Forty-five centimeters long, weighing almost seven kilos, with a varnished wooden cabinet and a solid aluminum front panel. The Primus lives up to its Latin name (“the first”): it sits in the middle of the Sonoro range, between the Prestige model with its CD player and compact radios like the Stream. The German manufacturer from Neuss has concentrated the essence of its audio expertise here in a format that can replace a complete hi-fi system, minus the optical drive.
The Primus is not just a simple radio sitting on a shelf. Its acoustic system combines two coaxial drivers (a 19 mm tweeter centered on a 76 mm midrange) with a 133 mm subwoofer installed under the chassis, facing the floor. This downfire configuration uses the space between the cabinet and the surface it stands on to radiate the bass. The bass-reflex port, also located on the underside, completes this setup.
Five Class D amplifiers deliver a total power output of 80 watts RMS: 2 × 20 W for the tweeters, 2 × 20 W for the midrange drivers, and 40 W for the low frequencies. A digital signal processor (DSP) manages frequency distribution and powers several predefined EQ profiles (Pop, Rock, Jazz, Classical, Flat). The system performs well in rooms of up to around 25 m².
The “3D Sound” mode is worth a closer look. Activated from the menu, it widens the soundstage by creating a sense of space that exceeds the physical limits of the cabinet. The effect doesn’t turn the Primus into a fully separated stereo system, but it adds an appreciable spatial dimension, particularly with classical and acoustic recordings.
The Primus centralizes virtually every audio source you might want. The built-in tuner receives FM and DAB/DAB+ digital radio. Via Wi-Fi, it provides access to more than 25,000 Internet radio stations and podcasts. Spotify Connect, Amazon Music, and Deezer are integrated directly into the interface (older versions, referenced as SO-410-XXX, also offered Qobuz, Tidal, and Napster).
On the back, the connections include a 3.5 mm jack auxiliary input, an RCA line input (for connecting a vintage turntable, an external CD player, or any other analog source), an optical digital input (handy for connecting a TV), an RCA line output (for connecting an additional subwoofer or an external amplifier), and a USB port limited to charging on current versions.
The front headphone jack offers wired private listening. Bidirectional Bluetooth, based on Qualcomm aptX technology, not only allows the Primus to receive music from a smartphone, but also to send sound to a wireless headphone. This feature is still uncommon on radios in this category.
Sonoro has provided three control methods. On the aluminum front panel, a notched rotary knob adjusts the volume and navigates through the menus displayed on the 2.8-inch color TFT screen. Programmable direct-selection buttons allow instant access to your favorite stations or services. This is often the fastest method for everyday use.
The supplied remote control reproduces these functions at a distance. It runs on a CR2032 button cell battery. The OKTIV mobile app (available on iOS and Android for recent SO-3400-XXX versions) offers full control from a smartphone: navigating between sources, searching for stations, managing favorites, and adjusting sound settings. Its response time may feel a bit slow for users who are used to browsing large music libraries quickly, but assigning favorite stations to the shortcut buttons on the device itself largely mitigates this limitation.
Older models (SO-3400-100- and SO-410-XXX) use the UNDOK app instead of OKTIV.
The wooden cabinet, hand-sanded according to Sonoro, receives several layers of varnish. The rounded corners, a visual signature of the brand, soften the lines. The front panel and controls are made of solid aluminum, with finishes available in matte black, gloss white, matte graphite, champagne, or matte white depending on the series. The unit weighs around 6.7 kg, giving it reassuring stability.
The TFT screen features a polarizing filter and automatic dimming that adjusts brightness to the ambient light. An alarm clock function is built in, allowing you to wake up to the radio or a traditional alarm tone.
This attention to manufacturing quality earned the Primus the Red Dot Design Award 2021 and the Plus X Award in the design, quality, and functionality categories.
Can the Primus be connected to a TV?
The optical digital input (Toslink) can receive sound from a TV equipped with an optical audio output. The Primus then acts as an audio system for the television, with the option to fine-tune the sound using the built-in equalizer.
How does the bidirectional Bluetooth work?
In standard reception mode, the Primus receives music sent from a smartphone or tablet via aptX Bluetooth. In transmission mode, it can send sound to a wireless Bluetooth headphone, making it convenient for late-night listening without disturbing others in the room.
Which app should be used to control the Primus?
Recent versions (product number starting with SO-3400-XXX, except SO-3400-100-) use the OKTIV app, available on iOS and Android. Older versions use the UNDOK app.
Can an external subwoofer be added?
The RCA line output on the back lets you connect an additional subwoofer or link the Primus to an external amplifier. The built-in 133 mm subwoofer remains active.
What are the differences between the Primus and the Meisterstück?
The Meisterstück is larger (57 cm wide versus 45 cm), heavier (around 9 kg), and has a built-in CD player. Its midrange and high-frequency drivers are separated, whereas the Primus uses coaxial drivers. The Meisterstück is better suited to larger rooms, up to around 35 m².
Sébastien
Good product, but the sound is a bit too heavy on the bass. I’ve reduced it almost to the minimum; I was expecting better sound…
Comment from January 20, 2026 — Experience from January 09, 2026
Thomas
It's hard to find a more compact system while maintaining audiophile-grade sound quality.
Ideal for providing sound in a small room like a bedroom or kitchen.
Ability to play any digital music format in a user-friendly way thanks to the app.
Plus, the finish is very clean and the unit looks great on a nice piece of furniture!
Comment from April 11, 2024 — Experience from March 30, 2024
