The Fifth Element #85 Sealed Boxes
I'm convinced that Villchur's acoustic-suspension "bookshelf" loudspeakers, beginning with the Acoustic Research AR-1 of 1955, were the key innovation that opened up hi-fi to apartment dwellers and to buyers of suburban tract houses who lacked the floor space required by the previous, larger mechanical-suspension loudspeaker designs. That floor-space factor became even more important with the widespread acceptance of stereo after 1956.
There being no free lunch, the tradeoff inherent in acoustic-suspension loudspeakers was and is low efficiency. Getting deep bass out of cabinets much smaller than before required amplifiers much more powerful than before. The march to market domination of the acoustic-suspension loudspeaker advanced in inverse proportion to (and was the proximate cause of) the declining market share of vacuum-tube amplifiers. Solid-state amplifiers could drive acoustic-suspension loudspeakers to room-filling volumes.
However, many early transistor amplifier designs did not sound very musical. The "specification wars"ie, the marketing of amplifiers by advertising their output-power and harmonic-distortion specifications rather than how they soundedonly led the industry even further astray. Therefore, I am well aware that some thoughtful observers (Art Dudley, perhaps?) might view the entire era of acoustic-suspension speakers as the wrong road taken.John Marks