Owner’s Manual
Wisdom Audio S55i
In-Wall Subwoofer
Table of Contents
Introduction .................................................................................................... 4
About this manual ..................................................................................................4
Description .....................................................................................................5
Regenerative
Transmission Line™ ...............................................................................................5
Unpacking the S55i .........................................................................................6
Room Acoustics & Placement ..........................................................................7
Start With the Room ..............................................................................................7
Rigid Walls ......................................................................................................7
Speaker Placement .................................................................................................8
Left & Right Speakers ......................................................................................8
Center Channel ...............................................................................................8
Remote Setup via Modem ......................................................................................8
Surround Speakers ..........................................................................................9
Subwoofer Placement ............................................................................................9
Room Treatment ..................................................................................................10
Professional Acoustic Design ...............................................................................10
References ........................................................................................................... 11
Installing the S55i in a Wall...........................................................................12
Installing the S55i in the Ceiling ....................................................................14
Tips and Ideas ......................................................................................................22
Black out the HVAC and snorkel ...................................................................23
Limited access situations ...............................................................................24
Installing under the oor ...............................................................................24
North American Warranty ............................................................................26
Standard Warranty ............................................................................................... 26
Harsh Conditions Use .......................................................................................... 26
Obtaining Service .........................................................................................27
Specications ................................................................................................28
S55i Dimensions ............................................................................................29
Notes ............................................................................................................. 30
Introduction
Congratulations on purchasing your Wisdom Audio in-wall subwoofer. The
S55i’s Regenerative Transmission Line™ technology delivers tremendous bass
performance in terms of depth, dynamics, and distortion resulting in articulate bass that integrates seamlessly with high-resolution main speakers such as
Wisdom Audio’s Insight Series.
About this manual This manual focuses on the S55i subwoofer itself. In order to fully understand
the system, we recommend you also review the manual for the SC-1 System
Controller, or SW-1 subwoofer amplier, or MiniDSP-1 subwoofer processor,
without one of which this subwoofer will not perform correctly.
While we expect your local Wisdom Audio dealer to take care of the setup and
calibration of the system, we still recommend that you at least briey review this
and the other manuals to understand the system’s full capabilities.
4
Description
Your Sage S55i subwoofer uses a modern implementation of an old idea for high
quality, low distortion bass reproduction. While the roots of the Regenerative
Transmission Line™ go back to the 1950’s, it is the combination of modern computer modeling and the vastly more powerful motors of contemporary driver
design that make the RTL™ so special.
Regenerative
Transmission Line™
There is a class of bass enclosures that has been around since the 1950’s, which
can be described generically as “low frequency tapped waveguides” or “tapped
pipes.” It was an idea that was a bit ahead of its time then, since fully optimizing its use required both powerful drivers and computer modeling. But if you
are into such things, check out US Patent 2,765,864 (led in 1955), and an AES
paper published in 1959, “Analysis of a Low Frequency Loudspeaker System.”
We have published both on our website for your convenience, at
http://www.wisdomaudio.com/support_documents.php
We have utilized sophisticated modeling software in order to fully optimize our
enclosures, and have developed drivers that are specically optimized for this
application. We call our unique implementation of this relatively old idea a
“Regenerative Transmission Line™” subwoofer, or “RTL™” sub for short.
All dynamic drivers develop energy on both sides of the diaphragm, with the
rear energy being 180° out of phase with the front energy. If you allow the
driver to operate in free space (no enclosure), the front and rear energies largely
cancel each other out — especially at low frequencies.
In our Regenerative Transmission Line™ subwoofer, the energy from the back
side of the driver is sent along a long, folded path in such a way that its lowest
frequencies arrive back at the front side of the driver in phase, effectively summing to an increase of 6 dB in output. Thus, the energy from both sides of the
woofer cone is used in a productive way, resulting in a substantial reduction in
distortion and an effective surface area double compared to what you would
otherwise expect. As an example, the effective radiating surface area in the S55i
is roughly equivalent to a 8” diameter round woofer, yet the enclosure ts in a
3.5” deep stud bay.
The results are quite striking. Low frequencies are dynamic and responsive, and
integrate quite seamlessly with the fast and detailed Sage Series planar magnetic
hybrids.
5
Unpacking the S55i
Please exercise caution when unpacking your S55i.
Caution! As shipped, a protective steel construction shield is held in place
magnetically to seal the S55i from various construction debris, paint,
etc. The grille is in a separate cardboard sleeve in the shipping
box. Please locate and save the grille for later use, leaving the
construction shield in place until you are ready to play the S55i.
The S55i is fully assembled on delivery. The front surface has a smooth, resin-
coated paper nish that can be taped and spackled, and then painted to match
the adjacent drywall (gypsum board).
The end of the speaker that contains the grille assembly also includes the “pigtail” for connecting the speaker to the system, as well as some “feet” to support
the S55i slightly above the sole plate, to allow room for the wiring and the base-
board of the nished wall. (Rooms with unusually tall baseboards may require
the S55i to be mounted somewhat higher still.)
The grille itself is held in place magnetically. Removing the grille exposes the
black service panel, which only needs to be removed in the unlikely case that
one or more drivers needed to be replaced after installation in the wall.
The Regenerative Transmission Line™ opening occupies less than half the space
covered by the grille. You can see the serial number of your S55i by removing
the grille and looking int the RTL opening; it will be on the back, inside surface
of the S55i enclosure.
6
Room Acoustics & Placement
Wisdom Audio believes in equalization. Assume for a moment that you had a
“perfect” loudspeaker: as soon as you place it in your room, its perfection is
gone. In fact, even good rooms can introduce deviations of 20 dB to the response of the system. This is particularly true in the bottom two octaves, where
a subwoofer operates.
It seems strange to us to worry about tenths-of-a-decibel differences between
one component and another when there are 10-20 dB problems right there in
the room with you.
At the same time, room equalization is not a panacea. It does not solve all prob-
lems. In fact, and somewhat paradoxically, EQ works best when it has the least
to do. It is best used as the “nishing touch” on an otherwise good system. Un-
fortunately, most people do not understand that the most important component
in their system is their listening room.
This manual does not have the space for a full description of everything that
goes into creating excellent room acoustics; doing so would require a textbook
of several hundred pages. Instead, we will give you some ideas, and some references to pursue should you want to learn more.
Start With the Room There are many myths oating around pertaining to what a “good room” should
be like. One of the most common is that it should have non-parallel walls. Without going into the details, we recommend staying with rectangular rooms whose
dimensions do not share common divisors.
Thus a room with dimensions of 8’ by 16’ by 20’ would be quite poor (since the
dimensions are all divisible by a length of 4’, and 16 is also a multiple of 8). By
contrast, a room whose dimensions are 9’ by 16’ by 29’ would be much better,
since none of the dimensions are mathematically related to one another.
There are innite variations on this idea. If you have the exibility to choose (or
modify) your room dimensions to avoid such problems, do so. Either way, ca-
pable room optimization will be a big help making the most of what you have.
Rigid Walls Another myth that should be dispelled is the notion that the walls (and ceiling
and oor) of the room should be extremely rigid in order to reproduce good
bass. Rigid, inexible walls reect energy extremely well; thus you will keep
more of the bass energy in the room. This much is true. However, those rigid
walls will only increase the amplitude of the standing waves that your room
naturally supports. In simple terms, you will have more bass, but it will also be
more irregular, with larger peaks and valleys in the response.
Walls that ex a bit (but do not rattle) are much better. Coincidentally, traditional American residential construction standards (sheet rock on wooden studs) are
not a bad place to start. You can do better still with professional help, but studs
and sheet rock are better than poured concrete. (If your listening room is in the
basement, a false wall can easily be built in front of the concrete. You probably
need something like this for insulation and aesthetics anyway.)
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The ultimate in dedicated listening room construction involves the design and
construction of oating walls, ceiling and oor. This approach yields the added
benet (when done properly) of providing outstanding acoustic isolation from
adjacent spaces as well as superb bass reproduction. This approach goes well
beyond the scope of an owner’s manual; if you are interested, you should contact a professional acoustician who has specialized in this sort of domestic room
design.
Speaker Placement Within the room itself, placement of the speakers and the listener will have a
profound effect on the performance of the system, particularly below 300 Hz
or so. There is no “perfect” position that will solve all problems, but nding the
best compromise will make it easier to solve the remaining problems with good
room optimization such as in the Wisdom Audio SC-1.
Your Wisdom Audio dealer can help you with optimizing your speaker placement, which is never quite as simple as it seems it should be. The characteristics
you should listen for are several:
Left & Right Speakers Goal #1: Stable, 3-dimensional stereo imaging
This usually requires reasonable symmetry within the room. Mono (correlated)
pink noise can help here, though it does not replace listening to music. With
pink noise playing in both speakers, you should hear a tightly-dened little
“ball” of pink noise oating in space exactly halfway between the speakers.
Goal #2: Smooth, consistent bass
Oft-cited rules of thumb for smoother bass reproduction include both “placing
the speakers at different distances from the side walls vs. the wall behind them,”
and “placing them at ‘odd fractions’ of the room’s dimensions” (e.g., fractions
in which the denominator is an odd number, like 1⁄3, 2⁄5, 2⁄7, etc.). But nothing
replaces your experience in your room, combined with your dealer’s experience in a variety of rooms. Playing pink noise through the woofer sections of
your Wisdom Audio speakers (with the microphone at the listening position, and
prior to doing any equalization) and watching the results on a Real Time Analyzer (RTA) will let you see the results of your labors.
Center Channel Center channel height
Once you have a solid stereo image up front (when listening only to the Left and
the Right speakers), you need a center channel speaker for multichannel reproduction. It should be centered between the Left and Right, and centered on the
screen’s location, preferably at the same height as the Left and Right speakers.
This presents an obvious problem: you cannot place a speaker in front of your
television screen.
Ideally, a center channel speaker would be behind an acoustically transparent
front projection screen and would match the Left and Right speakers. Doing so
would ensure the best possible consistency of tonal balance, image height, and
dynamic capabilities for the critical center channel. This is how it is done in all
good commercial theaters.
Another possibility that works well in certain instances is to use the “phantom
center channel” feature of your surround processor. This works best when the
room is reasonably symmetrical and the listeners are more-or-less directly in
front of the TV. It uses the natural stereo imaging ability of the speakers to create
8
a center image where it belongs. f course, if people are sitting well off to one
LR
side in the room, the image tends to fall into the nearest speaker.
Failing an acoustically transparent screen or a phantom center channel approach, the important thing is to match the tonal and dynamic capabilities of the
Left and Right speakers while minimizing the change in image height as a sound
is panned across the front stage. Wisdom Audio has designed horizontally-oriented planar magnetic hybrid speakers that will match your Sage loudspeakers
superbly; place them as close to the edge of the screen as is practical.
Surround Speakers Surround channel geometry
In a 5.x channel system, the surround should be placed either directly to the
sides of or slightly behind the listening area (90°–110° from the center channel,
as seen from above). In a 7.x system, the surround speakers should be closer to
90° from the center speaker, and the surround back speakers should be at approximately 135°–150° from the center speaker. This conforms to industry standards, and ensures that you hear what was intended from a spatial placement
point of view. (Too often, the surround speakers are all behind the listeners, cre-
ating a big “hole” in the soundeld between the front and the back.)
Sub 1
C
0°
22°
30°
One possible exception to these guidelines: if you have a THX®-certied processor and are using the THX Advanced Speaker Array™ circuitry, you should
follow the guidelines in your owner’s manual for the processor. Using this
technology, it can actually be more effective to have the rear speakers in a 7.x
system directly behind you and immediately adjacent to each other.
Subwoofer Placement Subwoofers offer somewhat greater exibility in placement, since the frequen-
cies they reproduce are not readily localizable by the human ear. This is due to
the fact that the wavelengths they reproduce are more than ten feet (3 meters)
long, but our ears are located only about 6-7 inches (17 cm) apart. Thus these
extremely long waves do not contribute meaningfully to the imaging that the
main speakers create.
Sub 2
90°
110°
R
b
R
s
L
s
135°
L
b
a 7.2 channel system layout
150°
However, this fact does not mean that the placement of the subwoofers has no
effect on the sound quality in the room. Far from it. The subwoofers are the
9
most likely to suffer from the response irregularities introduced by the room
itself, operating as they do below approximately 80 Hz in most systems.
Recent research into the behavior of rooms as a function of speaker placement
has concluded that — if you have the freedom to do so — there are signicant
advantages to placing several smaller subwoofers around the room, rather than
relying on a single large woofer. Moreover, the optimum placement is usually
at 25% and 75% of the room width, or deep in the corners of the room. If you
have the luxury of doing so, this simple placement strategy can reduce the size
of the room’s response irregularities from 20 decibels down to perhaps as little
as 6-8 decibels—a tremendous improvement.
Reducing the room’s inherent problems to this degree provides a huge advantage. It allows products like our own SC-1 System Controller to put their considerable abilities to work on perfecting your system’s response, rather than on
trying to perform major corrective surgery.
Room Treatment Rectangular rooms have six reecting surfaces (four walls, ceiling and oor)
that reect sound to the listener, after various delays introduced by the indirect
routes the sound take on their way. These rst reections are particularly dam-
aging to sound quality. Looking at the simplest case of stereo reproduction, you
have a minimum of twelve rst reection points in your room that deserve some
attention.
Unfortunately, it is often difcult to do much about the ceiling and oor reections, even though they are arguably the most destructive. (The minimization of
these reections is one of the strongest arguments for the tall, line source loudspeakers that Wisdom Audio builds.) This leaves you with eight “rst reections”
that you should consider minimizing somehow. These points are easily found by
having an assistant slide a small mirror along the four walls of the room, while
you sit at the listening position. Any place on the wall where you can see a re-
ection of any speaker is a rst reection point. Concentrate on the rst reections for the Left and Right speakers rst.
If you can, arrange to apply either absorption or diffusion at these eight points
(don’t forget the wall behind you). Absorption can be as simple as heavy, insulated drapes; diffusion can be provided by a well-stocked bookcase with books
of varied sizes. Alternatively, you can buy purpose-designed room treatments
(some sources listed under References, below).
The important things to remember are these: a good room should have a balance of absorption and diffusion; and if you are going to treat only a few areas
of the room, the rst reection points are the most important ones to treat.
Professional Acoustic Design Does this all sound too complicated? For good reason: it is complicated.
The difference between the average listening room and one that is professionally
designed and implemented is huge. A great listening room will disappear to an
astonishing degree, letting the experiences captured in your recordings speak to
you directly. A well-designed room is also quieter and more comfortable. It can
easily become a favorite retreat for peace and rejuvenation.
10
If you decide to investigate the possibility of improving your room with the help
of a professional, it is important to nd someone who focuses on residential
spaces. Most acousticians are trained to deal with large spaces — airports, au-
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