I've read in last The Perfect Vision that they recommend putting the Servo-15 on a slab, 1 feet high!!! What should we use as a "slab"? I mean what people are using under their sub? Concret? What are my options here? And 1 feet high! Seriously? Mine is directly on a wood floor, and was wandering if this set-up (slab, 1 feet high) could really improve anything. Do people really put slabs under sub?