Here is my take on the pickups.
Firstly let me say this is not a real test as the conditions are suspect to say the least as described below.
Test was done on my NAD ampeg B15T. a very underpowered (no way it is true 100 watts) and not one of ampeg shinning moments. But a ok little rig to keep near my workbench. secondly volume played was not very loud as whole family was around but i moved out of workbench area to avoid other things adding sound...
More importantly the basses are all a little different in various ways.
Jaebird one is poplar body (i believe) maple neck, rotosounds with about 8-10 gigs on them several outside in the humidity, 63 thunderbuckers, neck pup slightly moved toward the neck..
Bachbird - Mahog body
? or mystery meat with a mahog veneer, mahog and rosewood neck, set neck not bolt on , Labella Hard Rockin string ) IMHO the best ROCK strings made - great piano like tones , also have them on my 76 bicentenial. Strings are probably 8 months or older but have never been played since installed. Mike Lull pickup...
Jaebird Too... - Mahog body with maple neck, D'Addario RW strings, couple of gigs on them including outside.., 66 thunderbuckers.
here is my take on the pups. test was done with all neck pups only at first. Only finger style, no pick
63 thunderbuckers - Readings 7.62 N & 7.88 Bridge, blended 3.96. Best deep bassy tones (could be placement as well as the strings) little weaker on the treble side (strings for sure) and scooped nicely in the middle. fast tarnish - shiney but yellowed - very different from my 76 pups dull tarnishing.. Bridge pup fixed the treble side when turned on. Great sound when playing with fingers up by the neck... As usual i differ from most of you "gibson" guys - So far these are my favorite of the 3.....
Lull - 7.97 reading very solid lows and best treble side (strings help alot...) nice scooped middle, Very clear sounding , more of a modern tone to me. Very similar to the 63 thunderbuckers but a little louder. Also a little clearer which i would say is the strings versus the rotos. still shiney like brand new..
66 Thunderbuckers. 8.33 N and 8.72 bridge, 4.31 blended. Very mid range driven sound (IIRC overwound pups tend to be that way) weakest on the treble side. more bass and mids. IN YOUR FACE.... may have to break out the heavy stuff to get a true tubey thickness sans the "gain" control issue. starting to tarnish
Provisos
Clearly this is a flawed test and so i will change out the D'addarios very soon and rotos too and try again. Fingers only so none of this holds true to you picksters....Test done right after spending some time fooling with my new fodera so i had on my R&B and jazz ears.......Also this was thru a small SS head without any change to the gain and volume between basses so i was not getting the best out of each just a neutral position. I have an outdoor classic rock (how i hate those words...) show this weekend on a pier so humidity may be a real factor. Weather permitting i will do a better taste test with a least a hybrid head (hartke or eden) and real volume and get some tubey grind. thinking about a 2 Ev15 cab plus?
?
Jim