Yes JBLs can sound different from other JBLs. My L55s sound nothing like the L212s or PT800s. But the L212s and PT800s sound quite similar (at least my custom L212s). But the difference between the L55s/L212 is a progression from the early '70s to the late '70s~early '80s with the L250.
But I find that other speaker brands won't come close to the JBL sound. Actually maybe some Canadian speakers do, as a result of Floyd Toole and Sean Olive both working for Harman and the Canadian National Insitute, or whatever it is called, before.