These monitor speakers are considered by many as the finest studio monitors ever made, and are used by a large proportion of the highest profile mastering and recording studios thought the world. They comprise of twin 15" bass drivers, a mid range and tweeter per unit. Our speakers are 'soffit' mounted (in the speaker wall) for the perfect sound as designed. The ATC SCM-300A system includes a proprietary, stand-alone, 140-pound chassis sporting tri-amplified (275-watt LF, 200-watt MF and 100-watt HF per channel), class-A-biased stereo amplifiers and ATC-provided speaker cabling. These are the world renowned P4 amplifiers.