None. As a subjectivist, the audiophile is convinced the old light bulb (which is better anyway than the new ones) is still lit, and discounts any measurements to the contrary. He convinces several of his audiophile friends to come over and they all enjoy "the light," describing the experience on Internet forums and blogs, using terms usually reserved for food or sex.
How many audiophiles do you need to change a lightbulb?
Only one.
But ten to discuss whether you need a 60W or a 100W bulb.
Ten more to discuss the relative merits of screw-in vs. bayonet fixture.
Ten more to discuss the relative merits of LED and halogen.
Ten more...…………………..