The main idea with that is to get the tweeter a bit *above* ear height. What that does is smooth out a response wrinkle in the *upper mids*, not in the HF range...it's just that the usually quoted "tweeter above ear height" refers to the fact that the mid driver is virtually always located right underneath it. One thing you might want to look at though is the bass response. If you have floor standers then raising them may take a little off the bottom-end response, *unless* you can provide some type of front baffle that goes from the floor to the bottom of the speaker cabinet...that recouples the bass to the floor. Even stand-mounted monitors can benefit from that idea, preserving low-end response that would otherwise be wasted. The material be anything that's relatively rigid, even cardboard, so you can use any sort of wood or tile or whatever that has suitable appearance - as long as there is no air gap along the front of the whole of the speaker cabinet from the woofers down to the floor. With my floorstanders i wound up making a pair of stands (with flat fronts) about 7" high and that smoothed the upper mids out for without decoupling the bass. Regards. John