replace Mid-range speaker of Green Mountain Audio Imago VI

Thanks for your advice. I removed and reinstalled the speaker and couldn't find any cause for what I thought was buzzing. Upon careful listening, I determined the annoying sound was either distortion or crackling air which occurred only in some recordings and mostly during quiet/soft passages of piano solos. For example, on Reference Recordings' Dick Hyman Plays Fats Waller, Track1 has no distortion, but Track 2 has distortion throughout, especially when it starts softly. The speaker is an ETON 4-300-25sHEXb. Here's a photo of this speaker. If I replace it, how likely will it sound different from the good one without the crossover being adjusted to compensate, and if needing adjustment, how can I get that done? What is the best way to source a new one?

The crossover plays an essential role in what the speakers sound like.  If  you simply replace what you think is a faulty driver with an exact replacement, the crossover inside the speaker should perform as it did with the original, though some break in time for the suspension may be necessary.  Perhaps I'm not fully understanding the question, but before replacing a driver, I'd try switching the drivers between your two speakers and see if the problem follows the alleged faulty driver....should only take a few minutes, and there's no cost.  If the problem follows, it narrows it to the driver.

Thanks to all responders. I found a good repair shop (South Florida Speaker Repair) who repaired the surround in each driver. They not only look like new, they sound as wonderful as they used to. Heaven has returned.

Congrats! They really are great speakers.