A guitar pickups could be used for a bass pickup but generally bass pickups have more turns to give the instrument lots of bottom end. Some early Gibson EB-Bass pickups would use 20,000 turns of magnet wire per coil that sounded deep without a lot of clarity. Generally all guitar or bass pickups use a directed magnetic field or poles to magnetize the strings, a coil wound to a desired number of turns with a particular gauge of magnet wire and desired pickup placement either towards the bridge for more treble or towards the neck for more bass.

Usually pickups have some type of adjustment either adjustable poles, adjustable height and even sliding towards the neck or bridge. There are various designs for many types of bass pickups starting with single coil, split pickups (Fender Precision Bass) Humbucking, Stacked pickups and other custom designs. Active pickups have become very popular with bass builders and are used for tight bottom and clarity. You can put .0047 mfd. capacitor in series as Rickenbacker did on several bass models and a sound made popular by Chris Squire in the group “Yes”.