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BidirectionalBlumleinRoyer Labs SF-12

Multi-Pattern Ribbon Stereo Microphone

The SF-12 contains two complete ribbon capsules, each aimed ±45° from center in a Blumlein configuration. The mic includes an adapter cable that provides two standard XLRM connections.

Each ribbon is 1.8 microns thick. Transient response is described as “superb.” The frequency response is flat from 40Hz–15,000 Hz.

The SF-12 was originally designed in 1987 by Bob Speiden, and owes its heritage to a stereo ribbon created by Bang & Olufsen. A press release from Royer Labs in 1999 explains the backstory:

Royer Labs

Royer Labs builds the SF-12 as designed by Speiden but with a few changes including improved transformers (providing higher output and extended response), a lighter mass ribbon, and upgraded mechanics in the ribbon transducer that sounds identical to Bob’s original design but lends itself to better mass quantity production. It is unmistakenly influenced by the B&O Stereo Ribbon, but there are a number of significant differences that give the SF-12 a superior frequency response, higher SPL handling charisterics, and greater output.

The Royer Labs SF-12 is also known as: SF12, speiden SF-12.

The mic was released in 1999.


Frequency Response - BlumleinClick Graph to Compare!
SF-12 Blumlein Frequency Response Chart
Pickup Patterns Pads & Filters
Bidirectional (2.5 mV/Pa; 30 - 15,000 Hz)
Blumlein (2.5 mV/Pa; 30 - 15,000 Hz)
Ribbon Construction Impedance SPL/Noise
Length: 31.7mm
Width: 1.58mm
Gauge: 1.8 microns
300 Ohms (Low) Max SPL: 130 dB
Weight Length Max Diameter Interface(s)
369g (13.02oz) 206mm (8.11'') 25mm (0.98'')
  • 3-pin XLR male (2)
Power Specifications

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