royer SF-24 User manual

TABLE OF CONTENTS
Model SF-24
Active Stereo Ribbon Velocity Microphone
Introduction page 2
Active Ribbon Technology page 3
Description page 4
Applications page 5
Ribbons in the Digital World page 5
User Guide page 6
Operation page 7
Using the RSM-24 Shock Mount page 9
Connecting the SF-24 page 11
Amplification Considerations page 12
Stereo Microphones & Ground Loops page 14
Equalization & Ribbon Microphones page 14
Hum, Noise & Mic Orientation page 15
Microphone Technique:
- General Placement Tips page 17
Specialized Stereo Recording Techniques:
- Classic Blumlein Technique page 20
- Mid-Side (M-S) Technique page 21
Care & Maintenance page 23
Features & Specifications:
- Features page 24
- Specifications page 25
Wiring Diagram page 27
Frequency Response & Polar Pattern page 27
Notes page 28
Warranty page 32

Active Ribbon Technology
The heart of the SF-24 is its proprietary electronic system con-
sisting of specially designed toroidal transformers and electron-
ic buffering stages. This system provides excellent frequency
response, extremely low noise and distortion, and high SPL
handling (130 dB) without the use of pads. It gives the SF-24
an output level comparable to that of condenser microphones,
and its buffer stages provide a low impedance output and pres-
ent a perfect impedance load to each of the ribbon elements.
Unpowered ribbon microphones suffer substantially degraded
frequency response and lowered gain when they are paired to a
preamp with too low an input impedance. With the SF-24’s
active electronic system, the microphone’s frequency response
and output are not effected by variations in the input impedance
of the following preamp.
Sonically the SF-24 differs from the unpowered SF-12 in one
subtle way; due to the extra iron in the SF-24’s much larger
transformers, low-end frequencies sound slightly tighter and
more focused.
Key Points:
• No longer is it necessary to mate a ribbon microphone to an
ultra-high gain, low noise preamplifier for optimum perform-
ance. Any preamplifier of nominal gain will provide good
results with the SF-24.
• No longer is it necessary to carefully consider impedance
matching characteristics when choosing a preamplifier.
Microphone loading is a non-issue and consistent performance
is assured, regardless of the preamplifier’s impedance
characteristics.
• No longer is it necessary to be concerned about damaging the
ribbon element with phantom power. The active electronics
need phantom power to operate - a first for ribbon microphones.
• No longer is it necessary to worry about the effects of long
cable runs degrading the performance of your ribbon micro-
phone. The active electronics provide a robust low impedance
signal that can handle long cable lengths with minimal loss of
signal.
Introduction
SF-24 Active Stereo Ribbon Microphone
Congratulations on your purchase of a Royer Labs model SF-
24 active stereo ribbon microphone. The SF-24 is a handcraft-
ed precision instrument capable of delivering superior sound
quality and exceptional performance. The SF-24 represents a
new level of performance for ribbon microphones, combining
sophisticated technological advancements with old-world
craftsmanship. The SF-24 incorporates two independent head
amplification systems that operate on standard 48-volt phantom
power, similar to standard condenser microphones. This
enables the SF-24 to deliver the same sensitivity that the
recording industry has grown accustomed to with modern con-
denser microphones. In addition, the active circuitry complete-
ly isolates the ribbon element from impedance mismatches,
shortcircuits and other anomalies that can degrade microphone
performance or damage the sensitive ribbon element. The SF-
24 breaks the long-standing taboo associated with ribbon
microphones and phantom power; it actually requires phantom
power to operate.
This instruction manual describes the SF-24, its function and
method of use. It also describes the care and maintenance
required to ensure proper operation and long service life. The
User Guide section of this manual offers practical information
designed to maximize the performance capabilities of this
microphone.
Royer Labs products are manufactured to the highest industrial
standards using only the finest materials obtainable. Your
model SF-24 went though extensive quality control checks
before leaving the factory. Normal care is all that is required to
assure a lifetime of trouble-free service.
Please read this manual thoroughly in order to become familiar
with all of the SF-24’s capabilities. It will assist you in making
the most of your microphones’ superior acoustic properties.
This manual is a handy reference guide and we suggest you
refer to it whenever questions arise on the use and care of your
SF-24 ribbon microphone.
2 3

Applications
The SF-24 is a highly versatile microphone, ideally suited for a
wide range of critical recording applications. From drums,
acoustic stringed instruments and stereo vocals to ensembles
like big band, orchestra and jazz groups, your SF-24 will cap-
ture performances with uncanny realism and a beautifully full
stereo image.
Because of the SF-24’s coincident crossed figure-8 pattern, M-
S (mid-side) recording from one microphone is easily achiev-
able. Once a recording has been completed using the proper ori-
entation, the soundfield can be adjusted from pure monophonic
to “super wide.”
Although spaced microphones can produce similar stereophon-
ic results, such recordings when summed to mono can suffer
from “comb filter” effects: peaks and dips in the frequency
response. When the SF-24 is used for M-S recording, the feel-
ing of space changes but the sonic quality does not. For more
detailed information on the M-S technique, see the chapter
Recording Techniques: Mid-Side (M-S) Recording in this
manual.
The SF-24’s small size and optical black chromium finish cre-
ate minimal disturbance in the visual field, especially important
where the microphone must not obstruct the view of an
audience or of a motion picture or TV camera.
Ribbons in the Digital World
Digital recordings benefit greatly from the properties inherent
in ribbon microphones. Since A to D converters cannot distin-
guish between the sound source being recorded and the com-
plex distortion components often associated with condenser
microphones, they sometimes have difficulty tracking the sig-
nal, resulting in ringing and edgy-sounding tracks. With ribbon
microphones, ringing is almost nonexistent due to the ribbon’s
lack of distortion artifacts and high frequency peaks. A to D
converters have less difficulty tracking the ribbon generated
signal, resulting in very smooth digital recordings free of
microphone-related edginess.
Description
The SF-24 active stereo coincident ribbon microphone is the
only microphone of its kind available, combining high audio
performance with outstanding separation and imaging. It is a
modern ribbon design, with no audible diffraction effects or
cavity resonance. The SF-24's active electronics produce an
output comparable to phantom powered studio condenser
microphones and because the ribbon elements are electronical-
ly isolated from the outside world, the possibility of ribbons
becoming damaged as a result of faulty wiring, brownouts or
phantom power supply defects is virtually eliminated.
The SF-24 is a compact, stereophonic ribbon microphone array
consisting of two matched microphone elements that are placed
one above the other. Each transducer is positioned at 45º to the
left and right of center, or 90º from each other. When held ver-
tically, connector down and the “ROYER” logo facing the
sound source, the upper element is the right channel and the
lower element is the left channel, from the perspective of an
observer behind the mic. The microphone elements are each bi-
directional (figure-8) and may be addressed from either side
with equal sensitivity. The in-phase signals are achieved when
the microphone is addressed from the front, as indicated by the
“ROYER” logo. If, however, the microphone is suspended
upside down, the connections to the preamplifier should be
reversed since what was the left transducer is now responding
to signals from the right and vice versa.
Your SF-24 is equipped with a 5-pin XLR type extension cable
and a splitter cable that fans out to twin 3-pin male XLR con-
nectors. As shipped from the factory, the connectors are marked
“upper” and “lower,” since referring to them as "left” and
“right” could lead to confusion.
The SF-24 is reasonably tolerant of shock and vibration, but
care should be taken to prevent accidental stretching of the rib-
bon elements. This is covered in the Care & Maintenance sec-
tion of this manual. The performance of the microphone is
unaffected by changes in temperature or humidity.
4 5

could result from this mistake.
3. Be certain that the input channel fader or volume control is
set to minimum before plugging in any microphone.
Preamplifier gain trim should be set to minimum. Plug the
microphone in and activate the phantom power switch. The
microphone’s electronics will stabilize in a few seconds.
4. When the microphone becomes operational, bring the two
channel faders to 0-dB (unity) and use the trims to set the
desired level. This technique maximizes the signal-to-noise
performance of the preamplifier or console input channel.
5. When disconnecting the microphone, bring the channel
faders down and unplug the microphone cable ends. It is also
advisable to turn off the phantom power before unplugging the
microphone whenever possible.
6. If the studio has the microphone lines brought to a patch bay
(tie lines), never crosspatch a microphone line when phantom
power is applied or the monitor volume is raised. This could
cause damage to your microphone, preamplifier or monitor
speakers.
Operation
There are a few important facts that are key to understanding
how to use ribbon microphone intelligently.
1. With ribbon microphones, rejection in the “dead” areas is
very strong. Due to this directionality, ribbon mics should be
placed at 1.3 times the distance normally used with omni-direc-
tional microphones, or at approximately the same distance used
for cardioid microphones. This method is used to achieve the
same ratio of direct to reflected sound.
2. In the horizontal plane, ribbon microphones do not discrimi-
nate against the “highs” off axis, nor do they boost them on
axis. Therefore, several instruments or vocalists can be placed
in front of the microphone without favoring the performer in
the center of the group.
User Guide
Using the SF-24 Active Ribbon Microphone
The head amplification system utilized in the SF-24 was
designed to operate with standard 48-volt simplex phantom
power sources only. The microphone will not work at all if
phantom power is not provided to the microphone! This aspect
of an active ribbon microphone is in sharp contrast to the com-
mon wisdom normally applied to ribbon microphones, in which
phantom power usually spells danger or destruction to the rib-
bon element. Royer’s active series ribbon microphones require
phantom power to operate.
To ensure long service life of your SF-24 active ribbon micro-
phone, care should be taken when connecting the microphone
to a phantom power source. We have prepared a few tips to
ensure that your SF-24 will perform perfectly for many years.
We offer the following information as a general set of good
habits that apply to both active ribbon mics and solid-state
condenser microphones as well.
1. Always be certain to use the SF-24’s five-lead stereo cable,
which splits out to two short 3-pin cables with male XLR con-
nectors labeled “Upper” and “Lower.” Do not substitute exten-
sion cables of unknown wiring! The SF-24’s pin-out is Pin-1
shared ground for both ribbon transducers, Pin-2 signal hot (in-
phase) for the upper transducer, Pin-3 signal cold (reverse-
phase) for the upper transducer, Pin-4 signal hot for the lower
transducer, Pin-5 signal cold for the lower transducer. If addi-
tional extension cables are used, be sure they are in good serv-
iceable order. Standard microphone cables provide a shielded
ground carried along to Pin-1 and a balanced differential signal
carried along Pins-2 & 3, with Pin-2 signal hot and Pin-3 signal
cold.
2. Although it is usually safe to “hot plug” most phantom pow-
ered microphones to a preamplifier or console with the phan-
tom activated, we suggest that if it is possible to de-activate the
phantom power prior to plugging the microphone in, do so. This
minimizes any chance of random voltage surges entering the
microphone. More importantly, it reduces the possibility of
loud pops being transmitted to your monitor speakers should
the volume control be raised. Serious damage to your speakers
6 7

Using the RSM-24 Shock Mount Accessory
Description
Your SF-24 is supplied with a Royer RSM-24 suspension type
shock mount designed specifically for this microphone. The
RSM-24’s specially formulated polymer mounts provide maxi-
mum isolation from shock and vibration while holding the SF-
24 securely in place, allowing the microphone to be safely
positioned at any angle.
The RSM-24’s Delrin support tubes are relieved on the inside
to minimize contact with the microphone. Teflon strips are
bonded to the inside of the Delrin tubes and serve as a means to
slide the microphone in and out of the shock. It is normal for the
Teflon strips to develop wear marks with repeated use.
Features
The shock easily accommodates 3/8"-16 male, or 5/8"-27
female microphone stand threads using the thread adapter that
accompanies the shock assembly. The threaded arm allows the
shock to be affixed to a microphone stand in three different
positions. The support frame is machined from solid T-6 hard
aluminum, then black anodized for long life and a clean unob-
trusive appearance. The clutch mechanism provides easy posi-
tioning of the shock with minimal pressure. There is also a
relief button that enables the clutch handle to be repositioned
out of the way.
Usage
It is important to use the RSM-24 shock mount correctly.
Making sure that the microphone is inserted properly into the
shock mount will minimize any chance of the mic coming loose
and will assure proper orientation of the transducer elements. It
is also important to make certain that the mic is inserted and
removed gently to avoid unnecessary shock to the ribbons.
Properly Inserting the Microphone into the Shock
Examine the shock carefully. Observe that the upper Delrin
support tube has a slot inside the tube that faces the same direc-
tion as the logo. This slot is used to orient the center, on-axis
Several performers can be grouped at both the front and the
back of the microphone, with one proviso: Since the outputs are
out of phase at the front and back of the microphone, cancella-
tion can result if two tenors are placed on opposite sides at
equal distances and are singing in unison. Therefore, listen to
the feed before committing to it.
3. The Royer model SF-24 is a phantom powered microphone
and must be connected to a preamplifier or console cable of
delivering 48-volts at a minimum of 4-milliamperes per chan-
nel. Faulty or improperly wired cables could cause your SF-24
to become inoperative. Since the active electronics offer elec-
trical isolation to each ribbon, miswired cables should not cause
damage to the ribbons themselves.
4. Never attempt to “test” the SF-24 (or any ribbon micro-
phone) with an ohmmeter. Damage to the delicate electronics
could occur.
Always provide adequate protection for your SF-24 (or any rib-
bon microphone). If the microphone is to remain set up on a
stand when not in use, place a “mic sock” over it until it is to be
used. As even light wind can stretch the SF-24’s ribbon ele-
ments, do not carry the microphone around without placing a
mic sock over it. Failure to follow this commonsense practice
may yield a stretched ribbon and compromised performance!
5. Avoid dropping the microphone. An accidental fall to a hard
surface could stretch one or both ribbons and, depending on the
nature of the fall, possibly require a complete overhaul of the
microphone
8 9

Note:
If, after a time, body oils or other contaminants make it difficult
to insert or remove the microphone from the shock mount, a
small amount of talc can be used to "lubricate" the microphone
housing. Use talc very sparingly and do not let any of it get into
the ribbon transducers, as it can compromise the ribbons’
performance.
Connecting the SF-24
The SF-24 is supplied with cable set consisting of a 25-foot,
5-pin male/female XLR microphone cable and a separate Y-
type splitter cable. The splitter cable converts the stereo sig-
nals from the microphone cable to a pair of standard 3-Pin
male XLR plugs that provide the RIGHT and LEFT signals to
a stereo or two-channel preamplifier. With the microphone
positioned upright (logo facing sound source), the UPPER ele-
ment is RIGHT and the LOWER element is LEFT, as viewed
from the observer's perspective. The splitter cables are labeled
UPPER and LOWER rather than RIGHT and LEFT to avoid
confusion when the microphone is suspended upside down.
Although the active electronics are robust and the ribbon ele-
ments are electronically isolated from the outside world, it is
wise to make all your electrical connections prior to activating
phantom power. Avoid cross-patching any microphone tie lines
with phantom power activated, as this is equivalent to having a
momentarily "defective" cable as the patching cords are insert-
ed. This not only stresses the microphone's electronics but can
harm a phantom power source and produce loud thumps in your
speakers.
Since the SF-24 is active, its low impedance output allows for
long cable runs with minimal affect on the microphone’s per-
formance. High-frequency response losses and noise pickup
will be minimal even with cable runs up to several hundred feet.
position of the microphone. This is crit-
ical in establishing accurate left/right
positioning relative to the sound source.
The microphone is inserted in such a
manner that the "ROYER" logo on the
microphone nestles comfortably in this
slot. (Figure 1)
Hold the mic by placing the transducer
(ribbon element) end in the palm of one
hand. While holding the shock mount
in the other hand, gently insert the
microphone's base into the upper tube
first. Be sure that the logo on the micro-
phone aligns itself with the slot in the
upper support tube as you feed the mic
through. (Figure 2) Continue to feed
the microphone through the upper tube
and into the lower tube where it will
stop when it reaches the lip at the bot-
tom of the lower tube. Do not force or
jerk the microphone into position!
Removing the Microphone from the
Shock
Removal is simply the reverse process.
Firmly grip the microphone with one
hand and gently slide it out of the
shock. (Figure 3) It may help to gently
push from the bottom of the micro-
phone while removing it from the
lower tube. Again, be sure not to force
or jerk the microphone. Ribbon ele-
ments are sensitive to abrupt shocks
and blasts of air, so be gentle.
10 11
Figure 1
Figure 2
Figure 3

stretch well before its electronics would reach an overload con-
dition. Due to the high output potential of the SF-24, it is rec-
ommended that the microphone preamplifier you pair it with
have a switchable pad to prevent the possibility of overloading
the preamplifier’s input stage electronics. Some preamplifiers
are more thoughtfully designed than others, with a suitable pad
that is placed before the preamp’s active electronics, not incor-
porated into a “feedback loop” as is sometimes found. The lat-
ter design could still produce distortion due to overloading even
if the pad were used. Although this is rarely an issue, we felt
that it was important to cover the subject.
In conclusion, preamplifier coloration is optional and a matter
of personal taste. Some people love the effect of coloration
while others strive for absolute transparency.
Amplification Considerations
Almost any stereo microphone preamplifier (or pair of mono
preamplifiers) with nominal gain characteristics and built in 48-
volt phantom power sources will give excellent results with
your SF-24 active ribbon microphone. Unlike standard ribbon
microphones, which depend on a proper impedance match to
deliver optimal performance, the input impedance of your pre-
amplifiers will have minimal affect on the SF-24’s performance
because the ribbon elements are loaded perfectly via the
microphones’ internal electronics.
Careful consideration should be given to the quality of the
microphone preamplifier. Studio grade preamplifiers usually
sound much better than cheaper ones. Headroom, noise floor,
transparency and coloration are all factors to consider in deter-
mining which preamplifier is suitable for your studio or live
application. Other features are usually secondary and fall into
the category of conveniences or interface capabilities (such as
digital or optical outputs).
Agood preamplifier should sound natural, with no sign of edgi-
ness or excessive noise. Vacuum tube preamplifiers sound
warm, yet wonderfully airy and transparent. Do not expect a
vacuum tube preamplifier to be as quiet as a solid-state preamp,
as electron emissions from tubes tend to convey more “ther-
mal” noise than transistors. Tube preamplifier noise is far less
of an issue with the SF-24 than with conventional ribbon micro-
phones because the SF-24’s high output will override the noise.
Transformer coupled designs tend to sound punchy and full-
bodied and offer the added benefit of true electronic isolation.
This greatly enhances their ability to interface with other equip-
ment with minimal noise or hum. There are many excellent pre-
amplifiers on the market today. Choose one that fits your budg-
et and offers good performance, but remember that you get
what you pay for. If you have the opportunity to audition one or
more preamplifiers before you buy one, do so. Microphones
and preamplifiers work together as a team and some are just
better matches than others.
The SF-24 is capable of substantial output signal, especially
when used for high SPL applications like drum overheads. It
will not overload or produce distortion up to its SPL handling
capacity of 130 dB SPL. In actuality, the SF-24’s ribbons would
12 13

phone can replace a quality condenser mic, but the EQ friendli-
ness, inherent in ribbon microphones does allow for an
enormous amount of flexibility.
The reason that ribbon mics take EQ so well is their inherent
low self-noise, unusually smooth frequency response character-
istics and freedom from off-axis coloration. Dialing in high
amounts of equalization on condenser or dynamic microphones
also means dialing in extra amounts of the microphone's distor-
tion products and self noise: garbage that contributes to an
unnatural, unpleasant sound. Because distortion and self-noise
are almost nonexistent in ribbon microphones, high levels of
EQ can be used without adding harshness or excessive noise.
Hum, Noise and Mic Orientation
All dynamic element microphones, including ribbons, are sus-
ceptible to picking up stray alternating magnetic fields. Power
transformers (such as those found in guitar amplifiers) and
alternating current motors are the most likely sources of hum.
In-wall wiring and electrical utility transformers are other like-
ly sources. A well-designed microphone provides shielding to
minimize the effects of such stray magnetic radiation. In some
cases complete isolation is impossible and the result is usually
hum or buzz. Unpowered ribbon microphones can manifest this
condition to a greater degree because of their higher gain
requirements. With vintage ribbon microphones that often
employ large, bulky magnet structures and are often poorly
shielded, the problem can be worse.
The SF-24 reduces this condition because the essential gain is
provided at the microphone, negating the need for additional
gain to be supplied by the preamplifier. In addition, the Royer
SF-1, SF-12 and SF-24 family of microphones are designed to
minimize the effects of unwanted radiation by integrating the
transducer barrel as part of the magnetic return circuit. Royer’s
SF-series ribbon microphones go one step further by incorpo-
rating toroidal impedance matching transformers, which have a
natural ability to repel magnetic radiation.
Unwanted noise (hum) can only come from external sources.
Fortunately, simply repositioning a ribbon microphone is the
best way to get rid of unwanted noise. If hum is detected, the
microphone is in the proximity of an alternating magnetic field.
Stereo Microphones and Ground Loops
Some preamplifiers are prone to developing ground loops when
used in conjunction with stereo microphones such as the SF-24.
Ground loops can develop in the preamplifier with any stereo
microphone, regardless of the type (i.e. condenser, dynamic,
ribbon). A ground loop manifests itself as unwanted noise, buzz
or hum (usually 120 Hz).
The condition is brought on when the left and right transducer
elements are plugged into two inputs of a stereo or multi-chan-
nel preamplifier. The pair of three-pin male XLR connectors of
the stereo microphone cable usually shares Pin-1 as ground, so
they are grounded to each other through the cable set. If the
grounding scheme within the preamplifier is poorly designed,
or the distances to internal ground are too great, a ground loop
develops.
You can perform a simple test to check for this condition
(preferably done with a pair of headphones to avoid feedback).
Plug one side of the stereo microphone into either preamplifier
input. Listen to the output of the preamp. All should be quiet
except for the mic signal. Now plug the second side into the
next preamplifier input. If a noise or buzz develops, you have a
ground loop. The ground loop may be very slight or more pro-
nounced, depending on the preamp. Battery powered preamps
usually do not exhibit this problem, and neither do well
designed, line-operated mic preamps. The simple fix is to dis-
connect one of the microphone’s two Pin-1 ground connections.
Abetter method is to make a small ground-lift adapter fash-
ioned from a male-female XLR barrel adapter. Switchcraft
makes a very nice one and it takes less than five minutes to wire
it up. Simply connect Pin-2 to Pin-2, Pin-3 to Pin-3, and leave
Pin-1 disconnected. Correcting the problem at the preamplifier
is preferable, but is often more difficult and/or expensive.
Equalization and Ribbon Microphones
One of the great strengths of ribbon microphones is how well
they take EQ. Even with substantial amounts of equalization,
ribbons retain their natural, “real” quality. For example, when a
lead vocal is being performed on a ribbon microphone, you can
actually boost the upper-end frequencies to the point where the
ribbon mic emulates the performance curve of a condenser mic
with excellent results. This is not to say that a ribbon micro-
14 15

Microphone Technique
General Tips for Using the Royer SF-24
The following are good basic starting places for recording with
the SF-24. These positions are known to produce good results,
but experimentation is the key to getting the most out of your
recordings! Photographs of many of the following techniques
can be found on our website -- royerlabs.com
It is important to remember that the SF-24’s ribbon elements
can be damaged by wind. When the SF-24 is mounted on a
boom stand, be sure the stand is moved slowly. When the
microphone is taken down, put it in its box immediately or, if it
is to remain in its shock mount, place the mic sock over the rib-
bon end of the microphone. Leaving the microphone out
unprotected is inviting a re-ribbon.
Ensemble Performances
The SF-24 records ensemble performances beautifully. Simply
find the point in the room where you hear the best blend of the
instruments and room sound and place the microphone there,
with its logo facing the performers.
Strings
For stereo recordings of stringed instruments, start by position-
ing the microphone a few feet off the body of the instrument.
Depending on the acoustics of the room, you may want to move
the microphone closer to or further from the instrument to add
or minimize ambience. For violin, position the SF-24 horizon-
tally, two or more feet above the instrument. For larger string
sections, try placing the microphone slightly above the instru-
mentalists and angled down; a distance of three or four feet will
do the job nicely.
While listening (preferably with headphones) to the mic, move
it around. The mic will “find” the noise source quite easily. For
example, if you are miking a guitar amplifier and suspect the
amplifier’s power transformer may be the source of unwanted
hum, move the mic around the amp. You will probably find that
the hum is louder as you approach the amplifier’s power supply
and quieter when you move it away. Eliminating the hum can
be fairly simple and requires finding the “null” point of the
hum. The “null” point is the position that places the micro-
phone’s magnetic components away from the lines of the
noise's radiation. Slightly rotating the microphone is usually all
that is required to cancel out the hum. This is similar to the pro-
cedure guitarists use to eliminate hum from single coil guitar
pickups: turning around slowly while listening for the hum.
There will be a “magic position” where the hum disappears
completely.
Hum and other noise is often picked up in microphone cables.
Since the output of Royer Active Series mics is 15 to 25 dB
higher than with traditional ribbon microphones, any noise
picked up in the mic cables will be at a corresponding lower
level, and hence less likely to be objectionable.
16 17

results. If the room sounds good, try positioning the mic 10 to
20 feet from the piano.
If you position the SF-24 somewhere between the soundboard
and open lid of the piano, there will be some amount of reflect-
ed sound from the lid. Careful positioning can minimize or
accent lid reflections, depending on what sound you’re striving
for.
Choir and Orchestra
An SF-24 can produce dramatically good recordings of an
orchestra or choir. If possible, position the SF-24 at a height of
ten feet or so and a few feet behind the conductor. The wide
stereo pickup will reproduce the orchestra or choir with a stun-
ning you-are-there realism. The rear lobes of the figure-8 ele-
ments bring the ambient qualities of the recording environment
into the recording, adding to the natural feel of the recorded
performance.
Percussion
The SF-24 records percussion instruments naturally, without
upper frequency hype or low-end boominess. Congas, bongos
and the like can be recorded with left/right stereo effect by posi-
tioning the mic within a few feet of the instruments. Shakers,
bells, triangles and other instruments that are often problematic
in the upper frequencies will record naturally and unabrasively.
Vocal with Acoustic Guitar
For recording a vocal with acoustic guitar,
two separate mono tracks are required
with little leakage between the tracks. One
stand and one SF-24 can do the job nicely
when the two axes of sensitivity are cor-
rectly oriented (see illustration).
Note:
The SF-24 is not recommended for close-
miking loud amplified instruments. Its sensitive ribbon ele-
ments were not designed for extremely high SPL applications
like close-miked electric guitar. For close-miking high SPL
sound sources, ruggedness is a must and we recommend using
our R-121 or R-122 ribbon
microphones.
Drum Overhead
Position the SF-24 horizontally
over the center point of the kit, two
to three feet above the cymbals.
For a centered snare drum, aim the
Royer logo at the snare. Adjusting
the height of the SF-24 by even 6-
inch increments will produce dra-
matic variations in how the cym-
bals sit with the rest of the kit.
Many times an overhead SF-24 is
all that is needed for tom-toms and
cymbals.
For jazz recordings, EQ is generally not required. For more
aggressive drum tracks where cymbals need to sizzle, you can
brighten them by adding a few dB of 10K to 12K.
Brass
Brass records beautifully with ribbon microphones. For an
overall picture of a brass section within a larger recording ses-
sion, try placing the microphone two to three feet above the
instrumentalists and angled down, at a distance of three to eight
feet from the section. For a solo brass section, position the SF-
24 vertically at a height of five to eight feet and anywhere from
five to 20 or more feet from the section.
Close miking brass is a job for the Royer R-121 or R-122 -- we
do not recommend close-miking with the SF-24.
Reed Instruments
Normal working distances are about a foot or two from a solo
reed instrument. For multiple instruments, try placing the
microphone slightly above the instrumentalists and angled
down, at a distance of three to six feet.
Piano
There are several positions that will give excellent results with
the piano. Start with a distance of one foot to several feet from
the knee of the piano. A more direct “up front” sound will be
achieved when the microphone is placed closer to the sound-
board. If it is possible to remove the piano lid, an SF-24 sus-
pended horizontally over the soundboard will give outstanding
18 19

stereo miking with cardioid mics as “X-Y.” When figure-8’s are
used, it is more commonly referred to as “Blumlein” recording.
Mid-Side (M-S) Technique
In the early days of stereo radio broadcasting, the Mid-Side
recording technique was developed to allow for 1) simultane-
ous stereo and mono feeds from the same mic array and 2) elec-
tronic manipulation of the width of the stereo image. In M-S
recording, one mic faces sideways, one faces forward as shown
in Figure 2, and they are connected as shown in Figure 3.
With the SF-24 in a vertical position, cable end down, the lower
ribbon element is the “mid” microphone and the upper ribbon
element is the “side” microphone. By facing the Royer logo
directly at the center of the
performance, then rotating
the microphone 45º counter-
clockwise (viewed from
above), the upper ribbon ele-
ment will now face the center
of the performance, the lower
element will be at 90º to the
performance, and your SF-24
will be properly oriented for
M-S recording. If the micro-
phone is to be mounted
upside down, make the proper
adjustments in your
wiring orientation.
If the outputs of the mid and side elements are made equal using
gain controls, the stereo pickup will be similar to that of two
microphones placed as a Blumlein X-Y pair, delivering a wide
stereo image. As you reduce the level of the “side” element, the
width of the stereo image will narrow until, with the side ele-
ment turned all the way down, you have just the “mid” element
panned center for a mono pickup.
Specialized Stereo Recording Techniques
Classic Blumlein Technique
For many years, “coincident” microphone setups have been
widely used for picking up sounds in stereo as naturally as pos-
sible. The “Blumlein” technique, named for A.D. Blumlein,
involves the use of two figure-eight microphones positioned as
in the sketch (see Figure 1); so that one faces left and the other
faces right, at an angle of 90º (i.e., each displaced 45º from
center).
Each microphone ultimately feeds one speaker in a stereo sys-
tem, and due to the direc-
tionality of the microphones,
the result is a very well
defined “stereo effect” on
playback. For classical
music, particularly, the
reproduction can be very
satisfying.
The SF-24 stereo micro-
phone is two identical
microphones in just this
Blumlein orientation: if the
microphone is placed in
front of the performance,
with the Royer logo facing
the center of the ensemble to be recorded, the microphone will
give a stereo recording as per the Blumlein technique. Because
of the togetherness of the SF-24’s ribbon transducers, sound
will arrive at both ribbon elements at the same time. This means
that the two channels can be summed to mono with no comb fil-
ter effects, and room reverberation (undesirable in mono) is
cancelled to a surprising degree.
For the sake of clarity, engineers commonly refer to similar
20 21
Figure 2
Figure 1

Care and Maintenance
The SF-24 is a solidly built, precision instrument. All that is
required to ensure proper operation of this microphone is to
follow some commonsense rules.
1. To avoid transducer damage, do not expose the microphone
to severe shock or vibration. If the microphone is accidentally
dropped, test it to see if damage has occurred before returning
it to service. Low output or a dull sound would indicate a
damaged ribbon.
2. Do not expose the microphone to direct blasts of air or
strong air currents. Use a windscreen or suitable blast filter
when close miking a vocalist or certain types of wind instru-
ments. P-popping does not necessarily damage the ribbon ele-
ment but may produce unacceptable preamplifier overload and
could cause damage to speaker systems.
3. Do not expose microphone to liquids or caustic smoke.
4. Do not expose the microphone to strong alternating electro-
magnetic fields, i.e. the power transformers in amplifiers, or a
hum may result.
5. Use a soft cloth to clean the microphone body. A small
amount of denatured alcohol can be used to remove fingerprints
and other stains.
6. Keep metal filings away from the microphone at all times.
7. When not in use, store the microphone in its protective car-
rying case. If the microphone is to remain set up on a mic stand
between sessions, cover it with its mic sock (provided with your
SF-24).
8. Leave disassembly of the microphone to a trained techni-
cian. There are no user-serviceable parts inside.
If the outputs of the “mid” and “side” elements are recorded on
separate tracks, the electrical connections shown in Figure 3
can be made at the mixer outputs and the adjustment of the
stereo separation can be done during mixdown, rather than
during the actual recording.
Space does not permit a fuller discussion of the M-S intensity
stereo format, first described by Alan D. Blumlein over 50
years ago. We suggest the following reading on the subject:
W. Dooley & R. Streicher
“M-S Stereo: A Powerful Technique for Working in Stereo”
J. Audio Eng. Soc., Vol. 30 pp.707 (1982 Oct.)
22 23
Figure 3

CAUTION!
Due to the transducer’s powerful magnets, it is a good idea to
keep recorded tapes, spring-wound watches and personal cred-
it cards with magnetic coding away from the microphone to
prevent possible damage.
Features and Specifications
SF-24 Features:
• Excellent stereo imaging and separation in one micro
phone
•Smooth, wide frequency response
•Active electronics offer greatly enhanced output and a
constant, optimized impedance to the ribbon element
• X-Y, M-S or mono recording from one microphone
•Extremely low residual noise
•Ribbon elements are unaffected by heat or humidity
•Absence of high-frequency phase distortion
•Excellent phase linearity – even off axis
•Equal sensitivity from front or back of microphone
•Consistent frequency response regardless of distance
•No power supply required
•Compact size
24

Accessories: Protective carrying case,
protective mic sock,
25’ shielded 5-conductor cable
with 5-pin connectors, adapter
cable terminating in two (2)
XLR 3-pin male connectors,
RSM-2 shock mount
Optional Accessories: WS-12 blast filter,
10 dB in-line pads
Microphone Warranty: Lifetime to original owner.
(Repair or replace at Royer’s
option) Ribbons not included in
warranty.
Ribbon Elemen Warrantyt: One Year
For up-to-the-minute information on Royer products and their
usage, visit our website at www.royerlabs.com
26
SF-24 Specifications:
Acoustic Operating Principle: Electro-dynamic pressure
gradient with active
electronics
Polar Pattern: Symmetrical Figure-8
Generating Elements: Two 1.8-micron
aluminum ribbons
Frequency Response: 30 HZ – 15,000 HZ
± 3 dB
Sensitivity: >-39dBv Ref 1 v/pa
Self Noise: <18dB
Output Impedance: 200 Ohms @ 1kHz
Recommended Load Impedance: > 1000 Ohms
Maximum SPL: > 130 dB
Output Connector: Male XLR 5 pin
Power Requirements: 48-Volt Phantom
(per channel) only
Supply Current: 4 mA per channel
Dimensions: 270mm X 39mm (base)
X 25mm (top)
(10 5/8" X 1.5" wide
(base) X 1" wide (top))
Weight: 531 grams (18.7 ounces)
Finish: Optical Black Chromium
18K Gold (optional)
25

Notes:
28
Wiring Diagram
Polar Pattern
Frequency Response
27
0˚ 30˚
60˚
90˚
120˚
150˚
180˚
210˚
240˚
270˚
300˚
330˚
Upper Microphone
Lower Microphone

29 30

Warranty
Royer Labs warrants the SF-24 to be free from defects in
materials or imperfect workmanship. This lifetime warranty is
offered to the original owner and is not transferable. Royer
Labs will repair or replace an SF-24 that fails to meet factory
specifications during the warranty period (ribbon elements
excluded). No other warranties are implied. To validate this
warranty, product registration and proof of purchase must be
on file with Royer Labs. This warranty does not apply if the
product has been damaged by accident or misuse, or as a
result of repair or modification by other than a Royer Labs
customer service facility authorized to service this product.
Should it ever become necessary to service your SF-24, please
contact the factory for a return authorization number and
packaging instructions. In our continuing effort to improve our
products, Royer Labs reserves the right to make improvements
without notice or obligation. Specifications are subject to
change without notice or obligation.
Serial Number_____________________________
Upper Sensitivity________Resonance__________
Lower Sensitivity________Resonance__________
Date of Purchase___________________________
ROYER Labs
2711 Empire Ave.
Burbank, CA 91504
Telephone: [phone]
Fax: [phone]
31