SSL equalizers provide the ability for you to boost or cut the output of specific frequencies on the fly to fine tune your music and movies to suit your personal auditory preferences. The S4EQ is a four band preamp equalizer with front, rear and subwoofer outputs. It also features two illumination options (switch from cool green to sinister red at the touch of a button) and gold-plated connectors to allow for clean processing of sound. Signal-to-noise ratio >90dB. THD <0.01%. For technical questions about this product please visit our website, soundstormlab.com, or call a technician at 888.38.STORM. When it comes to building an impressive and affordable home-quality theater in your vehicle, Sound Storm is your solution. Let us prove to you that everything else is just noise.