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Tutorial 04 – Gathering Impulse Responses (Objects)

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The following is a brief overview of how to record impulse responses from software, outboard gear and acoustic objects using REAPER and Room EQ Wizard. This is supplementary to my (Jack’s) portion of Wednesday’s tutorial. I highly recommend that you also read this.
 
 
Gear
 
(the above will suffice from making IR from software plugins in REAPER)
 
But…,
 
…if recording IR from a piece of outboard gear (a reverb device, a guitar pedal, etc), you will also need:
  • Audio interface
  • Outboard gear
  • Cabling from interface to outboard gear
  • Cabling from outboard gear to interface
 
…if recording IR from an acoustic object (an acoustic musical instrument, a small container, a concert hall, the Sahara Desert, etc), you will also need:
  • Audio interface
  • Loudspeaker
  • Microphone
  • Cabling from interface to loudspeaker
  • Cabling from microphone to interface
 
 
Signal chain:
 
IR from software plugins from REAPER:
Room EQ Wizard (REW) test signal -> target plugin in REAPER -> REW measurement -> export IR from REW as .WAV
 
IR from outboard equipment
REW test signal -> audio interface (output) -> outboard gear (input) – > outboard gear (output) -> audio interface (input) -> REW measurement -> export IR from REW as .WAV
 
IR from acoustic object
REW test signal -> audio interface (output) -> loudspeaker -> acoustic object -> microphone -> audio interface (input) -> REW measurement -> export IR from REW as .WAV
 
 
Collecting IR
 
Setup and test signal chain (this process will look a little different depending on what you are recording, and what equipment you are using)
  • Set-up your REAPER environment (If recording IR from a software plugin in REAPER)
  • Set the parameters of the outboard gear (if recording IR from a piece of outboard gear}
  • Position microphone, speaker and object (if recording IR from an acoustic object)
  • Check levels (you want AT LEAST 4-5dB of headroom)
 
In REW:
  • Set audio device (preferences)
  • Make a measurement (measurement panel)
  • Set sweep to cover auditory frequency range (measurement panel -> ‘Measure using…’)
  • Set desired length and number of sweeps (measurement panel -> ‘Measure using…’)
  • Check levels
  • Start measuring
  • Export (file -> export -> ‘export impulse response as WAV’)
 
 
Editing IR
  • Locate the IR that you just collected
  • Import into REAPER (drag and drop onto the arrange window)
  • Edit the region to remove silence from the start
  • Zoom in to ensure you start *right* at the beginning
  • Select the region (click on the IR)
  • Open Render panel (file -> Render…)
  • Set to render ‘Selected media items’ (Render panel -> Source)
  • Name file (Render panel -> Output -> File name)
  • Choose sample rate / bit-depth
  • Render! (Reder panel -> bottom right hand corner -> ‘Render 1 file’)