Cutting and Routing of speaker holes can be very nicely done with the dremel circle cutting attachment. I built my theater sound system with a dremel.
I built a set of MTM main speakers plus a center speaker! The majority of the cabinets are made from 3/4'" select grade aspen with the sides being 3/4" oak veneer plywood. The main speaker holes are for 6 1/2" woofers and a 4 5/16" silk dome tweeters the center speaker uses 5 1/4" woofers and a 4 5/16" silk dome tweeter.
After centering my holes and using a compass to get my circles, drill a 1/8" hole for the circle guide. Next, drill a hole to install hole cutting bit. Next, I recessed the mounting flange area first. I used a dremel 1/4" router bit #654, in the circle attachment. Determine how deep the recess area is to be and make setting. Several small cuts are better then one deep one, don't over work the dremel. Insert guide pin in center hole and adjust dremel out to outer edge. Power up and slow plunge bit into wood then slowly go clockwise, take your time and let the tool do the work. FOR SAFETY: Allways wear safety glasses and keep both hands on the unit at all times. If you have several holes, do the outer edge first to keep them uniform.
Once done ,do all recessing starting from the inside out. Otherwise the bit will cut from the backside causing unit to jump & lurch and giving you a rough cut and possibly causing unit to jump out. This is not a toy, it can hurt you! Once done, cut your hole area out. I found the unit to work well with most wood and MDF in particular. As a rule of thumb, allways practice with power tools on s**** wood first, better to make mistakes there then on your project.