I regret not getting clearer pictures to zoom in and see the words on the instruments but I felt the need to be discreet as I was just walking by, these ocean-front home garages are rarely/NEVER left open unattended. What is this mystery chamber?
One more different angle picture in the comments, you can see the seating bench in the chamber.
It's a few houses down from one certain house where JFK & Marilyn Monroe played hide the salami together, where also years later Paul McCartney & John Lennon were last together in the same place (or something Beatles last time something). Paris Hilton also had a house here further up the road before the January 7th fires consumed it. These homes are usually empty because the people who own these houses have several homes all over the world, so these are just an occasional beach retreat for them, an eyesore and ocean-view-blocker for everyone else.
Anyway my point is, it's a popular well-known area, right by the ocean, which means everybody wants a piece of it, both major highway & billionaire beachfront homes. In fewer words:
Pacific Coast Highway.