I don't think it is fair to assess all of the Perception set surround mixes based on the 5.1 mix of the first album. I think one has to keep in mind that for some albums they may have only been recorded on three or four track tape. There is only so much an engineer can do to mix an album in 5.1 when they may only have three or four tracks to work with. Also, just because you have four tracks to work with, it doesn't mean that you have every instrument isolated in each track, you may mave multiple instruments bounced onto the same track, so there is only so much actual seperation one can extract for a surround mix, without getting into digital tools to try to isolate tracks or faux-surround.
In the case of The Doors' first album, Bruce Botnick has said it was recorded on four track, though he mentions (in this article:
SoundBard – Bruce Botnick on the Perception of Surround Sound and Harnessing The Doors’ Hi-Res Audio Fire) that the way it was originally recorded really only gave him three tracks to work with for most songs for that album, with the exception of "The End", where Botnick mentions that for that song they had every member of the band isloated on an individual track of the 4 track tape. Botnick even says in the interview that starting with the Doors' second album, Strange Days, they moved up to 8-track, which gave him much more to work with for surround mixing the rest of the albums:
"Botnick: Oh yeah. When we got into the second album and beyond, we were into 8-track. I could position things in the rear speakers. I feel when people go out and get a surround disc, they should
get a surround disc. Bring the neighbors over to hear a surround system! If there’s nothing coming out of the surround speakers but reverb, it’s a disappointment."
(Edited for clarity)
