I'm a stickler for high-frequency reproduction. While the majority of instruments don't create fundamental notes in the range of most tweeters, I do think that accurate treble harmonics separates good speakers from exceptional ones that are capable of placing what sounds like live instruments into the room. In my experience, most speakers fail at this, as the simple and easy path to what might initially sound like detailed and "live" sounding highs are recessed mids, tilted up treble, or a combination of both. This strategy wears out its welcome quickly. It takes a high degree of experience, engineering, crossover design, driver selection, etc, to do this right. I've owned very good AMT speakers, Revel Be series speakers, Ascend RAAL ribbon speakers (as well as their LX model which uses a fantastic SEAS dome tweeter), and my desire for good treble steered me towards all of them.
I blindly purchased KH 150s having never heard a Neumann speaker before, not knowing what exactly to expect of their high-frequency abilities. Clearly they measure ruler flat with impressively low distortion, but would they provide that otherwise difficult-to-define sense of air and "liveness" that I prefer? For the most part, yes, they do. I'd gladly put them up against the Revels and the Ascend LXs in this area, and it would not surprise me if in blind testing, the 150s were actually preferred. To me, they only take a back seat to the Ascend ELX ribbon towers. That's not at all a knock on the Neumanns as the ELXs are freakishly good, particularly for their size and price point. The Ascends are also quite wide in dispersion, so in the right rooms and at the right listening distances, they can provide a sense of spaciousness that would be very difficult for a narrower-dispersion speaker to match. The Neumanns are intentionally designed for narrower, controlled dispersion. Changing out the tweeter to a completely new model because a few people on the internet say they're old isn't going to change that aspect of Neumann's design. And without going to a completely different design, I'm at a loss as to what could be appreciably improved.
