Reduce the sound on PWM fan

I want to reduce the lower and upper limit of my PWM fan when not overclocking. I'm thinking about using a DPDT toggle. Having 12 v lead from CPU fan header going into switch. No restriction coming out for overclocking, but I want to restrict the lower limit when not overclocking.

I noticed Zalman makes a resistor based reducer for a PWM fan using a resistor, but it only reduces the upper limit of the fan.


Most of the fan controllers use volt mod, so you loose the PWM functionality.

Does anyone know how to reduce the 12v lead on a PWM fan to impact the the lower and upper limit of the PWM fan? I still want to use the PWM fan functionality but I want the ability to slow the fan beyond the lower value set by the manufacturer. Because I want to keep the PWM funcitionality, I don't think I can use the normal 5V or 7V mod. Does anyone know if you could use a diode series on the 12v lead to work on a PWM fan to reduce the voltage? Any other ideas?