Need someone good with math involving watts and amps

[Church]

Why not leave it PWM if PWM is better?

Because some analogue, not pwm fans might get extra noise under pwm regulation. IIRC In normal 4pin pwm fan there is separate wire for pwm synchronisation, that solves that issue, but with analogue fan with normal 3pin these voltage spikes might differ at different rpm at which point coils should actually charge and push to turn rotor and at one position have more voltage, at different less, so possibly resulting in that extra noise.
Otherwise pwm of course is better then analogue regulation in several ways - it's circuitry is cheaper, as doesn't require monstrous heatsinks to dissipate redundant power, it can handle much higher current, with pwm minimum rpm-s can be lower (as less of a problem minimum startup voltage to start turn motor, because it's always full 12V or 0V). But probably because that pwm rpm regulation is newer, and many analogue fans/pumps exist, some choose analogue regulation as safe bet for everything. (eg. Aquaero).

[terramir]

Interesting, thanks for sharing

So, in essence, the fan will see voltage control, but the controller is converting 12V to a lower voltage through PWM + Capacitor?

The advantage of this is simply not generating heat in the controller?

Sorry for the dumb questions, just trying to get at least a little pinky around the topic. I've had a few people indicate on my 38mm fan tests that the problem is lower voltage, and PWM is the better way to go....yet it sounds like this controller is converting PWM to lower voltage. Why not leave it PWM if PWM is better?

Yes less heat, but not no heat, there are always some losses.
see below on the PWM question

Because some non pwm fans might get extra noise under analogue regulation. IIRC In normal 4pin pwm fan there is separate wire for pwm synchronisation, that solves that issue, but with analogue fan with normal 3pin these voltage spikes might differ at different rpm at which point coils should actually charge and push to turn rotor and at one position have more voltage, at different less, so possibly resulting in that extra noise.
Otherwise pwm of course is better then analogue regulation in several ways - it's circuitry is cheaper, as doesn't require monstrous heatsinks to dissipate redundant power, with pwm minimum rpm-s can be lower (as less of a problem minimum startup voltage to start turn motor, because it's always full 12V or 0V). But probably because that pwm rpm regulation is newer, and many analogue fans/pumps exist, some choose analogue regulation as safe bet for everything. (eg. Aquaero).

This noise thing can be solved by properly choosing the capacitors for the output, however the problem is that different kinds of fans will create different kinds of induction noise (electrical noise) hence choosing the right filter capacitor, unless you over-design (which is more expensive) is difficult, when designing a generic fan controller. To really do a fan controller well you would either need to do two things, A. limit the voltage to about 11.1V max usually it's about 11.3V-11.6V why the lower voltage, because you would need to add a shottky diode and another filter capacitor in order to prevent induction noise from messing with the controller and eliminate voltage spikes.
Or B. Design a controller that works well with a specified tested limited range of fans
My $.02
terramir