Full-range speakers have many problems, that's why we use multiple drivers in the first place. Well designed speakers don't destroy the phase either, and even

Full-range speakers have many problems, that's why we use multiple drivers in the first place. Well designed speakers don't destroy the phase either, and even if they did, which they don't, there's also active crossovers that can do all kinds of fancy stuff. Nothing's perfect, but multi-way speakers are a much better solution than expecting a single speaker go from 30-20000Hz.