University of Huddersfield Repository Moore, Austin An Investigation into Non-Linear Sonic Signatures with a Focus on Dynamic Range Compression and the 1176 Fet Compressor Original Citation Moore, Austin (2017) An Investigation into Non-Linear Sonic Signatures with a Focus on Dynamic Range Compression and the 1176 Fet Compressor. Doctoral thesis, University of Huddersfield. This version is available at http://eprints.hud.ac.uk/id/eprint/34118/ The University Repository is a digital collection of the research output of the University, available on Open Access. Copyright and Moral Rights for the items on this site are retained by the individual author and/or other copyright owners. Users may access full items free of charge; copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational or not-for-profit purposes without prior permission or charge, provided: • The authors, title and full bibliographic details is credited in any copy; • A hyperlink and/or URL is included for the original metadata page; and • The content is not changed in any way. For more information, including our policy and submission procedure, please contact the Repository Team at: [email protected]. http://eprints.hud.ac.uk/ AN INVESTIGATION INTO NON-LINEAR SONIC SIGNATURES WITH A FOCUS ON DYNAMIC RANGE COMPRESSION AND THE 1176 FET COMPRESSOR AUSTIN MOORE A thesis submitted to the University of Huddersfield in partial fulfilment of the requirements for the degree of Doctor of Philosophy The University of Huddersfield October 2017 ! Copyright statement 1.! 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Such Intellectual Property Rights and reproductions cannot and must not be made available for use without the prior written permission of the owner(s) of the relevant Intellectual Property Rights and/or Reproductions ! 2! ! Abstract Dynamic range compression (DRC) is a common process in music production. Traditionally used to control the dynamic range of signals and reduce the risk of overloading recording devices, over time it has developed into a creative colouration effect rather than a preventative measure. This thesis investigates sonic signatures, distortion, non-linearity and how audio material is coloured during the music production process. It explores how methodologies used to measure distortion and timbre can be used to define the sonic signature of hardware compressors and other pieces of music production equipment. A grounded theory and content analysis study was carried out to explore how producers use DRC in their work, how they describe its sound quality, which compressors they frequently use and which audio sources they process with particular types of compressor. The results from this qualitative study reveal that producers use compressors to manipulate the timbre of program material and select specific compressors with particular settings for colouration effects. Tests were carried out on a number of popular vintage hardware compressors to assess their sonic signature. Firstly, a comparative study was conducted on the Teletronix LA2A, Fairchild 670, Urei 1176 and dbx165A. Secondly a comprehensive in-depth analysis was undertaken of the 1176 to fully catalogue its sonic signature over a range of settings and to compare results from a vintage Urei Blackface 1176 and a modern Universal Audio reissue. Objective analysis was conducted on the compressors using Total Harmonic Distortion (THD), Intermodulation Distortion (IMD) and tone burst measurements. Complex program material was analysed using spectrum analysis, critical listening and audio feature extraction. It was found the compressors all have subtle nuances to their sonic signature as a result of elements in their design colouring the audio with non-linear artefacts. The 1176 was shown to impart significant amounts of distortion when used in its all-buttons mode and with fast attack and release configurations. This style of processing was favoured by producers in the qualitative study. ! 3! ! Table of Contents List%of%Tables% 7! List%of%Figures% 9! Dedications%and%Acknowledgements% 13! Chapter%1:%Introduction% 14! 1.1!Introduction! 15! 1.2!Motivation! 15! 1.3!Other!Related!Work! 16! 1.4!Developing!a!Methodology! 16! 1.5!Research!Questions! 17! 1.6!Chapter!Overview! 18! Chapter%2%:%Research%Methodologies% 20! 2.1!Research!Methodologies!Introduction! 21! 2.2.1!Descriptors!and!Metaphors! 21! 2.2.2!Qualitative!Research!Methods! 22! 2.3!Conclusion!and!Choice!oF!Qualitative!Method! 24! 2.4!Implementation!oF!the!Qualitative!Method! 25! 2.4.1!InFormation!on!the!Data!Sample! 25! 2.4.2!Recording!Descriptors! 28! 2.4.3!Grouping!by!Compressor,!Gain!Reduction!Type!and!Source! 28! 2.5!Objective!Methodologies! 29! 2.6!Distortion!Measurements! 29! 2.7!Observing!Distortion! 31! 2.8!Tone!Burst!Measurements! 32! 2.9!Implementation!oF!Objective!Measurements! 33! 2.10!Timbre!Studies! 34! 2.11!Audio!Features! 35! 2.11.1!Audio!Features!Extraction!Process! 36! 2.12!Details!on!the!Features!Extracted!in!This!Thesis! 37! 2.12.1!Energy!Related!Features! 37! 2.12.2!Spectrum!Related!Features! 38! 2.12.3!Time!Domain!Related!Features! 40! 2.12.4!Psychoacoustic!Related!Features! 40! 2.13!Principle!Component!Analysis! 41! 2.14!Conclusions!on!Research!Methodologies! 42! Chapter%3%:%NonHLinearity,%Audio%Equipment%and%Dynamic%Range%Compression% 44! 3.1!NonWLinearity!in!Music!Production! 45! 3.2!Hard!Clipping! 47! 3.3!SoFt!Clipping! 49! 3.4!Other!Ways!a!Signal!Can!Be!Clipped! 51! 3.5!Other!Forms!oF!Distortion! 53! 3.6!Audio!Equipment!and!Distortion! 54! 3.7!Compressors! 57! 3.8!Compressor!Design! 59! 3.8.1!Attack!and!release! 60! 3.8.2!NonWlinearity!From!Time!Constant!Settings! 63! 3.8.3!Side!Chain!and!Level!Detector! 65! 3.8.4!FeedWForward!and!FeedWBack!Designs! 66! 3.8.5!The!EfFect!oF!Knee! 67! ! 4! ! 3.8.6!Gain!Reduction!Section! 67! 3.9!Design!Analysis!oF!Four!Popular!Compressors! 68! 3.9.1!The!Teletronix!LA2A! 68! 3.9.2!The!Fairchild! 70! 3.9.3!The!1176! 71! 3.9.4!The!dbx165A! 73! 3.10!Conclusions!on!NonWLinearity!and!Equipment! 75! Chapter%4%:%How%Producers%Use%Dynamic%Range%Compression%in%Music%Production % 77! 4.1!Introduction!to!DRC!Study! 78! 4.2!Popularity!oF!Compressor!and!Gain!Reduction!Type! 78! 4.2.1!Grouping!by!Gain!Reduction!Type! 79! 4.3!Popularity!of!Sources! 82! 4.4!Results!From!the!Grounded!Theory!Analysis! 83! 4.4.1!Results!From!Axial!Coding! 85! 4.4.2!Results!From!Selective!Coding!and!Core!Categories! 86! 4.5!Analysis!by!Source! 87! 4.6!Analysis!and!Overview!oF!Quotes!Extracted!from!the!Grounded!Theory!Research! 89! 4.6.1!Compression!For!General!Colour!and!Temporal!Changes! 89! 4.6.2!Compression!on!Vocals! 91! 4.6.3!Compression!on!Bass! 92! 4.6.4!Compression!on!Drum!Sources! 93! 4.7!Analysis!oF!Common!1176!Time!Constant!Settings! 95! 4.7.1!Content!Analysis!Methodology! 97! 4.8!Content!Analysis!oF!1176!Presets! 97! 4.9!Analysis!oF!Video!Material! 98! 4.10!Studio!Engineer!Settings! 100! 4.11!Conclusions!on!DRC!Study! 101! Chapter%5%:%Analysis%of%Four%Hardware%Compressors% 104! 5.1!Introduction!to!Analysis!oF!Four!Popular!Compressors! 105! 5.2!Testing!For!NonWLinearity! 105! 5.3!Comparison!oF!Compressor!Time!Constants! 115! 5.4!THD!and!Time!Constant!Testing:!Conclusions! 119! 5.5!Measurements!Using!Complex!Program!Material! 120! 5.5.1!InFormation!on!the!Audio!Material! 121! 5.6!Results!From!Bass!Material! 123! 5.6.1!Audio!Features:!Bass!Material! 127! 5.7!Results!From!Vocal!Material! 130! 5.7.1!Audio!Features:!Vocal!Material! 134! 5.8!Results!From!Room!Mic!Material! 136! 5.8.1!Audio!Features:!Room!Mic!Material! 142! 5.9!DiFFerences!in!Gain!Reduction! 144! 5.9.1!DiFFerences!in!Bass!Material! 144! 5.9.2!DiFFerences!in!Room!Mic!Material! 145! 5.9.3!DiFFerence!in!Vocal!Material! 147! 5.10!Conclusions!on!DiFFerent!Amounts!oF!Gain!Reduction! 147! 5.11!Principle!Component!Analysis!oF!Audio!Features! 149! 5.11.1!Bass!Material:!PCA!Results! 149! 5.11.2!Vocal!Material:!PCA!Results! 150! 5.11.3!Room!Mic!Material:!PCA!Results! 151! ! 5! ! 5.12!Conclusions!From!the!Chapter! 152! Chapter%6%:%An%InHDepth%Investigation%into%the%1176% 155! 6.1!The!1176!Analysis:!Introduction! 156! 6.2!Test!Tone!Methodology! 156! 6.3!Testing!Program!Dependency:!Two!1176s! 157! 6.4!THD!at!Input:!Two!1176s! 164! 6.5!THD!During!Compression!Activity:!Two!1176s! 171! 6.6!Testing!Intermodulation!Distortion!(IMD):!Two!1176s! 177! 6.6.1!The!EfFect!oF!Ratio!on!NonWLinearity! 178! 6.6.2!The!EfFects!oF!Time!Constants!on!NonWLinearity! 182! 6.7!Conclusions!on!Tone!Based!Testing! 184! 6.8!Complex!Program!Material!Analysis!Introduction! 188! 6.9!The!1176!On!Vocals! 188! 6.9.1!Vocal!Time!Constant!1! 190!