Physically separated MTM drivers acoustically interfere off-axis because both radiate overlapping high frequencies

Evidence

In Figure 8.9(a) it is seen that the MTM (Midrange-Tweeter-Midrange) design has two “midranges”, which actually are woofer/midranges. These acoustically interfere with each other at increasing horizontal angles because they are physically separated and both radiate sound up to high frequencies in order to cross over to the tweeter. — Toole, Floyd E, Sound reproduction- the acoustics and…, 817

Categorization

• DEFINE: Explains the mechanism behind the MTM horizontal dispersion problem: two spaced drivers sharing a high-frequency crossover range cancel off-axis.