I would dispute that there has been much technological advancement in speakers, and even amplification, in 30 years. Sure, some components like capacitors and diodes are much better but the basics haven't changed much. With the exception of the Manger driver, there is nothing really new. Stiffer cone materials from poly to graphite has been around for quite a while and basic circuit topologies haven't radically changed, only altered, not necessarily refined.
I had an amp with no global feedback in the early 80's. Granted, the average consumer gear was made for average consumers, which was still better sound quality than the MP3s of today. The "hi-end" is much more diverse now than it ever was but, likely, if it weren't for the Asian market, most of the specialty brands would have disappeared by now.
What has changed is the normal size and shape of speakers. Consumers wanted less obtrusive, narrower designs and/or exotic decor. The 12 and 15 inch drivers of the 70's were replaced with 8" drivers in the 80's and 6" would probably be the norm today. Acoustic suspension is, for the most part, a remnant of the past.
Comparing old to new, you would have to account for relative cost to income and inflation. What you could afford in your 20's as compared to what you can afford in your 40's is irrelevant. Scarily similar though.
Inflation 7%
Initial $1000
+10 years $2000
+20 years $4000
+25 years $5500
Inflation 10%
Initial $1000
+10 years $2400
+20 years $6100
+25 years $9900
It's been my experience that approximate sound quality has the higher inflation rate, maybe higher. This doesn't mean that I'm going to start buying old stuff. That's just silly.
