This past weekend my brother purchased a pair of Velodyne ULD15 subwoofers with seperate amps/crossovers to augment his JBL 4311b. The price was right, $450 for the pair. These were purchased from the second owner who advised that the high and low crossover points had been changed by the first owner. From what I understand their are 2 resistors for the low pass and 4 resistors for the high pass inside the amp/crossover that would have to be changed. Does any member have any experience changing the crossover points on the Velodyne ULD models (12/15/18)? I listened to the ULD15 subs and they sounded very good but imo the crossover points should be set higher since his 4311b bass doesn't extend that low in his fairly large listening room. I was quite impressed with the Velodyne subs and considering the difficulty in locating/affording a B460 I would seriously consider purchasing a Velodyne ULD18 to go in my system (L300).