Function: Testis-specific potassium channel activated by both intracellular pH and membrane voltage that mediates export of K(+). May be involved in sperm capacitation and/or the acrosome reaction, essential steps in fertilization where changes in both intracellular pH and membrane potential are known to occur. In contrast to KCNMA1/SLO1, it is not activated by Ca(2+) or Mg(2+) (By similarity).