The quality of materials has improved markedly, but the philosophy of physics determining good speaker design remains conflicting among manufacturers. Therefore what to believe is lost to the consumer.
Shortening this complex topic to cardinal violations interfering with waveform reproduction: 1. cone drivers containing coils for midranges and higher, 2. sharp edges producing diffraction. 3. symmetry of driver placement, 4. passive crossovers with large value components, most containing coils, 5. improper impedance mismatched lead-in connections, 6. use of cheap copper alloys in the connections, etc, etc
If you think this excludes almost all speakers, then it should come as no surprise why few have heard the remarkable phenomena of when the artist appears in the listening room. It is a jaw dropping, if not a life changing, experience. That good.
Your answer to this simply boils down to: 1. Alot of study and hard work building your own, or 2. spending an extreme fortune, which is still not guaranteed to solve your problem.
I went with #1, followed the rules of physics, avoided the violations, a few of which were stated above, and achieved the performer-in-your-listening-room result. So it works. It was also a 30 year project.
There are alot of good responses in thie thread. Take every one of them.