UMII-18 requires a custom woofer cutout in all our 18" cabs. Please contact us if you intend to use this woofer!

Classic MBMs (Non-roundover) 18" & 21" Flat Packs


  • If your system seems to lack that "mid-bass" punch, you may need some MBMs (which is short for "music-bass modules" or "mid-bass modules").
  • The GSG "Roundover Series" MBM's are designed to complement theMarty Sub V2.0 Roundover line-up aesthetically. The Roundover MBM-18 has the same width and depth as the Marty Sub V2.0 line-up as well as the same height as the Roundover Marty Cube.  The 21" MBM is the same size as the 21" Roundover Marty Cube.
  • The MBM-18 is tuned to 27Hz and works great with a number of pro-audio drivers (Dayton PA460, LaVoce SAF184.03, etc.)
  • The MBM-21 is tuned to 28Hz and kicks up the output.  It works great with a number of 21" pro-audio drivers.  At this time, we recommend the LaVoce SAN214.50.

Additional information on MBMs can be found in the FAQ.

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