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Core Sound OctoMic™ -- Recording With OctoMic
OctoMic Recording Tips

(Last updated 09/12/2018)

Typical Recording Set-ups

OctoMic has an unusually extended low frequency response. If we wanted to go a bit overboard, we could calibrate it to be flat to well below 20 Hz and you could use it as an earthquake detector! But we reasonably limit its response so that it's usable down to around 25 Hz.

As with any high quality microphone that works well down to those very low frequencies, you must use a shock mount unless you really want to pick up footsteps, trucks rumbling by, distant thunder and subway trains. So please always use an effective shock mount. (See the OctoMic Accessories page for recommendations.)

OctoMic's output is a 12-pin jack. A 12-pin PPAc8 cable connects it to the PPAc8 transmitter. Since OctoMic's signal is unbalanced at that point and somewhat susceptible to picking up strong electrical interference, we recommend keeping that PPAc8 cable length as short as possible and routing it away from high power sources of interference.

The PPAc8 transmitter connects to two shielded EtherCon cables, each of which carries four channels. The EtherCon cables can run for more than 500 feet without degrading the audio signal.

The two EtherCon cables connect to two PPAc8 receivers. Each receiver has four XLR plug outputs, for a total of eight.

OctoMic's PPAc8 system can feed the signal to either an eight-channel recorder that has its own mic pre-amps, or an eight-channel microphone pre-amplifier/ADC (analog-to-digital converter) that feeds an eight-channel digital audio recorder. The recorder can be either a computer or a stand-alone digital audio recorder.

Using OctoMic with Portable Digital Audio Recorders

Zoom's F8 eight-channel portable digital audio recorder is probably the most cost-effective and simplest way to record with OctoMic. The combination makes very high quality 2nd-order ambisonic recordings. You can buy a Zoom F8 in the US for $1000 or less.

An alternative to the Zoom F8 is the Sound Devices MixPre-10T,

Other possible alternatives are the Roland R-88 and the SonoSax SX-R4+/SX-AD8+ combination.

Connect OctoMic to the recorders using OctoMic's PPAc8 system. The PPAc8's two receivers terminate in eight XLR connectors. Plug them directly into the recorders' eight XLR inputs.

Both the Zoom F8 and the Sound Devices MixPre-10T have very accurate, digitally-set level controls so it's very easy to match the levels across OctoMic's eight channels. Both recorders can gang the eight channels' level controls, so you can control the levels with one knob. Both recorders are recommended!

Microphone Pre-amplifiers and ADCs

To preserve OctoMic's calibrated performance, all eight OctoMic channels should be gain-matched to within 0.1 dB. Please use mic pre-amps and A-to-D converters that are designed to hold those gain tolerances across eight channels.

DAWs for Editing OctoMic Recordings

OctoMic's raw eight-channel audio output are in what's called "A-format". When you transfer them into your digital audio workstation for editing, convert them to standard 9-channel 2nd-order B-format with the supplied VVOctoEncoder VST encoder plugin.

The following DAWs can be used for editing 2nd-order B-format:

  • Reaper
  • Pro Tools HD
  • Cubase (pending)
  • Nuendo (pending)
  • Pyramix (v11.1 and higher)
  • Ardour
  • Digital Performer
  • Plogue Bidule
  • AudioMulch
  • FLStudio (with proper mixer and plugin I/O configuration)

If your PC runs Linux, you can use Fons Adriaenson's OctoProc software.

OctoMic's 9-channel B-format has been confirmed to work well with the Facebook 360 Spatial Workstation.

VVOctoEncode VST Encoder Plugin Settings

VVOctoEncode is the A-to-B-Format encoder VST plugin supplied with OctoMic. It was developed and is supported by David McGriffy (VVAudio.com). It allows you to select among three options during encoding.

The first option has the least processing noise and provides excellent spatial location cues.

The second option adds a slight amount of processing noise but has slightly stronger spatial location cues.

The third option adds a bit more processing noise but has even slightly stronger spatial location cues.

We advise that when encoding very quiet sound sources, that Option 1 be the default selection. When the sound sources are louder, we advise considering using Options 2 or 3.

Octofile A- to B-format Encoder for Linux

We have great news for OctoMic users who work in Linux environments!

Fons Adriaensen has released the source code for Octofile version 0.3.0.

Octofile is an A- to B-format encoder for Octomic.

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