Its the ratio between the front spring and back spring, the front spring controls how hard the hammer pushes on the power stem. The rear spring controls how hard the power stem pushes back. So between the two its how fast and for how long the powerstem is open.
The Front spring is what you should change to adjust the velocity. you only change the rear spring if you've gone through the range of front springs and not got the velocity you want. Softening the rear spring means the powerstem opens quicker and for longer, so a softer rear spring should increase velocity. and a harder front spring should do the same but by smaller amounts.
This is all from memory as my phantoms are 1991 original which has a dialer and another with 2008 internals, Which also have a dialer, to be honest never heard of a phantom without one. the anti kink was just a tube extension on the dialer.