SABINE Power-Q Operating Information Manual
The two-channel POWER-Q gives you
two full racks of gear -- all in one!
CURVE
TURB -
Automatic Room Flattening EQ
Program Shaping EQ
FBX Feedback Exterminator
Parametric EQ
Real-Time Analyzer
Compressor/Limiter
Downward Expander/Gate
Digital Delay
Digital Delay
Program Memory
Automatic Room Flattening EQ
Program Shaping EQ
FBX Feedback Exterminator
Parametric EQ
Real-Time Analyzer
Compressor/Limiter
Downward Expander/Gate
Digital Delay
Digital Delay
Program Memory
Table of Contents
1.0 Introduction..................................................................................................................4
2.0 Front and Back Panel Views and Controls...................................................................5
3.0 Block Diagram/Internal Signal Path .............................................................................6
4.0 Installation ...................................................................................................................7
5.0 Quick Start-up Reference ............................................................................................9
6.0 Overview and Philosophy ...........................................................................................10
7.0 Optimizing the Sound System and the Room with the POWER-Q: Five Steps ...........12
POWER-Q operating information
Background information
2.1 Main Menu windows (quick reference)
4.1 Where to install your POWER-Q in the sound system
4.2 Bypassing the POWER-Q
5.1 EQing an acoustic environment: Quick Instructions
5.2 Exterminating feedback: Quick instructions
6.1 Quest for loudness
6.2 Quest for clarity
7.1 Step One: The physical space
7.2 Step Two: Time alignment of speakers
7.3 Step Three: Setting the system and room to a “flat” response curve
7.4 Step Four: Tweaking the EQ
7.5 Step Five: FBX filters
8.0 Using the POWER-Q Digital Delay .............................................................................14
8.1 Digital delay applications and use
8.2 POWER-Q digital delay adjustments: Manual and automatic
9.0 Using the POWER-Q Automatic Room EQ ................................................................23
9.1 What is Automatic Room EQ?
9.2 How Automatic Room EQ works
9.3 Reference microphone choice
9.4 Reference microphone placement
9.5 POWER-Q controls for Automatic Room EQ
10.0 Using the POWER-Q Graphic Equalizer...................................................................29
10.1 Graphic equalizer applications
10.2 POWER-Q graphic EQ screens and options: Graphic EQ, Curve
Display , Reset Filters
1 1.0 Using the POWER-Q FBX/Parametric Equalizer ......................................................32
1 1.1 Types of filters: Fixed FBX, Dynamic FBX, and Parametric
1 1.2 FBX TURBO/Auto TURBO setup modes mode
11.3 POWER-Q FBX/parametric filter adjustments
1 1.4 Filter control menu: List Mode and Curve Mode
1 1.5 The “MORE” button for the FBX/parametric window
1 1.6 Preventing feedback in the event of equipment failure
12.0 Using the POWER-Q High and Low Pass Filters......................................................38
13.0 Using the POWER-Q Real-Time Analyzer................................................................39
13.1 Using a real-time analyzer
13.2 POWER-Q RTA adjustments
13.3 Using the POWER-Q RTA and digital delay settings to minimize comb filters
13.4 Using the POWER-Q RTA during performance
14.0 Using the POWER-Q Compressor/Limiter................................................................42
14.1 Compressor/limiter applications and use
14.2 POWER-Q compressor/limiter adjustments
15.0 Using the POWER-Q Expander/Noise Gate.............................................................44
15.1 Expander/noise gate applications and use
15.2 POWER-Q expander/noise gate adjustments
16.0 Saving and Loading Stored Configurations...............................................................46
16.1 Recall and storage options and use
16.2 Saving EQ Settings: Room EQ and Program EQ
16.3 Using the POWER-Q stored configuration window
17.0 Global Parameters: Configuring Internal Default V alues..........................................48
18.0 Password.................................................................................................................50
19.0 POWER-Q Options ..................................................................................................51
20.0 Remote Control of the POWER-Q ............................................................................51
20.1 Computer Requirements
20.2 Installing SABINE POWER-Q Remote Software
20.3 Using SABINE POWER-Q Remote Software
20.4 POWER-Q Remote Software Guide
21.0 POWER-Q Digital I/O Option.......................................................................................60
22.0 Bypass Options
23.0 Using the ADF: A Pro’s Guide, with Ken Newman ....................................................62
24.0 Troubleshooting T ips ................................................................................................64
25.0 Engineering Specifications........................................................................................65
26.0 Cautions and Warranty .............................................................................................66
Operating Guide Version 8 -- for POWER-Q firmware v2.40
Special thanks to Hans Drobilitsch of Hans Drobilitsch Audio GmbH. (Austria) and
Andreas Schneider (Chief Sound Engineer, Austria Center V ienna) for their valuable
contributions to the design and implementation of the POWER-Q
.
Section 1: Introduction
Section 1: Introduction
Congratulations and welcome to the new digital equalization and signal processing power of
the Sabine POWER-Q ADF-4000, two whole racks' worth of power in a single 2-U unit. Patch
the POWER-Q between the output of your mixer and the input to your crossover or power
amp, and you’re ready to harness the power of an arsenal of digital signal processing. (Note:
You can also use the POWER-Q in other configurations. See Section 4.1.)
The POWER-Q is truly remarkable because of its multi-tasking ability and ease of operation.
It's the latest breakthrough in the Sabine ADF Adaptive Digital Filter Workstation product line
and offers many of the features of the Sabine REAL-Q2 Real-Time Adaptive Equalizer - all in
one package.
The POWER-Q encompasses the following functions, all of which operate concurrently:
• Two separate, 2-channel, 31-band digital graphic equalizers
• Up to 12 additional filters per channel, configurable as any combination of:
• High and low-pass filters for each channel
• 2 channel fully adjustable compressor/limiter
• Full featured, filter-based RT A
• 2 channel digital delay for programmable time alignment of speakers by up to 83.2
mSec.
• 99 memory settings. Instant recall of all or selected parameters.
• Automatic Room EQ. Calibrate a system in any acoustic space to a flat response
curve automatically in just a few seconds.
• ClipGuard™ Adaptive Clip Level Control. This patented Sabine function
automatically prevents digital clipping and expands dynamic range to over 1 10dB.
• Optional remote control via RS-232 interface (for Windows™ computers)
• Optional Digital I/O: Allows user-selectable sample rate and input source.
• fully parametric filters
• fixed or dynamic automatic feedback control filters with Sabine’s patented
FBX Automatic Feedback Control technology
Y ou may quickly refer to the sections you need by scanning for the appropriate icons:
This manual is written to provide background information for implementing the POWER-Q’s
features in appropriate situations. These sections of the manual are denoted with the “BACKGROUND” icon.
Sections of the manual pertaining to operating the POWER-Q are indicated by the “HANDS
ON” icon.
Any information we think is essential is highlighted with an “IMPORTANT! READ THIS!” icon.
If you really can’t wait to get started using your POWER-Q immediately , refer to our “quick
start” section (Section 5). We do recommend you read the manual for a fuller understanding
and more complete utilization of the POWER-Q's features.
4
Section 2: Front & Back Panel Views & Controls
Fig. 1: POWER-Q Front Panel
Function Indicators for each channel
CLIP: CLIP LEVEL indicator lights when the input
Remote Control Indicators
MIDI: MIDI data
SERIAL: RS232 serial port data
DIGITAL: AES/EBU digital interface
*
Reference Mic
Clip Indicator
level is 3 dB below clipping level.
LIMIT: Indicates signal above limit or compressor
threshold.
SIGNAL:Lights when signal level is above -30 dBV
peak.
GATE: Indicates signal below gate or expander
threshold.
MORE Button chooses
additional POWER-Q menus
or soft key selections
CURVE
TURB -
Section 2: Controls
Up, Down, Left, Right
Cursor Movement Keys
Data Wheel
selects values
Reference Mic
Signal Indicator
Fig. 2: POWER-Q Back Panel
RS232 Remote
Control Connector
MIDI I/O
*
Connectors
Display Window
SERIAL REMOTE OPTION
RS232 POWER-Q
Network Connector
(for multiple POWER-Qs)
Soft Key
Menu Items
Soft Key
Selectors
Online Context-Sensitive HELP button
(When HELP screen is activated, "HELP" will
appear in lower right of display window. To escape
HELP screen, press HELP button again.)
ENTER Key
initiates action
Power On/Off
The POWER-Q will
automatically pass
signal through a
hard wire bypass
when the unit is
switched off.
DA-I/O OPTION
Digital Audio I/O
Connectors (XLR-3)
IEC-320/C14
AC Power
Connector
as of this publication, MIDI control of the POWER-Q is not yet implemented.
*
Channel B Input
and Output
(XLR-3)
Channel A Input
and Output (XLR-3)
Ground Lift Switch
(Differing ground potentials between or among interconnected
equipment racks may introduce hum or noise into the sound
system. The POWER-Q ground lift switch isolates the AC
ground from the chassis when in the extended position.)
Reference Mic
Input (XLR-3)
5
Sections 2 & 3: Menus & Diagrams
2.1 MAIN MENU WINDOWS (QUICK REFERENCE)
Fig. 3: Main Menu Items
Section 3: Block Diagram/Internal Signal Path
Fig. 4: POWER-Q
Internal Signal
Path
6
Section 4: Installation
4.1 WHERE TO INSTALL YOUR POWER-Q IN THE SOUND SYSTEM. The most common placement of the
POWER-Q is between the output of a mixing console and the input to a power amplifier. If your
system requires a crossover or additional delays (such as the Sabine DQX-206), put the POWER-Q
in line after the mixer, but before those units. The configuration looks like this:
Fig. 5: Most common
setup
A variation of this setup might involve using the POWER-Q as a “dual mono” unit. Patch the main
output of your mixer into Channel A of the POWER-Q, and the monitor output into Channel B.
Then plug Channel A POWER-Q output into your main power amp, and Channel B POWER-Q
output into your monitor power amp. This will allow use of the POWER-Q as if it were two separate mono units. The configuration looks like this:
Section 4: Installation
Fig. 6: Using the
POWER-Q as a "dual
mono" unit
Fig. 7: Using the
POWER-Q at a mixer
insert point
The POWER-Q may also be used at a mixer insert point, either for a single input channel, or for a
group or bus insert point. This will dedicate all of the features of the POWER-Q to a pair of single
channel inputs on your mixer or to a subgroup of inputs (for example, all the drums in your mix).
The patching will look like this:
7
Section 4: Installation
The reference microphone for the POWER-Q plugs in the back of the unit, into the jack labeled
“Ref A.” The “Ref B” jack is blank.
THE POWER-Q SHOULD NOT BE USED IN THE FOLLOWING CONFIGURATIONS:
·Do not plug a microphone directly into the channel A or B XLR input connections on the back
of the POWER-Q. These plugs are for balanced line level inputs, not microphones.
·Do not use the POWER-Q in an effects or auxiliary loop. Since such a patch is designed for
mixing processed (wet) and unprocessed (dry) signals together in a variable proportion, the
processing of the POWER-Q will be mixed with the unprocessed signal.
·Do not patch the output of any amplifier into any POWER-Q input. This will VOID your
warranty .
4.2 BYPASSING THE POWER-Q. The POWER-Q allows flexible options for bypassing all or part of its
internal processing. For more details please refer to Section 22.
A “quick bypass” can be accomplished simply by turning the unit off, which routes the input jack
directly to the output. However, please note two cautions when turning the POWER-Q on and/or
off:
1. If you turn the unit off, any suppressed feedback may suddenly reappear . As a precaution,
turn down the gain on your power amplifier.
2. When you turn the unit on, the unit will briefly be in bypass (for a few seconds) until the
processing is engaged. Suppressed feedback may occur during these few seconds. As a
precaution, keep your mixer and/or power amp turned down until the POWER-Q processing
engages.
8
Section 5: Quick Start-Up Reference
If you want to get going in a hurry , first make sure your POWER-Q is correctly patched into your
system. There are two main tasks the POWER-Q will perform: equalizing the tonal balance of the
system and eliminating feedback.
5.1 EQing AN ACOUSTIC ENVIRONMENT: QUICK INSTRUCTIONS. There are three basic methods of equalizing a sound system with the POWER-Q: Automatic Room EQ, Real-Time Analysis, or by ear .
Automatic Room EQ. Make sure you have a reference mic positioned correctly and plugged
into “Ref A” on the back of the POWER-Q (very important for optimal results). Select #1 (“AUTOMA TIC ROOM EQ”) from the MAIN MENU. Follow the on-screen instructions. Your system will be
analyzed and the EQ adjustments in the POWER-Q will be made in 10 seconds per channel.
Real-Time Analysis. Alternatively, you may elect to play pink noise through your speakers and adjust the Graphic EQ to balance the frequency response. To do this, first make sure you
have a reference mic positioned correctly and plugged into “Ref A” on the back of the POWER-Q.
Then select #4 (“REAL-TIME ANAL YSIS”) from the MAIN MENU, press the “MORE” button and
turn on the pink noise independently for Channel A. Use the superimposed Graphic EQ sliders to
make additional adjustments. Repeat the procedure for Channel B.
Section 5: Start-Up
Equalizing By Ear. You won’t need to plug in a reference mic to EQ your system by ear.
Select soft key #2 (“GRAPHIC EQ”) from the MAIN MENU. This will display the graphic EQ
screen, one channel at a time (you may select which channel with a soft key). You may adjust
individual filters using a combination of left/right arrow keys and the data wheel.
In addition to or instead of the Graphic EQ, you may affect system equalization with the POWER-Q
parametric EQ. This is accessed by selecting MAIN MENU option #3, “FBX AND PARAMETRIC
FILTERS,” and playing an audio source through your sound system and the POWER-Q. Twelve
filters and a high and low pass filter are available for each channel. These filters are accessed using
the up/down arrow keys and can be set to parametric (“PARAM”) using the data wheel. The data
wheel and left/right arrows set the frequencies, filter widths, and filter depths of all filters. Any changes
made to the parametric filters will add to the overall EQ of the system, including graphic EQ settings.
5.2 EXTERMINATING FEEDBACK: QUICK INSTRUCTIONS.
1. Once your room is equalized to your liking (or you may elect not to equalize and proceed
directly to feedback control, though we don’t recommend this), set up your microphones and
acoustic instruments in the positions where they will be used.
2. If you are using your POWER-Q in a 2 channel system, turn the power amp to zero gain for one
channel. This will allow you to set FBX Filters for the other channel.
3. Set all other controls for your sound system at the settings that will be used for performance.
Select soft key #3 (“FBX AND P ARAMETRIC FILTERS”) from the MAIN MENU. The POWERQ defaults to seven fixed FBX, three dynamic FBX and two parametric filters, and has up to 12
total filters available for each channel. (This means that using parametric filters for room
equalization by changing these defaults reduces the number of FBX filters available for feedback control.)
4. Press the MORE button until you see “TURB-” on the screen. Press the adjacent soft key .
5. Highlight “Automatic Setup” with the arrow keys.
6. Raise the master gain of your mixer until feedback is just starting, then press ENTER on the
POWER-Q front panel.
7. The POWER-Q will automatically raise its output gain and set filters, until either all available
FBX filters are set, or until the first dynamic FBX filter is set. Then the POWER-Q will reduce
its output gain to its original level.
8. Repeat this procedure for the second channel, turning down the power amp for the channel just
filtered, and turning up the gain for the second channel.
(This is just one scenario for setting FBX filters. Please refer to Section 1 1 for additional details.)
9
Section 6: Overview
Section 6: Overview & Philosophy
Live sound reinforcement can be a challenging business. Look what we have to deal with: The
guitar player turns up to 1 1 and still complains that she can’t hear herself. The podium speaker
points the mic at his sternum and mumbles, drowned out by the chatter of people eating dinner, in
a boxy hotel convention room. The rock singer asks for - no, DEMANDS - a monitor level loud
enough to hear over a drag race in a hurricane. The minister clips on the lavalier mic and wanders around while preaching, sometimes right past the speaker cabinet...
As an antidote to premature aging and undue stress, we at Sabine have dedicated ourselves to
simplifying the demands of live sound amplification by creating adaptive equipment that handles
some of the tedious (but important) mixing chores automatically . This allows sound engineers to
concentrate on making a mix sound good instead of dealing with acoustical problems!
The POWER-Q’s features are designed to help you achieve two important goals in sound reinforcement:
risk of sounding like a drill sergeant, let’s call this the desire to be LOUD and CLEAR.
6.1 QUEST FOR LOUDNESS. At least two bad things happen in the pursuit of loudness (putting aside
the deafness potential): feedback and lack of headroom.
getting more gain before feedback
, and
more clarity and definition in the sound
. At the
Let’s consider headroom first. The dynamic range of DSP is limited by the word length of an
individual datum: The more bits in a word, the greater the dynamic range. The POWER-Q offers
24 bit resolution and a dynamic range spec of >1 10 dB (with ClipGuard™). Plus, our ClipGuard™
Adaptive Clip Level Control system is designed to make it all but impossible for our units to clip
digitally; so if you’re hearing distortion in your system, it’s not likely coming from your POWER-Q,
because we’ve taken steps to prevent that. (Note: Make sure the FBX TURBO setup mode is off
before your program begins; see section 1 1.2.) Likewise, the compressor/limiter built into the
POWER-Q will raise the average gain level of your mix while protecting your speakers from hot
shot sound engineers whose goal in life is to explore the extremes of speaker cone flexion. All of
these functions are designed to maximize your gain without distortion.
Maximizing gain would be a far simpler matter if it weren’t for the problem created by adding gain
to a microphone in the presence of a speaker, which in turn reproduces the mic’ s sound, with the
mic in turn amplifying its own input, and so on. At some point, at least one frequency will regenerate. This is techno-speak for that dreadful ringing sound commonly known as feedback. The
nature and severity of the feedback will depend on the sound system and the acoustical environment, but feedback generally will occur before you reach the limits of your potential amplification.
This means that the most likely volume limitation of your sound system is not the power of your
amplifiers or the size of your speakers, but the threshold of feedback.
Enter the Sabine FBX. In the pre-FBX dark ages, feedback was often controlled by passing a mix
through a graphic equalizer and pulling out frequencies as close as possible to the ringing feedback. While this technique can reduce feedback, it also reduces the sound quality of the overall
mix. The one octave-wide filters of a third-octave equalizer (you read that right—the filters are
usually an octave wide, spaced on overlapping third-octave centers) are far too clumsy and
inaccurate to target feedback specifically . You don’t shoot a mosquito with a shotgun or do brain
surgery with hockey gloves. Shotguns, hockey gloves and graphic equalizers are valuable tools,
but only in the right applications. A graphic EQ is great to shape the overall sound of your mix
(and that’s why we’ve loaded your POWER-Q with two), but when you use it to control feedback
by pulling down EQ sliders, you’re also pulling out a big chunk of audio that is NOT feedback.
An FBX filter automatically detects feedback within a 1Hz resolution, places a tenth-octave wide
filter on it, and pulls down the level only as far as necessary to get rid of the feedback at a given
gain level. It is far more accurate in identifying and eliminating feedback and far less destructive
to your sound than even the best graphic equalizer. Plus it finds the feedback automatically in a
fraction of a second. You’d need to drink A LOT of coffee to react that quickly .
10
Section 6: Overview
The POWER-Q provides up to 12 feedback filters per channel, thus allowing you to excel in your
quest for loudness without compromising your second, equally important goal: QUEST FOR
CLARITY.
6.2 QUEST FOR CLARITY. Clarity in the sound coming out of your speakers is a result of a myriad of
considerations: the quality of the components you’re using, the skill you and others demonstrate
in setting up and operating the system, and the all-important acoustic properties of the room in
which you’re operating your system.
Now, it’ s no secret that some architects skipped class the day of the 20 minute lecture on room
acoustics, which is why so many rock concerts take place in basketball arenas and live sound
people sport premature gray hair. Standing waves, flutter echoes, boominess...the list of problems is as big as a lead singer’s ego. (Our congratulations to those architects who DO pay
attention to room acoustics.)
The good news is that in addition to all the graphic, parametric, and FBX control in your POWER-Q,
you are also the proud possessor of a full-blown Real-Time Analyzer. Y ou can generate pink noise
to help determine the frequency response curve of the surrounding acoustic space and compensate
for its peaks and valleys with your EQ controls, while viewing a graphic display of the results in real
time.
If you’d rather use your time to set up mics, patch in the rest of your gear or take a break, the
POWER-Q Automatic Room EQ feature will analyze the room for you and optimize your system
EQ to the response curve you specify . At the next venue, you can do a quick room analysis (in
less than a minute), then you can recall the memory of all your other EQ settings and every other
parameter previously set on the POWER-Q. You’ll be done before the guitarist finishes tuning
(unless he uses a Sabine tuner, in which case it might be a tie).
You can also use the POWER-Q for clearer sound by time aligning speaker stacks with our built-in
digital delay . You can delay sound in one set of speakers by as much as 83.2 milliseconds (with
20 microsecond resolution) to allow sound to reach listeners’ ears at the same time. This improves the phase consistency of the program, greatly enhances intelligibility , and synchronizes the
perceived sound origination point so the directional cues from your ears match the visual cues
from your eyes.
In conclusion, the POWER-Q is your friendly rack of goodies conveniently condensed to a 2U box.
It will automatically align your speakers, tune your system to any room, automatically detect and
eliminate feedback before and DURING performance, compress your mix bus, and remember
your setup for a given artist or application. Sorry , it doesn’t make cof fee, but with everything the
POWER-Q does for you, you’ll have plenty of time to make it yourself.
11
Section 7: Five Steps
Section 7: Optimizing The Sound System And The Room With
The POWER-Q: Five Steps
Remember, our quest is to amplify sound in a room to a desirable level without creating feedback
and distortion or sacrificing clarity. T o make the most of a sound system in a particular acoustical
environment, you will need to follow five simple steps:
1. Optimize the physical arrangement of your stage setup, speaker placement, and room
acoustics;
2. Time align your speaker stacks so that sound traveling from displaced speakers (and from
sound sources on stage) arrives at a designated reference position at the same time and/
or provides audio cues consistent with visuals;
3. “Flatten” the frequency response of your sound system in the acoustical environment so all
frequencies are heard in equal proportion at the reference position;
4. Adjust the equalization of the system to your personal preference or the requirements of a
particular application or performer (the POWER-Q will remember these settings and load
them from memory);
5. Apply FBX filters to live microphones to increase gain before feedback and insure maxi-
mum clarity , volume and microphone mobility.
The POWER-Q is amazingly useful for realizing steps 2 through 5 (see sections 8, 9, 10, 1 1, 12
and 13). Here are some suggestions for implementing all five steps.
7.1 STEP ONE: THE PHYSICAL SPACE. Unfortunately, the POWER-Q cannot physically rearrange your
stage setup or dampen reflective surfaces in your room. Y ou may not be able to build a bass trap
in a boomy room, find enough stage space to set the front-of-house speaker cabinets far enough
in front of the mic line to avoid howling feedback, or convince a night club owner to carpet the
dance floor. Ideally, a room with nonparallel, non-reflective surfaces that is large enough to
accommodate a full wave length (30 feet+) low bass frequency will provide you with fewer resonance points, a more evenly balanced room curve and less feedback. This acoustic ideal is
seldom found in the real world, so you should make the best of the situation with careful speaker
and microphone placement. To go beyond the limitations inherent in a less-than-desirable acoustical space, you’ll have to call in the artillery (electronics and equalization) to optimize your sound
system. This is why a device like the POWER-Q is worth every cent (and then some) of its very
reasonable price.
7.2 STEP TWO: TIME ALIGNMENT OF SPEAKERS. Compared to light or electronic signals, sound
travels very slowly . Sound traveling across a night club or concert hall, or from speakers at the
front of the stage to speakers half way to the back of the hall, is slow enough to often warrant
speaker time alignment with a digital delay . The sound emanating from a speaker farther away
from the listener is delayed relative to speakers close to the listener. The sound traveling to the
listeners’ ears from stage speakers takes longer to get there than the sound from the closer
speakers because most of the path for the latter is electrical. The correction is designed to allow
the sound from both sets of speakers to arrive at the listening position at the same time. (Obviously , in a situation where there is only a left and right front of house speaker stack, time alignment may be less of an issue. See Section 8 for a full discussion of these issues.)
The POWER-Q allows you to delay each output by up to 83.2 milliseconds. The delay time for each
channel can be set independently. For more details about setting the delay in your POWER-Q
output, refer to section 8.2. For more demanding delay applications involving up to six separate
outputs, automatic calculation of delay times and air temperature compensation, use the Sabine
DQX-206 delay/equalizer/limiter.
7.3 STEP THREE: SETTING THE SYSTEM AND THE ROOM TO A FLAT RESPONSE CURVE. Once the system
is in place and the speakers are time aligned, you are ready to even out (make equal, or “equalize”) the frequency response of the system in the room. This typically is done with broad filters,
such as the octave-wide filters of a 31-band graphic equalizer. Graphic EQ filters are spaced on
12
Section 7: Five Steps
third-octave centers, but are typically an octave wide, overlapping across adjacent filter controls.
You can vary the width of the POWER-Q’s filters by accessing the “GLOBAL PARAMETERS”
option on the MAIN MENU (see Section 17).
The POWER-Q excels at the task of room equalization, offering both automatic and manual
frequency response adjustment. In the Automatic Room EQ mode (see section 9), a reference
microphone (with a reasonably flat frequency response) is placed at your choice of listening
positions in the acoustical environment. The POWER-Q automatically plays a short burst of pink
noise, and measures the energy across the audible spectrum as heard at the reference mic. The
POWER-Q then makes automatic adjustments to produce as flat a response as possible at the
reference position. Y ou can make additional EQ adjustments (parametric and/or graphic) after
Automatic Room EQ, to tweak your system response by ear. The entire Automatic Room EQ
process takes less than a minute for both channels of the POWER-Q.
Alternatively , you may choose to equalize your system by playing pink noise over the loudspeakers
and observing the REAL-TIME ANAL YSIS of the propagated energy across frequencies as heard
by the reference microphone (see Section 13). You must then manually adjust the equalization
faders of the POWER-Q’s graphic equalizer section to produce the desired frequency response.
Note that the POWER-Q allows you to see both your equalization faders and the RTA response
the same window,
while you make adjustments.
which spares you the cumbersome task of scrolling from one window to another
in
7.4 STEP FOUR: TWEAKING THE EQ. Once the room is flat, you may want to customize the room
equalization to meet your own personal tastes or to match the entertainers' performance style.
You may do this either by making further adjustments with a second graphic equalizer (see
Section 10) or by inserting up to 12 parametric filters per channel for very precise adjustment (see
Section 1 1). These filters can be added in list (tabular) form or drawn as a response curve using
the data wheel. Once you have room and system tweaked to your ideal, you can save and name
up to 99 settings for future quick recall (Section 16).
7.5 STEP FIVE: FBX FILTERS. In live sound reinforcement, the true limitation for system loudness is
not usually the wattage of the amplifiers, the headroom of the mixer or the power handling maximum of the speakers. Before the system clips, you will almost certainly encounter feedback. And
for eliminating feedback, there is no better system than the Sabine FBX Feedback Exterminator.
Once the sound system is properly equalized, the narrow filters of the FBX will go a long way
towards increasing loudness without feedback. Placing the FBX filters in line WITHOUT first
using a graphic equalizer to reduce broad resonant room frequencies may produce several narrow
FBX filters clustered together closely at a point. This means you will quickly exhaust available FBX
filters trying to do a job better suited to a wider filter (i.e., a graphic EQ fader), you’ll reduce the
amount of potential increased loudness, and you won't get the maximum benefit of FBX.
The POWER-Q is the most complete system on the market that allows this much control over the
steps to maximize clarity and gain in any acoustical environment, using any sound system.
13
Section 8: Digital Delay
Section 8: Using the POWER-Q Digital Delay
8.1 DIGITAL DELAY APPLICATIONS AND USE. This section goes beyond the typical operating guide that
only explains the front and back panel adjustments of a piece of equipment. Instead, we discuss
the basic acoustical concepts needed to get the most out of the use of digital delay in sound
systems. If you are familiar with these principles, feel free to skip ahead. Some principles may
require additional delay channels and options available with the Sabine DQX-206.
Why Digital Delays? The most intelligible sound occurs when two people speak face to face.
The sound is loud and dry , and the direction of the sound aligns with the speaker. The most
intelligible sound systems are the ones that come closest to emulating face to face communication. If this is your goal, a digital delay is essential to your sound system.
There are three distinct applications for digital delays. The first and most important is synchroni-
zation of the loudspeakers to control excess reverberation and echo. Second, digital delays
help control comb filter distortion, and finally, digital delays are useful for aligning the acous-
tic image so the direction of the sound seems to be coming from the performer rather than from
the loudspeaker.
Loudspeaker Synchronization
Sound travels at about 1,130 feet per second in air, or about 1 foot per millisecond. On the other
hand, electronic signals travel almost one million times faster through your sound system to the
loudspeakers. The main task for digital delays is to synchronize multiple loudspeakers so the
sound traveling different distances arrives at the listener’s ears at about the same time. Synchronizing the loudspeakers reduces reverberation and echoes for improved intelligibility.
How to Synchronize Your Signals
There are several powerful tools available for precisely measuring the time a loudspeaker signal
takes to arrive at a certain point in the audience. Most of these tools are very sophisticated and
tend to be quite expensive. Fortunately, simpler tools are sufficient for most applications.
In the 1930’s, engineers synchronized the low and high frequency speakers in movie theaters by
feeding a sharp click through the system. They moved the speakers until they could only hear a
single sharp click coming from both speakers. You can use this same method with a common
child’s toy called a clicker. Pressing the thin metal strip makes a loud sharp click. A clicker is
especially useful when synchronizing the direct sound from the performer with the sound from the
loudspeakers.
Alternatively, you can use a phase checker especially for synchronizing the signals of two loudspeakers (either LF and HF or two full range systems) since most of the phase checkers include a
click generator and receiver. Phase checkers are quite affordable and have other uses besides
synchronization.
Processing (or Group) Delays
Converting signals back and forth from the analog to digital domain always delays the signal a
little. These conversion delays are often called processing (or group) delays, and usually range
between 0.9 and 5 milliseconds. You will notice that Sabine delays always display the processing
delay as the smallest possible delay value. For the POWER-Q, the processing delay is 1.38
milliseconds. You can bypass the unit for 0 seconds delay.
Not all manufacturers acknowledge processing delays in their specifications, but you
them into account when synchronizing your system. Make sure all digital equipment is on and not
bypassed when synchronizing. Also, be careful to make an appropriate adjustment in your delay
lines if you later add any type of digital equipment to the system.
14
must
take
Section 8: Digital Delay
Center Cluster Speakers
Center cluster speakers offer several advantages over systems that have speakers mounted on
the sides. The most obvious advantage is that the distance to the closest and most distant
locations in the audience is often almost equal, so most listeners hear about the same level.
Center clusters also offer two other advantages regarding visual imaging.
Studies have shown that people can detect even small horizontal changes in the direction of a
sound source, but vertical shifts are much less noticeable. This suggests that the sound from
center-cluster speakers is more likely to be visually aligned with the performer than loudspeakers
placed on each side of the stage.
All those in the audience who are closer to the performer than the center cluster will hear the
direct sound from the performer before they hear the sound from the loudspeakers. This makes
the sound seem to come from the performer, not the loudspeakers. (See the Precedence Effect
below.)
Comb Filter Distortion
Many who took high school science may remember ripple tank experiments where waves are
generated from two separate point sources. The waves from each source combine to form visible
interference patterns. In some places the wave crests and troughs are in phase so they combined
to make a larger wave. In other places the crests are out of phase, so the crest of one wave
source is canceled by the trough of the other. Ripple tank experiments show the interference
patterns are strongest when the amplitudes of the waves from each source are equal.
A similar interference occurs in sound systems when a signal is delayed and mixed back into the
original signal. These interference patterns are called COMB FILTERS because their frequency
response plots look like the teeth of a comb (see Figs. 8 & 9). There are a number of common
situations that cause comb filters. For example, when the program is played through two loudspeakers, the loudspeaker that is farther away interferes with the closer loudspeaker. Comb
filters are also created when a performer is picked up by two microphones, one closer than the
other. You even introduce comb filters by mixing digital effects back into the “dry” signal at the
mixer’s effects loop.
Fig. 8: COMB FILTERS. Input
signal mixed with a 2 msec.
delayed signal. (Both signals
have the same amplitude.
Max. filter gain is +6dB, and
max. depth is -4.)
15
Section 8: Digital Delay
Fig. 9: COMB FILTERS. Input
signal mixed with a 2 msec.
delayed signal. (Delayed
signal has 10dB less amplitude. Max. filter gain is
+2.5dB, and max. depth is -3.)
Reducing the amplitude of the
delayed signal reduces the
comb filters' effect.
Calculating Comb Filter Frequencies
The frequencies of the reinforcements and cancellations depend on the delay time (the time
difference between the arrival time of the original signal and the delayed signal). The frequency of
the first cancellation occurs at 1/(2t) Hz, where t = the delay time in seconds. The cancellations
are separated by (1/ t) Hz. Fig. 11 shows how the comb filters change with the delay time.
Fig. 10: Comb filters get closer
as delay time increases.
Comb Filter Amplitude
If the original signal and the delayed signal are the same amplitude, the reinforced frequencies
increase in amplitude by 6 dB, while the out-of-phase frequencies cancel completely to -4 dB.
Comb filters cause a lot of problems. The frequencies that are reinforced are prone to excite
feedback, while the out-of-phase cancellations make the program sound thin and over equalized.
Try this simple experiment to hear what comb filters do to your sound.
Fig. 11: Comb filters noticeably affect your sound.
16
Section 8: Digital Delay
Stack two identical full-range loudspeakers as shown in Fig. 12. Carefully align the HF horns and
wire the speakers in mono. Stand in front while listening to your favorite full-spectrum CD. Ask a
friend to move the top speaker slowly away from you. The degradation in sound quality you hear
is caused by comb filters. The experiment is most dramatic when you use good quality speakers.
Correcting Comb Filters
Comb filters are inevitable to some degree in every live sound system, and they cannot be
corrected with equalization. Fortunately, most comb filter problems can be reduced to a
minimum by synchronizing the signals and reducing the amplitude of the delayed signal. The
examples below show several practical applications.
The Precedence Effect: Aligning the Acoustic Image
Helmut Haas published a study in 1951 describing a series of experiments that demonstrated how
people perceive delayed signals and echoes. In his experiments, a listener was positioned
between two speakers placed 3 meters away; one was placed 45 degrees to the right and the
other was placed 45 degrees to the left. When the same program was played through both
speakers simultaneously, the listener perceived the acoustic image (the direction from which the
sound seemed to be coming) centered between the speakers.
When Haas delayed the signal going to one of the speakers by somewhere between 5 to 35
milliseconds, the listener perceived a shift in the acoustic image to the speaker heard first. While
the delayed speaker did not contribute to the apparent direction of the sound, it did make the
program seem louder and “fuller.”
Haas showed that you must increase the loudness of the delayed signal by about 8 to 10 dB
(twice the perceived loudness) in order for the acoustic image to move back to the original center
position. Increasing the loudness more than this, or increasing the delay somewhat more than 35
milliseconds, makes the delayed signal sound like an echo.
The phenomenon describing how the acoustic image follows the signal we hear first is called the
Precedence Effect. The phenomenon that makes two distinct sounds heard less than 35 msec.
apart seem like only one sound is call the Haas Effect. However, the terms are often used
interchangeably in the sound industry.
THREE APPLICATIONS FOR DIGITAL DELAYS
APPLICATION I: Under-The-Balcony Speakers
Fig. 12: Overhead view of
under-balcony application.
17
Section 8: Digital Delay
Fig. 12 shows a typical situation where the performer is amplified by a center cluster hanging
above the stage. Almost everybody in the audience will enjoy good sound, except those seated in
the shadow of the balcony. So we add an under-balcony speaker to fill in the shadow.
Now we have sufficient volume under the balcony, but the sound from the two speakers arrives at
the listener’s ears some 55 to 69 milliseconds apart. The two signals, along with their echoes,
result in an unintelligible cacophony. We must delay the sound from the under-balcony speaker to
synchronize the signals. Do we set the POWER-Q delay to 55 or 69 milliseconds? Obviously, the
geometry will not allow us to exactly synchronize every location under the balcony; we have to
compromise.
First, consider the program type. For spoken word programs, you will produce the best intelligibility if the signals from the under-balcony speakers arrive within 10 msec. of the signals from the
center cluster. Therefore we should set the delay to 65-69 msec. You can allow a little more
reverberation for programs that are mostly music.
Next, we must eliminate comb filter distortion. Find the axis where the levels of the center cluster
and under-balcony speaker are equal. (See "Comb Filter Distortion," p.15.) You can use the
POWER-Q to precisely synchronize the speakers along this axis to eliminate the most severe
comb filters. Comb filters off the equal-level axis are much less of a problem since a louder signal
is not affected very much by a weaker signal.
Finally, you can experiment with adding 5 to 10 milliseconds delay to both sets of speakers to
enhance the Precedence Effect for the audience seated near the performer.
In the final analysis, every setting is a compromise, and your ear has to be the final judge. Check
the sound in several different locations throughout the auditorium and correct the most severe
irregularities.
Application II: Center Cluster with Front Fills
Fig. 13 below describes a typical application that has a stage with a microphone, a center cluster
above the stage, and front fills in front of the stage. There must be thousands of installations
throughout the world like this that "get by" without digital delays. But with the POWER-Q, you can
improve the intelligibility and add a new quality without ringing up any significant costs. Use the
POWER-Q in this situation to align the visual image with the acoustic image. The program is
much more enjoyable when the amplified sound seems to be originating with the performer, not
the loudspeakers.
Fig. 13: Synchronizing center
clusters and front fills.
18
Section 8: Digital Delay
Find a central place in the audience where the center cluster is 6 to 8 dB louder than the direct
sound from the performer. Delay them so that their sound arrives 5 to 8 milliseconds after the
direct sound from the performer. Experiment by bypassing the POWER-Q in and out to hear how
the source of the sound seems to move from the loudspeakers to the performer and back. Now
your ears have the same directional information as your eyes, so the performance will sound more
natural and exciting. The best seats in the house just got better.
What about the front fills? Their purpose is to add intelligibility and listening comfort to the first few
rows nearest the stage by filling in the areas missed by the center clusters. Add about 8 msec. to
the front fills to take advantage of the Precedence Effect.
The 8 msec. setting presumes the performer is standing on the front few feet of the stage. But
some stages are well over 30 feet deep. What if there is a second performer standing 25 feet
behind the first? The direct sound from his or her voice will reach the first few rows about 25
msec. after the first performer's. The audience will perceive the first performer directly and the
second performer through the loudspeakers.
We can add the advantage of the Precedence Effect to the second performer by placing the
POWER-Q in the mixer's channel insert point and adding a 25 msec. delay.
Certainly taking advantage of the Precedence Effect is not as obvious to the audience as eliminating feedback, but it is nice to know you did all that is possible to make the performance enjoyable.
Application III: Synchronizing the signals of a far-throw and short-throw loudspeaker.
In order to reach the proper coverage in larger venues, we often stack two full range speakers - a
short-throw center cluster for the audience below and a far-throw speaker for the back of the
auditorium. It is almost impossible to perfectly align the stacked speakers mechanically, so comb
filter distortion becomes a problem in the area where the levels from both speakers are equal.
The same thing happens with speakers mounted on the right and left sides.
Fig. 14: Aligning far- and
short-throw speakers. (The
level from both speakers is
equal.)
It is impossible to remove comb filters with equalization, but the POWER-Q eliminates them in
short order without affecting the spectral balance for the rest of the audience. Find the axis where
the levels from the two speakers are equal. This is where the comb filters are most severe.
Carefully adjust the POWER-Q so that the signal from both speakers arrives at precisely the same
time. The POWER-Q provides 20 microsecond resolution for this purpose.
Use the same procedure to align speakers within a cluster when necessary .
19
Section 8: Digital Delay
8.2 POWER-Q DIGITAL DELAY ADJUSTMENTS: Manual & Automatic. To access the POWER-Q digital
delay controls, choose #7 (“DIGIT AL DELAY” from the MAIN MENU. Use the up and down arrow
keys to scroll the MAIN MENU screen, and the soft key or ENTER key to select DIGITAL DELAY.
You will be presented with the following screen:
Fig. 15: Auto Delay page
You may set the delay time for channels A and B independently, either manually or automatically.
Manual adjustment. Delay time can be set in milliseconds, feet, or meters, with an adjustment
resolution of 20 microseconds (approximately 1 cm, or half an inch). Adjusting any one delay
parameter automatically changes the corresponding readout in the unselected measurement
units. The time unit display will always be the most accurate. (The distance displays are approximations based on the speed of sound at standard temperature and pressure conditions: 1 127 feet/
second at 20 degrees C and 760 mm Hg atmospheric pressure.) The minimum delay time
allowable is 1.38 milliseconds per channel; the maximum is 83.2 milliseconds.
Note that manually adjusting the digital delay during audio program may cause discontinuities
(popping sounds) while the adjustments are made. This is unavoidable and will cease when the
delay is set.
Delay times may also be set manually from inside the POWER-Q REAL-TIME ANAL YZER
window. Refer to Section 13.3 for more details.
Automatic Delay Alignment. If you have positioned a reference microphone for RTA analysis, or
Automatic Room EQ, the same microphone can be used by the POWER-Q to measure the
distance from the speaker to the microphone. (The qualities of the microphone are not an important consideration for delay alignment, although they are for EQ adjustments). The POWER-Q will
then set the delay times for its two channels to allow the sound from each speaker to reach the
microphone at the same time, compensating for the different distances from the mic to the two
speakers.
To execute Automatic Delay Alignment, press the ALIGN soft key in the DIGITAL DELA Y screen.
The following screen will appear:
Fig. 16: Auto Delay Setup page 1
20
Section 8: Digital Delay
Your sound system must be set up and operational, and the gain of any equipment downstream in the signal path from
the POWER-Q must be turned up to operating level. You must also be able to play audio program (a prerecorded CD
will work fine) through the POWER-Q at concert levels. Finally , the reference microphone must be located in the
position you wish to use as your delay alignment reference.
When these conditions are met, press ENTER. The POWER-Q will display the following screen:
Fig. 17: Auto Delay Setup page 2
Play your audio program and press ENTER. The POWER-Q will verify that audio program is present at both inputs. If
there is no audio signal present in one or both channels, you will receive the following message. Note that there is no
reason to align speakers if you are only operating with one channel of the POWER-Q, and the unit will not allow you to
test only one channel when there is no signal present at one of its inputs.
Fig. 18: Auto Delay Setup page 3
Check your connections and signal path, and repeat the procedure.
If the POWER-Q detects the presence of a signal at its two inputs, it will automatically play a 1 Khz test signal, first to
calibrate the sensitivity of the reference microphone, and, second, to measure the time the signal takes to reach the
microphone after it is generated by the POWER-Q. This test will be repeated for the second channel. While the 1 Khz
signals are being tested, the POWER-Q will display page 4 as follows:
Fig. 19 : Auto Delay Setup page 4
In the event your microphone doesn’t hear a loud enough signal, you’ll see the following error message:
Fig.20: Auto Delay Setup page 5
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