A few years ago, they put the driver parts up for display on a show. It gave me the oportunity to see exactly how it all is built, and yes, it is as simple as previously revealed here. It gave me the oportunity to run a FEM model to see the Bl(x), and this is what I got:
As anyone who has been dealing with FEM simulations would know, there are very few variables involved once you have no paramagnets and no asymmetry. So it is safe to assume this is pretty accurate. What is unlikely to be accurate is the force factor itself, but any change in windings and magnet class would only rise or lower the same curve a certain amount.
Something else we know about the driver is based on a claim made several times by the company. The impedance peak at Fs is extremely low. It is claimed to be due to the low inductance, which is simply not true. The inductive and capacitive components forming this peak are the mass and the suspension of the driver. The electrical inductande do not play a role in this.
There are a few ways to get this peak low. One is to introduce mechanical loss leading to low Qms. Another one is that you could in theory make a driver that has low mass and extremely loose suspension, but it would not be able to play any bass in a real world enclosure. Changing Le would not affect this peak unless it is extremely high to begin with. Since we know these woofers are quite traditional in therms of T/S we can say for sure that they are very lossy. It is actually quite impressive to get that amount of loss without an aluminium voice coil former.
Regarding patents
@smowry , I am not sure there is any reason to be annoyed. There are only two possibilities here. One is that the patent is impossible to defend in court as it is easy to prove that it is prior art. The other one is that the detail it is approved based on is so tiny, it does not give any protection for the function of the product, and probably is still impossible to defend in court. We have the same situation with D Wiggins in 2003 or something where he re-patented an old Babb-patent from 1976 (the split gap). It was later revealed that it was approved based on the following:
1: A sentence in Babbco's patent stated, after the description of using two gaps and describing the possibility to add even more gaps, something like this: "Adding even more gaps would not have any practical advantage". Wiggins' attourney was able to convince the clerk that this sentence also included 2 gaps. While anyone with any understanding of the topic knows that using two gaps would add some advantage, while adding a third would not, the clerk obviously did not know this. This would off course make this patent impossible to defend in court.
2: A tiny groove in the pole piece between the two gaps were not added in Babb's patent in 1976. While it is an absolutely obvious thing to do in a world of T-shaped pole pieces, they were able to convince the clerk that this was a new invention. This too would probably have been pretty hard to get anywhere with in court.
