What is "west coast sound"

Bigtee got it right. Jrd351, too. The market was dominated by JBL (made on the West Coast) and AR (made in New England). Regional stereotypes (sorry) were reinforced by the conservative (flat, but a little compressed) sound of AR versus the more colorful (with ear-pleasing emphasis of highs and lows, and more dynamic) sound of JBLs, a la the respective social styles and mores.

I believe, in Jazz, it was used to describe the performance style of artists like Dave Brubeck, Paul Desmond, Gerry Mulligan (early), and others, offering an “easier-feeling”, less-driven performance style. "Cool." (Not to be mistaken with the "Cool" of, let's say, Miles Davis.)

Dweller rightly describes the San Francisco sound. More in general though, West coast - loose and relaxed. East Coast - uptight and controlled.

In music, West Coast is the sound Fleetwood Mac makes when it hires Stevie Nicks. Singer Nicolette Larsen is another good example.

The let's-all-get-along West Coast sound features a jingle-jangle (The Byrds) that the bitter East Coast sound (Lou Reed, Bruce Springsteen) lacks. Put another way, in West Coast the guitar chords sound on both the up and down strokes instead of chopped out with all down strokes.

Speaker Type, West Coast: Bass Reflex; East Coast: Acoustic Suspension.

AR was not only New England, but Boston, and they operated a demo studio (not a sales room) in Harvard square. Formal atire, optional.