The Collaborative International Dictionary of English v.0.48:
Sub-base \Sub"-base`\, n. (Arch.) The lowest member of a base when divided horizontally, or of a baseboard, pedestal, or the like. [1913 Webster]The Collaborative International Dictionary of English v.0.48:
Sub-bass \Sub"-bass`\, n. (Mus.) The deepest pedal stop, or the lowest tones of an organ; the fundamental or ground bass. [Written also sub-base.] --Ayliffe. [1913 Webster]