I seriously doubt that a parabolic would improve sound quality. The frequency response is generally really "peaky" - hard to equalize for good sound quality. The directionality also varies widely with frequency. The parabolic
reflector concept is useful for light or UHF-to-microwave radio signals. Because sound can bend around corners and doesn't always travel in a straight line, a parabolic reflector is less useful in concentrating sound.
John