Check the listing for details. Maag Audio EQ4M Mastering 6-band Parametric Equalizer. Condition: Very Good - Refurbished. Listed at 2245.50 USD. Maag Audio's EQ4M mastering equalizer is a no-compromise dual-channel, 6-band unit that works differently than other EQs you've likely used, with ultra-wide-range control from the subsonic, well into dog-frequency territory. The EQ4M's six bands, which include Maag's acclaimed Air Band, start with Sub, a +15dB/-4.5dB bell curve fixed at 10Hz - Maag's nod to the LF realities of modern digital recording. Moving up, you have the same (+15dB/-4.5dB) bells fixed at 40Hz, 160Hz, 650Hz, and 2.5kHz, whereupon the EQ4M's Air Band takes over. Air Band gives you boost-only (+15dB) shelving at 2.5kHz, 5kHz, 10kHz, 15kHz, 20kHz, or 40kHz. Owing to the transitional slope, frequencies below the shelf peaks are affected as well.