The fact that one can audition as many different speakers as one cares to seek out and listen to is, in the act itself, "custom tuning" the speakers to your ears. The eyeglasses analogy is only partly relevant; just as no two people have identical vision, no two persons have identical hearing. Further, with the glasses, there is not an infinite number of ways to configure the lenses (the design parameters reside among a limited range of "plus" and "minus" values) just as there are not an infinite number of ways to design a speaker; the design must be developed from an existing finite set of crossover parts. The notion of a "deep state" of speaker manufacturers is just another deep state of confusion.