Thiele-Small parameters vs box response

[jag]

I did this analysis (WinISD) sometime back, shows how the box response changes w.r.t. T/S parameters (Qts, Vas, and Fs). Note that the box volume and Qtc are not same in all the cases (but as recommended by WinISD). All are sealed boxes.

The yellow, dull (olive) green, and light blue curves are exactly the same. Hence only the light blue can be seen in the picture:

[jag]

Impact of box volume

[jag]

The parameters are highly interdependent - not really possible to change one without affecting the others. I was trying this purely theoritical exercise to get a better feel for these parameters. The results are extremely counter-intuitive. I have tried to explain as far as I could:

Case 1: Increase Qts while holding Vas and Fs constant

Vas constant - suspension stiffness constant
Fs constant - cone weight also constant
Qts increased - Since Qms cannot be changed, Qes has to increase (reduced motor strength).

This should reduce efficiency (not shown by WinISD). But, WinISD shows that F3 is reduced as well (at expense of some boominess - unless the box volume is increased correspondingly) - very interesting! Want lower F3? Reduce magnet strength on the driver, and bring that Bryston out of the closet!

Case 2: Decrease Fs while holding Qts and Vas constant

Vas constant - suspension stiffness constant
Fs decreased - Cone weight increased (Qms increased)
Qts constant - Qes has to decrease (more powerful motor).

The efficiency will probably remain unchanged. F3 should go down (as shown by WinISD).

Case 3: Increase Vas while holding Fs and Qts constant

Vas increased - Looser suspension
Fs constant - reduced cone weight.
Qts constant - Qms is more or less constant. Hence Qes is also unchanged.

The efficiency will increase because the cone is lighter. But, WinISD shows reduced F3 and increased boominess (unless box volume is increased proportional to Vas for reduced air stiffness). Any explanations?