The advent of the transistor enable U.S. manufactures to reduce cost in amplification. High power -low cost. The move from valves to transistors had little to do with sonic improvement. It was as they say all about money.
Most speaker design in the United States since 1970 has been built around more exotic driver materials and inexpensive transistors. Thus the vast majority of speakers on the market are multi-driver affairs with complex power eating crossovers. Too many modern speakers are Hifi-ish and
artifical .
The JBL line from the Paragon to the much desired Hartsfields rarely service. Were among the best sounding loudspeakers produced.
My AR'S are an early example of the move away from large music producing speakers to small one's with very little high end but an exceptable low end.
Today audio is only a supporter to video. The iPOD has replaced the CD.
Another move that makes economic sense , but only adds to the exceptability of low quality sound.
Music has paid a major part in the poor quality of today's music, pop music
for example rarely uses an orchestra. The center of most homes today is the entertainment center with the focus on video. The speakers and amplification takes a back seat.
We may wait around and hope but the days of the great music producing systems made in America is over , as are the great movies from Hollywood.