The term 'woofer output' refers to the sound produced by a speaker system. The two crossword solutions, ARF and BASS, are both related to this term. ARF stands for Audio Reproduction Frequency, which is the range of frequencies that a speaker can reproduce. BASS stands for BASS Amplitude Sound System, which is a type of speaker system that produces low-frequency sound waves. Together, these two solutions indicate that woofer output is the sound produced by a speaker system that is capable of reproducing low-frequency sound waves.