And without needing to handle bass, it doesn't have to. This sort of loading really controls the drivers and the bandpass is awesome for this as he can get a steep slope without phase shift. IEMs play by the rules of physics but have a different set of parameters than speakers as you're dealing with pressure waves instead of soundwaves. Though technically possible, this design would be extremely difficult to get a good result from a loudspeaker but is great for this use. I suppose you could actually do something like this for IEM bass as well but it gets large. They'd need strong motors, heavy diaphragms and a much larger tube. The passive EQ you'd need to sound linear in the low bass would be tough as well. When Jerry was saying that dynamics are sloppy, I think he meant it in a relative way. It's difficult to get both extension, perceived linearity and the sort of delineation at the same time compared to how he can control the character and response of his BA designs. He also requires great isolation so venting outside the shell is not in the mix. That would mean a small diaphragm dynamic with long excursion to achieve a low enough fundamental resonance point which will generally show less efficiency, control and more distortion. The limited shell volume (sans vent) also prevents using multiples as it's effectively the same as using one larger one. Smaller diaphragm that goes low is exactly what you want for this purpose (BA). The limit would be amplitude but he's crossed that bridge by tailoring multiple drivers a long time ago.