SP158A, SPT15A, SP308A, SPT30A Horn Loudspeakers Installation Instructions STEP 1 For sassier installation, remove the mounting base from the speaker by unscrewing the wing nut while at the same time pressing inwardly on the wing nut. Place the mounting base flush on the mounting surface and mark the location of the thees holes with either a marker or chisel. It is important that the three holes be exactly aligned with the mounting bass, otherwise you might stress the base or make the connection unsteady.