Abstract: An exponential horn for use in a speaker is provided and includes a horn having a mouth, a throat and horn wall sections connecting the horn mouth and the horn throat. The horn wall sections define a horn whose cross sectional area progressively increases at a selected rate from a value S.sub.o at the horn throat substantially in accordance with the function S(z)=S.sub.o e.sup.mz. S(z) is the cross sectional area measured at any distance z from the horn throat, m is the flare constant defined as 4.pi.f.sub.c /c, where f.sub.c is the cutoff frequency of the horn and is from about 300 Hz to about 500 Hz. The horn mouth is rectangular in shape and has a perimeter substantially equal to one wavelength of the cutoff frequency of the horn. The distance between the horn throat and the horn mouth is from about 10 inches to about 17 inches.