QSC AD-C.SUB AcousticDesign 6.5-Inch Ceiling SubwooferA high quality 6. 5 weather treated paper cone woofer on a dual voice coil in the AD C. SUB ceiling subwoofer from QSC ensures optimal thermal dissipation and a higher output with its small form factor. Low loss, low saturation 100W transformer with selectable taps (including 4 bypass) keeps frequency response accurate and consistent even in 70 100V applications. The transformer operates using a rotary selector under the snap fit magnetically attached