Looking for opinions (plenty Here); Thinking of building a GR Sub using a cylinder design (Like the older model HSU Research). Like the idea that they produce a smaller foot print for the volume, would use an outboard amp. Construction would be made of heavy sono-tube material, structurally strong, could have woofer on top or bottom, not sure what to do with passive radiator (understand it should not be place on the opposite side of woofer), is the passive radiator required? Sub to be used for HT, currently have Hsu Research and it works well with my A/V-3, just thinking of adding a second sub and like the cynlinder design. Thoughts please...Thanks