Tweeter Dome Puncture

Yeah, the dome is the driven element of the tweeter - it's what moves the air. Although a pinhole sized puncture in and of itself is probably not going to appreciably change the sound of the tweeter, it may be indicative of some sort of past impact that could have damaged it in other ways you can't see. Depending on who made the driver and how old it is, you may be able to either buy an identical replacement whole driver, or sometimes you can obtain a kit to replace just the dome/voicecoil/leadouts assembly while still reusing the same motor/faceplate structure for less money. In either case it probably won't be terribly expensive if it is available, but research it first to make sure it can be easily done, and maybe have the seller take that expense into account on the price.

There seems to be some confusion among us respondees as to what design of tweeter you are dealing with here. If the tweeter is a dome tweeter, then this is not merely a dustcap, as I stated above; that would only apply if it is instead a cone tweeter. But in either case, the repair method that Calvin refers to is what I was talking about when I said it could indicate further damage having been done in the past than you can now see. Listen up close to that tweeter alone to make sure no rasping or vibrating noises are coming from it that might signify a misaligned voice coil. Do the same with the other tweeter as a comparision.