Thanks CarveOne and Khalid! It's had a lot of work in development, seems like it's never ending.

adam_m- Good question! I'll try to put it in perspective;

Fixed speed router; Generally 25000 RPM to 30000 RPM, (like Khalid said), very noisy, lots of heat, tool wear and bearing wear and will melt plastic when cutting etc and can burn woods too depending on speeds and feeds.

Variable speed router OR any typical "speed control"; When you turn them "down" these just send less power to the router. So speeds are about 16000-30000 RPM range, and at lower speeds like 16000 there is very little torque. So if you are trying to use the lower speeds it will droop speed badly and have very little cutting power, or just stall, or speed will vary all over the place depending on cut depth etc. And under 16000 RPM you can pretty much forget about it, so you still get bad issues with melting plastic and aluminium melting onto the tool because you are forced to use too much RPM if you want to get any useful cutting power.

Super-PID closed loop speed control; This has a infra-red speed sensor pointed at the router shaft, so it measures the exact RPM of the router at all times. Then it uses a high-speed math algorithm called P.I.D. to adjust the power sent to the router, to keep the router spinning at the RPM you wanted. And it has an accurate tacho so you can set a chosen RPM based on speeds/feeds tables as people need for professional production.

So speed range is now 5000-30000 RPM, and you can get excellent power down to 9000-10000 RPM (used for most plastic and aluminium cutting etc) and even get significant amounts of usable power at the very low RPM range like 5000-9000 (where your router is almost silent!) that can be used to cut fussy materials like low-melt point plastics, fussy woods, and light cuts in materials for the purpose of getting good surface finish etc.

The idea of the Super-PID was to offer some (most?) of the performance benefits of a VFD spindle setup, but at a lower cost and an simple task of just connecting it to your existing router setup.