Understand that one of these cabinets will displace a good bit more air at 20hz then a single 18" model from Velodyne. At 20hz you are getting the full 40mm of xmax of the 18" passive radiator of each cabinet, 40mm is excursion the 18" Velodyne can only dream of. Not only that but you are talking about a pair of 18" passive radiators at 40mm xmax at 20hz. The 18" driver in the Velodyne subs is probably more in the 25mm xmax range so you are talking about 6 litres of displacement from the 18" velodyne model vs. 9.6 litres of displacement of each of my cabinets, or 19 litres total at 20hz. That's more then three times the output of a 18" model from velodyne at 20hz. Think about this next time you bid $1000 for a used unit from Velodyne
