Hey all,
A bit out of left field but looking for some expert insight...
I'm sitting on a technology that enables very long throw drivers and I'm trying to get a sense if there's any practical application in audio land for it.
Essentially it could be described as a multi phase voice coil. Kinda similar in concept to a linear coil actuator but there's a number of key differences in form/function. The tech was developed for robotics and aerospace but has started to find traction in a number of other spaces.
Essentially if you had a device which was:
-As fast/faster than a VCA
-Negligible cost to go from 5" to 10" to 20" etc of travel
-Forces in the hundreds of newtons and up as needed
Is that something that would have any sort of application in pro/commercial/ultra high end audio?
Thanks!
A bit out of left field but looking for some expert insight...
I'm sitting on a technology that enables very long throw drivers and I'm trying to get a sense if there's any practical application in audio land for it.
Essentially it could be described as a multi phase voice coil. Kinda similar in concept to a linear coil actuator but there's a number of key differences in form/function. The tech was developed for robotics and aerospace but has started to find traction in a number of other spaces.
Essentially if you had a device which was:
-As fast/faster than a VCA
-Negligible cost to go from 5" to 10" to 20" etc of travel
-Forces in the hundreds of newtons and up as needed
Is that something that would have any sort of application in pro/commercial/ultra high end audio?
Thanks!
Sounds cool.
I can see applications in the professional audio industry for sure. A couple of 15" cones moving 10" peak-to-peak would provide a lot of output in a small box. Put them in an arrangement where the cones are moving in opposite directions (see PPSL subs for an idea) for force cancellation, build it to the size that just about fits everything in, add heatsinking...
What sort of efficiency are we looking at here?
To give you an idea, a conventional motor (ie, most of the coil in the gap at any one time) would need a theoretical 200,000W to get to the excursions you're talking about.
Needing a large generator for each subwoofer may be a turn-off for some.
Chris
I can see applications in the professional audio industry for sure. A couple of 15" cones moving 10" peak-to-peak would provide a lot of output in a small box. Put them in an arrangement where the cones are moving in opposite directions (see PPSL subs for an idea) for force cancellation, build it to the size that just about fits everything in, add heatsinking...
What sort of efficiency are we looking at here?
To give you an idea, a conventional motor (ie, most of the coil in the gap at any one time) would need a theoretical 200,000W to get to the excursions you're talking about.
Needing a large generator for each subwoofer may be a turn-off for some.
Chris
I suppose the interesting part is what frequency it can sustain. Such excursion is mostly interesting at lower frequencies, it would be nice though if it could effectively meet a mid frequency driver. The higher the frequency it can meet, the wider it's application.
Second part would be it's suspension. If it's suspension allows it to create a seal between the front and back wave, it can be used in many enclosure types. If it's just a surface area without a suspension, it is limited to "open baffle" use mostly.
Not sure where that 200,000 W figure is coming from but I'm pretty sure it can be used with more domestic sources of power.
Second part would be it's suspension. If it's suspension allows it to create a seal between the front and back wave, it can be used in many enclosure types. If it's just a surface area without a suspension, it is limited to "open baffle" use mostly.
Not sure where that 200,000 W figure is coming from but I'm pretty sure it can be used with more domestic sources of power.
The M-Force is a moving magnet type motor where the voice coil is on the outside and the magnet attached to the cone. This is actually a common type of speaker for very low cost applications (door chime etc.) as it uses less magnetic material than a normal motor. The disadvantage in conventional moving magnet speakers is that they are intrinsically non-linear. The M-Force takes this old idea and drastically improves it with a finite element optimized motor and linking the cone via a rod so that the magnet can stay inside the coil. As the coil is stationary it can be bonded to a heat sink increasing its power dissipation. I will link in the papers on the prototypes of the M-Force next week as I don't have them here. There is also a closed loop feedback system based on differential pressure sensing used to linearise the driver. I have heard prices of $10,000 USD per unit and MOQ of 10 for M-Force boxes with the matching amp, but that's just rumor.
I have also been noodling around with ideas for effectively infinite stroke drivers using un-rolled BLDC motors (or even something like the servo drive using a conventional BLDC). Have you designed something capable of the requisite acceleration? I was going to start off by using a commercial linear actuator but I haven't found any suitable.
I have also been noodling around with ideas for effectively infinite stroke drivers using un-rolled BLDC motors (or even something like the servo drive using a conventional BLDC). Have you designed something capable of the requisite acceleration? I was going to start off by using a commercial linear actuator but I haven't found any suitable.
Found the paper on the powersoft motor:
http://www.powersoft-audio.com/en/d...-9060-a-novel-moving-magnet-linear-motor/file
http://www.powersoft-audio.com/en/d...-9060-a-novel-moving-magnet-linear-motor/file
I took a 15" driver and ramped up the power levels until about 110mm of one-way cone excursion was achieved.
Not scientific in the slightest, but it does raise some concerns about efficiency - the simulated driver has most of its coil in the gap, ie, reasonably high efficiency. As you increase moving mass (more coils), efficiency drops.
Chris
Instead of electrically powered, what about pneumatic or hydraulic actuated cones? Or, pneumatic over hydraulic, even?
😀
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Searching for his pseudo on other forums...a video on a kickstarter : Affordable Force Feedback Flight Sim Control Yoke by Iris Dynamics Ltd. —Kickstarter
And this :
"We have intentionally NOT published numbers on this yet as there are a number of factors that will have bearing on this number when we get to production. That being said with the caveat that all numbers are subject to change I can say that we have be able to measure up to ~3650g (~8lbs) of dynamic force using a load cell on one of our prototypes.
Now as for factors which will change this:
-Coil winging density
The prototypes were all made with hand wound magnetic coils. These coils were all wound on a mandral of the same size (so they have the same dimensions) however the length of wire used in each coil varied from ~150’ to 210’. A properly machine wound coil of the same dimensions should be able to pack in ~383’ of wire. The more wire the more the number of turns or “windings”. If you double the number of windings in an electromagnet you double the maximum force. We actually ended up making an internal iOS app for calculating these numbers, and decided to publish it: Connecting to the iTunes Store.
-Firing pattern
As the shaft moves back and forth in the yoke different coils need to be activated at different positions. At a minimum we have at least 2 coils active but in some positions we have the ability to have up to 4 coils active. Meaning at specific shaft positions we have the ability to effectively double the amount of force acting on the shaft. HOWEVER because we can only do this at specific shaft positions we are considering that “extra” force unusable as it would make the force curves unrealistic. So in software this additional force has been “de-rated”. That being said if you wanted to re-enable it in software there will be provisions made to do so"
And this :
"We have intentionally NOT published numbers on this yet as there are a number of factors that will have bearing on this number when we get to production. That being said with the caveat that all numbers are subject to change I can say that we have be able to measure up to ~3650g (~8lbs) of dynamic force using a load cell on one of our prototypes.
Now as for factors which will change this:
-Coil winging density
The prototypes were all made with hand wound magnetic coils. These coils were all wound on a mandral of the same size (so they have the same dimensions) however the length of wire used in each coil varied from ~150’ to 210’. A properly machine wound coil of the same dimensions should be able to pack in ~383’ of wire. The more wire the more the number of turns or “windings”. If you double the number of windings in an electromagnet you double the maximum force. We actually ended up making an internal iOS app for calculating these numbers, and decided to publish it: Connecting to the iTunes Store.
-Firing pattern
As the shaft moves back and forth in the yoke different coils need to be activated at different positions. At a minimum we have at least 2 coils active but in some positions we have the ability to have up to 4 coils active. Meaning at specific shaft positions we have the ability to effectively double the amount of force acting on the shaft. HOWEVER because we can only do this at specific shaft positions we are considering that “extra” force unusable as it would make the force curves unrealistic. So in software this additional force has been “de-rated”. That being said if you wanted to re-enable it in software there will be provisions made to do so"
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Interesting, I have some experience using those optical mouse sensors for motion control. Only the most recent models don't have a digital filter that introduces a 20 frame delay.
Looking at the BL product of the HST-18 we get 25.6 N/A and they are quoting peak force of 35.8 N. Presumably at many amps of winding current. This would suggest Thier motor is weaker which is limits the peak acceleration achievable by the cone, limiting the high frequency output.
Looking at the BL product of the HST-18 we get 25.6 N/A and they are quoting peak force of 35.8 N. Presumably at many amps of winding current. This would suggest Thier motor is weaker which is limits the peak acceleration achievable by the cone, limiting the high frequency output.
The peak acceleration experienced by a woofer cone is A*(2*pi*f)^2 where A is the maximum displacement from the centre position. Assuming a moving mass of ~0.5kg this limits excursion to: 2mm @30Hz, 4.5mm@20Hz, 18mm@10Hz.
If more of an M-Force system was desired this sort of thing could be used:
https://www-magneticinnovations-com...ds/2016/11/High-Acceleration-Linear-Motor.pdf
https://www-magneticinnovations-com...ds/2016/11/High-Acceleration-Linear-Motor.pdf
You got it!
And to papasteack, that is VERY old info 🙂 ~2013/2014 ish.
We've since transitioned more into specialty B2B and OEM licensing applications.
Unlike most linear induction motors we capture much more of the "thermally expensive" magnetic flux. As previously stated we are more of a multi phase voice coil or a linear coil motor/linear stepper but with some big differences in respects to how we design our geometries and commutate the phases.
This is an example of one package size that's going into production now for a theampark client
YouTube
Those specific units are in the 50 lbf range (220N)
If we wanted to build a crude prototype what would be the best way to build/source a long travel cone/spider?
With that stroke length and force just attaching an aluminium plate and moving it through the air as a dipole will produce prodigious bass. See:
Parthenon
In terms of a cone and surround you could do something super basic by hacking apart a passive radiator. You only need the cone and the front surround as the extra stability of the rear spider isn't needed.
The m-force people are using a weird corrugated cone for their high excursion driver.
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