Soundman D1 Interface + OKM II Classic Review

Wednesday, October 11, 2023

Soundman's newest addition to the line up , the D1 interface - a digital recorder that makes it possible to record in stereo using a smartphone (iPhone of Android) without the need of a standalone recorder. The Soundman D1 works with Soundman OKM binaural microphones as well as other stereo microphones.

The Soundman D1 interface operates at a high quality with a 24-bit resolution and a 96 kHz sample rate, making it as good (if not better) than a portable recorder. You can use the Soundman D1 with USB-A, USB-C, and Lightning devices. It features a TRS-3.5mm mic input for stereo recording and a USB-C output for connection to a PC or mobile phone. The adapter includes a TRS-3.5mm stereo headphone output for real-time monitoring. 

With microphone preamplification ranging from 0 to 30dB, the D1 ensures optimal audio capture. In terms of digital conversion, as mentioned earlier the D1 operates at a sample rate of 24bit/48KHz, delivering high-quality sound. The built-in headphone amplifier boasts 125mW, providing clear audio output. The USB-C digital connection allows for a seamless interface with various devices. The D1 is powered via the connected device through USB, offering convenience during use. It has an output voltage of 1.5V and is compatible with systems such as Mac OS Big Sur, Windows 10, iOS 14, and Android 9.0. It is suitable for use with PC/laptops, iPhones, and Android phones with OTG functionality (excluding Samsung series).

Key features of the Soundman D1 include its stereo recording capability, real-time monitoring function, and a 24bit/96KHz sampling rate. The split adapter design incorporates a TRS-3.5mm headphone monitor interface and a stereo microphone 3.5mm interface (TRS), enhancing its versatility.
OKM II Classic is a set of special in-ear binaural electret microphones that are worn in the ear and offer a unique ability to function through the line-in input of an audio device. Electret microphones typically require a power source, but the OKM II Classic microphones don't. They work via the line-in input without the need for additional power or adapters.

The in-ear design of the OKM II Classic allows a hands-free and comfortable way to capture binaural audio. This design allows you to position the microphones in the ears easily, mimicking the natural hearing perspective.The compact and lightweight build makes them portable, ideal for on-the-go recording scenarios. The microphone capsules are not in direct contact with the ear as they're freely suspended do, they don't capture or record physiological signals such as the pulse beat. At the heart of the OKM II Classic is its ability to capture high-quality audio even in windy days. The OKM II Classic binaural microphones are equipped with Rycote foam windshields which are permeable enough to allow sound in while suppressing unwanted wind noise. The binaural recording technique mimics human hearing, resulting in a three-dimensional, stereo sound output. The length of the OKM II Classic cable is 1 meter long and features a y splitter (located 39cm down the cable), as well as a transparent sleeve for cable management. The weight is 12 grams.

The microphones boast a wide frequency response (20 Hz - 20 kHz), ensuring that every nuance of the sound is faithfully reproduced. The primary goal of the OKM II Classic is to deliver a realistic binaural recording experience. By capturing audio from the same perspective as human ears, it provides a three-dimensional, stereo sound output that closely replicates how we perceive sound in the real world. For the Soundman OKM II Classic is rated at 115dB volume at 1 meter which means the microphones can accurate capture sounds up to 115dB before distorting without compromising the quality of the recording.

If the Soundman OKM II Classic is rated for 115dB at 1 meter, it suggests that it can handle relatively loud sound sources without introducing distortion or other unwanted artifacts into the recording. This can be particularly important in scenarios where capturing high-volume audio accurately is essential, such as recording live music performances or environments with elevated sound levels. The OKM II Classic measires 1 meter long.

One of the standout features of the OKM II Classic is its plug-and-play nature. Connecting to recording devices via standard audio jacks, these microphones are user-friendly without the need for complex configurations or additional equipment, making them accessible to both beginners and experienced audio users. The OKM II Classic microphones can be connected to a sound card on a computer so, you can record audio on a computer using the microphone inputs on the sound card. Recordings made with the OKM II Classic microphones can be played  via external speakers, although headphones is preferable due to the spatial location and three-dimensionality of the room, which can be more precisely experienced via headphones. The black plastic case seen pictured has a reel built-in designed to neatly store the microphones for transportation. 

Whether you're into field recording, live performances, or ASMR content creation, the OKM II Classic proves to be a versatile companion. Its ability to capture audio from the same perspective as human ears adds a layer of realism to your recordings.


You can also plug in the OKM II Classic microphones without the D1 interface, by plugging them into an audio source or recording device directly. That said, most audio sources/recording devices lack the necessary power so, you will need to use the Soundman D1 or Soundman A3 for both the microphone input and the line-in input. The Soundman A3 is an analog recorder designed to supply the OKM II Classic microphones with 6 volts, which is needed for recording very high sound pressure levels and for processing bass frequencies more effectively.The dimensions of the D1 interface are 4cm long x 4cm wide x 1cm thick. The built-in USB-C cable measures 9.5cm long. The weight is 15 grams

Selling points

  • Realistic binaural recording
  • Easy to carry
  • 4 year warranty
  • Suitable for various recording environments
  • Stereo sound output
  • Only electret microphone that works via the line-in input
  • Can handle relatively loud sound sources
  • Accurate sound reproduction
  • Compatible with computer soundcards
  • Plug-and-Play
  • Equipped with Rycote windshields
  • Soundman D1

Potential deal breakers

  • Less discreet than other microphone types
  • Requires the A3 amplifier to capture bass range clearly

In conclusion, the Soundman OKM II Classic stands out as a top choice for those seeking a binaural recording experience. Its realistic sound capture, ease of use, and versatility make it a valuable tool for audio enthusiasts and professionals alike. If you're looking to add a layer of immersion to your recordings, the OKM II Classic is a worthy investment. You can buy the OKM II Classic D1 Interface kit from

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