I made one years ago, the design was published in Speaker Builder. Just get a large lazy Susan ball bearing turntable from a hardware store, put it between two pieces of plywood. It can't be really small, though. The speaker has to sit atop it with the baffle on the center of the platter, so the platter diameter must be twice the depth of the largest speaker that you'll measure.
Bill Fitzmaurice Loudspeaker Design
The Laws of Physics aren't swayed by opinion.