Did you know the TRx2115A has optimized DSP settings to be used in high power music playback with the option of extended bass enhancement? The internal DSP (digital signal processing) is optimized for the time alignment and crossover point for the most efficient clean high output, but there are some optional added processing settings. The playback mode EQs the cabinet for high output music playback. This is ideal for DJs and banquet background music. DJs will especially like the bass enhance mode where another processing channel is inserted for frequencies below the normal capability of the cabinet. This processing channel boosts and regulates the power to these sub low frequencies, so they don't overwhelm the 15-inch speaker. This provides a smooth subwoofer-like output at moderate output levels. In smaller clubs or large halls not needing full output power, you can leave your subs at home and switch in the bass enhance mode. It's as if you have subwoofers connected to the system. If you need to be at full output levels, we recommend using external subwoofers, because the normal frequency range output of the TRx2115A can be twice as loud as the bass enhance mode. Not to worry, the internal DSP knows this and limits the bass enhance mode, so at high output levels your TRx2115A is safe even with bass enhance turned on.