A loudspeaker project runs in order: pick the driver from its parameters, choose the loading and volume, design the crossover, then measure. Skipping a step almost always means going back.
These five texts follow that sequence. They do not replace simulation software, but they explain what the numbers mean and where the costly traps sit.
They assume no prior build. Where a term matters, it is defined on first use; where a figure matters, the reason it matters is given rather than the figure alone. Measurement closes every one of them, because a crossover that looks right on paper still has to be checked in the room it will work in.