(Last updated 11/06/2016)
Typical Recording Set-ups
TetraMic 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 the compact shock mount we supply with
TetraMic or another one of your choice that is at least as
TetraMic's output is a 6-pin mini-XLR jack. A 6-pin PPAc adapter
cable plugs into TetraMic and connects to the PPAc transmitter. Since
TetraMic's signal is unbalanced at that point and somewhat susceptible
to picking up strong electrical interference, we recommend keeping that
adapter cable length as short as possible and routing it away from
sources of interference.
The TetraMic's PPAc system can feed the signal to either a four-channel
recorder that has its own mic pre-amps, or a four-channel microphone
pre-amplifier/ADC (analog-to-digital converter) that feeds a
four-channel digital audio recorder. The recorder can be either a
computer or a stand-alone digital audio recorder.
Using TetraMic with a Portable Digital Audio Recorders
Tascam's DR-680MkII eight
channel portable digital audio recorder is probably the most
cost-effective and simplest way to record with TetraMic. The
combination makes very high quality ambisonic recordings. You can buy a
DR-680MkII in the US for $600 or less.
Alternatives to the DR-680MkII are the Tascam DR-701D, Zoom
F8 or F4,
Devices MixPre-6. Of the three recorders, the DR-701D is the
smallest. The F8 has the most mic pre-amps: eight.
Connect TetraMic to the recorders using our PPAc system. The PPAc
receiver's XLR connectors plug directly into four of the recorders' XLR
All of the recorders mentioned have very accurate, digitally-set
level controls so it's very easy to match the levels across TetraMic's
four channels. The DR-680MkII and the two Zoom recorders can even gang
the four channels so that you can control the levels with one knob. All
four recorders are recommended!
Using TetraMic with an iPad
The folks at n-Track report
that their n-Track Studio 7 application runs great on the iPad. You can
record pristine 192 khz/24-bit multichannel audio without having to
carry around a heavy computer and with the ease of use typical of the
The iPad is compatible with USB devices that support Class Compliant
USB Audio. Those are typically the devices that work when you connect
them to a computer without having to install any driver software.
Check with them for recommendations about audio interfaces that work
well with Studio 7 and the iPad.
Using TetraMic with a recorder that doesn't have digitally-set
Connect TetraMic to the recorder's four XLR inputs using TetraMic's
If the recorder does not have level controls that are set digitally,
you would first set each channel's Sensitivity and Level controls, lock
them down so that they can't change, and then record a stable tone to
each of the four channels. Low-cost tone generators are available from
Behringer (the CT-100), Shure (the A15-TG) and other audio
In post-recording (back in the studio), adjust the levels of the four
recordings of the tone so that they are within a tenth of a dB of each
other. Note the adjustments in gain for each channel, and apply them to
Using TetraMic With a MOTU Traveler or 4Pre
If you're using a MOTU Traveler or 4Pre mic pre-amp, plug the
TetraMic's PPAc receiver cables into the Traveler's or 4Pre's inputs.
The MOTU Traveler can be used with PC, via a FireWire (IEEE-1394) interface,
or as a stand-alone front end with four channel recorders that have Line
inputs and excellent gain tracking between channels. The 4Pre can use
FireWire or USB.
When used with a PC, you can use any of the many digital audio
workstation software applications. Here at Core Sound we use Ross
Bencina's AudioMulch. One
requirement for the DAW software is that it has identical latencies for
all four channels to preserve sample sync. ASIO drivers seem to do this
well, and the MOTU Traveler is provided with ASIO drivers.
One stand-alone digital recorder that folks have used with great
success is the Sound Devices 744. While it only has two microphone
pre-amps (two short of TetraMic's four outputs), the MOTU Traveler's (or
4Pre's) four mic pre Line outputs can be plugged into the 744's Line
inputs. The 744 has the ability to set the gains on its Line inputs
digitally, precisely preserving gain matching across channels.
Recording with TetraMic, MOTU Traveler (or 4Pre) and a PC
We recommend recording using 24-bit word widths, at a minimum of 44.1
KS/s sample rate. Set gains for all channels to the same setting. If
you're recording large choirs or orchestras, a good start is 15 dB. Try
to get peaks at around -15 to -20 dB. If you're recording loud rock
concerts, set levels to 0 dB; note that to keep from overloading the mic
pre-amps you might have to also use the Traveler's (or 4Pre's) 20 dB pads
If you are using a DAW that can use VST plugins, you'll be able to
monitor the recording in real-time, fully decoded, and record either
A-format (four channels), B-format (also four channels) or files decoded
to any specific microphone and playback configuration (from 1 to a very
large number of channels). The VVTetraVST plugin does the calibration
corrections and the A- to B-format conversions. The VVMicVST plugin
does the decoding to set microphone parameters (e.g., number of
microphones, the angles at which they point, each one's directivity) and
match your playback system configuration.
If your DAW doesn't use VST plugins, then you'll record four channels
of A-format and do post-processing later. Post-processing consists of
applying the calibration functions for your specific TetraMic, and
selecting microphone and playback configurations. The post-processor
you'll use will be "TetraMic for VVMic", a Windows application that we
supply with TetraMic at no extra charge. See the section on
Alternately, if your PC runs Linux, you can use Fons Adriaenson's
TetraProc software using calibration files that Fons will provide for
you. Fons creates the calibration files using the same test data we use
here Core Sound to create the calibration data used with "VVMic for
TetraMic". Contact us for details.
Recording With TetraMic, a MOTU Traveler (or 4Pre) and a Sound
If you're recording with a standalone digital audio recorder, make
sure that the gains on all channels are set identically. What you'll be
recording is the raw TetraMic output, called "A-format".