Speed control wil seriously reduce the life of your motor - I really would caution you to do a little online searching and you will see what I mean. You need to use some sort of mechanical air flow restriction - like an air gate - and it wont cost you any more than the speed controller would.(http://www.amazon.com/Dust-Collection-Plastic-Peachtree-Woodworking/dp/B000H555B2) You also are going to need to find out what the max air draw is possible without drawing to much air from the Glowforge. You should simply find out what the dust filter fan OUTPUTS. Then you will need an airflow meter - hold it in front of your draw and adjust your gate until you have the correct air draw.