low-curvature vertical wavefront

[surfer]

Из спецификации акустической системы line array. Помогите, плиз, разобраться с такими терминами как low-curvature vertical wavefront, HF curvature в таком контексте:

The W8LC’s HF section comprises three 1" horn elements to produce a low-curvature vertical wavefront with an efficiency of 109dB at 1m for a 1W input. This optimal HF curvature enables W8LC enclosures within the array to be splayed up to 7.5° without introducing gaps in the HF vertical coverage.