I ran across this thread and can shed a little insight, not as the poster in the referenced thread, but as someone who is a fan of the approach he is taking and some of his equipment choices so bear with me. I'm not offended by being grouped with him or of the disdain for his approach, but I think there is at least some misunderstanding being displayed here. It might take a couple of replies to address the issues.
First, the 15" woofer he chose is about as good as it gets in my experience for his application. This is no typical pro audio driver, it was intended for home audio applications and just happens to work very well in PA systems, as well. It uses an old Altec cone profile, that when coupled with the phase plug shape that was chosen provides excellent performance (even off axis) compared to any other 15" driver I've encountered. It's pretty well flat to 1500hz even at 45 degrees off axis. On axis, it's well behaved up until about 4khz. It's very low and consistent inductance keeps performance consistent even when the volume knob moves towards 11. It displays lower power compression than any driver I've ever encountered. Even at rated power (500w), it's power compression is significantly better than most of it's competition at much lower power levels. I believe the JBL 2226 shows almost 3dB of power compression at 500w compared to about 1dB for the AE TD15M. The consistent and low Le makes it one of the easiest drivers to work with, as well. It's impedance is smooth consistent for a much wider range than even most smaller drivers making it easy to drive and easy to work with. In short, it's the best midbass driver I've ever used in any of my designs. It's dynamic ability is unparalleled to a degree that listening to some traditional favorites for midbass leaves me flat now (including dynaudio, seas excel, scanspeak revelators, and even some PHLs).
Second, if there is an issue with his design, I'd suggest that it's that his chosen horn isn't an ideal match for the midbass choice. The directivity match won't be as ideal as the transition from a 10" driver to the chosen waveguide. The superb off axis performance of the TD15M mitigates some of the issues, but they are still there. The coverage window won't be quite as wide vertically with a 15" driver but as long as you aren't using them as near field monitors, even this shouldn't be an issue in a normal room. The SEOS-12 + compression driver (actually, any of the SEOS designs) delivers very smooth and very consistent performance over a wide range. I've seen them used as low as 1200hz with the right compression driver choice and they are almost uncanny in their ability to sound the same anywhere in the room rather than the typical dome tweeters off axis performance being tonally different than it's on axis performance. There is a lot to be said for the constant directivity approach, especially in terms of mitigating room acoustics issues.
To address the original rant and to confirm some of the issues proposed, I do have to mention that I was a long term horn hater and believed that pro audio parts didn't belong in a typical listening room. This was often confirmed by listening to things like Altec A7s in basements and small rooms, or Klipschorns, etc. About 13 years ago, I had the opportunity to hear some Lambda Acoustics Unity Horns. I had very low expectations going in for the horn piece but knew I liked the woofers. Frankly, I was blown away and I heard them in two settings, in a large warehouse and in a intimate living room setting. There was no sense of the speaker being too large for the room, just the opposite. It sounded like I was listening to a small monitor speaker with a soft dome tweeter, but just with what felt like unlimited dynamics and scale. I'd never experienced anything like it, they just disappeared despite being physically overwhelming. The effortlessness has been unmatched to this day and it set me off on a quest to find out what was responsible for the performance. With a bit of elevator thinking and some actual research into small room acoustics, I've pretty well determined that my preconceived notions that big speakers can't work well in small rooms has been proven wrong. This isn't to say that listening to some LaScalas in a 12x10 living room wouldn't be painful, or that horns in general work well in small spaces, but a very good waveguide with constant directivity and smooth response can work superbly in small rooms because of their ability to dminish many of the problems we typically face with early reflections, for instance.
If I had even a small bit of advice for him, the only thing I would have suggested is to bump up to the SEOS-15 or SEOS-18 for a more ideal match.
I think many of you would be stunned by the performance he could achieve with those parts.
