Royer Labs SF-24V User Manual

Royer Labs

Model SF-24V

Vacuum Tube, Stereo
Ribbon Velocity Microphone

Operation Instructions Manual
& User Guide

Made in U.S.A.

TABLE OF CONTENTS

Model SF-24V Ribbon Microphone

Revised 2009

Introduction! 3

SF-24V Vacuum Tube Stereo Ribbon Microphone! 3

Active & Vacuum Tube Ribbon Technology! 3

Description! 4

Applications! 4
Ribbons in the Digital World! 5

User Guide! 5

Using the SF-24V Vacuum Tube Stereo Ribbon Microphone! 5

Operation! 6

Using the RSM-24 Shock Mount Accessory! 7

Description! 7

Features! 7

Usage! 7

Properly Inserting the Microphone into the Shock! 7

Removing the Microphone from the Shock! 8

Connecting the SF-24! 8

Power Supply Input Module! 9

Fuse Replacement! 9

Voltage Changeover! 9

Amplification Considerations! 10

Stereo Microphones and Ground Loops! 11

Equalization and Ribbon Microphones! 12

Hum, Noise and Mic Orientation! 12

Microphone Techniques! 13

General Tips for Using the Royer SF-24V! 13

Specialized Stereo Recording Techniques! 16

Classic Blumlein Technique! 16

Mid-Side (M-S) Technique! 16

Care and Maintenance! 18

Care for the Satin Nickel Finish! 18

Care for the Optional Optical Black Finish! 18

Care for the SF-24V’s African Padouk Presentation Case! 19

Features! 19

Specifications! 20
Polar Pattern! 21

Frequency Response! 21

Wiring Diagram! 22

Warranty! 23

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Introduction

SF-24V Vacuum Tube Stereo Ribbon Microphone

Congratulations on your purchase of a Royer Labs model SF-24V vacuum tube stereo ribbon
microphone. The SF-24V is a handcrafted precision instrument, capable of delivering superior
sound quality and exceptional performance. The SF-24V represents a new level of performance
for ribbon microphones, combining sophisticated technological advancements with old-world
craftsmanship. The SF-24V incorporates two independent head amplification systems that utilize
proven vacuum tube technology. This enables the SF-24V to deliver the same sensitivity that the
recording industry has grown accustomed to with modern condenser microphones. The
amplifying circuits are not limited by a 48-volt phantom power source, thus allowing the
SF-24V to deliver superior headroom. In addition, the electronic circuitry completely isolates
each ribbon element from impedance mismatches, short circuits and other anomalies that can
degrade microphone performance or damage the sensitive ribbon elements.

This instruction manual describes the SF-24V, 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-24V 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-24V’s
capabilities. It will assist you in making the most of your microphone's 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-24V vacuum tube ribbon microphone.

Active & Vacuum Tube Ribbon Technology

The heart of the SF-24V is its proprietary electronic system consisting of specially designed
toroidal transformers and electronic 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-24V an output level comparable to that of condenser microphones, and its
buffer stages provide a low impedance output and present a perfect impedance load to each of
the ribbon elements. Standard passive 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-24V’s active vacuum tube electronics, the microphone’s frequency
response and output are much less affected by variations in the input impedance of the following
preamp.

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Description

The SF-24V vacuum tube 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-24V's
active electronics produce an output comparable to phantom powered studio condenser
microphones and because the ribbon elements are electronically 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-24V 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 vertically, connector down and the
“ROYER” logo facing the sound source, the upper transducer is OUTPUT 1 and the lower
transducer is OUTPUT 2, from the perspective of an observer behind the mic. The microphone
elements are each bidirectional (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-24V is supplied with a dedicated power supply and 7-pin microphone interface cable.
The output for each channel consists of a chassis mounted 3-pin male XLR connector. These are
identified as OUTPUT 1 and OUTPUT 2, and correspond to the lower and upper transducers,
respectively.

The SF-24V is reasonably tolerant of shock and vibration, but care should be taken to prevent
accidental stretching of the ribbon elements due to rough handling. This is covered in the Care &
Maintenance section of this manual. The performance of the microphone is unaffected by
changes in temperature or humidity.

Applications

The SF-24V 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-24V will capture performances with uncanny realism
and a beautifully full stereo image.

Because of the SF-24V’s coincident crossed figure-8 pattern, M-S (mid-side) recording from one
microphone is easily achievable. Once a recording has been completed using the proper
orientation, the sound field can be adjusted from pure monophonic to “super wide" or
exaggerated when compared to crossed figure-8's.

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Although spaced microphones can produce similar stereophonic results, such recordings when
summed to mono can suffer from “comb filter” effects: peaks and dips in the frequency response.
When the SF-24V is used for M-S recording, the feeling 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.

Ribbons in the Digital World

Digital recordings benefit greatly from the properties inherent in ribbon microphones. Since A to
D converters cannot distinguish between the sound source being recorded and the complex
distortion components often associated with condenser microphones, they sometimes have
difficulty tracking the signal, 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.

User Guide

Using the SF-24V Vacuum Tube Stereo Ribbon Microphone

The head amplification system utilized in the SF-24V consists of two independently configured
military grade vacuum tube buffering circuits. Power for the tubes is supplied to the microphone
from a dedicated AC-line operated power supply that connects to the microphone through a 7-pin
microphone cable. The power supply provides a high voltage source and independent low
voltage sources for the vacuum tube's filaments. An electronic constant current source
automatically compensates for any change in the microphone's cable's length and provides the
correct voltage and current to each of the vacuum tube's heaters.

1. Always connect the microphone to the power supply before applying AC or turning the
supply on. Allow at least ten minutes of warm up time before using the microphone. This is
required to give ample time for the vacuum tubes elements to "settle."

2. The stereo outputs of the SF-24V are available at the power supply through a pair of male
XLR connectors. OUTPUT 1 corresponds to the upper transducer and OUTPUT 2
corresponds to the lower transducer when the mic is held vertically. Each output is
transformer isolated and fully balanced. The SF-24V’s output configuration is as follows:
Pin-1 is a shared ground for each output connector; Pin-2 is signal hot (in-phase) and Pin-3
signal cold (reverse-phase).

3. In rare instances, the common ground connection (Pin-1) between the two output connectors
can cause a ground loop. This can occur when poorly designed preamplifiers or certain types
of patch bays and/or wiring configurations are encountered. If this condition presents itself,

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lifting the Pin-1 connection from either connector (preferably done at the input amplifier or
patch bay) will usually cure the problem.

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 power switch. The microphone’s electronics will stabilize in a few minutes
but it may take up to ten minutes for optimum noise performance to be fully realized.

4. When the microphone becomes operational, bring the two channel faders to 0-dB (unity) and
use the preamplifier trims to set the desired level. This technique maximizes the signal-to­noise performance of the preamplifier or console input channel.

5. When disconnecting the microphone, bring the channel faders down then turn off the power

supply and unplug the microphone cable ends.

Operation

There are a few important facts that are key to understanding how to use ribbon microphones
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-directional 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 discriminate 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. 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,
cancellation 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-24V is a powered microphone and must be connected to its power
supply to operate.

4. Never attempt to “test” the SF-24V (or any ribbon microphone) with an ohmmeter. Damage
to the electronics could occur. Always provide adequate protection for your SF-24V (or any
ribbon microphone). If the microphone is to remain set up on a stand when not in use, place a
“mic sock” (provided) over it until it is to be used. As even light wind can stretch the
SF-24V’s delicate ribbon elements, 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!

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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 necessitating a complete overhaul
of the microphone.

Using the RSM-24 Shock Mount Accessory

Description

Your SF-24V is supplied with a Royer RSM-24 suspension type shock-mount accessory
designed specifically for this microphone. The RSM-24’s specially formulated polymer mounts
provide maximum isolation from shock and vibration while holding the SF- 24V 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-mount easily accommodates standard US microphone stand threads (5/8", 27-thread),
and an adapter is provided for European microphone stand threads. The support frame is
machined from solid T-6 hard aluminum, then black anodized for long life and a clean
unobtrusive appearance. The clutch mechanism provides easy positioning of the shock-mount
with minimal pressure. There is also a relief button that enables the clutch handle to be
repositioned out of the way. The shock mount has two orientation slots for easy X-Y and M-S
positioning. The X-Y slot faces forward and the M-S slot is 45º to the left.

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-mount carefully. Observe that the upper
Delrin support tube has one slot inside the tube that faces
forward, the same direction as the logo, and one slot that faces
45º to the left of center. The forward slot is used to orient the
center, on-axis position of the microphone. This is critical in
establishing accurate left/right (X-Y) 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. The 45º left-of-center slot is used to orient the
microphone for M-S recording. With the microphone logo
inserted in this slot, the upper ribbon element faces forward for
the "Mid" signal and the lower ribbon element faces sideways
for the "Side" signal. (Figure 1)

Figure 1

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