New single BR

I would be very afraid of such simplistic view, and very careful with conclusions based on these.

 For example B&C drivers are known for that the suspension is the main mechanical limit of the cone excursion.

Therefore at some point, mostly Cms eats up the whole force developed by the voice coil (which is not that high, with 50% or more coil out of the magnetic field).

The Qms and Qes relations only work with small signals, and relations can get absolutely different in not that high excursion.

Also carefully about ignoring certain elements in the math, as their chronology is important for the outcome. Rms is not just static parallel element to the Cms and for all frequencies. You cannot deduce one from each other and count with it like that to reach the right outcome.

But I´m happy to see that communities are diving into this science deep stuff.. J

thanks

Just to throw a curveball, I may have some 21SW115 that I can do a pretty good price on...

What drives this choice? I would be thinking between LF18N405 vs 18SW115 at that point  

Keen wrote: "Q is a measure of energy stored divided by energy dissipated, meaning that higher Q means more energy storage  "Dissipated energy" is loss" - Joachim Gerhard of Audio Physik   So high QMS is stiffer supspension. 21DS115 and 18DS115 are horn drivers, thick heavy cones, big motors, low damping (because the bass horn does the damping) the others are more suited to reflex. hth

Slightly the other way around I think unless my mind is wandering again. Q ~ (stored energy)/(energy lost per cycle) so comparing different systems with the same stored energy the one with the highest Q is losing the least energy per cycle. In case of suspension that would be a loose driver which has the least resistance to movement. You can also think of Q as proportional to the number of oscillating cycles it takes a system to lose its stored energy.

A stiff suspension driver that offered higher resistance to movement would have a comparatively lower Q value as it would dissipate the same stored energy in less cycles, because each one is performing more work.

Think of it is your large voice coil strong motor drivers are all low Q(es) because the strong motor makes them highly electrically damped. Same works for the mechanical damping which is often also seen in lower Cms and higher cone mass for lower Q(ms) drivers. And then all of this features into with Fs also.

Q is quite a mathematical abstract thing, but it directly relates to the linear coefficient term of 2nd order differential equations which are also the same reason people talk about alignments such as Butterworth etc.  All loudspeaker equivalent circuits can be simplified to a series of 2nd order equations working in parallel with each other.

It's a bit tricky getting your head around Q, I haven't yet, and I remeber lots of seemingly contradicting statements that only make sense once you learn more.