One of the things that made the Bassman sound SO good was it's ten inch alnico (aluminum, nickel and cobalt- a much more pure mixture back then) speakers. Four of them! These Jensen "bluebells" are considered to be on par with Celestion "blue" speakers or grey "Bulldogs" of the day. These days sets of four P10Qs, which was Jensen's code for said speaker, can bring up to $2,000 if in proper condition.