From the Alto site:the Sub 16 is a Low Frequency processor based on the DSP of the DYNAMATE but with internal software featuring a unique set of specially developed algorithms. On anything from off-the-shelf sub-box systems to custom bass installations, this unit can achieve remarkable results.
The SUB16 applies a combination of equalization, low-pass and subsonic high-pass filtering, automatic gain control and broadcast-type bass modeling. Its aim is not only to enhance the different flavors of bass, but also to offer control and protection.
The 8 groups of presets cover a wide variety of applications. 5 of the groups use multiband equalization to create bass contours that bring out the best from a variety of music, from Jazz and Classical to Dance and the ultra-lows of 'Street Bass'. 2 other groups provide steep bandpass filtering with different center frequencies for the subsonic high-pass or low-pass - this helps safeguard your speakers without in any way altering the character of the bass. Finally a group for those with butt-kicking bass systems that just occasionally like to chill out by matching the bass to the output from the front speakers - without losing the feel of the music. Now you can do it with a few button presses and without altering any of your carefully set amp or crossover settings.
Both channels also feature switchable polarity (phase) and time alignment (signaldelay).