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SO.4 Ultrasonic Omni Microphone

Regular price $99.99

Shipping calculated at checkout.


The SO.4 is an ultrasonic omni microphone with a natural and extended frequency range. These highly versatile and sensitive mini pencil microphones are housed in a nickel plated aluminum body. The SO.4 is great for capturing soundscapes, spatial depth, sound decay as well as the most intricate details and micro nuances. Utilizing the Primo EM258 capsule, the microphone has excellent ultrasonic frequency response and can capture audio well into the ultrasonic range (up to 70k!). Because the SO.4 is omnidirectional, its pickup response is similar to that of the human ear. The EM258 capsule is a favorite among field recordists, sound designers, location sound, artists working with sound, and especially those seeking to record in the ultrasonic range.  

We designed the SO.4 to be compatible with all of the Sonorous Objects Standard series accessories. 

We're excited to be able to provide a frequency response graph and response data table that is specific to the unique microphone capsule used in the SO.4 microphone. 

The SO.4 Microphone is assembled by hand in NYC.


What's Included

(1) SO.4 Microphone

(1) SO.4 Microphone Cable

(1) SO Standard Microphone Clip

(1 ) SO Standard Attachable Foam Windscreen

*above quantity amounts will be doubled when ordering a matched stereo pair. 


- Exceptional low self noise

- Highly detailed 

- Wide dynamic range and frequency response for accurate sound reproduction across the audio spectrum

- Excellent ultrasonic frequency response that extends well above 20kHz (up to about 70k)

-Balanced, transformerless output for increased immunity to noise over long cable runs

- Small Form Factor

- Utilizes SO Standard Series Accessories

- Frequency Response Data unique to the specific capsule used in the mic that you receive 

- Industry Standard High Quality Components and Parts used. Neutrik Gold Pin Connectors, Mogami Shielded Cable, Amphenol 3.5mm TRS Connectors

- Fabricated in house by hand in NYC.

*SO.1, SO.3, and SO.4 Accessories are interchangeable and cross compatible. These accessories are part of the SO Standard Series

*SO Standard XLR Microphone cable is NOT compatible with the SO.4 microphone.


Capsule | Primo EM258

Polar Pattern | Omnidirectional

Frequency Response | 20 Hz - 70 kHz

Signal to Noise Ratio | 74dB 

Self Noise | 20dBA

Maximum Input SPL | 115dB

Dynamic Range | 95dB

Sensitivity | -32dB (+/- 3.0dB @ 1kHz) Stereo Pairs are matched within 0.3dB @ 1kHz

Operating Voltage | 48v Phantom Power (IEC61938 Standard) with SO XLR Cable option only*. 3.5mm connector option operates on typical Plug In Power

*Included SO XLR cable contains special circuitry to allow microphone to interface with 48v Phantom Power. Third party cables XLR are not supported.

Enclosure | Nickel Plated Aluminum

Dimensions Unconnected | 1 1/4” Length x  1/2” Diameter

Dimensions Connected |  2 3/4” Length x  1/2” Diameter

Polarity | Positive pressure on the diaphragm produces positive voltage on XLR Pin 2. XLR Option Only.

Operating Temperature Range | -20°C ~ +60°C 

Storage Temperature Range | -40°C ~ +85°C

Cable | Shielded, Mogami, 6 ft length terminated with a three-pin industry standard XLR male connector, Gold Plated.* OR Amphenol Mono/Stereo 3.5mm connector

*SO XLR cable contains special circuitry to allow microphone to interface with 48v Phantom Power. Third party cables XLR are not supported.


SO.4 Microphone Product Manual PDF


Frequency Response

20 Hz - 70 kHz (testing data only goes up to 20 kHz)

Audio Recordings


*all recordings made with the SO.4 plugged into a Sound Devices Mix Pre-6 II. The recordings contain no post-processing

*any subsequent modifications to the information above will be recorded on the SO.4 Microphone Change Log in the Sonorous Objects Resource Wiki.

Be sure to check out our resource wiki for additional information, contents and downloads. 

Sonorous Objects Resource Wiki