DESCRIPTION:
Recorded directly into a Zoom H1, no amp, no eq, so what you are hearing is just the pick-up. The SPB4 is obviously hotter (higher output) than the SPB1, since its DC resistance is 13k compared to the 11.6 of the SPB1. The SPB3 on the other hand is 12.5k, so the 4 is possibly even hotter than the 3. It may not make all the difference on a portable recorder, but it probably does on a bigger amp.

Fender Precision Steve Harris
Sansone Strings 50-110 stainless steel
Klotz TM Stevens Signature (6 meters)
Zoom H1 Handy Recorder

Seymour Duncan SPB-4: https://www.thomann.de/it/seymour_duncan_spb_4.htm?partner_id=55684

Seymour Duncan SPB-1: https://www.thomann.de/it/seymour_duncan_sspb1_vintage_pbass_pickup.htm?partner_id=55684