Hi Kerry, Wayne, all
The idea with forced air cooling is that the air that is swept away after being heated carries away energy which would other wise accumulate, causing a temperature rise.
If you look around, you will see air transfer is the most common method available, everything from your car’s radiator to the heat sinks in your amplifiers use this approach, the air carries away the heat energy.
A typical V-8 car radiator can dump about 50KW of heat and its not that big, it just takes airflow..
Look at the link below which shows the effect of forced air cooling on a DC servomotor. This motor is similar to that used in a Servodrive and has stationary magnets with a rotating hollow wire armature (very similar to a Voice coil). These motors only have a cooling air path on the outside of the armature where the air path in my cooling Patent is on both the inside and outside of the VC.
In the Servodrives with power cooling (using this patent), cold air was taken in at one edge of the enclosure and hot air expelled at the other, the motor was not in the driver compression chamber.
On the VC drivers licensed under this Patent, the heat once removed from the VC, heated the enclosure and its aluminum back panel.
In the loudspeakers using the approach shown in the patent, they were able to get more than a factor of two in steady state power handing.
For this to work, it is critical for the air to flow thru the magnetic gap (intimate turbulent contact with the VC) as radiation is a poor mechanism at safe VC temps. Holes that allow air to bypass this path truly defeat the function. Also, doing it this way, one avoids any significant offset, which is a problem the other ways it could be done. As I have explained, this way avoids the radiator area feeling any pressure from the cooling system..
Scroll to the bottom of this link and look at the permissible dissipated power and thermal resistance as a function of air flow. Keep in mind, these are real Watts and not Loudspeaker Watts but the change would be similar (approaching a factor of four improvement). Also keep in mind, the air path is only on one side of the cup armature.
http://www.pacsci.com/support/low_inertia_pmdc/lowinertia55n msupport.html
Hope this helps.
Tom Danley