SYNTHESIS®FOUR
S4VC, S4HC
& S4Ai
LUSH-MOUNT
F
LOUDSPEAKERS
OWNER
MANUAL
’
S AND INSTALLER
’
S
CONTENTS
INTRODUCTION ......................................................................................................................................................3
NCLUDED.............................................................................................................................................................4
I
PEAKER PLACEMENT .............................................................................................................................................5
S
EFT AND RIGHT SPEAKERS ..............................................................................................................................5
L
C
ENTER CHANNEL SPEAKERS ...........................................................................................................................5
MBIENT SURROUND SPEAKERS .......................................................................................................................6
A
ANNELSYSTEMS
H
5.1-C
HANNEL SYSTEMS ..........................................................................................................................6
6.1-C
HANNEL SYSTEMS ..........................................................................................................................7
7.1-C
..........................................................................................................................6
S4Ai M
S4Ai W
W
P
S4Ai O
S4Ai D
OUNTING THE SPEAKERS....................................................................................................................................10
M
PEAKER-MOUNTING OPTIONS .......................................................................................................................10
S
EQUIREMENTS FOR MOUNTING .....................................................................................................................11
R
ONNECTING THE SPEAKERS TO THE REST OF YOUR SYSTEM.......................................................................................13
C
REPARING THE HOOKUP WIRE .......................................................................................................................13
P
INE-TUNING YOUR AUDIO SYSTEM .......................................................................................................................14
F
A
COUSTICAL PROBLEMS IN LISTENING ROOMS ..................................................................................................14
OOM REFLECTIONS......................................................................................................................................14
R
XCESSIVE USE OF ABSORPTIVE MATERIALS......................................................................................................15
E
”S
LAP” ECHOES............................................................................................................................................16
TTLES
A
R
ODES OF OPERATION ...................................................................................................................7
IRING GUIDE ..............................................................................................................................7
HICH DIFFUSE MODE IS THE RIGHT ONE FOR THE JOB? .............................................................................8
REPARING THE S4Ai FOR THE CORRECT OPERATIONAL MODE........................................................................8
RIENTATION – VERTICAL OR HORIZONTAL..........................................................................................9
UAL-DRIVE MODE......................................................................................................................10
.....................................................................................................................................................17
ACKGROUND NOISE ....................................................................................................................................17
B
ACKGROUND-NOISE SOLUTIONS ....................................................................................................................
B
S
TANDING WAVES .......................................................................................................................................18
TANDING-WAVE SOLUTIONS: ROOM RATIOS ...................................................................................................19
S
TANDING-WAVE SOLUTIONS: SPEAKER PLACEMENT .........................................................................................19
S
ANDING
T
S
T
S
ROUBLESHOOTING...............................................................................................................................................21
T
PECIFICATIONS...................................................................................................................................................23
S
-WAVESOLUTIONS: ABSORPTION .....................................................................................................19
ANDING
-WAVESOLUTIONS: ROOM EQUALIZA
TION
..........................................................................................20
18
INTRODUCTION
Thank you for purchasing JBL Synthesis®Four flush-mount home theater loudspeakers. These products represent the
®
synthesis of everything that JBL
preeminence in the field. They set new benchmarks in the use of “high technology” and provide you with the experience of being in the world’s greatest movie houses and concert halls – right at home! JBL Synthesis Four
speaker systems feature the following:
has learned about the emotional power of audio and video in more than fifty years of
THX ULTRA2™-LICENSED HOME AUDIO SYSTEM: When used with a THX
speaker system will deliver a state-of-the-art THX home theater experience to your living room. You will hear in
your home exactly what the director and sound engineer heard in the recording studio. The system will reproduce
the audio flawlessly and without distortion.
®
controller and amplifiers, your
FLUSH-MOUNT APPEARANCE: The S4Ai, S4VC and S4HC are designed to fit flush to your wall surface.
Designers and interior decorators will be pleased by their hidden appearance and stunning performance.
PURE-TITANIUM, HIGH-FREQUENCY TRANSDUCER DOME:
magnet structures are ultralight to accurately reproduce lightning-fast sounds – such as cymbal crashes –
extremely rigid to eliminate distortion and ear fatigue.
The pure-titanium diaphragms with neodymium
yet
ELLIPTICAL OBLATE SPHEROIDAL™(EOS™) WAVEGUIDE: First developed for our JBL Professional LSR studio
monitors, this unique structure enables Synthesis Four Series speakers to evenly disperse high frequencies, creating
precise imaging over a wide listening area.
PURE-TITANIUM, INVERTED-DOME, MIDRANGE TRANSDUCERS: The midrange drivers seamlessly comple-
ment the titanium-dome tweeter and offer nearly perfect pistonic motion, which eliminates the uncontrollable
flexing found in conventional cones. The inverted dome is driven precisely at its center, which cancels resonances
inherent in cone materials. The result is ruler-flat frequency response beyond the crossover point.
ANIUM
TIT
precise, undistorted bass reproduction that matches the titanium tweeter and midrange. The powerful neodymium
magnet provides its own video shielding (S4VC and S4HC), allowing for flexible placement near video monitors.
Cast-aluminum frames remain rigid even at the highest volumes, avoiding the distortion found in some other speaker
designs. The aluminum doesn’t affect the magnetic field, so driver movement is precise.
-ALLOY, INVERTED-DOME, LOW-FREQUENCY TRANSDUCERS: The low-frequency drivers deliver
COMMON VOICING: Synthesis Four uses common voicing across the front three channels. Since identical drivers
are used, each speaker has the same tonal qualities; thus, as a sound is panned from one side to the other
be no change in timbre.
, there will
MAGNETIC SHIELDING: All front speakers are magnetically shielded, allowing you to place them near video
monitors without generating interference or distorting the picture. (S4Ai is not magnetically shielded.)
3
INCLUDED
or or
One S4VC vertical channel
flush-mount loudspeaker
Eight 8-32 x 1/2" screws for
speaker installation
One S4HC horizontal channel
flush-mount loudspeaker
Four mounting L-brackets with
eight 1/4-20 x 3/4" screws
One S4Ai multipole ambient
flush-mount loudspeaker
One grille with grille frame
4
RCL
VIEWING
P
OSITION
FLOOR PLAN
SPEAKER PLACEMENT
Positioning your loudspeakers properly is critical in order to achieve the
sonic performance of a home theater. Please read the following section
and the “Fine-Tuning Your Audio System” section for guidance in correct
and optimal placement.
LEFT AND RIGHT SPEAKERS: If you have purchased a Synthesis Four
Digital Home Theater System, then the model S4VC will serve as your
front left and right main speakers.
Since the left and right speakers have been designed for maximum localization
of sound, they should be placed with the center of the speakers at about the
same height on screen as the actors would be, to aid in the illusion that the
actors’ voices are coming directly from their on-screen images. Ideally, the
speakers will be placed about 45 degrees apart from each other,
from the listening position, so that the distance between the speakers
same as each speaker’
s distance from the listener (see Figure 1).
viewed
is the
Figure 1. 5.1-Channel system
CENTER CHANNEL SPEAKERS
S4VC: If you have purchased the vertical channel speaker (model S4VC)
for the center position, be sure to place it vertically during installation in
order to take advantage of its sound-dispersion characteristics. If you mount
it horizontally
is being used with a perforated projection screen, it should be mounted
behind the center of the screen (see Figure 2). If a nonperforated projection
screen, plasma display or other fixed video device is being used in the
installation, the preferred center speaker is the model S4HC (below).
S4HC: If you have purchased the horizontal channel speaker (model S4HC)
for the center position, be sure to position it horizontally during installation
in order to take advantage of its sound-dispersion characteristics. If you
mount it vertically, it will not provide the correct dispersion pattern.
Although the preferred speaker model to be used with a perforated projection screen is the vertical model S4VC (above), the S4HC horizontal speaker
may be used instead and should be mounted behind the center of the
screen. If a nonperforated projection screen, plasma display or other fixed
video device is being used in the installation, then the recommended
location is directly below and as close as possible to the video display
(see Figure 3), although the inverse of this method will work also.
, it will not provide the correct dispersion pattern. If the speaker
Figure 2.
Figure 3.
5
RCL
FLOOR PLAN
Min. 2'-0"
SPEAKER PLACEMENT
NOTE:
It is extremely important to place the tweeter/mid-bass arrays for each of the center, left and right speakers at the
same height. The EOS waveguide containing the tweeter in the center channel speaker should be no more than two
feet higher or lower than those in the left and right speakers. This preserves the “localization integrity” of “sound
pans,”in which the sound appears to move from left to center to right. If the program material also appears to travel
up and down, it can destroy the illusion of panning effects and so should be avoided.
AMBIENT SURROUND SPEAKERS: Although it has been common for many years to use a number of surround
speakers in commercial movie houses, until recently, the traditional home theater configuration called for 5.1
channels, i.e., front left, center, front right, surround left and surround right, plus a low-frequency-effects channel.
The newer surround formats that are appearing in consumer audio equipment are calling for more complicated 6.1and 7.1-channel systems. The advantages of using additional speakers are many. Additional channels enable a more
versatile use of directionality for a more accurate surround presentation. Also, a higher overall sound-pressure level
can be achieved with less energy expenditure from any individual speaker.
Placement of the surround speakers remains critical.
5.1-CHANNEL SYSTEMS
The S4Ai multipole ambient surround speakers work optimally if they are
placed as far back from the screen as the viewing chairs are. If there are two
rows of chairs, these speakers should be placed between them.
The ambient surround speakers should be placed higher than the seating area,
at least two feet above (seated) ear level (see Figure 4).
The preferred method to mount the ambient surrounds is to put them directly in
the side walls. This lets each speaker radiate to the front and back of the room
and to reflect off the side walls.
There are a few instances in which the ambient surrounds would perform
better if mounted in the ceiling rather than the walls. If one or both of the walls
are “acoustically dead,”due to the presence of windows, fabric, furniture or
other absorption, it may be necessary to turn the ambient speakers sideways
and, instead of mounting them in a vertical orientation, mount them in the
ceiling in a horizontal orientation.
6.1-CHANNEL SYSTEMS
A 6.1-channel system can be thought of as a 5.1-channel system with the
addition of a rear center speaker placed midway between the two surround
speakers, and further to the rear than the surrounds. It should be placed at the
same height as the side surround speakers (see Figure 5).
Figure 4.
Figure 5. 6.1-Channel system
6
RCL
SIDE
L
EFT
SIDE
R
IGHT
REAR LEFT
REAR RIGHT
SPEAKER INPUT #1
SPEAKER INPUT #2
SPEAKER PLACEMENT
7.1-CHANNEL SYSTEMS
In a 7.1-channel system, two speakers are added for rear fill, in addition to the surround speakers in a 5.1-channel system. The two additional speakers are placed on
the rear wall or near the rear wall in the ceiling (see Figure 6).
S4Ai MODES OF OPERATION
The S4Ai multipole ambient surround speakers feature the unique capability of
being configured in any of three operational modes. Choose between Dipolar or
Bipolar operation for cinema reproduction, and Direct Radiating for music. Both Dipole
and Bipole modes are diffusive, meaning there is less energy on-axis than off-axis
relative to the front of the speaker baffle. As Figure 7 indicates, the S4Ai’s omnidirectional woofer faces toward the listening area, while dual sets of tweeter/
midrange (diffuse) arrays face toward the front and rear or from side to side in
the room. In Dipole mode the arrays play out of phase in relation to each other,
and in Bipole mode they play in phase with each other
To activate the Direct Radiating mode for music playback, use the JBL Synthesis
electronics package, including the SDP-40 surround processor, to trigger the
autoswitching relay in the loudspeakers. The input to the trigger connection is
located at the bottom of the speaker, next to the speaker terminals (see Figure 8)
and accepts two-conductor, #24 to #16 A
WG wire. The relay is activated by a con
stant 12V DC signal.
.
-
Figure 6. 7.1-Channel system
S4Ai WIRING GUIDE
Figure 7.
Single-drive – Dipole or Bipole
operation only – two-cond.
speaker wire
Figure 8.
Dual-drive – Bipole operation
only – four-cond. speaker wire
Each S4Ai speaker can be wired in single- or dual-drive mode. The best performance can be obtained by installing
four S4Ai speakers in a 7-channel system and wiring them in single-drive mode; that is one amplifier channel per
S4Ai speaker. If only two S4Ai speakers can be used in a particular application, then they should be wired in dualdrive mode so as to gain the advantages of a 7-channel system. Each S4Ai speaker receives amplification from two
channels –
side and rear – which can only be accomplished in the Bipole mode.
Single-drive w/Direct – Dipole or Bipole
and Direct Radiating operation – two-cond.
speaker wire and two-cond. trigger wire
Dual-drive w/Direct – Bipole and Direct
Radiating operation – four-cond. speaker
wire and two-cond. trigger wire
7
+
-
-
+
PHASE
SWITCH
PHASE
SWITCH
S
WITCH OUT (SHIPPED) SWITCH IN (OPTIONAL)
SPEAKER PLACEMENT
WHICH DIFFUSE MODE IS THE RIGHT ONE FOR THE JOB?
D
IPOLE MODE IS TYPICALLY USED WHEN:
• The speaker is located relatively close to the
listening position.
• Multiple side or rear speakers are being used in a small listening room.
• The speaker is mounted near, but not in, a corner
and will be subject to negative reflections from
nearby walls.
• The room is highly reflective.
BIPOLE MODE IS TYPICALLY USED WHEN:
• One speaker location is used to drive both side and
rear channels in a dual-drive configuration.
• The speaker is located relatively far away from the
listening position.
• Multiple side or rear speakers are being used in a
large listening room.
• The speaker is mounted in a corner, at a 45-degree
angle.
PREPARING THE S4Ai FOR THE CORRECT
Figure 9. Dipole phase relationship
OPERATIONAL MODE
It will be necessary to choose which of the two diffuse modes to use at the time of installation. The S4Ai is shipped
from the factory in the Bipole mode. If this is your choice and the speaker will be placed in the vertical orientation,
no changes are required and the S4Ai can be directly installed into its permanent location.
Setting the phase in relation to the other speakers in the room only applies when the S4Ai speakers are set in
Dipole mode. If you choose to use the S4Ai in Dipole mode, the following information for proper phase relations
between speakers will apply:
The S4Ai speakers are shipped from the factory with the phase switch in the OUT position. In this position, the positive phase array is pointing toward the left as you face the speaker
cone, the cone will move outward. Usually
should fire toward the front of the room. The array facing the rear of the room will have a negative orientation. That
is, when positive voltage is applied to the cone, it will move inward, in the opposite direction of the other array on
the speaker
. As shipped from the factory
tem. The speaker that will be placed in the left-side wall should have its phase switch pushed in so that the positive
phase array will be firing toward the front of the room when installed (see Figure 10).
. That is, when positive voltage is applied to the
, when the Dipole mode is used in a 5.1 system, the positive phase array
, the S4Ai is set up for placement in the right-side wall in a 5.1-channel sys-
8
RCL
S
IDE
L
EFT
S
IDE
R
IGHT
FLOOR PLAN
++
RCL
SIDE
LEFT
SIDE
RIGHT
REAR LEFT
REAR RIGHT
F
LOOR PLAN
++
+
+
BI
P
O
L
E
D
I
P
O
L
E
BIP
OLE
DIP
OLE
BIP
OLE
DIP
OLE
BIP
O
LE
DIPO
LE
SPEAKER PLACEMENT
In a 7.1-channel system, where two
additional S4Ai speakers may be
mounted in the rear wall, the positive
phase arrays for all speakers should
fire toward the rear corners, as shown
in Figure 11. Thus, the side left speaker
should be configured with its phase
switch in the IN position, and the
speaker on the right should be configured with its phase switch placed in
the OUT
the table on the right side.
position (see Figure 11). See
Figure 10. 5.1 System
Figure 11. 7.1 System
To change the operational mode
between Bipole and Dipole, move the
switch to the Dipole-mode position (see Figure 12). The switch can be
accessed from the back of the speaker, or from the front by removing the
upper half of the baffle.
Figure 12. Switch for
Dipole/Bipole mode
S4Ai ORIENTATION – VERTICAL OR HORIZONTAL
Phase Switch Setting in Dipole Mode
5.1 System 7.1 System
Side Left
IN OUT
Side Right OUT IN
Rear Left N/A IN
Rear Right
N/A
OUT
The S4Ai’s top baffle or “diffuse array” may be rotated 90 degrees clockwise so that the speakers can be placed in
either vertical or horizontal orientation and still be able to produce the correct dispersion pattern. This may be necessary, for example, if the S4Ai is being installed in a ceiling and the joists are running from front to back in the room.
In that situation, conventional in-wall side channels would be firing side to side rather than front to back. To correct
this and produce the correct pattern, remove the eight retaining screws from the “diffuse array” and rotate 90
degrees so the dispersion pattern is correct in relation to the room and the other surround speakers in the system. If
changing from the vertical to horizontal configuration, rotate the array clockwise. If changing from the horizontal to
vertical configuration, rotate the array counterclockwise (see Figure 13). In both cases, take care not to damage the
wiring, which will remain connected to either the Dipole or Bipole connector, as discussed above (see Figure 12).
9
SET THIS
SCREW TO
WALLBOARD
THICKNESS
ROTATE ARRAY CW
SPEAKER PLACEMENT
S4Ai DUAL-DR
IVE
MO
DE
As the S4Ai has the capability of producing both side and rear fields from a single location in Bipole mode while
dual-driven for cinema playback (see S4Ai Wiring Guide on page 7), some care must be taken when using the
Direct-Radiating mode with the autoswitching trigger for music playback.
Figure 13. Rotate top baffle for vertical or horizontal orientation
Use Speaker Input #1 (see Figure 8) for the side field so that the direct-radiating tweeter for both speakers plays the
correct information generated by the decoder. This can be accomplished by rotating the “diffuse array” 180 degrees
from default so that the speakers mirror each other in the installation.
See Figure 13, which shows how to rotate the array, but note that for Dual-Drive mode you will need to rotate the
array an additional 90 degrees from the position shown for a final position, in which the tweeter-midrange array that
started out on top ends up on the bottom (and thus with the tweeter facing to the right rather than the left).
MOUNTING THE SPEAKERS
SPEAKER-MOUNTING OPTIONS
The S4VC, S4HC and S4Ai models all use the same mounting bracket. There are two models to choose from, based
on the type of installation. In the case of new construction,
choose the S4PCB preconstruction bracket. For retrofit installation, use the S4RFB. Both are sold separately. The speakers
will fit into standard-construction 2" x 6" walls with 16" oncenter studs. For horizontal mounting, cross-bracing is
required; also at 16" on center
mounting either S4PCB or S4RFB, included with the brackets.
The speakers are directly attached to the mounting L-brackets
with hardware supplied in the speaker packing box, and can
be adjusted for proper mounting depth with a variation of up
to 2-1/2 inches. The actual depth will vary depending on wall
construction and acoustic materials applied to the wall surface (see Figure 14). To flush-mount the grille to the wall
. See separate instructions on
10
Figure 14.
MOUNTING THE SPEAKERS
surface, the speaker must be recessed in the wall no more than 1/4 inch. The grille pins fit directly into the speaker
cabinet via receiver bushings with 15 ft/lb of tension per pin. Use the marked speaker-depth-indicator flanges
(attached to the sides of the speaker baffle) to appropriately adjust the depth from the wall surface so that the
baffle is recessed 1/4 inch. This will ensure that the grille will sit flush to the wall surface.
REQUIREMENTS FOR MOUNTING
OPTION 1 – NEW CONSTRUCTION: The S4PCB mounting-flange bracket must be installed before the drywall
is installed in the room. Attach the included L-brackets to the speakers (see Figure 14), and attach them to the
mounting flanges at the appropriate recessed distance. The S4VC and S4HC require a minimum 6" wall depth.
The S4Ai requires a minimum 4" wall depth (see Figures 15, 16 and 17).
Figure 15. Mounting the S4VC
speaker using the S4PCB kit
Figure 17. Mounting the S4Ai
speaker using the S4PCB kit
Figure 16. Mounting the S4HC
speaker using the S4PCB kit
11
MOUNTING THE SPEAKERS
RE
QUIREMENTS FOR
MO
UNTING
OPTION 2 – RETROFIT/PREEXISTING
CONSTRUCTION: Use the S4RFB bracket.
Mount the S4RFB to the wall surface and secure
it to studs behind the wall. Attach the speaker
via mounting flanges to the appropriate recessed
distance. The S4VC and S4HC require a minimum
6" wall depth. The S4Ai requires a minimum 4"
wall depth (see Figures 18, 19 and 20).
Figure 18. Mounting the
S4VC speaker using the S4RFB kit
Figure 19. Mounting the S4HC
speaker using the S4RFB kit
Figure 20. Mounting the S4Ai
speaker using the S4RFB kit
NOTE: Do not attempt to install any type of mounting bracket other than the S4PCB, the S4RFB, or any other
bracket that JBL may supply for these speakers in the future. Drilling holes in the product or improperly
installing mounting brackets may void your JBL warranty and cause a safety hazard.
A JBL factory-authorized custom installer can install appropriate brackets. Contact JBL and your installer/dealer for
additional information.
12
CONNECTING THE SPEAKERS TO THE REST OF YOUR SYSTEM
To connect the Synthesis Four loudspeakers to the power amplifiers or receiver, use two-conductor insulated speaker
wire. We recommend #14 AWG wire as a minimum size. Your JBL dealer can recommend suitable cables.
Both the S4VC and S4HC utilize push-style friction binding posts that can accommodate up to #10 AWG stranded wire.
Since the S4Ai can be configured in three different ways, be sure to run the correct number and type of wires. Refer
to the S4Ai Wiring Guide on page 7.
PREPARING THE HOOKUP WIRE
1. First determine the distance between your amplifier and the most distant speaker in each group (fronts, surrounds,
back surrounds, subwoofers).
Now make the hookup wires for all speakers in each group this length, even if one speaker is much closer
2.
amplifier than the other. This will help maintain proper signal balance.
3. Strip off 3/8" of insulation from both ends of each conductor.
4. Twist each set of standard wires into a tightly bunched spiral.
5. Speakers and electronics terminals have corresponding (+) and (–) terminals. Most manufacturers of speakers and
electronics, including JBL, use red to denote the (+) terminal and black for the (–) terminal, although some electronics
manufacturers have adopted the new color
In that case, the positive terminal will be colored to correspond to the channel position, while the negative terminal
will be black.
It is important to connect all speakers identically: (+) on the speaker to (+) on the amplifier and (–) on the speaker to
(–) on the amplifier. Wiring “out of phase” results in thin sound, weak bass and poor imaging.
With the advent of multichannel surround sound systems, connecting all of the speakers in your system with the correct polarity remains equally important to preserve the proper ambience and directionality of the program material.
Now find a visual difference between the two conductors of each molded pair of speaker wires. Differentiating
marks can be a different color wire (copper or silver); a strand of yarn in one conductor; thin, raised ribs on one part
of the outer insulation; or a printed marking on one part of the outer insulation. It doesn’t matter which of the two
strands go to the (+) and (–) on the speakers and amplifiers, as long as all speakers are connected identically. Push
down on the binding post, insert the wire into the hole, and release.
-coding standard promulgated by the Consumer Electronics Association.
to your
13
FINE-TUNING YOUR AUDIO SYSTEM
t
1
t
2
Direct
Reflected
Result: (+6dB)
Direct
Reflected
Result: (–∞dB)
Copyright 2000 Lucasfilm Ltd.
t1t
2
A
n Additive
Frequency
A Canceling
Frequency
Copyright 2000 Lucasfilm Ltd.
+6dB
Sound Level
Peak and dips at various frequencies
Resultant Frequency Response From Reflection
Frequency
0dB
ACOUSTICAL PROBLEMS IN LISTENING ROOMS
A home THX audio system, such as the Synthesis Four system, addresses many of the problems common to high-quality
reproduction of music or soundtracks in a home environment. For example, the dispersion pattern of the front LCR speakers
minimizes the effects of floor and ceiling reflections. Still, the single most important variable in any sound system is the
listening environment. Room reflections create spurious false images and “comb filter” interference effects which alter
the tonality of the system while degrading the localization of specific sounds. Larger rooms sustain echoes that degrade
dialogue intelligibility and detail. All rooms have standing waves that emphasize certain frequencies at the expense of
others, based on the dimensions of the room.
Other concerns include environmental noise, which is often greater than people realize. Although they might become
accustomed to its presence and “tune it out,” it still reduces the perceived low-level resolution of the system. In
addition, the profound bass capabilities of a home THX audio system can create distracting rattles that lesser
systems might never evoke.
This section of the manual contains a variety of suggestions for addressing some of the peculiarities of the listening
environment to improve the accuracy of your Synthesis Four system’s sound reproduction.
ROOM REFLECTIONS
The most troublesome room reflections are usually
the early reflections of the front LCR speakers off the
, ceiling and side walls. These reflections reach
floor
the listener’s ears after a delay, with respect to direct
sounds, and blur the perceived image. They can also
degrade dialogue intelligibility through the same
mechanisms (see Figures 21 and 22).
The design of the Synthesis Four speakers minimizes
the floor and ceiling reflections. As an extra
enhancement, it is often a good idea to place a thick,
absorptive carpet between the front speakers and
the listening position, just to further reduce this primary reflection from floors with hard surfaces. A rug
made of wool will generally have more uniform
absorption characteristics than one made from synthetic fibers.
JBL Synthesis Four speakers have broad dispersion in
the horizontal plane in order to ensure a wide usable
listening area. This design choice can induce reflections off the side walls, especially in installations
where they are relatively close to the front speakers.
With conventional speakers, these reflections can be
reduced simply by angling the left and right speakers
inward somewhat.
Figure 21.
Figure 22.
14
Loudspeaker
Listener
Direct Path
Re
fle
cte
d Pa
th
Reflected Path
L
oudspeaker
Re
fle
cte
d Pa
th
Reflecte
d Pa
th
Listener
Direct Path
Absorptive Material Absorptive Material
SOLUTIONS TO ROOM REFLECTIONS:
DIFFUSION AND ABSORPTION
FINE-TUNING YOUR AUDIO SYSTEM
However, since it is not possible to
“toe-in” flush-mounted speakers, the
next step is the strategic placement of
absorptive materials on the side walls.
These range from commercially available fiberglass and dense foam to heavy
draperies and even large, overstuffed
furniture. The optimal position for these
materials can be found with a small
hand mirror and the help of an assistant.
Sit at the primary listening position and
have the assistant slowly slide the mirror along the wall. When you can see
any of the front speakers reflected in the
mirror, mark the wall at the mirror for
later placement of absorptive material
(see Figure 23).
A variation of this method is especially helpful in rooms that are already fairly “dead” acoustically. Rather than using
absorptive material in rooms like these, try using diffusion instead. Commercially built diffusers are available, but
large bookcases and irregularly shaped furniture will also serve the same purpose. They reflect sounds in a highly
random way that effectively “scatters” the sound in all directions. Place the diffuser where you would otherwise
place the absorptive material (using the “mirror trick”), to break up the first early reflections and scatter them
randomly throughout the room.
Figure 23.
Commercially available fiberglass, foam and diffusion panels may not be aesthetically acceptable in many installa
tions, particularly when the home theater room serves multiple purposes. All of these materials can be covered with
acoustically transparent cloth for design considerations. It is important that the cloth be acoustically transparent,
however
, or the effectiveness of the absorptive material will be greatly reduced. The simplest test for this is to hold
a large sample of the cloth in front of a speaker playing pink noise. If you can move the cloth in front of the speaker
without hearing a difference, the cloth is good for use in this application.
Large expanses of glass can be challenging. Glass reflects mids and highs, but often lets bass pass through, almost
as if the glass were not there. The result is a characteristically bright, rough sound that can be difficult to correct
electronically. The best treatment is generally the heaviest insulated drapes that can be found. (Incidentally, these
serve double duty, controlling light that might otherwise fall on the screen.)
The materials just discussed are ineffective at lower frequencies. See the discussion on standing waves for more
information about treating environments with low-frequency response problems.
EXCESSIVE USE OF ABSORPTIVE MATERIALS
Absorptive materials should be used judiciously, as overuse can acoustically deaden the room and create additional
difficulties. While the ideal home theater should be considerably “deader” acoustically than a typical living room, it
still needs some reflectivity and diffusion. In particular, the surround speakers depend on nonabsorptive surfaces for
their operation, since they radiate virtually no sound directly at the listeners.
-
15
Surround speaker
S
creen speaker
ROOM ABSORPTION FOR HOME THEATER SYSTEMS
• “Dead” zone absorbs
front-speaker reflection
• “Live” zone provides
surround propagation
Copyright 2000 Lucasfilm Ltd.
Loudspeaker
Listener
FINE-TUNING YOUR AUDIO SYSTEM
The best arrangement of the absorptive and nonabsorptive surfaces in the room can be seen in Figure 24. Most of
the room surfaces are relatively absorptive, with the notable exception of the rear wall and the highest portions of
the other walls, which should be diffusive.
Figure 24.
“SLAP” ECHOES
“Slap” echoes are common in rooms that have parallel walls with little
or no absorption or diffusion. Sounds tend to bounce back and forth
between the parallel walls many times before they die out, causing a
characteristic bright, “zingy” sound and interfering with the intended
tonal balance and acoustic nature of the soundtrack (see Figure 25).
Walk slowly through the room, clapping your hands. No clear reflections
should be heard at any point in the room – especially not near the pri
mary seating area. Listen for a “flutter echo” of the hand clap (a rapidly
repeating percussive sound, indicative of the sound bouncing between
two parallel walls). Again, the best home theaters are fairly “dead”
acoustically
to create the environment, rather than having the room’s native acoustic
signature color everything.
The solution for slap echoes is usually a combination of absorption and diffusion. Specifically, place absorptive mate
rial behind the front speakers (heavy drapes, fiberglass, dense foam) and elements that will facilitate diffusion in the
rear of the room (bookcases, irregularly shaped furniture, etc.). This will effectively suppress the slap echoes while at
the same time providing a diffusive surface in the rear for the surround speakers. This enhances the enveloping characteristic of the surrounds even further.
-
. This allows the program material and the playback system
Figure 25.
-
In those relatively rare cases in which you have the luxury of building the home theater room as new construction,
consider using nonparallel surfaces in the construction of the room. A difference of as little as 6 degrees will break
up the slap echoes very effectively
. For example, “flaring” the side walls out from the front by approximately
16
FINE-TUNING YOUR AUDIO SYSTEM
6 degrees and having the ceiling rise toward the rear of the room at a comparable rate will do wonders for the
room’s acoustics, if the wall design is solid and the angles are clearly intentional from the outset.
RATTLES
Rattles in the room are structural resonances (as opposed to standing waves, which are airborne resonances) that the
system may stimulate due to its broad frequency response and wide dynamic range. They are particularly prominent
for sounds in the lower frequencies, and can sound like distortion. Sources of rattles include: furniture, loose window
frames, walls, lighting fixtures, ventilation systems and even knickknacks on various shelves around the room. The
simplest way of identifying these rattles is by using a rattle test. This is an
20Hz to 500Hz, recorded at the reference level. Ten decibels of output level increase over the standard level may be
necessary in order to hear all the room rattles. Be careful with this test, as it is also a severe test of associated
amplifiers and speakers.
As the sweep makes its way up the frequency range, you will probably find a surprising number of rattles in your room.
All of these rattles will occur at one time or another during music or movies, but are usually perceived as background noise
or distortion in the system.
Once identified, eliminating the rattles is usually straightforward. As an example, small pieces of felt can be affixed
to the back of a painting (in the frame’s bottom corners) to prevent audible rattles against the wall. Likewise, strips
of felt can be wedged into a loose window rattling in its frame. Recessed lighting fixtures can be tightened up.
A piece of cloth can be placed under offending knickknacks.
extremely
slow low-frequency sweep from
Every home THX audio system should be subjected to the rattle test at least once – the difference in low-level
resolution and in freedom from pseudodistortion is sometimes large, while the effort involved is quite small.
BACKGROUND NOISE
The effect of background noise on system performance is dramatic, yet often overlooked. Most people might think of
it merely as a minor inconvenience, yet it has a profound effect on the way we perceive sound.
The presence of virtually constant background noise alters the way we perceive volume, since subjective loudness is
a relative measure. In a quiet room, even a 70dB SPL sound can seem fairly loud. In a noisy convention center, the
same volume would be barely audible. Since there is a practical upper limit to both the volume to which we should
subject ourselves and the volume a given system can reproduce, having a relatively noisy environment effectively
limits the perceived dynamic range of the program material. This, in turn, limits the dramatic effect that might have
been intended by the director or music artist.
Constant background noise also obscures, or masks, low-level signals that are frequently important in films. Many
scenes use subtle ambient noises to set the mood prior to an important event – without the full perception of the
whispered secret or the barely heard creaking of a door, the impact of the scene is diminished.
It has been demonstrated that even a relatively narrow-bandwidth noise can effectively reduce our hearing acuity
over a broad range of frequencies, far greater than the noise itself. When you add up all the various sources of noise
from electric motors, noisy heating/cooling systems and outdoor noises, plus noises that even audio and video components can introduce such as noisy transformers, motors in laser players or projector fan noise, our ability to discern
the low-level information in the soundtrack is greatly compromised – and the director’s intention along with it.
17
Copyright 2000 Lucasfilm Ltd.
Loudspeaker
Listener
FINE-TUNING YOUR AUDIO SYSTEM
BA
CKGROUND
Many sources of noise in a home environment can be addressed simply. Locating the home theater in the basement often
removes it from many household noises as well as isolating it from other family members. Taking care to completely seal
windows and doors can also make a significant difference in reducing outside noise.
Heating and cooling systems are more challenging. Sometimes, the answer may be as simple as using a “whistlediffusion grille rather than one that creates undue noise from turbulence. For new construction, using larger-diameter
air ducts for lower air velocity is very beneficial. You can go further by using ductwork that is lined with acoustically
absorptive material. Where possible, longer ducts that have several turns further reduce the sound of the airflow by
eliminating the straight path from the heating/cooling system to the room.
Some of the construction techniques used to minimize the transmission of external sounds into the listening environment include:
• Double or triple layers of drywall (gypsum board)
• Double wall construction, meaning two complete sets of studs (preferably stuffed with fiberglass insulation)
• Double wall construction with staggered studs (to minimize transmission of vibrations from one set of studs
to the next)
• Floating floor construction (again, preferably stuffed with fiberglass; this also can enhance the perceived bass,
since the subwoofers may cause structural vibrations through the false floor that can then be transmitted up
through furniture)
-NO
ISESOLUTIONS
free”
• Seal all windows, doors and vents
• Seal and caulk all apertures in the wall (electrical outlets, through-wall plumbing, etc.)
Finally, transient noises (traffic on the street, dripping faucets, etc.) distract your attention away from the program
material and remind you that you are in your home theater/living room, and not in the midst of the action of a movie.
STANDING WAVES
A “standing wave” is what causes a pipe of a particular length in a large
pipe organ to have its characteristic pitch. The pipe literally amplifies certain frequencies, based on its length and the wavelength of the frequency.
A typical rectangular room has three characteristic “lengths” and, thus,
three fundamental standing-wave frequencies. In addition, multiples of
these frequencies are also amplified. These frequencies are often referred
to as “room resonances” or “room modes,” i.e., the frequencies at which
the room tends to vibrate of its own accord. These resonances lead to
uneven frequency response, the greatest problems being in the 60Hz –
150Hz range for a typical living room (at lower frequencies in larger rooms).
See Figures 26 and 27.
Unfortunately, there is no way to eliminate the effects of standing waves
completely. The best that can be done is to minimize their effect through a
variety of strategies.
Figure 26.
18
Copyright 2000 Lucasfilm Ltd.
SUB
Low Relative PressureLow Relative Pressure
Copyright 2000 Lucasfilm Ltd.
• How to improve a
2nd-order standing
wave
•
The subwoofer
drives the + and –
areas equally,
resulting in reduction
of resonance
Listener
Resulting Modal Structure
+
+
–
Subwoofer
Copyright 2000 Lucasfilm Ltd.
• Improving a 2nd-order
standing wave
– Connect the 2
subwoofers together as
“in-phase”
– The 2 subwoofers drive
the + and – areas
equally, resulting in
reduction of resonance
– Experiment a lot
+
+
–
Subwoofer 1
Subwoofer 2
Listener
Resulting Modal Structure
Subwoofer
Output
From
Controller
Mono!
FINE-TUNING YOUR AUDIO SYSTEM
ST
ANDING
OOM RATIOS
R
-WAVESO
LUTIONS
:
In new construction, the best way to minimize
the audibility of standing waves is to plan for
an even distribution of them, so that their
effects do not “pile up” on top of each other. In
this regard, the ratios of room dimensions are
the critical factor. Rooms having equal dimensions are the worst, since the standing waves
in all directions reinforce one another. Room
dimensions that are even multiples of one
another should also be avoided where possible.
Figure 27.
STANDING-WAVE SOLUTIONS: SPEAKER PLACEMENT
Speaker placement also has an effect on standing waves and their audibility. In particular, placement of any speaker
(including subwoofers) where two walls and the floor meet will tend to stimulate all of the available standing waves,
causing the most irregular response. The displacement required to minimize a particular
standing wave depends on its frequency, with
lower frequencies requiring more movement
owing to their longer wavelengths. As a result,
minimizing colorations due to standing waves
often requires significant adjustment of subwoofer placement. Leave yourself some latitude
with regard to subwoofer placement when planning your system – the final adjustment will
probably have to be done on something of a
trial-and-error basis. See Figures 28 and 29 for
some suggestions.
Figure 28.
STANDING-WAVE SOLUTIONS:
A
In theory, it is possible to dampen standing
waves with absorptive material. The difficulty
is that the thickness of the absorptive material
would have to be approximately one-half the
wavelength of the lowest frequency requiring
damping. This means a five-foot thickness of
fiberglass would be required in order to damp
everything down to 100Hz – not very practical.
BSORPTION
Figure 29.
19
FINE-TUNING YOUR AUDIO SYSTEM
Standing-wave energy tends to be concentrated in the corners of rooms, which is why placing a subwoofer in the corner tends to increase its bass output. Because of this, it is possible to break standing waves up somewhat by “breaking up” the corner. This can be accomplished by placing a column of thick, absorptive materials in the corners (covered
by acoustically transparent cloth, of course). The column ought to be at least a foot on a side, and run from floor to
ceiling. A variation of this is to run an absorptive panel diagonally across the corner, leaving open air space behind it.
Both of these techniques are easily tried and sometimes quite effective.
STANDING-WAVE SOLUTIONS: ROOM EQUALIZATION
If a room exhibits severe standing-wave problems, the best solution is to know your own limitations; hire a trained
acoustician. These professionals have the necessary background to analyze the various room modes and recommend
appropriate action. This will sometimes take the form of a custom-designed bass trap, which may be easily constructed. But it takes specific skills to determine its optimal design.
In other cases, careful analysis and parametric equalization may be appropriate. Optimize everything else that you
can, then use EQ, if necessary
with care and a light touch to obtain optimal results. Professionals use it all the time, with excellent results –
because they know its limitations and how to apply it.
, to “touch up” the room. This is its best use. Parametric equalization must be applied
Never equalize a room by ear. Room analysis is not as straightforward as it may seem. The analysis should
using equipment with at least one-third-octave resolution, using both spatial and temporal averaging.
In any event, rooms requiring this level of treatment are relatively rare, and the skills necessary to handle them properly are highly specialized. Do not hesitate to use the professional services of an acoustician when you need them.
be done
20
TROUBLESHOOTING
SY
MPTOM
PR
OBABLECAUSE
SO
LUTION
No sound coming • Amplifier not turned on •Turn on amplifier.
from speaker
• Amplifier gain is low •Make sure that there is
mplifier gain for that channel.
a
• Correct source not •Select proper source.
elected or turned on
s
• Defective patch cords to amplifier •Check/replace patch cords.
• Speaker wires not • Check speaker wire
connected to amplifier connection to amplifier.
• Balance control set improperly •Make sure Balance control is set
at center, or 12 o’clock, position.
• Speaker wires damaged •Make sure none of the speaker wires
or shorted are frayed, cut or punctured. Make sure
no wires are touching other wires or
terminals and creating a short circuit.
• Speaker not configured •In Dolby
®
Digital or DTS®mode, make
correctly sure that the receiver/processor is
configured so that the speaker in
question is enabled.
®
• Center speaker is configured •In Dolby Pro Logic
mode, make sure the
incorrectly center speaker is not in phantom mode.
• Problem not diagnosed •To diagnose the likely source of the
problem, it is often helpful to switch the
nonfunctioning speaker with one that
is functioning correctly. Turn off all
electronics before exchanging the
speakers. Turn everything back on, and
determine whether the problem is in
the same place, or has moved with the
speaker. If the problem is in the same
place, the source is most likely with your
receiver or amplifier. If the problem has
followed the speaker, then contact your
authorized JBL Synthesis custom installer
or dealer for further assistance. If that
is not possible, visit our Web site at
www.jblsynthesis.com for further information.
21
TROUBLESHOOTING
SYMPTOM PROBABLE CAUSE SOLUTION
Bass is very weak • Subwoofers are wired out •Make sure that positive terminals on the
of phase subwoofers go to the positive terminals
on the amplifiers (red) and do the same
for the negatives.
• Subwoofers have not •Experiment with different locations.
been placed optimally
Poor or smeared imaging • Poor room acoustics •Use absorptive materials to minimize
early reflections.
•Aim speakers at listening area.
• Poor program source • Check another program source.
• Improper polarity •Check polarity of wire connections.
Indistinct dialogue • Slap echoes •Add absorption or diffusion materials.
• Miscalibration of center •Check output levels of surround processor.
channel output level
Uneven surround coverage • Poor speaker placement, • Place surrounds according to THX
strong reflections specifications.
•Add absorption and/or diffusion materials.
• Excessive absorption near •Remove absorptive material to provide
surrounds surround reflections.
22
SPECIFICATIONS
MO
# S4VC S4HC S4Ai
DEL
escription
D
-Way 8" (200mm) vertical 3-Way dual 6-1/2" (165mm) Configurable-array flush-
3
flush-mount speaker horizontal flush-mount speaker mount surround speaker
ower Handling
P
50W 250W 200W Single-driven or
2
175W-per-array dual-driven
ominal Impedance
N
Ohms 6 Ohms 6 Ohms
6
Sensitivity (2.83V@1M) 91dB 91dB 91dB
Frequency Response 65Hz – 20kHz 65Hz – 20kHz 80Hz – 20kHz
Crossover Frequencies 600Hz, 3.5kHz 600Hz, 3.5kHz Dipole Mode: 400Hz;
Bipole Mode: 800Hz, 3.6kHz,
Direct Mode: 2.5kHz
Bass Transducer(s) 8" (200mm) Titanium-alloy Dual 6-1/2" (165mm) titanium- 8" (200mm) Dual-voice-coil
inverted dome with rubber alloy inverted dome with inverted dome with rubber
surround and cast basket, rubber surround and cast surround and cast basket
shielded basket, shielded
Midrange Transducer(s) 4" (100mm) Titanium inverted 4" (100mm) Titanium inverted Dual 4" (100mm) neodymium
dome with rubber surround dome with rubber surround full-range with rubber
and cast-aluminum and cast-aluminum surrounds and castbasket, shielded basket, shielded aluminum baskets
High-Frequency 1" (25mm) Pure-titanium 1" (25mm) Pure-titanium Triple 1" (25mm) pure-titanium
Transducer(s) dome with rubber surround, dome with rubber surround, dome with rubber surrounds,
shielded, with EOS
™
waveguide shielded, with EOS™waveguide shielded, with EOS
™
waveguide
Dimensions (H x W x D) 23-7/8" x 14" x 5-1/2" 14" x 23-7/8" x 5-1/2" 23-7/8" x 14" x 3-3/4"
(606mm x 356mm x 140mm) (356mm x 606mm x 140mm) (606mm x 356mm x 95mm)
Weight 26 lb (12kg) 32 lb (15kg) 23 lb (10kg)
Connectors Two-conductor push-type, Two-conductor push-type, Speaker: four-conductor push-
10 –16-gauge
10 –16-gauge
type, 10 –16-gauge; Control:
two-conductor screw terminal,
16 – 24-gauge
All features and specifications are subject to change without notice.
JBL, Harman International, JBL Synthesis and Synthesis are trademarks of Harman International Industries, Incorporated, registered in the United States
and/or other countries.
Elliptical Oblate Spheroidal (EOS) is a trademark of Harman International Industries, Incorporated.
Dolby is a registered trademark of Dolby Laboratories.
DTS is a registered trademark of DTS, Inc.
Styrofoam is a trademark of the Dow Chemical Company.
THX is a registerd trademark, and THX Ultra2 is a trademark, of THX Ltd. All rights reserved.
23
JBL Consumer Products
250 Crossways Park Drive
Woodbury, NY 11797
8500 Balboa Boulevard
Northridge, CA 91329
818.830.8757
www.jblsynthesis.com
Part No. 361103-001 11/05
Declaration of Conformity
We, Harman Consumer Group International
2, route de Tours
72500 Château du Loir
France
declare in own responsibility that the products described
in this owner’s manual are in compliance with technical
standards:
EN 61000-6-3:2001
EN 61000-6-1:2001
Luc Guillaume
Harman Consumer Group International
Château du Loir, France 11/05
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