The Source Audio Soundblox Pro Bass Envelope Filter is an evolution of its hugely popular predecessor, the standard Soundblox BEF. As before, there are 22 different envelope filter effects to choose from including 2 Pole and 4 Pole Low Pass variations, Single Peak, Triple Peak, Peak/Notch variations, as well as Phaser settings. Each of these settings can be further modified with a variety of control options including positive/negative filter sweeps, sweep range, attack and decay speed settings, or frequency range selection.
In this Pro version, users are able to choose from four different modulation sources including standard envelope filter sweeps, selectable LFO wave forms, a passive expression pedal and the Hot Hand motion sensing ring. A Source Audio expression pedal input can be used to control filter modulation like in a standard wah pedal or a wide variety of parameters including sweep range, effect selection, LFO speed and more. As in other Pro Series pedals, the BEF Pro features three footswitches to hold six customizable presets but also includes an option for Tap Tempo LFO on one of the footswitches.