Some basses fitted with this bridge
The Hagstrom Bi-sonic bass pickup was made by Hagstrom in Sweden, throughout the 1960s. It was initially fitted to the 4-string Coronado bass by Hagstrom , with a six-pole piece equivalent for the six-strong Coronado - both models also available with Futurama branding. New York guitar builders, Guild started fitting Bi-sonics to their Jetstar, Starfire basses in the mid 1960s; and later onto some early versions of the Guild JS and M85 basses as late as 1970. Hagstrom replaced the Bi-sonic as their pickup of choice in 1966. with a smaller single coil unit. Guild continued to equip basses with Bi-sonics through to 1970, when they were replaced by Guild's own bass humbuckers. The black/chrome design of the Bi-sonics is quite distinctive, and some of this pickup's appeal must be visual. It is a large unit, arguably larger than necessary; although only a single coil design, the unusual means of adjusting polepiece height, widens the pickup footprint. But they have a great tonal response, and are very well regarded; the early Alembic customised electronics fitted to Starfire basses owned by Jack Casady (Jefferson Airplane) and Phil Lesh (Grateful Dead) were originally devised with Hagstrom pickups in mind.
From the 1966 Hagstrom catalog: With the incomparable Bi-sonic pickups, bass and treble frequencies are separated, so that simultaneous bass and treble creates a new dimension in sound
Due in part to their short production run, and also their desirability as a pickup, Bi-sonics are quite highly prized. A number of companies have produced recreations of this pickup, most notably Fred Hammon's 'Darkstar', Curtis Novak's BS-DS and even Guild, who offer them on numerous reissue Starfire and Bluesbird bass models.
List of vintage Hagstrom parts