Equalization cannot fix loudspeaker directivity problems because it only changes frequency response.

Evidence

An obvious message from Figure 12.12 is that measuring a steady-state room curve and equalizing it cannot guarantee excellent sound. Equalization can only change frequency response. In the loudspeaker in Figure 12.12(b) the dominant problem is non-uniform directivity as a function of frequency, and equalization cannot change directivity. The solution is a better loudspeaker. If the only information available is a room curve, this fact is not known. Comprehensive anechoic data on the loudspeaker would have revealed this in advance. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1322

Categorization

• ADDENDUM: Reinforces the ‘trees as infrastructure’ theme’s argument that single-point fixes (like EQ) can’t fix systemic design flaws — here, directivity is systemic while EQ is a point fix.