A liquid ejector increases the density of acoustic energy to eject droplets efficiently. Acoustic waves are introduced in generally planar form from a piezoelectric transducer into a liquid ink in a reservoir and are reflected from a reflecting wall of the reservoir. The reflecting wall defines a parabola in cross section. An ejection opening is located near a focal point of the parabola, opposite the transducer. The acoustic waves focus at the ejection opening, increasing the density of the acoustic energy in the ink at the ejection opening. Thus, ink droplets are ejected efficiently from the ejection opening.