I apologize in advance for what might be spotty participation. I travel and am highly involved in multiple projects. But on the other hand, I do appreciate this forum and the enthusiastic involvement you folks have in the sport.
Regarding phase / time integration: An optimum axis exists where the drivers' acoustic centers are equidistant from the ear. Thiel designs for a 38" ear height as a seated average. Since the objective is a point source, the coaxial / coincident upper range driver obviates time arrival problems there. But the woofer is distant in order to place it on the sloped baffle at the proper distance from the average-height ear. The closer you get, distance error becomes more likely, but not necessarily so. (a three or more element system would have only one solution, but this 3-way with the coincident mid-tweeter makes it a 2-element system with multiple solutions.) A measurement from your ear to the tweeter and the dust-cap of the woofer should be identical. If not, adjust your ear height or speaker tilt accordingly. Pink noise is also a helpful tool in finding the sweet spot.
Subwoofer placement presents many problems; room mode minimization competes with other listening factors. A previous question about the "below 80Hz" crossover frequency is germane. The lower the frequency, the less the ear-brain specifies position. Bass waves are long, so bass is everywhere. However, the real-world crossover slope allows the subwoofer to contribute into the mid and upper bass where the ear-brain does specify position. I like Thiel's augment mode where the crossover to the woofer is first order and only the subwoofer is higher order. By the way, that is tuned as a 4th order Linkwitz-Riley. (Note: this stuff is from long-ago memory and I am not fact-checking as I write.) I use a stereo pair of Thiel SmartSubs and place them at the proper ear distance for best integration and use the room-boundary controls to adjust for early wall reflections. I find the system amazingly accurate and effective and the result surpasses any other system of which I am aware. Keep in mind that when conventional subwoofer integration is employed, the frequency response at the listener position is optimized at the expense of all other positions in the room. Therefore the average power response in the room is wrong and the resultant sound is artificial. Remember that the ear-brain is synthetic, we create or fabricate the sound we are hearing and when the sound doesn't match the room, that is unsettling. Bass is especially subject to needing "psychoacoustic rightness" in order to be emotionally gratifying. Note, I realize I am skating into my personal research and conclusions with insufficient contextualization, but I want to get the concepts on the table for your edification.
Bottom line: I think that bass-generation position is very important and I position my subwoofers where they are distance-correct and let any room problems be addressed via Thiel's sophisticated distance controls or room treatment. Remember the magic of corner-positioned bass dumps. Pressure develops at the (normal) 8 corners of the room. Make holes / dumps there and room problems are drastically reduced. (Open a door or window, install a vent, and so forth.)
Regarding music: I was a singer-songwriter and recordist, which partially led to the formation of Thiel Audio. I prefer acoustic, authentic, ethnic-folk music with stellar production values. I appreciate all forms of music. I like live or live in the studio recordings and find the current multi-miced and processed amalgums to be generally uninvolving and unsatisfactory, no matter how well done. Our early research that led to our phase coherent products was validated by the high level of emotional connection to the music when played via a coherent solution as opposed to the normal, hi-fi, higher-order crossover solutions. Long story, short answer: Coherent Sources are perceived as real.
I presently design and build acoustic guitars with related research, teaching and mentoring. Tonewood creation and sales are also part of my offering. I am presently creating a high-resolution record-playback system to record and store sound samples of guitars under development for direct A-B comparison via selective playback exactly where recorded. Earthworks mics and preamps, yet unchosen ADA conversion, REAPER DAW on Mac, Classé DR-6 pre and pair of DR-9 power amps (hot-rodded) with Sennheiser HD800S open and Beyerdynamic 770 closed headphones, all six 9s solid wire configured in house. The recording rig will be used mobile and in this multi-purpose studio. We build guitars in the recording-listening space.
That's about all for now. Back to work.
