The SF-24 stereo ribbon microphone is a phantom-powered version of Royer's popular SF-12 stereo ribbon microphone. It combines the SF-12’s high-quality audio performance, outstanding stereo separation, and imaging with our exclusive active electronics system for ribbon microphones. The SF-24’s output of -38 dB is a full 14 dB more sensitive than our non-powered SF-12, putting its sensitivity on par with that of phantom powered condenser microphones. The unique electronics and custom-designed FET’s used in the SF-24 allow for ultra-quiet operation, with self-noise of lower than 18 dB.
Like an SF-12, the SF-24 is actually two matched ribbon microphones placed one above the other in a coincident pair, each aimed 45 degrees from center in the classic Blumlein configuration. The magnet/pole piece structure of each ribbon transducer delivers a wide, uniform frequency response with no substantial peaks or dips, and the 1.8-micron ribbons produce superb transient response. Frequency response is excellent regardless of the angle of sound striking the ribbons and off-axis coloration is negligible.
The SF-24’s extension cable comes with a Y adapter that splits into separate 3-pin male XLR connectors labeled “Upper” and “Lower” for the upper and lower capsules of the microphone (when held vertically).
Gain
Our active ribbon™ mics (SF-24 and R-122) are as sensitive as phantom powered condenser microphones, allowing you to use virtually any mic preamplifier or board pre. Conventional ribbon microphones are 15 to 30 dB less sensitive than condenser mics, necessitating the use of high-quality, high-gain microphone preamplifiers when recording softer sound sources like acoustic instruments, vocals, and room ambiance. The SF-24 contains two fully balanced, discrete head amplifier systems utilizing specially wound toroidal transformers and ultra-low noise FET’s, each delivering a sensitivity of -38 dB. This lets you mate an SF-24 to any preamplifier with average gain characteristics. Even with quiet sound sources, you’ll have enough level to drive any recording medium.
It is important to note that the SF-24’s higher sensitivity does not create additional self-noise. All of the SF-24’s increased level comes from its large, specially wound toroidal transformers – that wonderful thing called “free gain.” The level at each of the transformers is actually hotter than what comes out of the microphone. The phantom powered system operates at less than unity, adding no noise of its own. This system took years to develop and is in patent-pending status.
Impedance Matching
The electronics in the SF-24 provide a perfect load to the ribbon elements at all times, allowing the microphone to deliver 100% of its full sonic potential regardless of the input characteristics of the following mic-pre. Due to its low-impedance output, SF-24’s can also be used on extremely long cable runs with minimal signal loss.
A good impedance match is critical to ribbon microphones. Impedance mismatching loads a ribbon improperly, resulting in loss of low end, diminished body, lowered sensitivity, and overall compromised performance. With our Active Series ribbon mics, the ribbon element sees a perfect impedance at all times, regardless of the preamp you use, so its performance will never be compromised by the effects of improper loading. In addition, the ribbon element cannot be damaged by phantom power, electrical glitches, or miswired cables.
Recording
Like the SF-12, the SF-24 is uncanny for creating “you-are-there” stereo recordings that capture not only the instrument(s) being recorded but, depending on how the microphone is positioned, varying degrees of the acoustical space. In addition, the increased sensitivity and impedance matching circuitry allows for more consistent results in a variety of recording situations and with a wider selection of mic pre’s.
For mono recording, phase compatibility between the two sides of the SF-24 is excellent. This allows you to combine the two channels perfectly in mono without creating undesirable phase artifacts. This is particularly useful when capturing a wide sound field in mono; for instance, a singer who tends to move off the “sweet spot” of a mono microphone. Either side of the SF-24 can also be used individually as a mono microphone.
The SF-24 excels on classical piano, drum overheads, ensemble and orchestral recordings, a wide variety of percussion instruments, virtually all acoustic instruments, small vocal ensembles, large choirs, etc.
Recording in Mono
Phase compatibility between the two sides of the SF-24 is excellent, allowing you to combine the two channels for mono recording without creating phase artifacts. This is particularly useful when capturing a wide sound field in mono; for instance, a singer who tends to move off the “sweet spot” of a mono microphone. Either side of the SF-24 can also be used individually as a mono microphone.
Five years ago I purchased a Royer Labs SF-12 stereo ribbon mic, along with a pair of Royer's R-121 mono units. Finally realizing that a modern ribbon mic could stand comparison with the best of my tweaked-out vintage condensers was a veritable epiphany for me and, accordingly, I have used that SF-12 (and R-121s) on almost half of all the sessions I've done since that time.
After a session of very quiet contemporary acoustic music about three years ago, however, I started lamenting the fact that I would have been using my SF-12 even more, if it did not have such a low output level that no mic preamp in my kit could raise its voltage without adding so much noise that it would actually become distracting in a mix.
To make a long story short, in late August, 2001 I received Royer's first pair of SF-1A microphones - serial numbers 001and 002. They had not yet built an active stereo mic, and wanted my opinion on the sound of these prototype mono units - each of which, I was told, was exactly one-half of a stereo SF-12A (the working prototype name for the SF-24). The minute I plugged them in and turned on the phantom power, my mouth fell wide open. A few months later, Royer sent me a prototype SF-12A, serial #002, and during the past several years, I have used that one, as well as #003, since the company continued to tweak various amplifier and ribbon diaphragm thickness parameters until everyone was satisfied.
Features
Say what? Amplifier? Phantom power? Yessiree, these are active mics, complete with internal circuit boards! The phantom power from my Crane Song Spider mixer supplies plenty of current to run the SF-24's internal circuits, two special toroidal transformers mated to little boards which together raise the SF-24's level about 20 dB or so above a standard "passive" Royer ribbon mic. This puts its output level in the same ballpark as, say, my tweaked-out large-diaphragm vacuum tube Neumann SM-69. Make no mistake, using phantom power current does not mean that these mics output line level; they still require a preamp. But extra level is not exactly the point here, for gain with noise is not really worth very much. What was so special about those two prototype mics was that their noise level was virtually identical to that of any other condenser mic I own, and a far cry from the noise produced by my SF-12 when mated with the quietest of my high gain preamps - a Manley Mic/EQ 500 or Crane Song Spider mixer.
Since my first iteration of serial #002 incorporated the same transducer elements as Royer's passive SF-12 microphone (its minimalist electronics were purposely designed to be as transparent as possible) it sounded exactly like my SF-12, only noticeably louder, and much quieter. With Royer's active electronics, the ribbon "sees" an ideal load (just an inch or so away) at all times. Thus, its performance should be consistent regardless of a preamplifier's input impedance characteristics. Impedance mismatching is a common problem with standard ribbon mics and, to a lesser extent, with all microphones. This phenomenon is the rationale for the new mic preamps that offer adjustable input loading characteristics. The SF-24, on the other hand, sounds great with any preamp. Subsequent modifications to my SF 12A made it actually sound better than my SF-12 in such factors as transient response and hall ambience reproduction.
In Use
The first time I got to use my first SF-12A took place at the end of October, 2001, for a week-long Dorian Recordings session of the early music supergroup, Fortune's Wheel. As usual, I used it as one of four pairs of mics in my setup at Mount Holyoke College's Abbey Chapel (along with my other favorites at the time - AKG C 24, Neumann M 50s and SM 69) and the singers and string players liked its sound so much that it became the main mic used in the final mixdown. Even while picking up the quietest whispers from the group's soprano, Lydia Knutson, and the tiniest plucks from Robert Mealy and Shira Kammen's medieval vielles and harps, any noise contribution from the SF-12A was completely unnoticeable within the wonderful wash of sound captured in that stone chapel.
That session was the beginning of a long string of recordings I have made with my various prototype SF-12As. The mic I presently own is now representative of current production SF-24 models. I used it a few months ago on a solo piano recording of the music of Philip Glass, performed by Bruce Brubaker, at New York City's American Academy of Arts and Letters auditorium, and it helped establish a new "believe it or not" item in my recording career. After Bruce selected it as the best-sounding stereo pickup (up against the aforementioned mics, as well as SF-12A serial #003, which had a slightly thicker diaphragm), it received the distinction of being the first mic I was ever able to use all by itself for a solo piano recording! Its low noise level and superb ambience pickup was just perfect for capturing the sound of those hypnotic Glass Etudes in that most wonderful of East Coast chamber music recording venues.
Summary
I have been pretty lucky to be able to make recordings with Royer's SF-24 for two years before anyone got a chance! This is a great microphone.
Dr. Fred Bashour holds a Yale Ph.D. in Music Theory, and currently performs as a jazz pianist and church organist, in addition to working as a classical music producer and engineer.