The JBL's SUB18 is a high-output 18" studio subwoofer with a very low frequency response that can be used for applications that require a high, continuous output. This powered speaker is appropriate for demanding dance music production as well as film post production applications, having an in-room response below 18 Hz and a 137 dB peak output. When used with JBL's M2 Master Reference Monitor system (sold separately), the SUB18 allows the M2 system to provide three times more output.