I think a lot of the 'disagreement' from the purist standpoint of modifying original speakers comes from the perception of the workmanship, and the degree of modification. Take those -1b's that prompted this thread. If they were done like so....
-Perfectly finish the front face of the RD driver so that no screws or frame or anything 'unfinished' remains. The finish of the front face has to match the original wood and finish. Some clever woodworking involved here, so that only the radiating element of the driver is showing.
-Retain the tweeters, or better yet, add a bunch more to make it a true line array. Think Genesis II, 350SE, 2.2, that sort of thing...only with EMITs.
-Retain the original grillwork instead of the funky looking grill frames they put on there. Redo the grilles in perfect new black cloth.
Stuff like this results in better performance if done right, but also in a much less drastic appearance change, and a look that is 'right' for the speaker. Maybe this would satisfy the purist view a little better? I don't know, you guys tell me.
Back to the degree of modification. I always find it interesting that many purists strongly advocate for updating things like capacitors in the crossover network, but often stop there. Well, when you do that the speakers aren't 100% original anymore, and we know that the sound does change. So it always makes me curious...just how much is okay to do on the speakers without losing the 'purist' goal?
I guess I have a slightly different perspective. First, I do agree that there is something very special and very nostalgic about preserving a perfect set of speakers in original condition. And a speaker that has been kept/restored to that condition almost undoubtedly has greater value than a modded one. A perfect set of -1b's is a piece of audio history, and should be valued for that.
From my typical point of view, though, if you're going to take a step like putting new caps in the crossover network (for example), if you REALLY want your money's worth out of those caps- if you really want to hear the improved changes, then you should take other steps as well. Beef up the structure, do some vibration and resonance control, upgrade the electrical connections, whatever. All these little changes each allow the other ones to come through a little bit better, so you really get your money's worth out of each change.
So, I guess it's all about what you're after. Museum quality, or the potential of increased performance by removing cost constraints and incorporating more modern technology. For me, I think if you're going for the second option, it should definitely be done in a way that looks absolutely gnat's ass, though, and should make somebody go "Whoa!!!!" rather than "Ugh!" before the Play button is even pressed.
G~