Housekeeping
Project Studio Design
Solutions for better
sounding rooms
Copyright 2005 PMI, Ltd.
Housekeeping
• Please turn off cell phones
• We have lots to cover!
• Please keep questions on track
Copyright 2005 PMI, Ltd.
1
Introduction
• We WILL talk about the design of
project studios
• We will NOT talk about performance
spaces
• We will talk about multichannel rooms
• How many of you do film
post-production?
Copyright 2005 PMI, Ltd.
Topics Covered
• Introduction
• Designing the room
• Specifying the Gear
• Placing the Gear
• Wiring it up
• Calibration
• Planning
Copyright 2005 PMI, Ltd.
2
Project Studio Statistics
• 350,000 project studios worldwide
• 93% of A titles go through project
studio at some phase of production
• In homes, in studios, in postproduction facilities
• Translation to the outside world at
issue!
Copyright 2005 PMI, Ltd.
2 Types of rooms
• Sound Production (Tracking room)
–
Acoustic design of room contributes to
the character of the recorded sound
• Sound Reproduction (Control room)
–
Acoustic design of room provides a
neutral environment to audition prerecorded sound
–
Let’s talk about this !
Copyright 2005 PMI, Ltd.
3
Design References?!
• Listening rooms at home
–
What are they like?
–
IEC Room
•
Statistical average of consumer listening rooms
• Cars
–
What are they like?
• iPod ?
Copyright 2005 PMI, Ltd.
The End User Reference
High performance listening rooms
Copyright 2005 PMI, Ltd.
4
The End User Reference
High performance listening rooms
Copyright 2005 PMI, Ltd.
The End User Reference
High performance listening rooms
Copyright 2005 PMI, Ltd.
5
The End User Reference
High performance listening rooms
Copyright 2005 PMI, Ltd.
A Reference
• A standard of
quality: Film
studio
screening
rooms
• Documented
Standards
–
ISO 2969X
–
SMPTE 202M
Stag Theatre, Skywalker Ranch
Copyright 2005 PMI, Ltd.
6
Layout of a
post production dubbing stage:
• 3 Screen speakers
–
–
–
L
Sub
C
Left
Center
Right
R
• 3 Surround arrays
–
–
–
Left Side
Right Side
Rear
• Good sightlines
Left Side
• All seats face screen
Right Side
• Subwoofers
• Screen size is 0.93x
seating distance (50º)
Rear
Copyright 2005 PMI, Ltd.
Layout of a
Home Theater:
• 3 Screen speakers
• 3 Surround channels
L
C
Sub R
• Subwoofers
• All seats face screen
• Good sightlines
• Screen size is 0.55 of
seating distance
(30º) [0.71 for HDTV]
Left
Side
Right
Side
Rear
Copyright 2005 PMI, Ltd.
7
Designing the Room
Copyright 2005 PMI, Ltd.
Designing the Room
• Acoustic character
• Optical Environment
• Aesthetics
Copyright 2005 PMI, Ltd.
8
Designing the Room
The Sound
Copyright 2005 PMI, Ltd.
Designing The Room
The Sound – The basics
• The right shape
• Good sound isolation
• No background noise
• No rattles
• No distractions
Copyright 2005 PMI, Ltd.
9
Shaping the Room
Copyright 2005 PMI, Ltd.
Reflections in a
Rectangular Room
• Reflections are
evenly distributed
Copyright 2005 PMI, Ltd.
10
Reflections in a
Rectangular Room
• Reflections are
evenly distributed
Copyright 2005 PMI, Ltd.
Reflections in a
Room with Concave Wall
• Reflections are
focused to
listening position
Copyright 2005 PMI, Ltd.
11
Reflections in a
Non Rectangular Room
• Reflections are still
there
• Some are stronger
• Harder to predict
Copyright 2005 PMI, Ltd.
Reflections in a
Rectangular Room
• Reflections are
evenly distributed
Copyright 2005 PMI, Ltd.
12
Shaping the Room
• Stick to rectangular rooms!
• Other shapes can work, but are
difficult to predict and control
• Squares – Not great
• Circles, Ovals – Oh, Trouble!
• Bay Windows – More trouble!
Copyright 2005 PMI, Ltd.
Shaping the Room
• Other Factors:
–
Room orientation (Width or Length)
–
Capacity
–
Seating type
–
Finish grade
Copyright 2005 PMI, Ltd.
13
Shaping the Room
• Room orientation
–
Favor the length direction
–
Not too long and narrow!
• Around 1.3 : 1 works well
–
Several obstacles
• Fireplace
• Windows
• Doors
• Etc.
Copyright 2005 PMI, Ltd.
Acoustics
The Design Process
Copyright 2005 PMI, Ltd.
14
Acoustics
• Why talk about acoustics?
• Acoustics are audible!
• Contribute to over 50% of quality
• Acoustics are fixable
Copyright 2005 PMI, Ltd.
What’s Acoustics?
• It’s about the
speaker/room/listener interface
• It’s what separates “Major” studios
from “Project” studios
Copyright 2005 PMI, Ltd.
15
The Acoustic Interface
Source
Console
Power
Amplifiers
Equalizers
• Electronics
Interface is
under control
• Take control of the
acoustic interface
Copyright 2005 PMI, Ltd.
Warning !
Room acoustics will
mess you up !
Copyright 2005 PMI, Ltd.
16
The Acoustical Engineering Process
12 Steps
1.
2.
3.
4.
5.
6.
Dimension the room
Sound isolation
Noise control
Vibration control
Model decay time
Determine absorption
area
7. Determine
diffusion area
8. Treat echoes
9. Place listener
10. Place sound
system
11. Determine
treatment
locations
12. Tune it all
Copyright 2005 PMI, Ltd.
… But First a Bit of Theory
• Sound is
–
Vibrating air
–
Changing pressure
–
Perceived by our ear-brain
–
Frequency of pressure changes
determines pitch
Low
pitch
High
pitch
Copyright 2005 PMI, Ltd.
17
Acoustic Wavelength
Sound Propagates at 1.13ft/msec
+
Air
0
Pressure
A 1 kHz Signal
Ft.
1.13
2.26
+
A 500 Hz Signal
Air
0
Pressure
Ft.
2.26
-
Wavelength =
1130
Freq
Copyright 2005 PMI, Ltd.
Room Dimensioning
Standing Waves
Copyright 2005 PMI, Ltd.
18
Standing Waves
a.k.a. Room Modes
• Standing waves happen
when room dimension
is equal to sound
wavelength
Loudspeaker
Listener
• Also at 0.5, 1.5, 2, 2.5,
3, etc. times
wavelength
Copyright 2005 PMI, Ltd.
Standing Waves
• Standing waves cause
–
Resonances
–
Uneven frequency response
–
Poor bass impact
–
Different bass at each seat
–
Common problems are in the 30 Hz to
150 Hz range
Copyright 2005 PMI, Ltd.
19
A Resonant Frequency
• After
reflection,
signal
nulls
overlap
Copyright 2005 PMI, Ltd.
A Resonant Frequency
• After
reflection,
signal
nulls
overlap
Copyright 2005 PMI, Ltd.
20
A Non-Resonant Frequency
• No null
overlaps
• No
reflection
gain
Copyright 2005 PMI, Ltd.
Standing Waves
• All rooms will have some
standing waves
Length
• Resonance frequencies are set
by room dimensions
• Overlaps in resonance
frequencies =
Even more trouble
• Resonance overlaps depend
on ratios in room dimensions
Length/Width/Height
Width
Copyright 2005 PMI, Ltd.
21
Standing Waves
• Intensity of resonance
depends on wall stiffness
Copyright 2005 PMI, Ltd.
Standing Waves
A Second Harmonic Length Axial Standing Wave
You
The
producer
Loud
Quiet
Loud
Quiet
Loud
Copyright 2005 PMI, Ltd.
22
Standing Waves – What to Avoid
Frequency overlaps = double whammy!
You:
The
producer:
More Kick!
This guy is
nuts!
Copyright 2005 PMI, Ltd.
Standing Waves Pressure Representation
for 1st, 2nd, 3rd, 4th Harmonics
1st Harmonic
2nd Harmonic
11
22
11
44
3rd Harmonic
11
66
11
22
33
44
4th Harmonic
55
66
11
88
33
88
55
88
77
88
23
Standing Waves
Modal decay
• Example of
room modal
decay plot
• Long decay
• Most audible
effect of
room modes
Copyright 2005 PMI, Ltd.
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative amplitude
• Use bass absorption or absorptive walls
• Move seating location
–
Moves the listener out of peaks and dips
• Equalize
Copyright 2005 PMI, Ltd.
24
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
Copyright 2005 PMI, Ltd.
Standing Waves
Resonance Frequencies
Equation:
F = n1130/2D (in ft)
F = n345/2D (in m)
Where F is frequency
n is the harmonic
D is the distance between walls
Copyright 2005 PMI, Ltd.
25
Solutions to Standing Waves
Room Dimensions
• Determine room dimensions
• Determine modes (F=n1130/2d)
• Find resonance overlaps
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Room Dimensions (continued)
• Calculation programs
–
RPG Room Optimizer
–
CARA
–
THX Room Mode Calc
–
Ultimate AV online
–
PMI modeling program
Copyright 2005 PMI, Ltd.
26
Home Theater
ROOM MODES
ROOM DIMENSIONS (ft.)
Length: 19.690 feet
Width: 15.090 feet
Height: 9.840 feet
Modal Frequencies
new
new
M o da l
H a rm o n ic
1
2
3
4
Width
Height
28.69
37.44
57.42
57.39
74.88
114.84
86.08
112.33
172.26
114.78
149.77
229.67
143.47
5
Length
28.69
0
Length
10
Width
37.44
23.36%
20
30
187.21
Length
57.39
34.76%
40
50
60
70
80
57.39
1 28.69
37.44
0
0.00
50.00
112.33
74.88
287.09
149.77
229.67
172.26
114.84
57.42
100.00
150.00
200.00
250.00
300.00
350.00
Frequency (Hz)
287.09
Height
57.42
0.05%
Warning!
86.08
3
2
187.21
114.78
4
Harm onics
1130
AXIAL MODAL FREQUENCIES OF EACH DIMENSION
143.47
5
new
Speed Of Sound in ft./sec
Go To
Diaphragm atic Absorber
Performance Media Industries
Width
74.88
23.32%
Length
86.08
13.01%
Width
112.33
23.36%
Length
Width
Length
Height
Length
114.78
114.84
143.47
2.14%
0.05%
19.96%
Warning! Warning!
Width
149.77
4.20%
Warning!
Height
Height
172.26
13.06%
Width
187.21
7.99%
Height
229.67
18.49%
Height
287.09
20.00%
90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Room Shapes
Loudspeaker
• Complicates Acoustic
modeling and
computations
• Doesn’t get rid of
standing waves or
reflections
Listener
• Not recommended
Copyright 2005 PMI, Ltd.
27
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative amplitude
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Subwoofer and Speaker Placement
Loudspeaker
• Driving room
standing waves
in cancellation areas
can improve
response
• We’ll talk about this
later
Copyright 2005 PMI, Ltd.
28
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative amplitude
• Use bass absorption
Copyright 2005 PMI, Ltd.
Standing Waves
Absorb at least ¼ wavelength !
Loud
Quiet
Loud
Quiet
Loud
Copyright 2005 PMI, Ltd.
29
Solutions to Standing Waves
Absorption at Standing Wave Null
• Place absorber
panel at null
(high velocity,
low pressure area)
Original Modes
Absorber
Panel
Resulting Modes
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Diaphragmatic Absorption
• Absorber units are
resonating material tuned
to problem frequencies
Diaphragm
• Absorber box is filled with
“fuzz”
• Works up to 150Hz
• Design of bass absorber
is complex
• Unreliable!
Copyright 2005 PMI, Ltd.
30
Solutions to Standing Waves
Helmholtz Absorption
• Helmholtz units are
tuned to problem
frequency
• Absorber box is filled
with fuzz
• Works down to 80Hz
• Design of Helmholtz
absorber is complex
• Not very efficient
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
CineTrap Absorption
• Combination
Pistonic diaphragm
and Helmholtz
absorber
• F0 determined by
Mass – Spring – Air
• Reliable and
predictable
31
Solutions to Standing Waves
CineTrap Absorption
• Triple ported enclosure
• Front panel suspended
on springs
• Mineral wool inside
cavity to widen
resonance
• Port at bottom of
cabinet
Solutions to Standing Waves
CineTrap Absorption
• Main port at bottom
• Second chamber
resonating port on
bottom of cabinet
• Port extends up to
middle of cabinet
• Optimized by PAM
(Whise / Huon Labs)
32
Solutions to Standing Waves
The SpringTrap
• Two fundamental equations
• Ported resonant enclosure:
–
F = (c/2pi)(A/L’V)1/2
• Spring loaded panel resonance:
–
F = (1/2pi )(k/m)1/2
• Paper presented at AES 114th Convention,
Amsterdam, March 2003
• Patent Pending
Copyright 2005 PMI, Ltd.
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative amplitude
• Use bass absorption or absorptive walls
Copyright 2005 PMI, Ltd.
33
Solutions to Standing Waves
Resilient Walls
RSIC
DW
Hat-Channel
SoundBoard or
Vinyl Barrier
DW
Bass to
wall
Bass
from
wall
• Resilient walls don’t
reflect bass well
• Sound energy is
absorbed by the PAC
RSIC rubber isolator
• Add Soundboard or
Loaded Vinyl to spread
the resonance frequency
• You get isolation too!
Wall with PAC RSCI-1 Isolators
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Resilient Walls PAC RSIC1
Copyright 2005 PMI, Ltd.
34
Solutions to Standing Waves
Resilient Walls - Isomax
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Resilient Walls - Isomax
Copyright 2005 PMI, Ltd.
35
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative
amplitude
• Use bass absorption or absorptive walls
• Move seating location
–
Moves the listener out of peaks and dips
Copyright 2005 PMI, Ltd.
.8 *L
.68 *L
.55 *L
.45 *L
.32 *L
.2 *L
.8 *H
.68 *H
.55 *H
.45 *H
.32 *H
251
314
188
63
126
.2 *H
Solutions to
Standing
Waves
27
54
Seating
Placement
81
176
106
141
35
135
71
108
.2 *W
.32 *W
Stay away from
peaks or dips
.45 *W
.55 *W
.68 *W
.8 *W
.8 *L
.68 *L
.55 *L
.45 *L
.32 *L
.2 *L
Copyright 2005 PMI, Ltd.
36
Ways to Deal With Standing Waves
(Room Modes Can Never Be Eliminated)
• Change one or more dimensions
–
Minimizes resonance pile-ups
–
Aim for even modal distribution (>5% difference)
• Move subwoofer location
–
Drive mode out-of-phase to reduce relative amplitude
• Use bass absorption or absorptive walls
• Move seating location
–
Moves the listener out of peaks and dips
• Equalize
Copyright 2005 PMI, Ltd.
Solutions to Standing Waves
Equalization
Loudspeaker
1/3 Octave
Equalization
Pink Noise
Generator
Multiplexer
Microphone 3
Microphone 2
Microphone 4
Microphone 1
• Analysis
should be
spatially and
temporally
averaged
• Use Gold
Line DSP30
Analyzer, or
equivalent
Copyright 2005 PMI, Ltd.
37
Designing the Room
Sound Isolation
Copyright 2005 PMI, Ltd.
Sound Isolation
• Good sound isolation means:
–
use the room anytime!
–
No interference: lose none of the
sound subtlety
–
Privacy
Copyright 2005 PMI, Ltd.
38
Sound Isolation
• Demonstration: Action movie
• In room (Chap 14)
• Adjacent room: standard construction –
STC38 (Chap 16)
• Adjacent room: better construction –
STC60 (Chap 18)
• Adjacent room: best construction –
STC75 (Chap 20)
Copyright 2005 PMI, Ltd.
Sound Isolation – 2 processes
• Sound leakage
–
Isolate doors, windows, and plumbing
–
Isolate, seal and caulk all leakage paths
• Mechanical Transmission
–
Special wall structures
–
Floating floor
–
Floating ceiling
Copyright 2005 PMI, Ltd.
39
Airborne Sound Leaks
Turn it down!
Sound Source
AC Outlet
Copyright 2005 PMI, Ltd.
Preventing Leaks
Caulk
Weather
Strip
Seal everything!
Sound Source
Expand
Foam
AC Outlet
Copyright 2005 PMI, Ltd.
40
No Leaks
Privacy!
Sound Source
AC Outlet
Copyright 2005 PMI, Ltd.
Noise Transmission Detection
Listen!
Detect!
Fix It!
Weather
Strip
Pink Noise Bursts
Caulk
Expand
Foam
AC Outlet
Copyright 2005 PMI, Ltd.
41
Isolate Flanking Paths
AC outlets
Full Flanking
Offset
Offset and Isolated
Copyright 2005 PMI, Ltd.
Isolate Flanking Paths
Office
Sound Path
BAD
Hallway
In-Line Doors Allow a
Direct Path for Noise
Studio
Hallway
Bedroom
Sound
Path
Offset Doors Reduce
Sound Transmission
GOOD
Copyright 2005 PMI, Ltd.
42
Isolation Solutions
Wall Construction
Copyright 2005 PMI, Ltd.
The Mechanism of Sound
Transmission
Sound Waves
From Source
Some Energy
Reflected
Wall
Some Energy
Absorbed
Some Energy
Transmitted
Copyright 2005 PMI, Ltd.
43
Wall Construction Resonance
Sound transmission
at resonance frequency
Wall
• All wall surfaces have a resonant frequency where
they transmit lots of energy
Sound
Transmission
Copyright 2005 PMI, Ltd.
½” Drywall
Example
Resonance
Frequency
F
Wall Construction
Damped Resonance
Wall
Loaded Vinyl barrier or
Sound board
Sound
Transmission
Copyright 2005 PMI, Ltd.
With
Damping
Resonance
Frequency
44
Wall Construction
Constrained Layer Damping
Wall
Visco-Elastic polymer
Sound
Transmission
Copyright 2005 PMI, Ltd.
With Visco
Elastic
Resonance
Frequency
Isolation Strategies
• More Mass
• Damp resonance
• Decouple
• Larger airgap
Copyright 2005 PMI, Ltd.
45
Sound Isolation Strategies
Wall Construction - Decoupling
DW
DW
DW
Single Stud
RC1
SB or Vinyl
DW
RC1 Resilient Channel
Warning:This is hard to make work!
Copyright 2005 PMI, Ltd.
Sound Isolation Strategies
Decoupling – A better solution
DW
DW
Hat-Channel
SB or Vinyl Sheet
Isolation Bushing
2x DW
DW
Single Stud
STC40
PAC RSCI-1 Isolators
Easy to install
STC 58 ! !
Copyright 2005 PMI, Ltd.
46
Sound Isolation Strategies
Wall Construction - Decoupling
DW
DW
DW
Staggered Stud
DW
Double Wall
Copyright 2005 PMI, Ltd.
Studwall Isolation
dB SPL
Isolation
80
Noise Transmission Coefficients
Double Stud, 5/8”
Double Drywall,
double 3” insulation
70
60
Double Stud, 5/8”
Drywall, 3” and 6”
insulation
50
40
Staggered Stud, 5/8”
drywall
30
20
Double ½” drywall,
studs 16” OC
10
½” drywall on studs
16” on center
0
100
1000
10000
Copyright 2005 PMI, Ltd.
47
Staggered Stud Construction
Original 2 x 4
Top Plate
Retrofit
Additional
2 x 2 Top
Plate
Original 2 x 4
16 in
Added
2 x 4 Stud
2 in
16 in
Added 2 x 4
Additional
2 x 2 Sole
Plate
Original 2 x 4
Sole Plate
Copyright 2005 PMI, Ltd.
Isolating the ceiling and floor
–
Floating floor construction
Carpet + pad
3/4" T&G Plywood
Existing floor
–
Isolation Pads
Floating ceiling construction (PAC RSCI-1 Isolators)
Joist
Vinyl barrier or ½” soundboard
5/8” sheetrock
RSIC
Hat Channel
Copyright 2005 PMI, Ltd.
48
Background Noise
Copyright 2005 PMI, Ltd.
Background Noise
• Interferes with loudness
perception
• Masks low level signals and detail
• Transient noise is distracting
Copyright 2005 PMI, Ltd.
49
Background Noise
• Demonstration: Speech
–
No background noise
–
Low background noise: NC20 (Chap 6)
–
Medium background noise: NC30 (Chap 8)
–
High background noise: NC40 (Chap 10)
–
Stupid High Noise: NC50 (Chap 12)
(Chap 4)
Copyright 2005 PMI, Ltd.
Sources of Background Noise
• Local sources
–
HVAC
–
Plumbing
–
Fans
–
Pumps/Compressors
–
Washer/Dryers
–
Garage door openers
–
Projectors
Copyright 2005 PMI, Ltd.
50
Sources of Background Noise
• External sources
–
Traffic
–
Airplanes
–
Wind
–
Neighbors
Copyright 2005 PMI, Ltd.
100
Noise
Criteria
Curves (NC)
POSSIBLE HEARING
DAMAGE
CURRENT (1979)
PERMISSIBLE NOISE EXPOSURE
FOR 8 HOUR DURATION
(U.S. DEPT. OF LABOR OSHA)
-90
80
NC-75
-80
30
20
10
APPROXIMATE
THRESHOLD OF
HEARING
FOR CONTINUOUS
NOISE
NC-50
-61
NC-45
-56
NC-40
-52
NC-35
-47
NC-30
-42
NC-25
-38
NC-20
-34
NC-15
-30
NC-10
-26
125
NC25 for
basic room
NC15 for High
End room
-21
0
63
Targets:
VERY NOISY
-66
EXPECTED SUBJECTIVE RESPONSE OF
TYPICAL BUILDING OCCUPANTS TO THE
NOISE ENVIRONMENT
40
-71
-71
NC-55
NOISY
50
NC-60
MODERATE
NC-65
60
QUIET
-77
VERY QUIET
NC-70
70
250
500
1000
2000
4000
8000
OCTAVE BAND CENTER FREQUENCIES (IN HZ)
EQUIVALENT
SOUND LEVEL
(IN Dba)
OCTAVE BAND SOUND PRESSURE LEVEL (IN dB RE 2x10-5 N/M2)
90
51
Measuring Background Noise
• Use spectrum analyzer
• Use a low noise microphone
• Take a time and space average
• Use NC weighting
• Plug your ears, wait, unplug and listen
–
Use Earplugs, or fingers
Copyright 2005 PMI, Ltd.
Solutions to Background Noise
•
•
•
•
•
•
•
Large air ducts for lower air velocity
Longer ducts with several turns
Plenum silencers
Lined ductwork
“Whistle Free” air grilles
Isolate motors on suspension or move
Completely seal windows, doors, etc.
Copyright 2005 PMI, Ltd.
52
Background Noise
Summary
• Background noise degrades dynamic
range, detail clarity, and intelligibility
• Noise can be detected with test
instruments or earplugs and ears
• Treatments include seals, better walls,
slower air, quieter air handlers, etc.
Copyright 2005 PMI, Ltd.
Designing the Room
Vibration Control and
Rattles
Copyright 2005 PMI, Ltd.
53
Rattles
• Very prominent for low frequency
signals
• These are usually caused by acoustical
or mechanical coupling with loose
fixtures, lights, furniture, and doors.
• Rattles can sound like speaker or
amplifier distortion, and their
localization can be distracting.
Copyright 2005 PMI, Ltd.
Rattle Detection
Rattle !!
Single Tone Oscillator –
Sweep slowly from
20 Hz to 1 kHz
Copyright 2005 PMI, Ltd.
Listen!
Look!
Fix It!
Caulk
Felt
54
Rattles
(continued)
• Method: use slow varying frequency sweep
• Check
–
Furniture
–
Walls and Doors
–
Glass Surfaces
–
Fixtures
–
Track Lights
–
HVAC Ducts and Vents
–
Hung Pictures
–
Ventilation System
Copyright 2005 PMI, Ltd.
Solutions to Rattles
• De-couple loudspeakers from room surfaces
• Add elastic mass to surfaces
• Tighten loose fixtures
• Isolate fixtures with
–
Rubber Pads
–
Caulk
–
Insulation
Copyright 2005 PMI, Ltd.
55
Designing the Room
Reflection Decay Time
(aka Reverberation)
Copyright 2005 PMI, Ltd.
Reverberation
• Reverberation
is the result of
multiple
reflections
• Decay time
and spectrum
have to be
just right
Copyright 2005 PMI, Ltd.
56
Reverberation
• When the sound has bounced around the
room several times
• No net direction or time cues remain
• Small room reflections die out before
complete reverberation is achieved
• We call it reflection decay time
Copyright 2005 PMI, Ltd.
Decay Time
Level
Decay of an impulse sound
Direct
0dB
1st reflections
2nd reflections
-30dB
Reverb
-60dB
0.1
0.2
0.3
0.4
Time
Copyright 2005 PMI, Ltd.
57
Decay Guidelines
• Decay time should be .2 to .4 seconds
• Research shows that most people like the
same range of decay time
• Tm = 0.3 (V/3532)1/3 ±15% where V=room
volume in ft3
• Tm = 0.3 (V/100)1/3 ±15% where V = room
volume in m3
• Handy rule of thumb for project studios, look
for ~25% absorptive wall area
Copyright 2005 PMI, Ltd.
Decay Time
RT60
Time
Criterion 1: Time vs. Volume (500 Hz)
0.31s
0.28s
0.25s
2000
3000
4000
Volume (ft3)
Copyright 2005 PMI, Ltd.
58
Tolerance Limits for Decay Time
s
Criterion 2: Time vs. Frequency
Target it flat
Difference in decay time
+100%
+66%
200 Hz
+33%
+15%
Tm
0
4kHz
-15%
-50%
1000
100
63
Copyright 2005 PMI, Ltd.
10000
4000
Hz
8000
Frequency
Decay Time
Getting it right
• Use the right amount of “frictional”
absorption for the mids and highs
• Use the right amount of perforated panel
bass absorption
• Calculate the amount with the Sabine, Eyring
or Arau- Puchades equations
–
Know the absorption coefficient of materials
–
Be prepared to do lots of math
Copyright 2005 PMI, Ltd.
59
Decay Time
Getting it right
• The Sabine equation: Good but old
RT60 =
0.049V
Stotala
V is volume
S is absorption surface area
a is absorption coefficient
• The Eyring equation: Better and more recent
RT60 =
0.049V
-S ln(1-A)
V is volume
S is total room surface area
A is area-weighted averaged absorption
coefficient
Copyright 2005 PMI, Ltd.
Decay Time
Getting it right
• The Arau- Puchades equation: Best and latest
RT60 =
x/s
y/s
z/s
[ -S ln(1-α )] x [ -S ln(1-α )] x [ -S ln(1-α )]
0.161V
x
0.161V
y
0.161V
z
V is volume
S is total room surface area
α is area-weighted averaged absorption coefficient for each wall
x is area of Left +Right walls
y is area of Front + Rear walls
z is area of Floor + Ceiling
Copyright 2005 PMI, Ltd.
60
Decay Time
Getting it right
• Rule of thumb: cover 25% of walls with
absorption
–
Also treat ceiling first reflection
• Spread absorption materials around the
room surfaces
• Also use diffusion to smooth out decay
• Diffusion enhances absorption effectiveness
Copyright 2005 PMI, Ltd.
Designing the Room
Sound Reflection Control
Copyright 2005 PMI, Ltd.
61
Reflections = Distortion
Copyright 2005 PMI, Ltd.
Room Reflections
Loudspeaker
Pa
Re
fl
th
Direct Path
Re
d
cte
fle
ec
te
• Reflections cause
dP
ath
–
Blurring of image
–
Spectral imbalance
by comb filtering
Listener
Copyright 2005 PMI, Ltd.
62
Room Reflections
Did you Know?!
• At main seat you listen to
as much reflected sound
as direct!
• Need to get more direct
sound
Copyright 2005 PMI, Ltd.
Designing the Room
Sound Reflection Control
Absorption
Copyright 2005 PMI, Ltd.
63
Solutions to Room Reflections
Absorption
Copyright 2005 PMI, Ltd.
Solutions to Room Reflections
Absorption
Loudspeaker
te
ec
th
Re
fle
c
Direct Path
fl
Re
a
dP
Absorptive
Material
• Absorptive materials
ted
Pa
th
Absorptive
Material
Listener
–
Mineral wool
–
Fiberglass
–
Dense foam
–
Draperies
–
Stuffed chairs
• “Scrub” off acoustic
energy through
friction
• Treat the ceiling too!
Copyright 2005 PMI, Ltd.
64
Acoustical Treatments
Absorption Thickness
• 1” Panels work down to 1kHz (not enough)
• 2” Panels work down to 500Hz (better)
Absorption
• 4” Panels work down to 250Hz (best)
4”
250Hz
2”
500Hz
1”
1kHz
Frequency
Copyright 2005 PMI, Ltd.
“Floating” an Absorption Panel
Absorption
1st Absorption
On wall
Absorption on wall Only higher frequency reflections
are affected
Absorption away from wall
High and low frequencies
are tamed
Source
Away from wall
More LF’s absorbed
Frequency
Copyright 2005 PMI, Ltd.
65
Acoustical Treatments
Notes on Absorption
• Don’t “over absorb”
–
Dead rooms sound odd
–
Target reflection decay time: 0.3s
–
25% coverage of wall surface
Copyright 2005 PMI, Ltd.
Acoustical Treatments
Notes on Draperies
• Draperies are uneven acoustical
absorbers
• Performance affected by fabric weight,
pleat number, distance from boundary
• At least 3” air gap
• Velour mass 32 ounces per lineal yard
• 100% fullness
Copyright 2005 PMI, Ltd.
66
Reflection issues
Control room surfaces
• Work surfaces are large reflectors
• Work stations are reflectors
• Video displays are reflectors
• Place them all carefully
• Put “acoustic blinders” over work
station
Copyright 2005 PMI, Ltd.
Reflection issues
Control room surfaces
• Place
speakers on
stands
Blinder
• Use an
acoustic
blinder to
cut out the
reflection
Copyright 2005 PMI, Ltd.
67
Low Frequency Reflection
Control Strategies
• First reduce peak/dip errors through
proper placement
• “Resistive” Absorbers too thick
• Use Helmholtz and Diaphragm methods
Copyright 2005 PMI, Ltd.
Bass Absorption
• Use Perforated
wood surface
on box
• Tuning
equation:
ƒ0 =
200
p
(d) (t)
ƒ0 is frequency
p is perforation percentage
t is hole length
d is air space depth
Copyright 2005 PMI, Ltd.
68
Bass Absorption on the front wall
• Use Bass
absorber to kill
front wall
reflection
Copyright 2005 PMI, Ltd.
A Bass Absorber
Perforated enclosure
3/4” MDF backing board
Framing
1” 3pcf fiberglass
Perforated Board
Fabric
Copyright 2005 PMI, Ltd.
69
Designing the Room
Sound Reflection Control
Diffusion
Copyright 2005 PMI, Ltd.
Solutions to Room Reflections
Diffusion
Copyright 2005 PMI, Ltd.
70
Solutions to Room Reflections
Diffusion
Loudspeaker
Re
fle
cte
d
Direct Path
d
cte
fle
e
R
th
Pa
• Diffusive materials
Pa
th
–
Purpose-built
panels
–
Bookcase
Diffuser
Diffuser
Listener
Copyright 2005 PMI, Ltd.
Acoustical Treatments
Diffusion
• Need enough diffusion surface to
“smooth out” the soundfield
• Balance diffusion and absorption
• Keep some liveness to the room
• Mix diffusion in with absorption
• It’s the stuff that high-end studios are
made of
Copyright 2005 PMI, Ltd.
71
Acoustical Treatments
Diffusion types
• 2D diffusion redistributes incident
sound to a plane
–
Use along front portion if side walls to
diffuse front speakers
• 3D diffusion redistributes sound to a
hemisphere
–
Use it towards the rear of room for
surround speakers
Copyright 2005 PMI, Ltd.
Acoustical Treatments
Diffusion – 2D Diffusers
Cylindrical
Slotted
Copyright 2005 PMI, Ltd.
72
Acoustical Treatments
Diffusion - 3D Diffusers
Copyright 2005 PMI, Ltd.
Acoustic Treatment
Manufacturers
• StudioPanel
• RPG
• Acoustics First
• Kinetics Noise Control
• Auralex
• And many others!
Copyright 2005 PMI, Ltd.
73
Slap Echoes
Copyright 2005 PMI, Ltd.
Slap Echoes
• Echoes are
Loudspeaker
–
Repeated reflections
between two parallel
surfaces
• Slap echoes cause
Listener
–
Bright, “zingy” sound
–
Interference with
acoustic character
of sound
–
Timbral changes
Copyright 2005 PMI, Ltd.
74
Slap Echoes
Detection Methods
• Clap hands at
various locations
in room
• Listen for echo
• If possible, sit at
primary seat and
listen to a person
clapping at various
locations
Copyright 2005 PMI, Ltd.
Solutions to Echoes
Materials
• Absorptive
Loudspeaker
Listener
Absorber
–
Fiberglass panels
–
Foam panels
–
Drapes
• Diffusive
Diffuser
–
Diffuser panels
–
Bookcases
–
Furniture
Copyright 2005 PMI, Ltd.
75
Placing listeners
Copyright 2005 PMI, Ltd.
Seating Placement
• Don’t sit at Standing Wave Peaks or
dips
Copyright 2005 PMI, Ltd.
76
.8 *L
.68 *L
.55 *L
.45 *L
.32 *L
.2 *L
.8 *H
.68 *H
.55 *H
.45 *H
.32 *H
63
126
188
251
314
35
71
106
141
176
.2 *H
27
54
Solutions
to Standing
Waves
Seating
Placement
81
108
135
.2 *W
.32 *W
.45 *W
.55 *W
.68 *W
.8 *W
.8 *L
.68 *L
.55 *L
.45 *L
.32 *L
.2 *L
Copyright 2004 PMI, Ltd.
Listener/Speaker placement
•Position Left and
Right to form a 45
degree angle to
seating area
45º
•Balance between
stereo phantom
image and
multichannel
separation
Copyright 2005 PMI, Ltd.
77
Example Layout
Copyright 2005 PMI, Ltd.
Example Treatment Layout
A
B
Door with
absorber
panel
2D Diffusion
2’x7’ 130Hz
Bass absorber
unit
3D Diffuser
StudioPanel Absorption
5x10’
Absorptive
panel on
central ceiling
section
2’x4’ 2” Absorption panels
StudioPanel 2D Diffuser
107Hz Bass absorption units
3D Diffusion
In upper
areas
130Hz Bass absorption units
C
D
Copyright 2005 PMI, Ltd.
78
Example Treatment Layout
Left Wall
D
C
Surround speaker
Cylindrical Diffuser
2ftx2ft
StudioPanel Diffuser
2ftx4ft
StudioPanel Absorber
2ftx4ft
107Hz Diaphragmatic Absorber
2ftx5ft
Copyright 2005 PMI, Ltd.
Example Treatment Layout
Right Wall
A
B
Surround speaker
Cylindrical Diffuser
2ftx2ft
StudioPanel Diffuser
2ftx4ft
StudioPanel Absorber
2ftx4ft
107Hz Diaphragmatic Absorber
2ftx5ft
Copyright 2005 PMI, Ltd.
79
Example Treatment Layout
Front Wall
A
C
Cylindrical Diffuser
2ftx2ft
StudioPanel Absorber
2ftx4ft
130Hz Diaphragmatic Absorber
2ftx5ft
Copyright 2005 PMI, Ltd.
Example Treatment Layout
Rear Wall
A
C
Rear speaker
Cylindrical Diffuser
2ftx2ft
StudioPanel Diffuser
2ftx4ft
StudioPanel Absorber
2ftx4ft
3D Diffuser
2ftx2ft
Copyright 2005 PMI, Ltd.
80
Designing the Room
The Picture
Copyright 2005 PMI, Ltd.
Designing the Room
The Picture - Light Control
• Windows
–
Use black out shades
–
The fewer the better
• Doors
–
Must be closed when system is in use
–
Must have good seal to prevent light leakage
Copyright 2005 PMI, Ltd.
81
Designing the Room
Screen Light Reflection Control
• Light from screen will reflect on walls
and ceiling
• Light-colored walls will wash out
screen contrast – choose dark colors
• Make the room as dark as possible
–
Resolve the full difference between black
and white
Copyright 2005 PMI, Ltd.
82
Designing the Room
Visual Environment
• Make the room as neutral as possible
• Colors around the screen affect
perception of picture
• Observe these examples :
Copyright 2005 PMI, Ltd.
83
84
85
86
87
Copyright 2005 PMI, Ltd.
88
Copyright 2005 PMI, Ltd.
89
Designing the Room
The Picture - Light Control
• Lighting types
–
–
–
Ambient
Task
Artifact
• 3 Lighting Modes
–
Entrance/Exit
–
Screening (No light on the screen)
–
Work
Copyright 2005 PMI, Ltd.
90
Designing the Room
Interior Design
Copyright 2005 PMI, Ltd.
Designing the Room
Interior Design Guidelines
• Make the room an event
• Rely on interior designers
• Treatments are ugly; hide them!
• Be creative
Copyright 2005 PMI, Ltd.
91
Designing the Room
Interior Design Approaches
• Visible treatments
• The stretched fabric approach
• Other looks
–
Porous plaster
–
Perforated wood
–
Perforated metal
Copyright 2005 PMI, Ltd.
Acoustic Treatment
Integration
• Stretched fabric room
–
Most flexible design approach
–
Designate 8” zone for acoustics and
speakers
–
Integrate moldings
–
Use acoustically transparent fabric
–
For video use dark and neutral fabrics
Copyright 2005 PMI, Ltd.
92
Acoustical Treatments
Acoustically Transparent Fabric
• Fabric should be transparent up to
6kHz for Treatments
• Fabric should be transparent up to
16kHz for speakers
• Measure and listen to Pink noise from
speaker with and without the fabric
Copyright 2005 PMI, Ltd.
Specifying the Gear
The Audio System
Copyright 2005 PMI, Ltd.
93
Dolby Digital 5.1 EX
"6.1" Channels
Sub
L
Dolby
Digital
5.1 EX
C
+
R
+
-
-
Side
Right
Side Left
Rear
Copyright 2005 PMI, Ltd.
Multichannel Sound
The roles of each channel
• Center
–
Focal point for soundfield
–
Melodic lines, vocals, bass, solos
–
Highest acoustic energy of all channels
• Left / Right
–
Phantom center sounds with soft focus
–
Further back in soundfield
–
Sounds panned laterally
Copyright 2005 PMI, Ltd.
94
The roles of each channel
• Sides and Rears
–
Spatial definition (verb, delays, echoes)
–
Secondary instrumentation
–
Special effects
Copyright 2005 PMI, Ltd.
The roles of each channel
• LFE (Low Frequency Effects)
–
Bass exceeding 0dBfs
–
Disappears in 2 channel downmix mode
–
Special effects for listeners with
multichannel playback
–
Not usually needed in music !
Copyright 2005 PMI, Ltd.
95
The roles of the Subwoofer output
• Low bass below cutoff of your main
monitors
• Low bass that would overload your
monitors
• Low bass distributed through multiple
subs for cleaner, tighter bass
• Sum of L/C/R/Sl/Sr+LFE
Copyright 2005 PMI, Ltd.
Roles of each channel
Distribution of sound energy
Average
level
Sl
L
C
R
Sr
Copyright 2005 PMI, Ltd.
96
Studio Audio System Diagram
L
Sub
R
C
Source
Mixer
Equalizers
Power
Amplifiers
Sl
Sr
Rl
Rr
Copyright 2005 PMI, Ltd.
Basic System Requirements
• Sources: Mics, Keyboards, etc
• Outboard gear
• Console / Controller
• Room Equalizer (highly recommended)
• Amplification
• Speakers
Copyright 2005 PMI, Ltd.
97
What to look for in Sources
Microphones
• Good quality microphone
• Mic polar patterns
–
Omni
–
Cardoid
–
Hypercardioid
–
Figure 8
• Over what frequency range ?
• Warning: better mics pick up more room
tone
Copyright 2005 PMI, Ltd.
What to look for in Sources
Mic preamps
• Many choices
• Vacuum tubes
• Noise floor
• Coloration
• Gain range
–
30dB to 50dB typical
–
Ribbon mics need 60dB
Copyright 2005 PMI, Ltd.
98
What to look for in Sources
Keyboards
• Most all are unbalanced
• Use a balance converter
–
Passive transformer type
–
Active
Copyright 2005 PMI, Ltd.
What to look for in Sources
Direct boxes
• Not all equal
• Some saturate at high levels
• Choose better ones!
Copyright 2005 PMI, Ltd.
99
What to look for in Sources
Direct / Reamping converter
• For guitar re-amping use a
good impedance matching
converter box to avoid noise
Copyright 2005 PMI, Ltd.
What to look for in controllers
• Bass management
• Calibration features
• Solo/Mute of multichannels
• Multichannel source selection
–
DAW
–
DVD player
–
Surround decoders
–
Gaming system
Copyright 2005 PMI, Ltd.
100
What to look for in controllers
• Metering
• Multichannel metering
• Remote control
Copyright 2005 PMI, Ltd.
Which DAW to use ?
• You choose !!
Copyright 2005 PMI, Ltd.
101
Minimum System Requirements
• Room Equalizer
–
–
–
–
Analog
Digital
Manual
Automated
• Either way you need one!
Copyright 2005 PMI, Ltd.
Frequency Response Calibration
Room + Equalizer Phase Response
• 12 dB peak
error at 200 Hz
(yellow line)
• Phase error
(red line)
• Equal cut
introduces
inverse phase
error
• Amplitude and
phase are
corrected!
Copyright 2005 PMI, Ltd.
102
Equalization Requirements
• At least 1/3rd octave resolution from 80 to
1kHz for all main channels
• At least 1/12th Octave resolution from 20Hz to
80Hz for subwoofer
• Parametric is great
• Low noise
• Low distortion
• Ability to program presets recommended
Copyright 2005 PMI, Ltd.
Analysis – the useful way
Loudspeaker
1/3 Octave
Equalization
Pink Noise
Generator
Multiplexer
Microphone 3
Microphone 2
Microphone 4
Microphone 1
• Analysis
should be
spatially and
temporally
averaged
• Use Gold
Line DSP30
Analyzer, or
equivalent
Copyright 2005 PMI, Ltd.
103
Quick Check of Overall
Frequency Response
Using Etymotic ER-4S or ER-6 Earphones
Pink
Noise
Pink
Noise
Compare
CD
CD
Set earphone level to match speaker
Copyright 2005 PMI, Ltd.
What to look for in Amplifiers
• Power Rating
–
Enough to get to 105dB per channel
–
Speaker sensitivity –6dB rule
• Power at 4, 8, 16 ohms
• Protection circuitry
• Ability to play into low impedances?
• Reliability
• Fixed gain is easier
• Good sound!
Copyright 2005 PMI, Ltd.
104
Minimum System Requirements
Front Speakers
• Front Loudspeakers
–
3 identical speakers for LCRs
–
Appropriate directivity
–
Center MUST be the same make / model
as L & R
–
All horizontal or all vertical
–
Exception: Home THX systems with
dedicated matched horizontal center
Copyright 2005 PMI, Ltd.
Minimum System Requirements
Front Speakers
• 80 Hz to 20 kHz bandwidth
• 89 dB sensitivity
• 105 dB in-room SPL throughout the
bandwidth
Copyright 2005 PMI, Ltd.
105
Minimum System Requirements
Front Speakers
• Active Speakers – Several advantages
–
More efficient
–
Better control over response
–
Built in protection
Copyright 2005 PMI, Ltd.
What to look for in Speakers:
• Flat response in pass-band
• Uniform off-axis response
• Good dispersion (no “lobing”)
• Power handling
• Efficiency
• Bass Headroom
• Reliability
• Good sound!
Copyright 2005 PMI, Ltd.
106
What’s all this about directivity?
• It’s one of the most important things
• You often hear more reflected sound in
a room
• The sound returned from the room
should match the direct sound
Copyright 2005 PMI, Ltd.
Room Reflections:
Did you Know?!
• At the listening position
you listen to as much
reflected sound as direct!
• The room plays an
important part in the
sound you hear
• Speaker directivity will
affect reflected sounds
Copyright 2005 PMI, Ltd.
107
What’s all this about directivity?
• An idealized speaker:
–
The “pulsating sphere”
• Flat axial response
• Radiates evenly
in all directions
• Flat “sound power”
response
Copyright 2005 PMI, Ltd.
What’s all this about directivity?
• A real speaker:
–
Cones and domes
• Flat axial response
• Radiation depends
on frequency
• “Sound power”
response tilted down
Copyright 2005 PMI, Ltd.
108
What’s all this about directivity?
• A real speaker: Variable dispersion
Low Frequency
Mid Frequency
High Frequency
100Hz
1kHz
10kHz
Copyright 2005 PMI, Ltd.
How to get directivity?
• Some speakers have more focus than
others
• Stacks of drivers
• Horns
• Ribbons
Copyright 2005 PMI, Ltd.
The Obvious:
Two way with
Horn loaded
tweeter
109
How to get directivity?
Less Obvious:
Pattern control to
lower frequencies
Not Obvious: three
way tapered array.
Pattern control to
lower frequencies
Not Obvious: three
way line array.
Pattern control to
lower frequencies
Copyright 2005 PMI, Ltd.
What’s all this about directivity?
• Match the directivity
–
To the room
–
To the intended usage
• Higher directivity
–
Better clarity
–
Tighter imaging
• Lower directivity
–
Smoother quality
–
More envelopment
Copyright 2005 PMI, Ltd.
110
What’s all this about directivity?
• The traditional 2 way speaker is the
magic balance for 2 channel music:
Good envelopment and sufficient
directional cues at high frequencies
• 5.1 channel music and film may need
more frontal directivity to avoid
“cacophony”
• However, remember to match the
speaker to the room !
Copyright 2005 PMI, Ltd.
Center Speaker
• Beware of this type of center speaker
• Sound should be identical throughout the
listening area
Copyright 2005 PMI, Ltd.
111
Center Speaker Dispersion
No Lobing Allowed
Radiation pattern of traditional center speakers
around 2kHz
Copyright 2005 PMI, Ltd.
What about directivity of Surrounds?
• The traditional 2 way speaker is
OK – Sound dominated by
reflections from 3kHz down
• 5.1 channel music and film may
benefit from more envelopment
to avoid distraction:
Dipoles and Bipoles
Copyright 2005 PMI, Ltd.
112
What about directivity of Surrounds?
_
+
Dipole:
Deep null and lots
of envelopment
Bipole:
+
+
Broader waistline
More directionality
Copyright 2005 PMI, Ltd.
Surround Loudspeakers
Home Theatre Surround Soundfield Effect
Dipole
Direct
Copyright 2005 PMI, Ltd.
113
Surround EX Soundfield
in Cinemas
Side Left Array
L
LFE
Rear Array
C
R
Side Right Array
Copyright 2005 PMI, Ltd.
Surround EX for Home Theatres
L
Side Left
C
Sub R
+
+
-
-
Side Right
Rear
-
+
+
-
Copyright 2005 PMI, Ltd.
114
Minimum System Requirements
• Side speakers
–
Use dipole, bipole, or direct speakers
–
Balance envelopment and directionality
–
Flat sound power response
–
The issue of sound power response –
equalize or choose the right speaker
Copyright 2005 PMI, Ltd.
Minimum System Requirements
• Rear speakers
–
Use dipole, bipole, or direct speakers
–
Balance envelopment and directionality
–
Flat sound power response
–
The issue of sound power response –
equalize or choose the right speaker
–
Watch for “Front-Back Reversal” potential
Copyright 2005 PMI, Ltd.
115
What to look for in Subwoofers
• Powered or passive?
• Frequency response – smooth down to 35Hz
then 12dB/Oct roll-off Î Flat to 20Hz in-room
• Limiting
• Crossover adjustments
• Unfortunately, placement will be at one or two
pressure maxima (floor, side/front wall)
• Solution: Always use 2 or 4 subs placed so as
to reduce resonances
Copyright 2005 PMI, Ltd.
Audio Gear Placement
Copyright 2005 PMI, Ltd.
116
Gear Placement considerations
• Keep noisy components away
• Be careful with noisy video projectors
• Heat dissipation
• Ergonomics
• Organization
• Interface cable maximum run lengths
• Electrical interference
Copyright 2005 PMI, Ltd.
Gear Placement considerations
• Organization
–
–
–
–
–
How many rack spaces
Create spreadsheet list
I/O – think cable lengths (to Computer)
Patch bays
Usage types
•
Mic Preamps / outboard gear / etc.
Put most used gear in most accessible
location
– Maintain flexibility
–
Copyright 2005 PMI, Ltd.
117
Speaker Placement
Several Considerations
• “Nearfield” or “Farfield”
• Boundary reflections
• Standing waves
• Horizontal placement width
• Seated ear height
• Relationship to picture
Copyright 2005 PMI, Ltd.
Front Speaker Placement
General Guidelines
• Keep away from corners and floors
• Provide for equal acoustical environment
across front
• Do not place speakers
horizontally unless
properly designed
for it
Copyright 2005 PMI, Ltd.
118
Speaker Placement
Summary
• Position of speakers affect their sound
• Find best position through:
–
Computer modeling
–
Measuring in-room with analyzer
–
Listening
• Aim speakers appropriately
–
Fronts towards the listening area
–
Surround towards the room
Copyright 2005 PMI, Ltd.
Boundary Effects
Loudspeaker/ Room Interactions
• Reflection issues at low frequencies are
called “boundary effects”
• Peaks and dips in bass/mid frequencies
depend on speaker location
• Low frequencies are hard to absorb
• In multi-channel systems, each speaker
may have a different boundary interaction
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Boundary Effects
Goals
• Smoothest frequency response across
the listening area
• Good tonal match between front
speakers
• Articulation
• Speech clarity
Copyright 2005 PMI, Ltd.
Boundary Effects
• Evaluation
–
• Correction
Computer predictions
•
CARA
•
RPG Room optimizer
–
Use circulating pink noise
and listen for timbral
variations
–
Use pink noise and RTA to
measure spectral
variations
–
Avoid multiple equal boundary
distances
–
Change speaker position
–
Match boundary conditions for
the front speakers
–
Flush mount speakers
–
Use low frequency absorption
–
Equalize
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Front Speaker Placement
Unequal Boundaries
Unequal
Reflected
Path Lengths
Copyright 2005 PMI, Ltd.
Front Speaker Placement
• Aim for
unequal
reflection path
lengths for
floor / side /
front wall
• Distribute peakdip frequencies
Side
Floor
Front
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Bass Absorption on the front wall
• Use Bass
absorber to kill
front wall
reflection
Copyright 2005 PMI, Ltd.
Solutions to LF Reflections
Bass Absorption
Side
Floor
Front
• With Bass
absorber, front
wall response
is smoother
• The remaining
error can be
equalized
• Can also use
Bass absorbers
on front wall
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Front Speaker Placement
• Use planning and modeling for best
boundary conditions
–
RPG room optimizer
–
CARA
Copyright 2005 PMI, Ltd.
Modeling Software
RPG Room Optimizer
123
Modeling Software
CARA
Modeling Software
CARA
124
Front Speaker Placement
Copyright 2005 PMI, Ltd.
Front Speaker Placement
Reducing boundary effects
• Move speakers
away from
walls
• Reduces
reflection
effects
• Robs you away
from precious
real estate
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Front Speaker Placement
Another strategy: Baffle mounting
• Removes reflections
from front wall
• Cleaner bass response
• More bass headroom
• Bass boost needs EQ
• Baffle is best convexshaped
• Covered with absorption
• Preserves real estate
Copyright 2005 PMI, Ltd.
Front Speaker Placement
Baffle mounting example
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Front Speaker Placement Guidelines
Vertical Plane
•
•
•
•
Place at seated ear height
Place at mid-height of screen
Keep Difference Center / Left-Right < 10º
Remember to:
–
Eliminate a standing wave
–
Reduce reflections and boundary effects
Copyright 2005 PMI, Ltd.
Front Speaker Placement Guidelines
Horizontal Plane
•Position Left and
Right to form a 45
degree angle to
seating area
45º
•Balance between
stereo phantom
image and
multichannel
separation
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Front Speaker Placement Guidelines
Horizontal Plane
• L/R form a 45 degree angle to seating area
• Ensure adequate phantom image
• Ensure proper coverage (aim speakers)
• Avoid any nearby obstructions
(workstations, displays, etc.)
• Remember to:
–
Eliminate a standing wave
–
Reduce reflections and boundary effects
Copyright 2005 PMI, Ltd.
Front Speaker Placement Guidelines
“Nearfield” or “Farfield”
• Speakers don’t know what field they’re in
• Consumers sit in “midfield”
–
Transition area between direct and reverberant
energy [ F. Toole, 2005 AES119]
–
Typically 12 feet
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Layout of a typical
Home Theater:
• 12 feet from front
speakers
L
C
Sub R
• Side surrounds on
side wall firing in
• Rears on rear wall
Left
Side
Right
Side
Rear
Copyright 2005 PMI, Ltd.
Front Speaker Placement Guidelines
“Nearfield” or “Farfield”
• Speakers don’t know what field they’re in
• Consumers sit in “midfield”
– Transition
energy
– Typically
area between direct and reverberant
[ F. Toole, 2005 AES119]
12 feet
• Why not sit in “midfield”?
– Sit
at 8 to 12 feet
– Don’t
nitpick the small stuff; focus on the whole
picture!
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Front Speaker Placement
The Best Solution for post work
• Use acoustically transparent screen
whenever possible
Acoustically Transparent Screen
L
C
R
Copyright 2005 PMI, Ltd.
Front Loudspeaker Aiming
• Aim speakers towards the listening
area
–
Vertical Plane – “Toe In”
–
Horizontal Plane – Aim up or down
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Front Speaker Coverage
Lobing Problems
• Radiation pattern of “DiAppolito” speakers
around 2kHz
• Aim them!
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Subwoofer Placement
• Use planning and modeling
• Esthetics vs. Acoustics
• Use in mono
• Eliminate a room resonance
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Subwoofer Placement
• Multiple subwoofers can be better
• Move seats if needed
• Use bass absorbers if needed
• Measure frequency response
• Listen to single tone sweep
Copyright 2005 PMI, Ltd.
Subwoofer Placement
Loudspeaker
• Driving room
standing waves
in cancellation areas
can improve
response
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Standing Waves
Pressure Polarity
1st Harmonic
• The acoustic
polarity
changes
around the null
_
+
1/2
Copyright 2005 PMI, Ltd.
Standing Waves
Pressure Polarities
1st Harmonic
2nd Harmonic
_
+
1/2
_
1/6
3/4
4th Harmonic
_
+
1/2
+
1/4
3rd Harmonic
+
_
+
5/6
+ _ +
1/8
3/8
_
5/8
+
7/8
133
Subwoofer Placement
Driving Standing Waves
• The subwoofer
drives the 2nd
order standing
wave resonance
Original Resonance
–
+
+
Subwoofer
Copyright 2005 PMI, Ltd.
Subwoofer Placement
Reducing Standing Waves
• Move subwoofer to
null
Original Resonance
–
+
Subwoofer
+
• The subwoofer
drives the + and areas equally,
resulting in
reduction of
resonance
Resulting resonance
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Subwoofer Placement
Reducing Standing Waves (continued)
• Improving a 2nd order
standing wave
– Connect the 2
subwoofers together
as “in-phase”
Original Resonance
+
Subwoofer 1
–
–
The 2 subwoofers
drive the + and - areas
equally, resulting in
reduction of
resonance
–
Experiment a lot
+
Subwoofer 2
Subwoofer
Output
From
Controller
Resulting Resonance
Copyright 2005 PMI, Ltd.
Subwoofer Placement
Reducing Standing Waves - A good solution
• 4 subwoofers
• They can be small
and hidden
• It’s the latest
research findings
• Todd Welti et al.
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Subwoofer Placement
Another good solution
• 2 subwoofers
• More SPL
• More standing
waves
Copyright 2005 PMI, Ltd.
Side Speaker Placement
• Use Planning and Modeling
• To the sides or slightly behind listeners
• 24” (60 cm) above seated ear height
• Ensure adequate coverage
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Side Speaker Placement
Dipole Speakers Guidelines
• Place on sidewalls or ceiling with null towards listeners
• Place high in room for best reflections (about 2 meters)
• Dipoles can get lost in large reverberant rooms
Acceptable Mounting Locations
for Surrounds Along Room Length
Acceptable Surround Placement Areas on
Ceiling and Side Walls
Copyright 2005 PMI, Ltd.
Dipole Side
Speaker Typical Position
• Place on side walls or ceiling, with null
pointing towards listeners
Null
Null
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Dipole Side Speaker Placement
Ceiling Placement
Null
• Aim null at listening position
• Good alternative to sidewall placement
Copyright 2005 PMI, Ltd.
• Good for aesthetics
Dipole Side Speaker Placement
For Mid-Room Seating Position
ll
Nu
Nu
ll
• Make rear
wall the first
reflection
to ensure
surround effect
• Aim null
at listening
position
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Dipole Side Speaker Placement
Seat on Back Wall
2 Feet
Null
• Place on side
walls or ceiling,
2 feet (60cm)
from rear wall
• Aim null
at listening
position if
needed
Null
Dipole Side Speaker Placement
Room with Multiple Rows - 1
2 Feet
Null
• Aim null
for most
even
coverage
Null
139
Dipole Side Speaker Placement
Room with Multiple Rows - 2
2 Feet
–
+
–
Null
• Invert polarity
of rear pair
+
Null
• Adjust position
for even
coverage
Null
+
Null
–
–
+
Side Speaker Placement
Direct Radiating Speakers
• Place on side walls
• Slightly behind
listener area
• Place high in room
(about 6 feet)
• Avoid placing close
to listeners
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Direct Surround Speakers
Placement and Aiming
• Aim
across
room
• Don’t aim
toward
listener
Copyright 2005 PMI, Ltd.
Direct Surround Speaker Placement
Seat on Back Wall
1 Foot
• Aim across room
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Dipolar Rear Speaker Placement
for Surround EX
Sl
-
+
• Place rear
speakers at
2 meter (6 feet)
height
Rl
+
+
• Place at 150°
from front
center
Rr
-
+
Sr
Copyright 2005 PMI, Ltd.
Dipolar Rear Speaker Placement
for Surround EX
Sl
-
+
• Place rear
speakers at
2 meter (6 feet)
height
Rear
+
• Good solution
for small
couches
-
+
Sr
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Direct Rear Speaker Placement
for Surround EX
Sl
-
+
Rl
• Place rear speakers at
2 meter (6 feet) height
+
• Place at 150° from
front center
• Watch for
Psycho-Acoustic
inversion
+
– Try asymmetrical
placement
Rr
-
+
Sr
Copyright 2005 PMI, Ltd.
Speaker Placement
The “Magic Layout”
• Front speakers placed for best
interaction with the room
(measure them with an analyzer)
• L/R form a 45 degree triangle
• C at same height as L/R
• LCR arc is unnecessary (set
delay time for each spkr in the
monitoring control / equalizer)
• Side speakers to sides of
listeners
• Rear speakers behind listeners
C
L
R
Sub
Left
Side
Right
Side
Rear
Rear
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An example room
studio.jory.org
Copyright 2005 PMI, Ltd.
An example room
studio.jory.org
Copyright 2005 PMI, Ltd.
144
An example room
studio.jory.org
Copyright 2005 PMI, Ltd.
Video Gear Placement
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Video Component Placement
• No direct light onto the screen
Copyright 2005 PMI, Ltd.
Video Component Placement
• If possible provide low level neutral
light behind the screen
Copyright 2005 PMI, Ltd.
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Screen placement guidelines
• Vertical viewing angle to middle of
screen <15º
Copyright 2005 PMI, Ltd.
Screen height
Comfort Angle limit:
15º
15º
Copyright 2005 PMI, Ltd.
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Screen height - Sight Lines
15º
Clear sight line
Copyright 2005 PMI, Ltd.
Wiring it all up
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Wiring Considerations
• Use decent quality cable
• Learn how to solder
• Make up wiring list
• Total up wire length for each type
• Create parts list
Wire
– Connectors
–
• Patch bay layout
Copyright 2005 PMI, Ltd.
Wiring Considerations
• Power distribution
• Don’t run with audio lines
• Grounding
–
Go back to same outlet
–
Star ground
–
Measure ground voltage differences
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Wiring – Color coding
• Patch bay coding
–
–
–
–
–
–
–
–
–
Sound Generating devises
Mic preamps
Recording / Playback devices
Encoders
Decoders
Monitors
Tie Lines
Mults
Misc.
Copyright 2005 PMI, Ltd.
Tuning it All
Analysis and equalization
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Electrical Level Calibration
• Digital reference level: -20dBfs
• => 20dB Headroom
• Electrical levels: 0 VU = +4dBm = 1.23V
• Verify and adjust levels throughout
• Calibrate the outputs first
–
1kHz @ -20dBfs => +4dBm
• Calibrate inputs next
–
Take calibrated output and feed to input
–
Set input gain for –20dBfs at meters
Copyright 2005 PMI, Ltd.
Level Calibration of DAW
• Acoustic: Use midband pink noise
signals at +4dBm output
reference disk or internal test tones
– For music, calibrate for 85dB
– For film, calibrate surrounds to 82dB
–
Mid-Frequency test noise internal
to most good surround processors.
The signal is centered in the
500Hz to 2kHz region to improve
measurement accuracy
Level
500Hz
2kHz
Frequency
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Level Calibration
External multichannel source
• Electrical:
–
Use –10/+4dB balanced adapter with gain
controls
• Acoustic: Use test DVD with midband
pink noise
–
Calibrate for 85dB across all channels
Copyright 2005 PMI, Ltd.
Level Calibration
Time synchronization
• Compensate for differences in speaker
distance
• Set delays for nearest speakers
• Sound propagates at 1ft/ms
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Analysis – the useful way
Loudspeaker
1/3 Octave
Equalization
Pink Noise
Generator
Multiplexer
Microphone 3
Microphone 2
Microphone 4
Microphone 1
• Analysis
should be
spatially and
temporally
averaged
• Use Gold
Line DSP30
Analyzer, or
equivalent
Copyright 2005 PMI, Ltd.
Frequency Response Calibration
Room + Equalizer Phase Response
• 12 dB peak
error at 200 Hz
(yellow line)
• Phase error
(red line)
• Equal cut
introduces
inverse phase
error
• Amplitude and
phase are
corrected!
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Equalization Requirements
• Pink noise source
–
20 Hz–20 kHz, switchable to each channel
before the crossover (5.1 Audio Toolkit)
• Real time analyzer
–
20 second time averaging
–
The ability to average 4 or more readings
from mic multiplexing
–
1/12 octave resolution in low frequencies
Copyright 2005 PMI, Ltd.
Quick Check of Overall
Frequency Response
Using Etymotic ER-4S or ER-6 Earphones
Pink
Noise
Pink
Noise
Compare
CD
CD
Set earphone level to match speaker
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Tools
Copyright 2005 PMI, Ltd.
Ulysses Ray Tracing
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SMAART Live
Copyright 2005 PMI, Ltd.
Gold Line DSP30
• RTA
• 1/3, 1/6, 1/12th Octave
• Averaging
• NC
• RT60
• Integrated solution
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TEF 25
• RTA
• TDS
• MLSSA
• Log sweeps
• Phase measurements
• Many more
Copyright 2005 PMI, Ltd.
Planning
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Planning is key
•
•
•
•
•
•
•
•
Mission statement
Goals
Macro to Micro
Time schedules
Budgets
Parts lists
Wire lists
Expect it to all cost more than planned
Copyright 2005 PMI, Ltd.
Good Reading Materials
• Acoustics and Psychoacoustics, Howard, David M., Angus,
James, Focal Press, 1996, ISBN 0 240 51482 9
• Audio Engineering Handbook, Benson, K. Blair ed.
McGraw-Hill Book Company, 1988
• Building a Recording Studio, Cooper, Jeff, Synergy Group,
Inc., Los Angeles. To order call 1-800-468-4322
• The Master Handbook of Acoustics, Everest, F. Alton, TAB
Books, Division of McGraw-Hill Inc., Blue Ridge Summit,
PA. To order call 1-800-468-4322
• Project Studios, P. Newell, Focal Press, ISBN 0 240 51573 0
• Room Acoustics, Kuttruff, Heinrich, Applied Science
Publishers 1973/1991
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Conclusion
• Project studio design is very complex
• Pay attention to all details for a good
system
• I hope you enjoyed the presentation
• Thanks,
Anthony Grimani
Copyright 2005 PMI, Ltd.
Contact Info
Anthony Grimani
PMI, Ltd
9A Mono Avenue
Fairfax, CA 94930
info@pmiltd.com
415 454 2087
www.pmiltd.com
Copyright 2005 PMI, Ltd.
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