On-camera ORTF stereo microphone – the “Aurochs*

* Extinct European ancestor of domestic cattle. The mic looks a bit like a bull.

front view ORTF stereo microphone “Aurochs” and shock-mount
rear view ORTF stereo microphone “Aurochs” and shock-mount
The ORTF technique simulates the spacing between human ears with two cardiod microphone capsules. Therefore the stereo picture sounds very natural and immersive.

This microphone is mainly designed to be an on-camera stereo microphone. As an ORTF-style stereo microphone, it embraces the surrounding sounds and records an immersive soundscape of the environment. You can locate moving sound sources in the stereo field from left to right. It is sort of a counterpart to shotgun microphones, which are designed to narrow focus and exclude as much of the environment as possible.

This microphone plus the whole set is a new option for video cameras and smartphones, especially for documentary indoor and outdoor. But you can attach it to any sound recording device providing PIP (plugin power) — and with an extra custom cable to XLR inputs with phantom power. You could use it even wireless with a splitter cable and two transmitters.

Size and weight

Size ORTF microphone: 59 mm x 179 mm x 45 mm
Weight ORTF microphone: 49 g
Size shock mount: 60 mm x 60 mm x 49 mm
Weight shock mount: 27 g

Characteristics

Connection: 3.5" TRS stereo socket
Required plugin power: 5 V ± 50 %
Mount: 1/4" thread
Housing material: Nylon PA12, Ultrasint® TPU01

Specifications (capsule)

Directional characteristic: Uni-directional (cardioid)
Sensitivity: -31 dB ± 3 dB at 1 kHz
Impedance: 0.6 kΩ ± 30 % at 1 kHz
Signal-to-noise ratio (SNR): 78 dB at 1 kHz
Operating voltage: 5 V
Current consumption: 600 μA max
Max input sound pressure level (SPL): 125 dB

Typical frequency response

Mounting options for the “Aurochs” stereo microphone

What's included in the ORTF basic set?

The set is designed to be flexible, convenient to use and most important: silent. When you record sound on-camera, the whole setup including the operator should be as quiet as possible.

The solution was to use of rubber washers for every mounting point. I didn't find a manufacturer with all the measures I wanted, so I decided to punch them out by hand from industry quality rubber sheets.

Included in the set you find mounting options for every standard connector and some extra washers for replacement and optimizing your camera rig. There are adapters and extensions for 1/4", 3/8" (which includes ARRI-Locating Pins), a cold shoe adapter and a mini ballhead. Without camera cage you can mount the mic to the hot shoe. If you use a cage you can mount it where ever it suits you best.

The only TRS cable with angled male jacks (and I tried a few) which fitted well on every socket is Rode SC2. Therefore I include it, too. Unfortunately many camera sockets (including my GH5) tend to make a very loose connection. This Rode TRS cable worked fine everywhere.

righain Etsy shop

ORTF outdoor case closed
The set comes in a robust outdoor case.
ORTF outdoor case open
Set with ORTF stereo microphone, shock-mount and mounting options
This is what you will find in the case.

The construction of the ORTF stereo mic

Choose the best but keep it simple.

The ORTF-microphone nicknamed “Aurochs” hosts the latest cardioid capsules by Primo Microphones, Japan. These are electret capsules, therefore plugin power (PIP) is needed to make the mic work. Almost all video cameras do provide plugin power. Please check the manual and specifications of your camera. The two capsules are matched for equal sensitivity with a maximum difference of 0.3 dB (mostly less). The mic is passive, no extra batteries are required. There are no fancy electronics, just some resistors and a high quality TRS socket.

The housing and shock mount are 3D-printed with HP Multi Jet Fusion. The body is made from sturdy Nylon PA12 with a wall thickness of at least 2 mm, whereas the ground plate and the shock mount are printed in rubber-like and almost unbreakable Ultrasint® TPU01 and provide good shock and sound absorption. The TRS socket is made by Lumberg Connect, internal cables are made by Mogami, resistors by PRP Audio.

All parts are carefully chosen or designed to be reliable, durable and repairable. If a capsule or socket should fail, they can be replaced easily. For protection of the capsules the foam pop filters should stay attached anytime. Microphones in general do not like moisture and this one is no exception.

How does it sound?

The sensitivity of this mic ist well suited to record sound in common environments. Recording very loud sound sources, e. g. a heavy metal concert or machines in an industrial hall, might lead to distortion.

In my opinion the overall sound is decent and very open. It shows fine details and the frequency response is very flat for a cardioid electret capsule. The frequency curve shows a slight bass roll-off by 6 dB from 400 Hz down to 80 Hz and some up and down in high frequencies. High frequencies do affect the rendering of sibilants, therefore I use a custom EQ preset to level that out:

Download EQ preset for Adobe Audition

Download EQ preset for Davinci Resolve

The noise floor is acceptably low for most situations. In quiet scenes some hiss might be noticable. The recorded tracks react very well on de-noising in post production. In a test I could reduce the noise floor by 9 dB in Izotope RX 10 without getting audible artifacts.

A bigger issue than self-noise is the fact that most cameras themselves produce sounds which the mic will pick up. Depending on the model there are fans and an IBIS is not silent either. I don't use autofocus, so that potential source of noise isn't an issue for me. Eliminating the source of noise (focus manually, shut down IBIS) might help, or you can try to increase the distance to the mic in your rig. If your camera model is very noisy and not controllable, maybe this mic isn't the best solution for you to be on the camera.

Generally the mic preamps of cameras are not really clean. To assess the full potential of this ORTF mic, some recorder like the Zoom F3 or another XLR-connector is the way to go.

You have to be very close to a strong sender to hear RF noise. An iPhone directly at the capsules didn't produce any noise. Very close to e.g. a router (less than 1 m) some noises might be audible.

The shock mount

shock-mount “crucifer” top view
The shock mount deserves a nickname, too. I call it “Crucifer”.
shock-mount “crucifer” side view
It is 3D-printed as a single piece of Ultrasint® TPU01.
shock-mount “crucifer” bottom view
Only a 1/4" thread and a 1/4" screw are added.
shock-mount “crucifer” and Rode NT5
The shock mount can handle heavier microphones like the Rode NT5 (up to about 200 g).

I'm thinking about offering a set with only the shock mount and some connectors for different mounting options. That might be useful to people who don't need the ORTF microphone. Please contact me if you are interested.