The TAS review for the s-9 is out. It's an interesting one. Since it's not available for free, I guess I'll post about the nitpicks. The reviewer has 2 nitpicks, one of which ends up being only half a nitpick:
1) because of the waveguide, he feels that the treble drops off a lot, and perhaps too much, depending on personal taste, when moving off axis. In truth, more of the treble drops off at the same rate, since the waveguide creates limited constant directivity. What he means is that in a conventional speaker without a waveguide, the 2-10 or so khz range remains high, even very far off axis, while the top octave or so drops likes a rock, whereas with the waveguide, the entire range of the tweeter falls off more evenly. He implies that this affects off axis listening - what he more or less literally says is that unless you are in the sweet spot - which he implies is small - you'll never hear what the speaker is truly capable of. However, in an article on his personal website, he states this: "True stereo for off*axis listeners is impossible: An approximate version of the correct sonic picture is all that can be provided." In my experience, the off axis response is certainly no worse than other conventional speakers. It isn't as good as the sweet spot, and it's obvious since the sweet spot is so sweet, but that isn't to say that the rest of the room doesn't sound like music. In fact, because of the limited high frequency being dispersed into the room off axis, the reviewer claims that this more closely emulates live music, where there is considerably less top end in the reverberant field.
2) He mentions that there is a small peak at 2khz and has shown this via measurements (not posted in the review.) This is odd because I don't recall seeing that peak in the anechoic plots that were provided for the speaker at the showing I attended, and I'm not sure I heard it. The reviewer used a relatively long gate. If the measurements he took are supposed to be valid from 700hz up. I'll take his word for it, he's a math professor at UCLA and I bet he heard them a heck of a lot longer than I did.
I'll save the big praise portions of the review for those actually interested in the speaker/review. Well, here's one comment, "I had an almost immediate memory of the real sound of a string orchestra. Few speakers fail to be humiliated by such a recent memory of reality. The S9s were really convincing in this nearly direct comparison with live music. And with their unstrained dynamic behavior, they were convincing on large scale music like full orchestra, as well. [Referring to listening to the s-9 during the time that he was also preparing the St. Matthew's Chamber Orchestra for a concert.]"
And closing comments, "To me the S9s embody so many effective and unusual ideas that they unquestionably need to be heard and thought about. One might hope for a bit smoother mid/upper-mid/lower treble. But that aside, will the controlled radiation pattern and the associated approach to overall room sound seem as wonderfully natural to you as it did to me? Listen for yourself, and be sure that you listen positioned correctly. Then think about what live music really sounds like. I think you will come away as impressed as I did."
He posted some further remarks and measurements on his webpage: http://regonaudio.com/NuForce%20S9%2...upplement.html
Above 200hz, the THD barely peeks over 0.3% a couple times. Not too bad. He also claims (less clearly in the review than on his personal page) that the 2khz peak is basically easily fixed with eq.