DS1398 2x4" Horizontally Opposed Driver Masking Speaker w/ClipThe DS1398 contains dual, horizontally opposed speakers which produce uniform sound dispersion ideally suited for reverberant under floor cavities or shallow ceiling plenums. Product Features For use in floor cavities as shallow as 1. 75 Performance engineered dual drivers with tuned ports well suited for sound masking ETL listed to conform to UL 1480 and CSA C22. 2 62368 1 Dual horizontally opposed high performance drivers 80. 7dB SPL Front Vented