Tom - I would be the thermal culprit. I think thermal management is more important than generally believed. I am systematically addressing the mantra of shortcomings of Thiel speakers over four decades. Among those complaints is "they’re fine for vocal or folk or light jazz, but don’t try to rock with them" and variations thereof. It’s true, our development regime included primarily those mild forms of music. Of course we did what we could to manage heat if it didn’t cost much. When we began using aluminum cones, we went to aluminum voice coil formers. Those coupled cones could easily get hot enough to vaporize spit. The 01 and 03 were sealed boxes and we routinely got burned-out voice coils and resistors and melted caps if too close to a resistor. (Aluminum VCs introduce eddy currents and had to be abandoned.) The stories go on.
A big aha was when I got some Thiel subs. Nice subs. One solution is a thermistor on the voice coil to feed more power to overcome the higher resistance of a hot VC. Hmmm, not sustainable. And on and on. I want to dissipate, not overcome.
Now, consider the excruciating detail of Jim’s reciprocal circuits to correct driver behavior, control impedance rise and smooth out resonances. Those models are temperature critical. And those selected, ideal temperatures rarely exist in real life. A cold speaker will not sound good nor measure well. A hot speaker’s measurements are far outside of acceptability, and sound bad. In pro speakers many strategies are employed to keep the temp right. Ever see the fans blowing on the ribbed magnets of stadium drivers? Ever see one whose fan fails? You get the picture.
So, I have put thermal performance way up the list of necessary solutions. I’ve developed some techniques that stabilize temperatures while doing no harm. Regarding parallel resistors, sometimes yes. A modeling program or a thermometer or your finger can identify which resistors would benefit. Also, coils generate heat. Stand them on standoffs and consider air-flow around them. (They get hot enough to melt the varnish holding them together.)
Regarding boundary turbulence, my aha moment was hearing a particular harshness when I got some CS3.6s. We’ve addressed it here before. It turned out to be boundary layer perturbation, primarily on the flat areas of the baffle, but also on the cones and surrounds. By definition there is no motion at the fluid (air) / solid interface, and laminar flow increases as a function of distance, depending on properties of the fluid. Air isn’t linear per amplitude. Nano models built for aerospace research conclude the boundary layer to act essentially chaotic, like whitewater rapids or worse. My approach includes study of theory and extensive experimentation. My goal is to manage the propagation from the high-impedance sheer (source) wave to the uniform low-impedance transmission medium of the room air. I am using micro scale textures, some fixed and some mobile. Douglas Pauley has patented some solutions which we are jointly developing via our 02 workhorses. The resultant ease, naturalness and articulation are improved to a surprising degree.
Your paint is probably addressing the same phenomena. In early Thiel days we discovered that a particular light spatter coat on the baffle sounded better than flat-smooth. I see that these present 2008ish 2.4s still have that spatter pattern on the flat baffle, but are smooth on the curved edges. My speculation is that smooth passed marketing with higher marks, and the curved sections are far less problematic than flats. I like my results with cellulose micro flocking on those curves.
Your room treatments and active laminar flow device sound intriguing. For now my situation constrains me to concentrating on the speaker itself. Someday I hope to be apprised of what you’re doing and how I might get my mind around it.
The question always comes up whether enough listeners care enough to support these exotic tweaks. I don’t know, but it sure is fun learning about how things work. Einstein said something like "relativity is easy, fluid dynamics is hard." We’re wading in fluid dynamics.
