I personally feel that the materials used in the 40's and earlier were probably more often than not longer lasting, easier to maintain naturally, and perhaps more gentle sounding than the majority of synthetic materials used today. I have radio speakers and victrolas in my collection that still sound just fine. Sometimes the cone drivers can sound quite good.
The design methods in this first golden age of audio were far more hunt and peck than most modern design methods. Yet, this trial and error methodology still resulted in good sounding speakers that are still frequently regarded as good sounding.
It seems that the only real currency that buys you sound quality is just effort of the designers and manufacturers that goes into the product itself.
There are numerous more and usually smaller higher points thoughout audio history (and the present day) than a black and white blanket view of history will let you see.
I am a total sucker for history. My present day cabinet designs use Fostex 3"ers that go back to the 1970's in the Orcas and a clone of an old pioneer 8" driver (BoFu) in the Thrasher. The Bofu also goes back decades of consistent production and refinement as well.
The quality of sound that this iterative refinement represents is hidden further inside the value engineering of the parts used in these drivers than can be apparent just looking at them. This fact is and should be kindof scary to anyone out there starting up a fullrange speaker driver company.
In terms of my own company, I began working with cabinets first inside Cain and Cain and then on my own for these specific fullrange single driver models from Fostex and Pioneer 13 years ago and ever since as my production of them has grown, I have made very slight, typically unannounced, iterative refinements that take place between large production batches of those cabinet models. Just like the Pioneer and Fostex drivers, and as those drivers have changed slightly, so too have my cabinets to make the most of their ever improving, modern-day-classic sound. Though I have tried out hundreds of different fullrange drivers from many, many companies high end and low end, my best designs so far and therefore my role in this industry has instead been to make the classic cabinets that needed to be there for these classic drivers that are still in current production and still gradually improving.
-Clark