Shure DFR11EQ User Manual
Shure
Main Menu
Brothers Incorporated
222 Hartrey A
Evanston IL 60202-3696 U.S.A.
venue
Model DFR1
1EQ User Guide
DFR11EQ
Digital Feedback Reducer and Graphic Equalizer
With Software Interface for Windows
*
1996, Shure Brothers Inc.
27A8523 (PJ)
Printed in U.S.A.
TABLE OF CONTENTS
Main Menu
INTRODUCTION 2
Features 2
Added
Features When Interfaced with a Personal Computer2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
THE
DFR1
1EQ 3.
Overview 3
DFR11EQ Theory 5.
Setup
for Feedback Control7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connecting
COMPUTER
Overview 10
Software
Using
the Feedback Reducer Panel
Using
the Graphic Equalizer
Viewing
Exiting
the DFR1
Accessing
DFR11EQ
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the DFR1
INTERF
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Functions
Response Curves
Connected DFR1
Settings
1EQ in a Sound System8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ACE 10.
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1EQ Application
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1EQs 16.
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12.
13.
14.
15.
15.
17.
Scenes 18
APPENDICES 19
Appendix
Appendix
Appendix
Appendix
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A. Specifications
B. Rack Mounting the DFR1
C. Connectors and Cables
D. W
arranty 25.
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1EQ 20.
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19.
21.
*Trademark Notifications
Shure is a registered trademark of Shure Brothers, Inc. Windows is a registered
trademark of Microsoft Corporation. Crystal is a trademark of Crystal Semiconductor
Corporation. Motorola is a registered trademark of Motorola, Inc. IBM is a registered
trademark
of the IBM Corporation.
1
INTRODUCTION
Main Menu
The Shure Model DFR11EQ is a single channel signal processor that combines a
feedback
designed to be placed in a sound reinforcement signal path to automatically detect and
control
designed for installed sound reinforcement applications: theater, conference rooms,
meeting halls, etc. The DFR11EQ is also an effective setup tool for controlling major
feedback
detected
but
algorithm
The
and
computer control with the supplied Windows* interface software.
reducer and graphic equalizer in a single, half-rack enclosure. The DFR1
acoustical feedback and
modes in live music applications.
The feedback reducer of the DFR11EQ automatically inserts narrow notch filters at
feedback frequencies.
are narrow enough so their ef
constantly searches for feedback, with or without the presence of program audio.
feedback reducer functions on its own or under external computer control.
The
graphic equalizer of the DFR1
adjustable high pass and low pass filters. The graphic equalizer can be accessed via
1EQ is
equalize overall sound system response. The DFR1
These notch filters stop a sound system from feeding back,
fect on audio
1EQ is made up of thirty 1/3-octave, constant Q filters
quality is minimized. The feedback detection
1EQ is
Features
Adaptive Notch Filter algorithm (patent pending)
which automatically detects feedback and deploys
up to 10 narrow band notch filters.
Crystal* 20-bit A/D and D/A converters
(Analog-to-Digital, Digital-to-Analog) for 104 dB
dynamic range.
48 kHz sampling rate for flat response to 20 kHz.
1
/
rack space chassis allows rack mounting of
2
one or two units in a single rack space with no
sagging or bending.
Shure Link Interface allows multiple units to be
programmed with a single computer
No internal batteries. Settings and DSP program
stored in internal EEPROM chip.
Electronically balanced input with combination
1
/
-in. and XLR connector
4
balanced or unbalanced outputs.
. Can be used with
.
Independently driven, cross-coupled, balanced
1
/
-in. and XLR outputs. Can be used with
4
balanced or unbalanced inputs, without signal
loss.
+4 dBu/–10 dBV DIP-switch-selectable input and
output levels.
Motorola* DSP56009 processor engine with full
24-bit internal processing.
RS-232 interface for external computer control
and firmware updates.
Internal linear power supply switchable between
120 and 240 V
cumbersome external power supply
Meets UL, CSA, VDE, and CE requirements for
safety.
Solid state bypass eliminates unreliable
mechanical relays and switches.
Added Features When Interfaced with a Personal Computer
Tamper-proof,
graphic equalizer
dB for each band.
constant-Q, 30-band,
.
Can boost up to 6 dB or cut 12
1
/3-octave
Response Curve V
response of the feedback reducer
equalizer
ac eliminates the need for a
.
iewing. Displays frequency
, graphic
, or both.
Adjustable 12 dB/octave high pass and low pass
filtering.
Front/back panel lockout control.
Numerical display of active feedback filter
frequency and depth.
Storage of multiple scenes to floppy or hard disk.
2
Q
Overview
Main Menu
Front Panel
THE DFR11E
BYPASS Button and LED. Press this button to
suspend feedback reducer operation and remove
filters from the audio path. Does not affect the
graphic equalizer. When the LED illuminates, the
feedback
reducer is bypassed.
SIGNAL LED. Illuminates when input signal is
present.
Intensity varies with input signal level.
CLIP LED. Illuminates when the input signal is
6 dB of clipping.
within
CLEAR Filters Button and LED. Press this
recessed button to reset all the feedback filters.
Clears filters even if Lock Filters is enabled. LED
illuminates
Back Panel
as the button is pressed.
LOCK Filters Button and LED. Press this button
to lock the filters at their current values. When the
LED is on, the unit will not change or add any
feedback
filters.
FILTERS LEDs (10). Indicate when individual
feedback
is
added, the LED flashes, then stays on.
filters are active.
When a filter changes or
NEW Filter LED. Flashes in unison with the
feedback
a
new feedback filter or changing an existing one.
POWER
the
on. When the power is off, the unit is bypassed
automatically.
filter LEDs when the detector is deploying
Switch and LED.
power on. LED illuminates when unit is powered
Press this button to
turn
Power Connector with Integral Fuse. Connects
to
the
9-Pin RS-232 Port. Connects the unit to a
computer.
DSP
Shure Link Interface. Allows linking of up to 16
DFR11EQs
DIP Switches.
AC power. The fuse is
connector.
For use with DFR11EQ software and for
firmware upgrades.
which may be accessed by computer
See
DIP Switches
located in the drawer below
.
.
Output Connector—
cross-coupled, balanced outputs can be used with
balanced or unbalanced inputs. Can be switched
between
switch. 1/4-Inch and XLR are driven independently
and either can be balanced or unbalanced without
affecting
+4 dBu/–10 dBV line-level operation by DIP
the other
Input Connector—Combined XLR and
balanced
Active
unbalanced outputs. Can be switched between +4
dBu/–10
3
dBV line-level operation by DIP switch.
1
/4-Inch & XLR. Active,
.
1
/4-Inch.
input can be used with balanced or
DIP Switches
Main Menu
system requirements. Switches 5 through 10 change other available
below.
The
DIP switches located on the rear panel are used for adapting the unit to the sound
options,
DIP
SWITCH
1–4
5
6
7
8 unused — —
9
10
Device ID see below see below
Filter Bandwidth Select
Determines
Graphic Equalizer Defeat
Bypasses the graphic equalizer
Front Panel Lockout
Disables the front panel controls,
except the power switch. Protects
current settings from tampering.
Output Level
Input Level
FUNCTION POSITION
UP DOWN
High
the Q of the feedback
.
filter
.
narrows as it deepens
Front panel buttons
Q
1/10-octave
EQ On
Unlock
operational
+4 dBu
+4 dBu
see the table
Low Q
1/10-octave
widens as it deepens
EQ Of
f
Lock
Front panel buttons
inactive
–10 dBV
–10 dBV
Shure Link Device ID
When
multiple DFR1
15.
DIP switches 1 through 4 on the rear panel are used to set the Link Device ID. T
the
Device ID, align the switches according to the illustrations below
preset
to Device ID 15.
DEVICE
123
DEVICE ID 4
123
DEVICE ID 8
123
DEVICE ID 12
ID 0
4
4
4
1EQ’
s are linked, each one is assigned a Link Device
. The unit comes factory
SWITCH UP
DEVICE ID 1
123
DEVICE ID 5
123
DEVICE ID 9
123
DEVICE ID 13
4
4
4
SWITCH DOWN
DEVICE ID 2
123
DEVICE ID 6
123
DEVICE ID 10
123
DEVICE ID 14
4
4
4
ID, 0 through
o change
DEVICE ID 3
123
DEVICE ID 7
123
DEVICE ID 1
123
DEVICE ID 15
1
4
4
4
123
4
123
4
123
4
4
123
4
DFR11EQ Theory
Main Menu
Feedback and DFR11EQ Operation
When
acoustical feedback occurs in a sound system, it is because the gain of the
is
too high. Since no sound system (microphones, loudspeakers, room acoustics, etc.) has
an absolutely flat frequency response, feedback will occur at specific frequencies before
others; these are the frequencies with the most gain. If the gain at only these specific
frequencies
back, without a perceptible dif
DFR11EQ.
At
discriminate between feedback and non-feedback sounds (speech and music). When this
algorithm
path
to reduce the gain at the frequency which is feeding back. If
the
filter depth is increased in 3 dB increments (up to –18 dB) until the feedback stops.
After the DFR11EQ stops the feedback at one frequency, the sound system may start
feeding back at another frequency. In this case, the DFR11EQ inserts another notch filter
into
the audio path at the new frequency
reduce
DFR11EQ Limitations
The
sound
is reached after 4 to 8 notch filters are set. This is because generally there are only a few
dominant
below).
dB improvement of gain-before-feedback in a typical system. However
much
out
all of the frequencies, better results will be obtained by lowering the gain of the system. If
the
system still has insuf
such as different microphone or loudspeaker placement. There are several excellent
publications which delve deeper into the issue of feedback and sound systems, including:
Acoustic Feedback – How to Avoid It, Vivian Capel, Bernard Babani Publishing, ISBN
0–85934–255–7; Sound Reinforcement Handbook
Leonard
Davis, Howard W. Sams and Co., ISBN 0–672–21857–7; “Understanding Sound System
Design”,
Matt
Anderson and Jon T
100
is lowered, then the system can operate with more overall gain before it
the heart of the DFR1
detects feedback, it smoothly inserts a –3 dB, 1/10-octave notch filter into the audio
feedback.
DFR1
1EQ (or any other notch filter system) cannot entirely eliminate feedback in a
system, it can only help to reduce it.
frequency
The DFR1
response peaks above the response of the entire system (see diagram
1EQ works very well controlling these peaks. The user can expect a 6 to 9
overall gain, then all of the frequencies have too much gain; instead of trying to notch
Publishing, ISBN 0–88188–900–8; Sound System Engineering
Rick Frank, Shure
system
feeds
ference in tonal quality
1EQ is a very
powerful algorithm that can accurately and quickly
. This is the operating principle of the
the feedback does not stop,
. The DFR1
1EQ can insert a total of 10 notch filters to
In a typical system, a point of diminishing returns
, if the system has
too
ficient gain, then other changes must be made to the sound system
, Gary Davis and Ralph Jones, Hal
Brothers, # AL1
, Don and
174; “Basic Handbook of Feedback Reduction”,
Carolyn
atooles, Shure Brothers, # AL 1280.
95
90
85
80
75
70
65
60 100 200 500 1000 2000
FREQUENCY (Hz)
5
5000 10000 20000
Fixed and Dynamic Notch Filters
Main Menu
The
DFR1
1EQ can control the notch filters as either
10 notch filters are factory preset as 5 fixed and 5 dynamic filters. There is no difference
between
set and a new feedback frequency is detected, the DFR11EQ will remove the oldest set
dynamic filter and re-deploy it at the new feedback frequency. The fixed filters remain
unchanged.
fixed
adjusted
is
dominant
and loudspeaker placement, and will not change appreciably. However, feedback can still
occur, for instance, when someone’s hand or head approaches a microphone. A good
setting for this type of system would be 7 fixed filters for the non-changing feedback
frequencies,
has
dynamic
is different, some experimentation is recommended to get the best results from a given
sound
dynamic and fixed filters until all 10 filters have been set. After
However
filter
, the existing filter will deepen. The number of fixed versus dynamic filters can be
via the DFR1
An
example of
one that has fixed microphone and loudspeaker locations. In this type of system, the most
frequencies
and 3 dynamic filters to catch the feedback frequencies caused by the talker
On
the other hand, more dynamic than
several non-stationary wireless microphones.
in this type of system to obtain maximum feedback protection. As every application
system.
, if feedback occurs at the same frequency as an existing dynamic or
1EQ’
s Windows interface.
a system that would benefit from more fixed filters and less dynamic filters
of feedback are defined by the room dimensions and the microphone
High Q vs. Low Q Filters
The
DFR1
1EQ of
first,
High Q, is the default setting. A High Q
is increased. This attenuates the minimum amount of signal possible to ensure system
stability, while maintaining excellent sound quality. This setting is appropriate for most
applications.
The
Low Q setting maintains the filter’s shape as it is deepened, so the width of the
effectively widens as the depth increases. Using this setting attenuates the signal more,
producing a greater system stability than the High Q setting, but with slightly diminished
sound quality. This setting is appropriate for systems such as a speech-only PA where
stability
is an absolute must, but the sound quality can be compromised a bit.
fers two selections for the shape of the 1/10-octave notch filters.
dynamic
fixed filters would be appropriate in a system that
Eight or even all 10 filters could be set to
filter’s width stays very narrow as the filter depth
or
fixed.
The
DFR1
all 10 notch filters are
1EQ’s
.
The
filter
Filter Locking
The
feedback filters can be locked from the front panel of the unit or from the computer
interface. When locked, new filters will not be deployed and existing filters will not be
deepened, even if feedback is detected. The DFR11EQ’s algorithm is designed to
accurately differentiate feedback from non-feedback sounds such as speech. However,
certain sounds such as electric guitar feedback or test tones, which sound like feedback,
may
cause the algorithm to deploy an unwanted filter
For
most applications, locking the feedback filters is unnecessary
the application will contain material which sounds similar to acoustic feedback, then it is
prudent
to lock the filters after ringing out the sound system.
6
.
. As a rule of thumb,
if
Setup for Feedback Control
Main Menu
The DFR11EQ will operate stand-alone as a feedback reducer. However, when
connected to a personal computer running the supplied DFR11EQ software, additional
options
the
is a preemptive measure in which the system gain is raised beyond the normal setting to
deliberately make the system feed back. The DFR11EQ will then set its filters, and the
system gain is then reduced slightly, and the system is stable and useable. This set-up
method
an
system, but filters are not set prior to use. The DFR11EQ adds extra insurance against
feedback:
catch it. This set-up method is used for systems which already have sufficient
gain-before-feedback, but need protection from the occasional stray feedback which can
occur
Setup
1.
2.
are available. See
There
are two basic ways in which to set-up the DFR1
“Insurance Policy” method. Both are valid for dif
is primarily used for systems which are operated near the feedback point and need
extra margin of stability
For the “Insurance Policy” method, the DFR11EQ is simply installed in the sound
the system is not expected to feed back, but if it does, the DFR1
due to non-stationary microphones or user-adjustable gain controls.
Connect the DFR1
Computer Interface
.
1EQ in the desired signal path location. See
In a Sound System.
Set the input and output level DIP switches to the appropriate settings for the
sensitivities of the connected equipment.
for details.
1EQ: The “Ring Out” method and
ferent situations. The
“Ring Out” method
1EQ is there to
Connecting the Unit
WARNING:
of
f if the DFR11EQ input is set to +4 and the output is set to –10. If the DFR1
input is set to +4 and the output is set to –10, then the DFR1
attenuator
DFR1
receive too strong a signal. It is recommended that you avoid using this setting.
3.
Set the system gain to minimum, and power up all of the equipment.
4.
Slowly raise the gain of the system, and set the gain of each microphone to achieve
the desired level.
5.
The red CLIP LED should illuminate only on the highest signal peaks. If it illuminates
more frequently
the level of the signal coming into the DFR1
6.
At this point it is highly recommended to equalize the sound system with the
DFR11EQ’
equalizer
sound system.
Other equipment may potentially be damaged after DFR1
, lowering the signal to the proper level for the power amplifier. If the
1EQ is turned of
, check to see that the input level switch is set properly
s built–in graphic equalizer (see
. The DFR1
f, this attenuation is bypassed and the power amplifier will
1EQ.
Computer Interface
1EQ’
s feedback reducer is more ef
Ringing Out the System (“Ring Out” method only)
1. If
necessary, clear any notch filters in the DFR1
T
urn of
f the BYP
2.
Slowly raise the gain of the signal going through the DFR1
occurs, the DFR11EQ will insert a filter deep enough to stop the system from feeding
back.
3.
Repeat step 2 until all fixed filters are set. (There are 5 fixed filters, unless changed
by the user via the computer interface.)
4.
Lower the gain by 3 to 6 dB to stabilize the sound system.
ASS and LOCK LEDs if they are not already of
1EQ by pressing the CLEAR button.
1EQ power
1EQ
1EQ is acting as an
. If it is, lower
) or an external
fective on a well–equalized
f.
1EQ. When feedback
Power Down
When power is removed from the DFR11EQ, all settings (graphic equalizer, feedback
filters, button states) are automatically saved to the DFR11EQ’s internal non-volatile
memory.
On power up, all settings are recalled automatically
7
.
Connecting the DFR11EQ in a Sound System
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Main Menu
The
DFR1
1EQ should be placed where an equalizer would be in a signal path — it should
be the final piece of equipment a sound signal passes through before going to a power
amplifier.
placed
flexibility,
sound system.
NOTE
Between the Mixer Main Output and the Power Amplifier
input
will affect all input channels. This setup is ideal for using the DFR11EQ as a feedback
reducer
Other signal processors (for example, delay or reverb ef
before the DFR1
1EQ along the signal path.
fects devices) should be
The following four diagrams show typical connections. Because of its utility and
the DFR1
1EQ can be connected in a large
variety of dif
ferent setups to benefit a
: See Appendix C. for descriptions of all cable and connection wiring.
The DFR11EQ is most commonly placed between the main output of a mixer and the
of a power amplifier
and as a graphic equalizer
, after any dynamics control processors. At the main output, the
.
unit
LINE IN
LINE
OUT
At a Subgroup Insert
When
using a multiple bus mixer, the DFR1
insert. The unit will affect only the channels associated with that subgroup: the other
channels
SUB SEND
SUB RETURN
will remain unaf
LINE
OUT
MAIN
MIXER
fected.
LINE
DFR11EQ
LINE OUT
IN
LOUDSPEAKER
POWER AMPLIFIER
1EQ can be connected to a single subgroup
LINE
IN
LINE
DFR11EQ
IN
POWER
AMPLIFIER
MIXER
LINE OUT
LOUDSPEAKER
8
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