Manual-4
THX 44 CONNECTION
Refer to the Home THX Audio System Block Diagram in
the THX 44 Data Sheet for proper location of the THX 44.
When first connecting the THX 44 to other components,
leave the power supply for last
. This gives you a chance to
correct mistakes before damaging fragile speakers, ears and
nerves.
INPUTS
Inputs are actively unbalanced and fitted with parallel
RCA phono pin jacks and DB-25 connectors.
Use only one.
They do
not
sum. Attempts to use both results in severe
distortion.
OUTPUTS
The Outputs mimic the Inputs with one big exception: you
may use both if desired. Use cables meeting the Home THX
Interconnection Specifications available from Lucasfilm.
SIGNAL LEVELS
The THX 44 is designed for Home THX Audio reference
levels of 0dBr (150mV rms), and provides a minimum
headroom of 34.5 dB above reference, making it virtually
unclippable.
With all LEVEL controls located in their 0 dB detented
positions, the THX 44 operates with unity gain from Input to
Output. No additional gain settings are necessary. Use the
THX 44 only for specific equalization.
be chosen that have a similar sound, and the THX 44 can do
the “fine tuning”. Use a one-third octave realtime analyzer,
and “flatten” the system as described in your analyzer
manual. The THX 44 must be connected between the control-
ler (or preamp) and the power amplifiers.
DOLBY DIGITAL AUDIO SYSTEM ALIGNMENT
The THX 44 is perfectly suited for discrete 5.1 systems by
following the same principles of flattening the room response
of each channel. The surround channels may be accommo-
dated by using another THX 44, ideal when the processor has
outputs for stereo subwoofers or a sixth main channel.
Otherwise, the Rane THX 22 controls duplicate the THX 44’s
for the surround speakers, making it an ideal match for the
THX 44 in 5.1 systems.
SETTING CURVES USING THE THX 44
Our unique interpolating constant-Q circuitry makes
setting curves easy. For the graphic sections, what you see is
what you get – more so than on any other equalizer. Referring
to your room result curves, begin by positioning the sliders to
create the inverse curve shown by the instrumentation.
Remember, most applications require only a few dB of boost
or cut. If more is required, use architectural and mechanical
means: add, remove, or relocate acoustically sensitive items
(speakers, drapes, carpets, mirrors, etc.) as required.
USING THE BYPASS SWITCH
The THX 44 provides you with an overall BYPASS
switch & indicator as a useful tool for optimizing settings.
Use the BYPASS switch for making quick “A-B” compari-
sons, i.e., comparing “A”, equalized (BYPASS
out
, LED
off
),
versus “B”, unequalized (BYPASS
in
, LED
on
). To do this
freely, without danger of system damage, you must pay
attention to how much equalization is being used. Failure to
do so can produce alarming results.
Since the THX 44 always operates at unity gain in the
BYPASS mode, comparison when a lot of boosting, or cutting
has been done, can result in startling level differences
between the two. Therefore you want to keep the system level
down until you first use the BYPASS switch.
Be careful the
first time you use it.
BALANCED AMPLIFIERS
Two situations can cause hum or grounding problems:
A. When the THX 44 is installed at a distance greater than 10
feet from the controller or amplifiers (which is not recom-
mended for unbalanced wiring).
B. When an amplifier with a balanced input is connected to
the unbalanced Output of the THX 44.
For solutions, see RaneNote 110, “Sound System Inter-
connection”, downloadable from Rane's web site.
The best option is the Rane BB 44x, a 4-way balancing-
isolating-level matching device with RCA and XLR connec-
tions. Again, see our web site.
OPERATING INSTRUCTIONS
HOME THX AUDIO SYSTEM ALIGNMENT
Follow the alignment procedure specified by Lucasfilm
Ltd. as described in the “Home THX
®
Audio System Room
Equalization Manual” supplied in this manual. Use only the
recommended test equipment. It is not possible to align a
Home THX Audio system without the use of proper proce-
dures and a one-third octave realtime analyzer with averag-
ing, and the special THX “Wow” Laserdisc (only supplied
with some THX controllers or a licensed THX installer). It
cannot be done by ear.
The purpose of the THX 44 in a home cinema system is to
flatten the response between speakers and the room. There are
no special curves to follow; these are within the controller—
not the THX 44. The THX 44 should be aligned for a flat
average response from each Channel.
DOLBY PRO-LOGIC AUDIO SYSTEM ALIGNMENT
Though the THX 44 meets Lucasfilm’s THX
®
specifica-
tions, it is also suitable for Dolby Pro-Logic systems so that
Left, Center, and Right Channels to have matching responses.
Though the THX 44 can help non-THX speakers, ±6 dB may
not be enough boost/cut to compensate between different
speaker designs. Left/Right and Center speakers should first
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