I don't currently own a Westone Thunder1
I discovered this bass accidentally...I'd never heard of it
After much online perusal, turns out:-
(1) They were inexpensive but damn good as far as the Thunder 1,2 and 3 go.....(also the headless model was very good)
(2) Spectras weren't as good as the Thunders
(3) They were built rock-solid and had a good tone
(4) They use 18volt system (2 batteries) and had a switch for "passive/active"
(5) Very popular bass in the UK during the eighties.....