Is it taboo to mod a speaker?

I own Magnepan speakers and people mod the heck out of them! fuse bypass, tweeter attenuation bypass, crossover upgrades and internal re-wiring. I won't do any of it(affraid of lost resale value) and maggies are unusually mod friendly. I wouldn't think of trying to upgrade a speaker, if for no better reason then the lost value. I am baffled how some folks think they know more about designing speakers then those who do it for a living! Of course a speaker is designed with in a certain price range(compromises are made) but they work with what they have as a whole! taking or adding anything to that is a risk- the old the total is greater then the sum of its part theory. I wouldn't plan on getting much out of any modified component, its always so hard to prove(I recall more then 1 dispute here is due to a mod)- of course all of this doesn't mean that some folks don't get lucky either- do it right and you may never worry about resale value :o)

Often the high cost of modifying speakers...not to mention the uncertain outcome...is best applied to simply upgrading to an entirely new speaker...which exhibit some of the attributes one was looking to modify in their original speakers...

Everyone else has covered pretty well. The only mods I've done and would recommend to speakers is deadening the cabinets with "dynamat" equivalent. That one is usually an improvement with no downsides/tradeoffs. Changing a driver and doing it properely is quite a bit of work and usually not worth it. I've read conflicting claims about the foam rings to help with diffraction. Someone has done some measurements on them and they don't quite work as the manufacturer claims--I believe.

Most speaker mods involve things like crossover component quality upgrades, internal wire upgrades, or binding post upgrades, in addition to various cabinet-deadening strategies such as coatings, adhesives/sealants, or sheet appliques. Some folks go as far as changing, removing, or augmenting the cabinet stuffing materials, but both that, and any driver changes done in isolation (in other words, not as a manufacturer-sourced upgrade in conjunction with adequate testing and concurrent crossover mods as needed), will stand a very good likelihood of changing the sound in unintended - and probably detrimental to accuracy - ways. The only other things commonly done involve various stands or footers. I agree with Phasecorrect: If you want an upgrade here, you're better off looking for different speakers in most cases.

Best done by the original designer of the speaker!Changeing XO's or using up to date parts is a plus.Little tweeks like changeing Binding Post and Internal Wiring can be DIY.