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New  recording  techniques  for  solo  double  bass     Cato  Langnes   NOTAM,  Sandakerveien  24  D,  Bygg  F3,  0473  Oslo   catola@notam02.no,  www.notam02.no  

    Abstract   This  paper  summarizes  techniques  utilized  in  the  process  of  recording  solo   double  bass  performances  by  Håkon  Thelin.  The  aim  of  the  project  was  a  CD   production  with  performances  of  some  of  the  compositions  used  by  Thelin  in  his   work  as  an  artistic  research  fellow  at  the  Norwegian  Academy  of  Music.  The   pieces  feature  vast  dynamic  ranges  and  variations  in  playing  techniques.  Micro   tonality,  harmonics  and  various  bowing  techniques  are  integral  parts  of  the   instrument’s  sound.  The  challenge  was  to  capture  and  bring  forward  the  fine  and   delicate  nuances  resulting  from  the  playing  techniques,  while  at  the  same  time   preserving  the  free,  open  resonance  of  the  double  bass  in  the  concert  hall  used   for  the  recordings.  These  requirements  sparked  an  investigative  process  that   ultimately  led  to  the  technical  solutions  that  are  presented  here.       Project  background   I  have  been  a  sound  engineer  and  producer  of  rock  and  contemporary  music  for   more  than  two  decades.  For  a  long  time  I  have  wanted  to  use  microphone   techniques  that  are  common  in  rock  productions  for  recording  classical  and   contemporary  music.  During  the  fall  of  2008,  composer  Anders  Vinjar  and  I   experimented  with  stereo  techniques  where  we  compared  omnidirectional  and   cardioid  microphones.  I  was  quite  skeptical  towards  omnidirectional   microphones,  since  their  lack  of  directionality  compared  to  cardioid   microphones  inevitably  reduces  the  source  separation  between  the  recording   channels.  However,  the  superior  depth  and  correct  frequency  response  resulting   from  the  omnidirectional  recordings  was  a  pleasant  surprise.  After  these  first   experiments  I  started  working  with  combinations  of  cardioid  and   omnidirectional  pairs,  with  very  positive  results.  I  used  the  cardioid  pair  to  focus   on  salient  details  in  the  soundscape,  whereas  the  omnidirectional  pair  was  used   to  record  the  timbre  surrounding  the  source.  This  work  led  to  a  more   comprehensive  investigation  of  the  vast  range  of  possibilities  afforded  by   combinations  of  different  microphones  with  different  characteristics.     We  began  recording  the  works  for  Thelin's  CD  during  the  winter  of  2009.  Thelin   works  with  new  and  unconventional  playing  techniques,  and  he  wanted  to  use   the  recorded  medium  to  convey  and  reinforce  details  that  are  not  easily   perceived  in  a  concert  situation.  He  has  created  his  own  musical  language   predominantly  inspired  by  folk  and  contemporary  music  and  by  the  timbral   potential  found  in  the  double  bass.  Thelin's  repertoire  and  technical  style   requires  a  close  and  extremely  detailed,  but  simultaneously  natural  rendering  of   the  instrument.  The  recordings  that  will  be  discussed  here  formed  part  of  the   documentation  for  Thelin's  research.  The  investigative  aspect  permeated  the   entire  process  to  a  considerable  degree.  


Recording   Eight  microphones  were  placed  at  different  distances  and  angles  from  the  double   bass  in  order  to  capture  all  the  nuances  in  Thelin's  playing,  and  the  ambience  in   the  room.    

 

Fig.  1.:  Six  out  of  eight  microphones  at  different  angles  and  distances.     Close  range  single  microphones   Thelin  uses  a  DPA  4021  attached  to  the  instrument  for  amplification  in  concert   situations.  We  attached  the  microphone  to  the  strings  just  below  the  bridge,   pointing  diagonally  up  towards  the  f-­‐hole.  This  mounting  is  also  used  for  his   concerts  (Fig.  2).    

Fig.  2.:  DPA  4021  mounted  below  the  bridge.    

 


In  order  to  achieve  a  warm  character  in  combination  with  the  good  bass   response  that  a  large  membrane  microphone  yields  in  a  mix,  I  interchangeably   used  an  AKG  414  or  a  Neumann  U87,  depending  on  the  composed  material.  This   was  placed  as  close  to  the  instrument  as  possible,  at  the  right  side  of  the  bridge   when  seen  from  the  front.  For  practical  reasons,  a  space  of  30  cm  between  the   bass  and  this  microphone  was  necessary  for  Thelin  to  be  able  to  bow  freely  (Fig.   10).  The  purpose  of  this  close-­‐miking  technique  was  to  capture  the  low-­‐ amplitude  harmonics  and  Thelin's  bow  bouncing  techniques  that  produce   minimal  sound  pressure,  and  therefore  cannot  be  well  captured  at  further   distances.  This  miking  technique  also  added  a  solid  mid-­‐range  signal  to  the  mix.     Some  of  Thelin's  playing  techniques  feature  much  activity  on  the  high  end  of  the   fingerboard.  Because  of  this,  we  decided  to  place  an  AKG  461  microphone  quite   close  to  the  fingerboard  to  capture  these  details.  It  was  however  not  necessary  to   use  this  microphone  on  all  of  the  material  (Fig.  3).    

  Fig.  3.:  Placement  of  AKG  461  for  close  miking  of  the  fingerboard.  

  Close  range  stereo  pair   Sound  pressure  waves  radiate  from  the  double  bass  in  highly  diverse  patterns   and  across  different  frequency  ranges,  and  knowledge  about  these  acoustic   radiation  patterns  is  crucial  in  order  to  select  microphone  placements  that  yield   an  optimal  recording  of  the  instrument.  The  double  bass  is  ultimately  a  bass   instrument;  however,  in  order  to  obtain  depth  in  timbre,  it  is  important  to   capture  the  many  rich  frequencies  from  600  Hz  and  upward.  This  is  especially   beneficial  if  the  bass  is  used  in  pop/rock/jazz  contexts,  where  these  upper   frequencies  are  crucial  for  the  bass  to  be  heard  clearly  and  distinctly  in  the  mix.    


Fig.  4.:  Illustration  from  Jürgen  Meyer  &  Uwe  Hansen  (2005).  Acoustics  and  the   Performance  of  Music.  Berlin:  Springer.     The  late  double  bass  professor  at  the  Norwegian  Academy  of  Music,  Knut  Güttler   produced  the  CD.  His  extensive  knowledge  of  how  sound  radiates  from  a  double   bass  was  hugely  important  during  the  recording  sessions.  On  his   recommendation,  I  alternated  between  placing  a  pair  of  DPA  4015  wide-­‐cardioid   or  Neumann  KM  130  omnidirectional  microphones  pointing  toward  each  f-­‐hole   at  45-­‐degree  angles.  In  regards  to  placement,  a  compromise  was  reached  where   the  need  for  Thelin  to  move  the  bow  and  hands  freely  was  balanced  against  the   need  for  as  close  of  a  recording  range  as  possible.  I  ended  up  with  the   microphones  placed  at  a  distance  of  approximately  50  cm  from  the  f-­‐holes  with  a   70  cm  separation  between  the  two  microphones  (Fig.  4).  This  gave  such  good   results  that  the  stereo  pair  was  used  as  the  main  stereo  track  when  mixing.  The   technique  works  very  well  also  for  cello  recording.     The  dynamic  range  a  close  microphone  picks  up  is  larger  than  what  you  get   when  you  set  up  microphones  far  from  the  source.  Be  careful  with  the  recording   levels  on  extremely  close  mikes  –  ask  the  musician  to  play  through  the  loudest   part  and  leave  6  dB  headroom  when  you  adjust  the  levels.  It  is  most  often   necessary  to  use  compression  on  close-­‐miked  tracks  and  often  to  adjust   automation  or  use  clip  gain  adjustments  to  avoid  distortion  through  the   compressors.    


Fig.  5.:  Placement  of  a  DPA  4015  stereo  pair  and  4021  (on  the  instrument).  

 

  Spaced  stereo  pair   Throughout  my  career  I  have  accumulated  broad  experience  in  recording   chamber  music  ensembles  for  documentation  purposes  and  for  radio   broadcasting.  In  these  situations,  I  have  often  used  a  spaced  pair  of  cardioids   placed  as  close  to  the  ensemble  as  possible,  without  allowing  any  instrument  to   become  more  dominating  than  the  rest  due  to  its  proximity  to  the  microphones.   This  placement  technique  requires  careful  monitoring  through  headphones  in   order  to  find  the  ultimate  balance  between  the  musicians  and  the  recording   space.     Usually,  I  prefer  capturing  as  much  of  the  direct  signal  as  possible  without  too   much  reverb  from  the  room.  I  used  this  technique  on  the  Thelin  recordings  as   well.  In  Lindemansalen  (small  orchestra  concert  hall)  at  the  Norwegian  Academy   of  Music,  we  ended  up  positioning  a  spaced  par  of  cardioids  2-­‐3  meters  in  front   of  Thelin,  pointing  outwards  (A-­‐B  technique)  at  an  angle  of  approximately  90   degrees.  These  microphones  were  placed  quite  high  so  they  had  to  be  pointed   down  towards  the  instrument,  thus  avoiding  the  capture  of  reflections  from  the   floor  (Fig.  6).  For  microphones  placed  at  these  positions  I  have  experimented   with  both  omnidirectional  and  cardioid  pairs  in  A-­‐B  formation  (as  opposed  to   near-­‐coincident  X-­‐Y  where  the  angle  is  inverted  and  the  microphone  heads  are   brought  together).  The  omnidirectional  microphones  often  yield  a  fuller  timbre   with  plenty  of  depth.  And  they  pick  up  more  ambience  from  the  room.  Cardioids   tend  to  capture  details  such  as  bowing  and  valve  clicking  more  accurately.    


Fig.  6.:  Placement  of  AB  stereo  pair,  top  left  in  picture.     Ambience/room  microphones   Recordings  of  acoustic  instruments  are  more  interesting  if  you  also  capture  room   acoustics.  To  a  certain  extent,  this  is  also  inevitable.  The  sessions  with  Thelin   were  recorded  in  Lindemansalen  and  Levinsalen  (small  chamber  concert  hall)  at   the  Norwegian  Academy  of  Music,  and  both  halls  have  superb  acoustics.  In  order   to  capture  the  timbre  of  the  room  the  way  it  is  typically  experienced  by  an   audience,  we  used  a  pair  of  omnidirectional  microphones  placed  about  10   meters  in  front  of  the  bass,  with  an  equivalent  distance  between  the  two   microphones.  The  long  distance  to  the  instrument  required  quite  a  lot  of  preamp   gain,  and  the  recording  contained  a  great  deal  of  noise  from  the  room  in  addition   to  unwanted  sub-­‐bass  from  about  50  Hz  and  below,  probably  from  the   ventilation  system.  In  the  mix,  therefore,  these  channels  were  filtered  through  a   50  Hz  low  cut  before  used.  Reverb  in  the  final  mix  is  based  mainly  on  these   ambience  channels.     Double  MS   A  double  MS  microphone  set-­‐up  was  not  used  at  all  in  Thelin's  project,  but  this   technique  has  yielded  good  results  in  many  other  projects,  and  therefore   deserves  mention.     If  one  wishes  to  further  develop  recordings  of  room  acoustics  in  the  mixing   process,  the  double  MS  technique  provides  the  possibility  of  experimenting  with   the  stereo  width  through  the  decoding  process  and  a  subsequent  balancing  of  the   resulting  channels.  For  MS  recording  one  uses  a  forward-­‐pointing  cardioid   microphone  (mid)  together  with  a  figure-­‐8  microphone  (side)  that  captures  the   right  and  left  side  of  the  room.  The  microphones  are  recorded  to  separate  tracks   and  are  easy  decoded  to  a  stereo  signal.  You  can  import  your  tracks  to  any  DAW,  


duplicate  the  figure  -­‐8  track  and  invert  one  of  the  duplicated  tracks.  Move  the   two  figure-­‐8  tracks  to  a  stereo  track  (side)  and  mix  it  with  the  cardioid  track   (mid)  and  you  get  a  nice  stereo  signal.  Double  MS  recording  includes  an   additional  backward  pointing  microphone  that  enhances  the  perception  of  depth   in  the  room.  These  signals  can  be  decoded  into  4  or  5  channels  if  the  goal  is  a  5.1   mix.  The  decoding  process  is  well  described  in  the  Schoeps  Surround  Brochure,   which  can  be  downloaded  here:   http://www.schoeps.de/en/products/categories/doublems       Phase  issues   The  recordings  were  all  done  with  Sound  Devices  788T  recorders  and  imported   to  Pro  Tools  for  editing  and  mixing.  When  using  multiple  microphones  on  one   source,  playing  it  back  later  will  introduce  phasing  problems  because  the  source   sounds  will  reach  the  microphones  at  different  times  (Fig  7).  Before  editing,  we   could  clearly  hear  comb-­‐filtering  artifacts  between  the  microphones  that  were   relatively  close  together,  and  very  distinct  echo  effects  between  the  close-­‐range   and  ambience  tracks.    

Fig.  7.:  Edit  window  in  Pro  Tools  after  import  of  files,  pre  phase-­‐correction.   Notice  that  the  signals  have  different  starting  points.    

 


Fig.  8.:  Post  phase-­‐correction.  Once  phase  was  in  place  it  started  to     sound  nice,  issues  with  comb  filter  effects  and  echo  was  eliminated.     The  first  thing  that  needed  to  be  done  was  to  position  the  files  into  phase.  I  used   the  DPA  4021  microphone  that  had  been  mounted  on  the  bass  as  the  main   reference,  it  being  closest  to  the  source  (Fig  8,  the  purple-­‐colored  track),  and   brought  all  the  other  tracks  in  line  with  the  attacks  on  this  track.     In  regards  to  the  stereo  pair,  a  great  deal  of  what  makes  the  difference  between   the  right  and  the  left  channels  is  time-­‐of-­‐arrival  between  the  two  microphones.   This  is  especially  true  for  the  AB-­‐setup  used  here,  as  opposed  to  the  XY-­‐method,   where  difference  in  amplitude  is  the  most  defining  factor.  In  any  of  these  cases,   one  should  take  care  not  to  correct  phase  within  the  pair,  but  rather  as  a  rule  of   thumb  treat  the  pair  as  one  when  dragging  the  tracks  into  phase  with  the  rest.   However,  phase  issues  do  occur  in  stereo  recordings,  potentially  generating   comb-­‐filtering  effects.  For  the  ambience  microphones,  which  were  spaced   approximately  10  meters  apart,  there  was  a  significant  difference  in  the  time-­‐of-­‐ arrival  of  the  signal.  To  deal  with  this  issue,  I  made  some  adjustments  between   the  left  and  the  right  side  and  made  sure  that  the  most  salient  features  in  the   attacks  were  in  phase  with  each  other.       Editing  and  mixing   Mixing  was  done  together  with  Håkon  Thelin.  With  the  number  of  microphone   placements  and  recording  techniques  at  our  disposal,  we  were  quite  free  to   shape  the  sound.  We  had  a  considerable  degree  of  control  between  the  relatively   dry  close-­‐range  recordings  of  the  instruments  and  the  room  ambience,  and  we   could  quite  simply  extract  details  in  the  mix  by  compressing  the  close-­‐range   tracks  and  thereby  bringing  details  to  the  forefront,  without  affecting  the  overall   mix.    


The  omni/wide-­‐cardioid  close-­‐mike  pair  was  used  as  the  main  sound  source  in   the  mix.  The  pair  provided  good  representation  of  dynamics,  with  a  full  and  rich   stereo  image.     Frequencies  below  60  Hz  were  filtered  out  of  the  tracks  recorded  with  the  4021   microphone,  and  the  tracks  were  subjected  to  heavy  compression  in  order  to   bring  forward  micro  details  in  the  playing  as  clearly  as  possible.  The  compressor   was  used  basically  as  a  limiter  (short  attack  and  release,  1/10  to  1/20  ratio,  and   the  threshold  was  lowered  to  a  level  just  above  when  the  compressor  started   distorting).  In  some  of  the  mixes  a  duplicate  of  the  large  diaphragm  microphones   track  was  compressed  the  same  way.  When  I  raised  the  level  of  these  tracks  in   the  mix  it  still  sounded  dynamic  and  open,  and  all  the  delicate  details  in  the   playing  came  through  clearly  in  the  mix.    The  middle  of  the  stereo  image  sounded   solid  and  full  when  the  large  diaphragm  microphones  were  combined  with  the   close-­‐microphone  pair.  Some  very  soft  parts  were  still  almost  inaudible  in  the   mix,  and  this  was  fixed  with  automation  of  volume  on  the  close-­‐microphone   tracks,  bringing  also  the  extremely  silent  parts  to  an  audible  level  (Fig.  9).    

 

Fig.  9.:  Amplitude  automation  in  Pro  Tools.  

 

  Fig.  10.:  DPA  4021  mounted  on  the  instrument,  Neumann  U87  (large  diaphragm   microphone)  at  approximately  30  cm  distance,  DPA  4015  pair  pointed  at  f-­‐holes.  


Fig.  11.:  Bussing  and  compression  in  Pro  Tools.  

    Bussing  and  compression  in  Pro  Tools     There  was  a  clear  contrast  in  the  tracks  with  the  DPA  4021  and  the  AKG   414/Neumann  U87s.  This  is  to  some  extent  due  to  the  difference  in  microphone   characteristics.  Both  close-­‐miking  setups  provided  good  capture  of  the  fine   details  in  Thelin's  playing,  and  worked  well  with  the  extreme  variation  in   dynamics.  Due  to  the  longer  distance  from  the  instrument,  the  large  diaphragm   microphones  U87s  and  414s  had  slightly  more  room  ambience  than  the  4021.   The  instrument-­‐mounted  microphone  gave  richer  bowing  sounds,  and  stronger   low  frequencies  in  attacks  where  the  bow  changed  direction.  It  is  however   difficult  to  establish  a  general  rule  for  what  provided  the  best  solution,  and  we   ended  up  using  both  tracks  in  the  mix.  (Fig.  10)     A  combination  of  the  close  microphones  provided  good  results.  In  the  mix,  all   close-­‐miked  tracks  were  sent  to  the  same  bus  and  compressed,  while   simultaneously  being  routed  directly  to  the  master  bus  without  compression  -­‐  a   technique  known  as  parallel  compression  (Fig.  11).     Recordings  will  often  sound  dull  if  not  placed  in  a  room.  Without  placement  in  a   room,  the  recording  provides  a  representation  of  how  the  instrument  sounds   from  the  perspective  of  the  musician,  which  is  not  necessarily  the  more   interesting  perspective  for  listener.  In  the  same  manner  that  the  close-­‐miking   provided  a  good  representation  of  the  musician's  perspective,  the  microphone   position  2-­‐3  meters  in  front  of  the  instrument  was  useful  for  providing  a  natural   sense  of  the  room  in  the  mix;  an  audience's  perspective.  I  have  with  good  results   used  a  double  MS  rig  for  the  same  purpose.  If  you  have  enough  microphones  and   tracks  available  it  is  a  good  idea  to  do  both.  Both  techniques  provide  good   representation  of  a  sound  source  in  room  and  the  MS  recording  may  be  decoded   to  both  stereo  and  surround.  In  situations  lacking  ambience  microphones,  or   where  the  ambience  recordings  are  too  noisy  to  be  used  in  the  mix,  I  have   created  artificial  room  ambience  by  feeding  the  signal  from  such  stereo-­‐  or   double  MS-­‐setups  into  the  artificial  reverb,  rather  than  using  the  signal  from  the  

 


close  microphones.  This  has  reduced  the  degree  of  quick  transients  and  sharp,   ”squeaking”  sounds  in  the  reverberation,  and  has  made  it  sound  more  soft  and   dense.     The  ambience  microphones  were  exclusively  used  for  adding  natural  reverb  to   the  recordings.  Heavy  bowing  and  hard  pizzicatos  sound  poorly  with  added   reverb,  while  softer  bowing  will  benefit  from  more  ambience.  When  balancing   these  concerns,  a  lot  of  amplitude  automation  was  used  for  the  ambience  track.   We  reduced  the  reverb  in  the  sections  where  Thelin  would  play  louder,  and   turned  it  up  in  the  softer  parts  (Fig.  12).  In  order  to  achieve  a  homogenous   reverb,  a  lot  of  precision  work  with  automation  was  required  at  the  transition   points  between  soft  and  loud  amplitudes.    

Fig.  12.:  Automation  of  volume  on  surround  tracks  in  Pro  Tools.  

 

  The  master  bus  was  subjected  to  EQ  and  compression.  The  EQ  lifted  some  areas   of  the  frequency  spectrum  that  did  not  sound  energetic  enough  in  the  mix,  and   the  compressor  was  set  to  reduce  the  loudest  peaks  with  approximately  2  dB.       Summary   The  experiences  from  making  recordings  with  Håkon  Thelin  have  been  of  use  in   almost  every  recording  session  I  have  done  since  that  time.  If  time  and  resources   allow,  I  now  use  close-­‐miking  to  capture  smaller  details,  stereo  pairs  for   capturing  the  ensemble  as  a  whole,  and  stereo  or  double  MS  for  the  acoustics  of   the  room.  If  the  pieces  have  been  previously  recorded,  I  listen  to  them  for   reference,  and  discuss  them  with  the  musicians  and  composer  to  achieve  an   understanding  of  what  they  are  looking  for  and  would  like  to  emphasize.  I  spend   a  lot  of  time  analyzing  the  recording  situation  in  order  to  decide  where  to   position  microphones  to  capture  the  small  details  of  the  music,  how  to  achieve   the  best  possible  separation  of  instruments,  and  how  to  best  describe  the  room   where  the  music  is  performed.     Music  is  almost  always  complex,  even  with  only  one  performer.  Instruments   sound  different  depending  on  how  close  you  are  to  the  sound  source.  This  is  not   only  related  to  the  frequency  characteristics  of  the  room,  but  also  due  to  how   lower  frequencies  travel  further  through  the  room  than  higher  frequencies,  due   to  their  higher  energy  levels.  When  you  are  located  far  away  from  the  sound   source,  you  will  not  hear  the  higher  frequencies  at  the  same  level  as  the  musician   does,  since  they  will  be  absorbed  before  reaching  the  listener.  The  same   principle  applies  for  the  acoustics  of  the  room  –  the  reverb  time  for  lower   frequencies  is  longer  than  for  higher  frequencies,  so  they  will  linger  for  a  longer  


time  in  the  room.  Certain  details  in  the  sound  of  instruments  will  drown  when   they  are  played  together  with  other  instruments,  or  emerge  far  away  from  the   listener/microphone.  That  makes  close  miking  essential  for  recording  them.  It  is   important  to  pay  attention  to  phase  and  the  sounds’  travel  time  to  the   microphones  when  multiple  microphones  are  used  to  capture  the  same  source,   and  the  microphones  are  placed  far  apart.  Regarding  music  for  solo  instrument,   as  this  paper  describes,  or  small  ensembles,  phase  issues  are  fairly  easy  to   correct,  compared  to  more  complex  recordings  with  huge  ensembles.     The  question  at  every  recording  session  is  how  many  microphones  are  required,   and  how  they  should  be  positioned  to  give  the  desired  balance  between  the   instrument  and  the  existing  acoustics  to  the  listener.         More  information  about  Thelin’s  research  project  can  be  found  here:   http://haakonthelin.com/multiphonics/    


New recording techniques for double bass