Mastering Audio – the art and the science 2nd edition by Bob Katz

  1. Ear Training Excersizes
    1. Learn to Recognize the Frequency Ranges
      1. Start ear training with pink noise and then move to music
      2. Boost each range of a 1/3 octave graphic eq until you can recognize the approximate range
    2. Learn the Effects of Bandwidth Limiting
    3. Learn to Identify Comb Filtering
    4. Listen to the Sound of Great Recordings well-reproduced. Perception of Dynamics, Space and Depth
    5. Proximity Effect Game
    6. The Sound of Overload
    7. Identify the Sound Quality of Different Reverb Chambers
    8. The differences between sampled pianos and the real thing
    9. Mono, Weak Stereo, Good Stereo
    10. Listening Acuity – Identifying Tiny Differences
    11. Recognize Hum Frequencies
      1. 50hz, 60hz, 100hz, 120hz, 150, 180hz
  2. Ensure devices ‘bypass’ are really bypass.
    1. Do this by taking the signal and duplicating it and inverting it and play with original signal to ensure no sound
  3. Dithering
    1. When reducing wordlength, add dither
    2. Avoid dithering to 16 bits more than once on any project
    3. In any project, sample rate conversion should be the next to the last operation and dithering to the shortest wordlength must be the last
    4. Peak limited material with high levels may overload with the addition of dither and some peaks could take it slightly past the top so to be sae, drop the gain of peak limited material by 0.1db when dithering
  4. Meters
    1. Reconstruction Meter: Even more sophisticated
      1. Is basically an oversampling meter
      2. TC Electronic (System 6000) and Sony (Oxford) have an oversampling limiter and reconstruction peak meter. RME’s Digicheck software includes an oversampling meter
    2. Practice Safe Levels
      1. If you are mixing with a standard digital meter, keep peaks below -3dbFS especially if you are using aggressive bus processing
    3. Peak Level Practice for Good 24-bit Recording
      1. Would have to lower the peak level of a24-bit recording by 48db to yield an effective 16 bit recording
      2. Won’t lose any dynamic range if you peak to -3dBFS or even as low as -10dBFS and end up with cleaner sound
  5. Gain Staging – Digital Chains
    1. Headroom of the Processor
      1. Can test digital systems for headroom, clipping and noise using digitally generated test tones and FFT analyzers
      2. Feed a 1khz sine wave at about -6dbFS and turn up the 1khz eq by 10db and observing the output clips. Then turn down the output gain control until the output is below 0dbFS and verify by listening or FFT measurements that the internal clipping stops
  6. How to put and album in order
    1. How to end the album. It is almost never a big uptempo number.
    2. Spacing the album
      1. Another type of space is to make the downbeat of the next song be in time with the rhythm of the previous. This can sound very nice but not if overused.
      2. Vinyl and tape noise act as a filler. When there is dead silence between tracks, spaces always seem longer
    3. Redbook – The Sony/Philips Redbook specifies all parameters for a CD
    4. Mix engineers send unfaded material so it can be refined in the mastering
    5. Adding tails – trick is to feed just the tail of the music into a high-quality artificial verb and capture that in the workstation
    6. Adding room tone – Room tone is essential etween tracks of much natural acoustic and classical music. Recording engineers should bring smaples of room tone to an editing session
  7. EQ Techniques
    1. What is good tonal balance?
      1. Always shows a gradual high frequency rolloff
      2. Everything starts with the midrange
    2. Parametric: Q and Bandwidth
      1. The parameter Q is defined mathematically as the product of the centrer frequency divided by the bandwidth in Hertz at he 3dB down (up) points measured from the peak (dip) of the curve
    3. Focusing the EQ
      1. Three techniques for finding a problem frequency
        1. Classic approach is to focus eq direction by starting with large boost and fairly wide Q and sweep thru frequencys to find the problem and then narrow the Q and dip.
        2. Keep a keyboard handy to determine the key of the song and use relative pitch to determine problem and then translate that note to dip the problem
        3. Last technique works good for fast bass runs where several notes stick out. Run a high resolution FFT and watch notes as they are played and see which one sticks out
      2. Shelving EQ’s
        1. Resonant shelf more natural. Can help a vocal from sounding thick while implementing a bass boost.
      3. Baxandall
        1. Useful in mastering
        2. Instead of reaching a plateau, the Baxandall continues to rise
        3. Simulate by placing a parametric EQ at the high frequency limit (20khz) with a Q of around 1
      4. Loud and Soft Passages – begin mastering on the loudest part of a song because psychoacousticians note EQ peaks affect partial loudness more than dips
      5. Fundamental or Harmonic? Since fundamentals of a crash cymbal can be lower than 1.5khz, boosting harmonics too much makes a cymbal sound tinny.
      6. Linear phase EQ – Theory
        1. EQ’s produce phase shift when boosted or cut. The higher the Q, the more phase shift (phase distortion)
      7. Dynamic EQ – Dynamic EQ emphasize or cut frequency ranges dynamically. Threshold set a level above or below which a band is dynamically boosted or cut.
      8. FIR means Finite Impulse Response. IIR Infinite Impuse Response. See John Watkinson’s The Art of Digital Audio for more explanation.
      9. See for the Weiss website
  8. Manipulating Dynamic Range (for fun and profit)
    1. The term dynamic range refers to the difference between the loudest and softest passages of the body of music.
    2. Four varieties of dynamic range modification
      1. Downward compression – bringing high level passages down. Limiting is a special case
      2. Upward compression raise the level of low passages. E.g., Dolby encoding
      3. Upward expansion takes high level passages and brings them up even further. Used to enhance dynamics and/or restore lost dynamics
      4. Downward expansion – brings low level passages down further. Used to reduce noise, hiss, leakage. A noise gate is a special case.
    3. Art of Changing internal levels of a song
      1. Alec Nesbitt’s book The Technique of the Sound Studio. If need to take a loud passage down, the best place to lower the gain is at the end of the preceding soft passage before the loud part begins. Look for a natural dip or decrease in enger and apply the gain drop during the end of the soft passage before the crescendo into the loud part
    4. Compression and Limiting and Mastering
      1. BBC research in the 1940’s demonstrated that distortion shorter than about 6-10 ms is fairly inaudible
      2. With digital recording and solid-state equipment, some transient distortion as short as 1ms will audibly change the sound of the initial transient
    5. Compression in Music Mastering
      1. One way to start compressing in order to help obtain punch or attitude is first to find the threshold,
        1. using a very high ratio, say 4:1, and very fast release time (say 100ms)
        2. then adjust the threshold until the gain reduction meter bounces as the syllables you want to affect pass by and you hear the bounce.
        3. This ensures the threshold is optimally placed around the musical accents you want to manipulate, the “action point” of the music.
        4. Then reduce the ratio to very low (say 1.2:1) and raise the release time to about 250ms to start.
        5. Note that too low a threshold will defeat the purpose which is to differentiate the “syllables” of the music, with too low a threshold, everything will be brought up to a constant level.
      2. Typical ratios and thresholds
        1. One trick to compress as inaudibly as possible is to use an extremely light ratio, say, 1.01 to 1.1 and very low threshold, perhaps as low as -30 to -40.
    6. Compressors with unique characteristics
      1. Analog compressor designers choose from several styles of gain manipulation. The most common are
        1. Optical – the release time slows down for the last portion of the release for a gentle easy going sound – good
        2. VCA (voltage controlled amplifier) – faster release times for a more aggressive sound
        3. Vari-mu
        4. PWM (pulse width modulation)
    7. Sidechain manipulation
      1. The most popular sidechain EQ is a highpass-filtered signal which helps prevent the bass drum from pushing down (modulating) the rest of the music
    8. Fancy compressor controls
      1. Compressors with multi-thresholds can be simulated by running two or more compressors in series. The first compressor performs a gentle overall compression with a low threshold and ratio and the second more aggressively controls some offensive peaks at high levels.
    9. Upward compression
      1. It is a psychoacoustic fact that the ear is much more forgiving of the upward “cheating” of soft passages than the awkward “pushing down” of loud passages.
      2. Take a source, and mix the output of a compressor with it (parallel compression)
      3. Two ways to approach parallel compression
        1. Transparent parallel compression
          1. Threshold -50dbfs, very low threshold puts the parallel compression into heavy gain reduction almost all the time
          2. Attack time as fast as possible – one millisecond or less if available
          3. Ratio 2:1 or 2.5:1
          4. Release time medium length of 250-350 ms to avoid breathing/pumping
          5. Crest factor set to peak
          6. Output level or makeup gain adjust to taste
        2. Tonalizattion or attitude
          1. Set the threshold in the middle of the musical action resulting in up to 5-7db of gain reduction (sometimes as little as 1-3db)
          2. Attack time is medium (start with 125ms)
          3. Ratio to taste set for the aggressiveness of the desired action in conjunction with the output level.
          4. Release time to taste set to work in tandem with the attack time to obtain maximum rhythm and punch
          5. Crest actor set to RMS
          6. Output level or makeup gain adjusted to taste. Rarely past -6db
    10. Upward Expansion
      1. The honor for the first digital upward expander goes to the Waves C1 plugin
      2. The Waves C4 plugin is the first single processor to perform all four dynamics processes
      3. The usable range of ratios for mastering with upward expansion is small, from a very gentle 1.01:1 to 1.2:1
  9. Noise Reduction
    1. A 1-4db dip around 3-5khz for where the ear is most sensitive to hiss
    2. A decrackler or descratcher processor can make an excellent distortion softener or remover
    3. Cedar’s powerful Retouch and Algorithmix Renovator are excellent noise reduction systems
    4. Psychoacoustically, the presence of noise increases apparent high frequency response
    5. Basic order of noise processing – to minimize artifacts and deal with the interaction of processes it is best to treat noise in a particular order
      1. Any tonal artifacts that stand out (hum, buzz) use a simple or complex filter
      2. Declicking, first automatic then manual
      3. Decrackling
      4. De-distortioning
      5. Broadband denoising
      6. Overall program EQ, filtering
  10. Top Processors
    1. GIK Acoustic Panels – Schroeder curve measurements determine whether there is sufficient balance of live and dead surfaces
    2. JL Audio Fathom f112 subwoofer
    3. Lipinski L-707 loudspeakers and amp
    4. TC Electronic Finalizer 96k
    5. Tascam DV RA1000
    6. Audiofile Engineering Spectre
    7. Sony Oxford plugins
    8. Universal Audio UAD-1
    9. Waves
  11. How to make Better Recordings
    1. See for the “Honor Roll” of good recordings
    2. Never use a peak limiter on a mix to “protect” metered level
    3. Use subtractive mixing
    4. Use K-system meters…for example the UAD meter in their limiter
  12. Additional Mastering Techniques
    1. Mono check for loudspeaker integrity
    2. Stereo balance of the program material
    3. DC Offset removal
      1. The best solution for DC offset is a very steep linear phase high-pass filter below 20hz
    4. Fattening with tubes
    5. When stems are not available
      1. First instrument affected by attack time of mastering compressors is the snare which allows us to be selective on that instrument, especially if compressing the 1-2khz range. Can greatly improve the impact and clarity of the rhythm, particularly the snare
      2. By using upward expansion with relatively short attack time.
      3. Frequently possible to enhance or punch the bottom end of the bass drum without significantly affect the bass instrument by using a low-bass-frequency compressor with a relatively long attack time in conjunction with an EQ
    6. Can produc4e the “loudest” master with he fewest compromises by using a small amount of several processes in a row rather than by engaging just a single process.
  13. Analog and Digital Processing
    1. Digital processing produces dissonance from harmonic components which beat against the sample rate producing inhardmonic beat or intermodulation products (aliasing distortion).
      1. The term inharmonic means that the type of distortion is not part of the integer harmonic series
      2. Distortion or noise may be just what the music needs
        1. Accomplish this via passing the signal thru the highest resolution electronics which add little or no distortion
        2. then add a touch of sauce with a selectively fuzzy component.
        3. This approach needs to be methodical, controllable and easily reversible
    2. Any audio source can gain depth and separation when passed thru certain analog components due to their “friendly” distortion.
      1. Pleasant bonus (artifact) of the analog chain
        1. Measured separation may even be less, Psychoacoustically
        2. The distortion appears to increase separation and depth.
  14. Depth and Dimension
    1. The Haas effect
      1. Helps to increase definition, depth and fullness
      2. Says that very short echoes (less than 5ms) produce an ambiguous (confused) image.
      3. Echoes from about 10-40ms become fused with the direct sound (only loudness enhancement occurs)
      4. Haas delays in mixing enhance spatial qualities
      5. Even if echoes occur from a different direction than the original source the brain will continue to recognize the location of the original sound as the proper direction of the source.
      6. The Haas effect allows added delays to enhance and reinforce an original sound without confuse its directionality
      7. When the delay is too long or delayed signal too loud, it starts to be perceived as a discrete echo called the Haas Breakdown point.
      8. The Haas breakdown point is shorter for percussive sounds…15ms for a kit while up to 30-50ms for strings
      9. Use panned and leveled delays in the 12-40 ms range
      10. Haas delays are more effective than EQ at repairing the sound of a drumset that was recorded in a dead room.
      11. To create layers in the mix, put single delays on some instruments and multiple (or no) delays on others
      12. Try doubler and quadrulper delay plugins with builtin panning
  15. Technical tips and tricks
    1. Be careful of sample rate mismatches which will result in pitch changes that are only heard much later.
      1. There is metadata in a digital file header that can be tweaked with Soundhack or Sample Manager (both Mac programs)
  16. Recommended Reading, CD’s for Equipment Testing and Ear Training
    1. Microphones: Design and Application by Lou Burroughs
    2. Acoustics and Psychoacoutics by David Howard and James Angus
    3. Fundamentals of Digital Audio by Alan Kefauver
    4. Digital Sound Processing for Music and Multimedia by Ross Kirk and Andy Hunt
    5. The Sound Studio: Audio Techniques for Radio, Television, Film and recording by Alec Nisbett
    6. Mastering Engineer’s Handbook by Bobby Owsinski
    7. Principles of Digital Audio by Ken Pohlman
    8. The Art of Digital Audio by John Watkinson
    9. Psychoacoustic Noise-Shaped Improvements to CD and other Linear Digital Media by M.A. Gerzon, P.G Craven, J.R. Stuart, R.J Wilson
    10. Collection of definitive articles on grounding, shielding, power supply, EMI, RFI, by Neil Muncy and Bill Whitlock
    11. Complete Ear Training Software ofr Musicians…rising software Auralia
    12. Checkpoint Audio Professional Audio Test Reference by Eelco Grimm
    13. David Moulton’s Audio Lecture Series, Golden Ears audio ear-training self-study course by David Moulton

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