HPL2 Processor Ideal headphone sound with HPL binaural. It is very important to reproduce the sound heard on the speakers with headphones without disturbing the mix balance of the sound source in order to obtain the original sound. This plug-in simulates ideal room acoustics and front-facing speaker placement by processing stereo sources with binaural technology. It eliminates the problem of hollow sound and horizontal sound source localization caused by using headphones, and provides a new perspective for grasping the mix.