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

Use of the microphone

It 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, 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.

ORTF microphone with custom cable at Zoom F6
The ORTF mic attached to the Zoom F6. A stereo cable based on the Simple P48 circuit is used for this setup.
Rig with Lumix GH5 and ORTF stereo microphone
Rig for the Lumix GH5 — both for tripod and handheld. The TRS cable goes directly into the camera's mic input.

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

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

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?

Please use good headphones when listening to the samples.

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. The noise floor is acceptably low for most situations. In quiet scenes some hiss might be noticable. If self-noise is too much: 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. Shuting off 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.

ORTF mic on the GH5 handheld rig in Berlin-Friedrichshain. Nice stereo effects are going on.
A tram passing by in stereo.
ORTF prototype on the GH5. This demo of Berlin club scene was very loud: De-clipping with Izotope RX 10 in post.
ORTF prototype on the GH5. Water, wood, birds and background noise at Müggelsee in Berlin.
ORTF prototype on the GH5. Garden next to the village church.
ORTF prototype on the GH5. Insects, birds, roosters, planes.

What's in the ORTF 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

Set with ORTF stereo microphone, shock-mount and mounting options
This is what you will find in the package.

Custom made TRS cable

I prefer a non coiled, soft cable. For cable management I use a piece of Velcro®. You will find a piece in the standard set.

You can order a custom cable, just you tell me how long you want it. The cable should be as short as possible but 2–3 cm longer than measured (a little extra space for cable management and bending the mic). Soldering TRS jacks takes some time and the two Neutrik jacks alone cost about 10 €, therefore the price will be higher than something you can buy at Amazon. The the cable length doesn't matter much in the calculation. You can order 3 meters for a long boom pole if you wish.

custom made TRS cable

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.

ORTF mic connected via XLR and 48 V phantom power

There is a way to connect the aurochs to professional preamps with XLR and 48 V phantom power: Credits to David McGriffy, Richard Lee and many thanks to Jules Ryckebusch, who reminded me of this possibility. A simple circuit brings down 48 V to 5 V for the electret capsules of the ORTF microphone. The circuit is small and can be integrated into XLR connectors. If you own a good external recorder or use a professional camera with XLR inputs, that's the way you'll get the best possible signal from this microphone.

The electrical parts are packed into a study cable with Neutrik connectors. For different use cases and rigs there will be different cable lengths available: Longer and shorter split, longer and shorter overall length.

The samples were recorded in 32 Bit 192 kHz and normalized. Some EQ was applied for lowcut (both) and linearisation of the frequency response (aurochs). Download EQ presets for Adobe Audition and DaVinci Resolve.

Aurochs, Zoom F6, voice, kalimba
Rode NT5, Zoom F6, voice, kalimba

The level of self-noise of the mics is very similar in both examples.

Comparison ORTF aurochs and Rode NT5
Setup for comparison between ORTF aurochs and Rode NT5
Stereo cable for phantom power
Custom stereo cable for aurochs at XLR inputs with 48 V phantom power.

Professional audio dream team on the camera rig

If you connect the ORTF microphone to a Zoom F3 mounted on the camera, you will get the best possible sound that this microphone can offer.

The ORTF mic is connected via XLR. The line output of the Zoom F3 goes to the mic input of the camera for decent scratch audio. This gives you fallback audio tracks in case you forget to press the record button on the Zoom F3.

You can use any other XLR-Adapter like e.g. Panasonic DMW-XLR1, Sony XLR-K3M or Tascam CA-XLR2d.

ORTF microphone and Zoom F3
ORTF microphone and Zoom F3
ORTF aurochs with Zoom F3 on the GH5. Only normalized and EQed. Thanks Lina!
ORTF aurochs with Zoom F3 on the GH5. Only normalized and EQed.