Crest Factor Before we can discuss amplifier headroom, we first need to discuss the music we are listening to. And the concept we need to understand is that of crest factor. Sine waves are the simplest tone. Sine waves are the "test tones" that many people use in this hobby for various reasons, although most likely familiar to everyone as the source used in the typical SPL competition. Sine waves are a periodic waveform. That is, these sine waves or test tones are quite simply a repeating wavef