The loudspeaker engineering community has known this since the late 1940s. Neither Leo Fender nor Jim Marshall were loudspeaker engineers, so the blame for poor electric instrument speaker designs that persist to this day can be attributed to them.
The one band I'm in has just invested in active PA speakers, it's a bass bin each side with a vertical array of eight tiny 3" speakers on top. Sounds great.
The other band has an active bass bin each side and an active FRFR speaker on a pole above - similar principle.