Hi all, more PU qus. Looking at these barts for a chambered 6 string fretless I'm currently designing. http://www.bestbassgear.com/bartolini-g6-pickups.htm I'm thinking the "classic series" with the open freq range would be best. Love to hear your thoughts. Also wondering, could I use them passive or do they really need a pre? P.s. crazy idea; what about 3 of them ala Big Als?