly. The shorting ring will help to lower the inductance rise in the voicecoil. And we should be using the term Faraday ring rather than a shorting ring but that has become the common term that is now used.
Thank you for the reply on Femm. I will look for the loudspeaker example and see how easy it is to change the parameters. If I have a question I will contact you and ask for your help as you do seem to have a handle on the input of the drawing. I understand Dave saying to saturate the pole piece to limit the magnetic flux modulation, but I think he is missing the effect of the back EMF of the movement of the voicecoil and this is one of the functions of the shorting ring if used correctly. The shorting ring will help to lower the inductance rise in the voicecoil. And we should be using the term Faraday ring rather than a shorting ring but that has become the common term that is now used.
If you have a saturated pole piece, the inductance is also lowered. Under ideal circumstances, only the inductance of an air coil remains.
Baseballbat,
If you look at most of the better compression drivers the pole piece is in saturation but JBL and others are still using a shorting ring even in that instance. It could be a copper platting or even silver in the case of JBL from what I remember. Saturation can be in a part of the circuit and not in the overall magnetic circuit and this may play a part in all of this. The saturation could be only in the gap area of a focused gap while the rest of the magnetic steel is far from saturated.
If you look at most of the better compression drivers the pole piece is in saturation but JBL and others are still using a shorting ring even in that instance. It could be a copper platting or even silver in the case of JBL from what I remember. Saturation can be in a part of the circuit and not in the overall magnetic circuit and this may play a part in all of this. The saturation could be only in the gap area of a focused gap while the rest of the magnetic steel is far from saturated.
I use version 4.2 Normally it is in the example folder under C:\femm42\
I put it in zip:
View attachment SpeakerMotor.zip
regards
I put it in zip:
View attachment SpeakerMotor.zip
regards
Jef,
Thank you very much. I have been reading the manual and some others that I have found on the net. It is not a simple program to use. I did find that if you use a dxf file you can import the file from a cad program. If I wasn't afraid of giving away my magnetic circuit I would let you see what I am doing. I plan on patenting the design so I am having to be careful with what I can say.
Steven
Thank you very much. I have been reading the manual and some others that I have found on the net. It is not a simple program to use. I did find that if you use a dxf file you can import the file from a cad program. If I wasn't afraid of giving away my magnetic circuit I would let you see what I am doing. I plan on patenting the design so I am having to be careful with what I can say.
Steven
There are usually a number of distortion mechanisms going on and it will take a number of design features to correct them.
Silver or copper pole caps tend to deal with inductance rise. Wide range drivers like the JBL LE8t use silver plating. (even in the Alnico versions). SEAS has used Copper caps extensively. Less inductance equals wider bandwidth.
For LF distortion an undercut core pole will improve symmetry and lower 2nd harmonic distortion at low frequencies and high excursion. It also decreases the dL/dx component that promotes DC offset or jump.
The "flux" rings deal primarily with the high 2nd harmonic distortion throughout the mid frequencies (not just tied to high excursion). I know that saturated top plates or pole pieces will reduce this effect but I don't think they reduce it as much as a large aluminum ring around the core pole, as used by JBL and McIntosh. Saturation is also an expensive solution since you have to design with a lot more magnet than you achieve the motor strength benefit of.
Here is a good reference paper highlighting most of the cause and effects, by Gander at JBL
http://www.aes.org/tmpFiles/elib/20130215/3936.pdf
Regards,
David S.
Yes, anything in the gap is similar to making the gap bigger and losing flux. Silver plating for inductance doesn't loose much volume and the copper caps I've seen are fairly thin for the same reason.
The aluminum flux rings are typically pretty thick so they would never be put in the gap itself. Usually they seem to work well at the root of the core pole. I believe they act as a shorted turn there resisting the flux modulation (tendency of the signal applied to the coil to drive the operating point around a minor loop) but I'm not real strong on magnetic theory.
Regards
The aluminum flux rings are typically pretty thick so they would never be put in the gap itself. Usually they seem to work well at the root of the core pole. I believe they act as a shorted turn there resisting the flux modulation (tendency of the signal applied to the coil to drive the operating point around a minor loop) but I'm not real strong on magnetic theory.
Regards
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