Signal Processing Huber, Ch. 12
Plug-ins • Software-based processing • Plug-in format (host system) • TDM (Digidesign ProTools Windows/Mac) • VST (Windows/Mac) • Audio Units (Mac) • DirectX (Windows) • MAS (MOTU for Windows/Mac) • RTAS (Digidesign ProTools LE Windows/Mac)
Inline vs. Side-Chain Processing • Inline (insert): all signal routed through processor. Output is entirely the signal from the processor. (EQ, Dynamics, Pitch correction) • Side-Chain (aux send): copy of the signal is routed through processor. Output is a mix of unprocessed and processed signal. (Reverb, chorusing, etc.)
Reasons to use EQ (Huber p. 445) • To correct for specific problems in a recording or room • To overcome deficiencies in the frequency response of a mic or in the sound of an instrument • To allow contrasting sounds from several mics or tape tracks to blend together in a mix • To increase the separation between mics or recorded audio tracks by seeking to reduce those frequencies that excessively “leak” between channels. • To alter a sound purely for musical or creative reasons.
Peaking Filters • Most common form of EQ curve • Bell curve frequency response around a center frequency • Q/Bandwidth • BW measures the range of frequencies between the upper and lower -3 dB (half-power) points on the curve • Q is inversely related to bandwidth Q = CF/BW
Shelving Filters • Rise of drop in frequency response at a selected frequency, that tapers off to a preset level for the remainder of the spectrum • Commonly found on consumer bass/treble controls
Dynamic Range Processors • Compressor • Expander • Limiter
Compression • Proportionately (by a ratio) reduces the amplitude of a signal that rises above a user-definable level (threshold). • Electronics/amp can manage the dynamic range • Dynamic range is appropriate to overall level of playback medium • Better match instrument dynamic range to other recorded tracks in mix.
Compression Settings • Input Gain • Threshold • Output Gain • Ratio • Attack time • Release time • Meter display