Abstract: An exponential folded horn loudspeaker enclosure is built so that all of its components are coaxial with respect to a line that is equidistant from three cooperating surfaces, including floor or ceiling, as well as the customary two walls of a corner. Perfect symmetry with all three cooperating surfaces permits a smooth transition to these surfaces, so that they become a balanced extension of the exponential horn, more than doubling its effective length. Approaching the configuration of a large ideal horn, this geometry is uniquely free of discontinuities and artificial resonances that are needed in other enclosures for boosting low frequency response; therefore, efficiency and fidelity of low frequency response are greatly increased over other enclosures of comparable size.