Thiele, A. N., "Loudspeakers in Vented Boxes: Parts I and II," J. Audio Engineering Soc., Vol. 19, No. 5, May 1971, pp. 382–392 (Reprinted from
 
	The above paper may be of interest if you are technically minded. It describes the design of bass reflex enclosures using second order control theory. I think audio reproduction has been revolutionised in recent years by the use of adaptive equalisers in tuner amplifiers where the response of the venue is scanned and the frequency response of the system adjusted accordingly. Using this very ordinary speaker systems can produce high quality results. I first saw this demonstrated when I was a student where students had to present a project as part of their course work to their fellow students and academics.