I'm designing a sub driver and have identified a Bl value I'm aiming for of around 30Tm.
Through simulation of the magnet and coil I have this plot of Bl against displacement.
The displacement values at the bottom are a bit misleading. But basically 30mm is mid point of the coil length. So i get the desired 30Bl value there. But I'm wondering what effect the drop off as we move away from the centre of the coil has on motor strength? I know that a flatter Bl(x) curve is preferable. But what is the real world effect of having a drop off like we see here?
Thanks
Through simulation of the magnet and coil I have this plot of Bl against displacement.
The displacement values at the bottom are a bit misleading. But basically 30mm is mid point of the coil length. So i get the desired 30Bl value there. But I'm wondering what effect the drop off as we move away from the centre of the coil has on motor strength? I know that a flatter Bl(x) curve is preferable. But what is the real world effect of having a drop off like we see here?
Thanks
Yes, they are.
Less motor strength=less control of the cone movement.
Vance Dickason covers some basics here:
https://audioxpress.com/article/kli...gy-for-nonlinear-compensation-of-loudspeakers
Wolfgang Klippel has loads of articles and white papers getting into all the aspects of what you are looking at.
Yeah, it's basically the way I've set my model up. But take 30mm to be 0mm. So it peaks in the middle of the coil.
Thanks for the links. Will take a look!
Thanks for the links. Will take a look!
Odd order harmonic distortion. Moving the center of the coil off of the peak will introduce some even order components. For lowest distortion, you want the Bl to be constant through the voice coil's range of motion.
I fixed the simulation to show the correct displacement values.
So how is range of motion determined? And would you happen to know what factors of the magnetic and coil help to keep Bl constant?
I'm currently trying to research the mathematics behind it but it's quite hard to find papers that relate magnet & coil design to Bl.
Thanks
So how is range of motion determined? And would you happen to know what factors of the magnetic and coil help to keep Bl constant?
I'm currently trying to research the mathematics behind it but it's quite hard to find papers that relate magnet & coil design to Bl.
Thanks
Overhung / underhung?
The coil must have access to a constant field over its whole xmax. So to begin, the field must be longer than coil_height + xmax (p-p), or?
Then, is there an impact on B as the coil is travelling the field? I think its here that it gets complicated... L is at least constant as long as we don't approach c ;-)
But this isn't a super-duper-tweeter, right!?
//
The coil must have access to a constant field over its whole xmax. So to begin, the field must be longer than coil_height + xmax (p-p), or?
Then, is there an impact on B as the coil is travelling the field? I think its here that it gets complicated... L is at least constant as long as we don't approach c ;-)
But this isn't a super-duper-tweeter, right!?
//
Over hung coil, for a sub driver!
Coil is 28mm and top plate currently 9mm. So there's an overhang of 9.5, which is roughly Xmax, or call it 11 as standard practice seems to be adding 1/4 coil length on.
Does the field have to be constant over coil + Xmax for an overhung driver? I can see why it would need to be the case for underhung.
Would it not be coil-Xmax for overhung?
Cheers.
Coil is 28mm and top plate currently 9mm. So there's an overhang of 9.5, which is roughly Xmax, or call it 11 as standard practice seems to be adding 1/4 coil length on.
Does the field have to be constant over coil + Xmax for an overhung driver? I can see why it would need to be the case for underhung.
Would it not be coil-Xmax for overhung?
Cheers.