Increasing the efficiency of carbon nano tube, thin film loudspeakers

Components of a small prototype carbon nanotube (CNT), thin film loudspeaker were designed and constructed in order determine their sound generation efficiency and sound pressure output. The loudspeaker efficiency was increased as the number of CNT film layers was decreased. The films, however, could withstand higher input power levels and generate higher sound pressures with more layers, up to four layers. With more than 4 CNT film layers, the input power level that resulted in catastrophic burnout was reduced due, presumably, to non-uniformities in the overlapping CNT film layers. Outside an enclosure, the CNT film layer mounted on a finned heat sink and base plate displayed unwanted, narrowband band-stop behavior. Neither the height nor spacing of the fins had a significant effect on the frequency, bandwidth or magnitude of the reduction in sound pressure. When the base plate with the heat sink was placed inside the enclosure, the resonant modes of the enclosure reduced the effect of the heat sink stop band. Combined with a horn and with all efficiency improvements incorporated into it, the small prototype CNT loudspeaker's efficiency was 10 to 15 dB greater than that of a much larger prototype CNT thin film loudspeaker.