Being one who has "hot rodded" speakers for several decades (including earning a patent for my own design):
It is impossible to describe the before/after results of "upgrades" unless you strap yourself down in front of the speakers and actually listened to them. Even those with excellent command of vocabulary, and engineering degrees can't fully encapsulate the sonic benefits of "doing it better."
My goal is never to "paint a mustache on the Mona Lisa", but rather respect the intent of the original designer who, perhaps, would have benefited from being free from production considerations, ease of in field service, time and budget constraints. And, of course, newer materials and newer "thinking" that were not around when the speaker was developed in many cases. Not long ago, I saw a promotional video of a well-respected high-end manufacturer introducing their new "flagship" model, highlighting the assembly process. A pair of good $30 side cutters and a roll of silver solder would have immediately improved the focus and detail, while reducing the harshness of the upper midrange As I stated before: "production efficiency, and ease of service in the field." Price: over $40k/pair.
We perform mods on speakers in various price ranges, including vintage speakers. I am still surprised (often stunned) just how much music you can get out of these boxes via cheap and/or vintage drivers when you get things out of way that make them sound worse -- or just open them up, and let them play.
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