Royer Labs SF-12 is a passive stereo coincident ribbon microphone — two matched 1.8-micron aluminum ribbon elements mounted one above the other in a true Blumlein configuration (crossed figure-eights, 45 degrees off center) within a single ingot iron body. The SF-12 is fully passive: the absence of any active electronics eliminates any internal overload point, maintaining full frequency response all the way to the maximum SPL rating of above 130 dB. Each of the two transducers uses a proprietary crossfield motor assembly: four Neodymium magnets with Permendur iron pole pieces minimize the front-to-rear acoustic path length, extending the high-frequency ceiling without artificial boost. The ingot iron body forms part of the magnetic return circuit, actively containing stray flux — the source of the microphone's relatively high sensitivity for such a compact package. The SF-12 design originates with Bob Speiden; Royer produces it with upgraded toroidal transformers, a lower-mass ribbon, and improved transducer mechanics.
Crossfield motor and ingot iron body — the physics behind the SF-12's sound
A stereo ribbon setup built from two separate microphones — on a stereo bar or in separate housings — always introduces a small but measurable spacing between capsules. The SF-12 is genuinely coincident: both elements occupy the same acoustic point, eliminating inter-channel time-of-arrival differences and producing stereo imaging that collapses to mono without artifacts. The crossfield motor in each transducer — four Neodymium magnets with Permendur pole pieces — shortens the front-to-rear acoustic path to the minimum achievable, directly extending the high-frequency response while maintaining the flat characteristic of a well-designed ribbon. The 1.8-micron ribbons, each weighing approximately one-third of a milligram, deliver transient response comparable to a condenser microphone. Negligible off-axis coloration means the SF-12 maintains consistent character regardless of the angle of incoming sound — critical when miking wide sections or ensembles where sources span a broad horizontal arc.
Recording configurations and mono operation
The SF-12 supports two configurations from a single mic position: classic Blumlein and M/S — the latter requiring only matrix processing in the console or DAW, enabling post-session stereo width adjustment without moving the microphone. The lower element corresponds to the left channel and the upper to the right, referenced from behind the microphone. Phase compatibility between the two channels is complete — summing to mono creates no artifacts. Either element can be used independently as a standalone mono figure-eight microphone. As a passive design, the SF-12 requires a high-gain, high-input-impedance preamplifier; its sensitivity of above -52 dBv is at passive ribbon levels, which distinguishes it clearly from the active SF-24. The extension cable terminates in a Y-splitter to two 3-pin XLR connectors labeled Upper and Lower. Applications: drum overheads (jazz, rock, classical), orchestra and choir, piano, acoustic guitar, ensembles, voice-over, ambient capture. Lifetime warranty; first ribbon replacement free.
KEY FEATURES
- Passive stereo coincident ribbon microphone in Blumlein configuration
- Two matched 1.8-micron aluminum ribbon elements (99.99% Al), each ~1/3 mg — fast transient response
- Crossfield motor per transducer: 4x Neodymium magnets + Permendur pole pieces — short acoustic path, HF extension
- Ingot iron body as part of magnetic return circuit — low stray flux, high relative sensitivity
- No active electronics — no internal overload point up to maximum SPL
- True coincidence: both elements at the same acoustic point — perfect mono compatibility
- Supports Blumlein and M/S configurations from a single mic position
- Each channel usable independently as a mono figure-eight microphone
- Negligible off-axis coloration; consistent response regardless of incidence angle
- No audible diffraction effects or cavity resonance
- High-efficiency matching toroidal transformers; very low magnetic leakage
- Ribbon elements unaffected by heat or humidity
- Extension cable with Y-splitter (XLR5 → 2x XLR3), labeled Upper and Lower
- Lifetime warranty; first ribbon replacement free
TECHNICAL SPECIFICATIONS
- Acoustic operating principle: electrodynamic pressure gradient (passive)
- Polar pattern: symmetrical figure-8 (Blumlein)
- Generating element: 1.8-micron aluminum ribbon (99.99% Al)
- Motor assembly: crossfield — 4x Neodymium magnets + Permendur iron pole pieces per transducer
- Frequency response: 30–15,000 Hz +/- 3 dB
- Sensitivity: above -52 dBv re. 1V/Pa
- Output impedance: 300 ohms @ 1 kHz (nominal)
- Rated load impedance: above 1,500 ohms
- Maximum SPL: above 130 dB
- Output connector: XLR 5-pin (stereo)
- Dimensions: 206 mm (L) x 25 mm (W)
- Weight: 369 g (13 oz)
- Finish: Matte Black Chrome; optional Dull Satin Nickel
- Includes: SF-12 microphone, extension cable with Y-splitter (XLR5 → 2x XLR3), wooden case
