HUM Audio ARM-1S is a phantom-powered active ribbon microphone with a 1-inch (25.4 mm) aluminum ribbon element, 1.8 microns thick — the shorter-ribbon variant of the ARM-1 line, distinguished from the ARM-1L (2-inch ribbon, blue suspension details) by white suspension spider details. Fully discrete active electronics on 48V phantom power deliver -39 dB sensitivity (1 mV/Pa) — at condenser microphone levels — eliminating the insufficient gain and impedance matching problems typical of passive ribbon designs. The shorter ribbon of the ARM-1S produces a more neutral, tonally balanced character compared to the ARM-1L, making it the preferred choice when accurate, flat response without tonal coloration is required. Hand-built in Poland, reviewed in Sound On Sound.
Short ribbon — neutral, tonally balanced character
The shorter ribbon element (1 inch vs 2 inches in the ARM-1L) results in a slightly higher low-frequency boundary (40 Hz vs 30 Hz in the ARM-1L) and a flatter, more neutral tonal character without the emphasized low end and midrange presence of the longer ribbon. Sound On Sound describes the ARM-1S as smoother and tonally balanced — in drum room applications it gave a natural, flat representation of the kit in the room without accentuating any frequency range. An internal transducer shockmount isolates the ribbon element from mechanically transmitted vibrations; an additional external spider shockmount completes the isolation — a dual anti-vibration system. The ribbon element is shielded with copper. A three-position HPF switch (OFF / 100 Hz / 50 Hz, 6 dB/oct) located at the XLR connector base allows proximity effect control without an external equalizer. Active electronics provide a low 22-ohm output impedance — the microphone works with any preamplifier without impedance matching considerations.
Applications and comparison with ARM-1L
The ARM-1S is particularly suited to string sections, piano, woodwinds, acoustic guitar, vocals, drum overheads, and ambient recording, where accurate, natural character without frequency emphasis is required. The ARM-1L with its 2-inch copper-shielded ribbon has a fuller low end and slightly more presence in the upper-mids (6–10 kHz) — preferred for electric guitars, brass, and sources where more pronounced tonal contouring is desirable. Both models share an identical body (286.5 mm length, 60 mm diameter), the same active electronics, the same HPF circuit, and the same spider mount. The only difference is ribbon length and tonal character. The microphone ships with an external spider shockmount, a mic head dust protection cover, and a flight case.
KEY FEATURES
- Phantom-powered active ribbon microphone with 1-inch (25.4 mm) 1.8-micron aluminum ribbon
- Discrete active electronics — -39 dB sensitivity (1 mV/Pa), condenser microphone output level
- Short ribbon = neutral, tonally balanced character without coloration (vs ARM-1L: more contoured)
- Frequency response: 40 Hz – 14 kHz +/- 3 dB
- Maximum SPL: 138 dB
- 22-ohm output impedance — works with any preamp without impedance matching
- Switchable HPF (3 positions): OFF / 100 Hz / 50 Hz, 6 dB/oct — at XLR connector base
- Dual anti-vibration system: internal shockmount + external spider
- Phantom power 48V +/-5V
- Gold-plated XLR connector
- Identical body to ARM-1L — difference only in ribbon length and detail color (white vs blue)
- Applications: strings, piano, woodwinds, acoustic guitar, vocals, drum overheads, ambience
- Included: ARM-1S microphone, external spider shockmount, mic head dust cover, flight case
- Hand-built in Poland; 2-year warranty
TECHNICAL SPECIFICATIONS
- Acoustic operating principle: electrodynamic pressure gradient with active electronics (phantom)
- Polar pattern: figure-8
- Generating element: 1-inch (25.4 mm) aluminum ribbon, 1.8 microns thick
- Frequency response: 40 Hz – 14 kHz +/- 3 dB
- Sensitivity: -39 dB re. 1V/Pa (1 mV/Pa)
- Maximum SPL: 138 dB
- Output impedance: 22 ohms (electronic)
- Recommended load impedance: 150 ohms or greater
- HPF: 50 Hz and 100 Hz, 6 dB/oct, switchable (OFF/100 Hz/50 Hz)
- Power: phantom +48V +/-5V
- Anti-vibration system: dual (internal + external spider)
- Body length: 286.5 mm
- Body diameter: 60 mm (upper)
- Spider external diameter: 126 mm
- Flight case dimensions: 320 x 230 x 155 mm
- Finish: matte grey with white details (distinguishes from ARM-1L: blue details)
- Included: ARM-1S microphone, spider shockmount, mic head dust cover, flight case
