Film-Tech
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Copyright 1998 by SMART Devices Inc.
5945 Peachtree Corners East
Norcross, GA 30071-1337
Table of Contents
TCX924 THREE WAY ELECTRONIC TIME DELAYED CROSSOVER
SECTION 1 INTRODUCTION .......................... 2
SECTION 2 INSTALLATION .................................... 2
SECTION 3 CALIBRATION .................................... 3
SECTION 4 SCHEMATICS .................................... 4
SMART products are designed to deliver unsurpassed quality in workmanship and performance. The
following information gives detailed instructions on the installation and operation of the SMART TCX924
crossover. We strongly encourage new owners of the TCX924 to thoroughly read this entire manual before placing their new SMART product into service. This will ensure that the TCX924 will be operated
properly to give the superior performance that it was designed to deliver.
For service or installation assistance, please call our
Technical Support Department between the hours of
8 a.m-5 p.m. E.S.T., Mon.-Fri.
1-800-45-SMART
LIMITED WARRANTY: SMART products and accessories are warranted against malfunction or
failure due to defects in workmanship or materials for a period of one year from the date of shipment. If a problem occurs during the warranty period, the unit will be repaired, or replaced at our
option, without charge for materials or labor. If air freight is requested by the dealer, the difference
between air and surface charges will be billed to the dealer. This limited warranty does not cover
products that have been abused, altered, modified, or operated in other than specified conditions.
Prior factory approval is required on all returns. Returned equipment or defective parts must be
shipped freight prepaid to us by the dealer or customer.
Our limited warranty does not cover damages resulting from accident, misuse or abuse, lack of responsible care, or failures not attributable to manufacturing defects, except as provided herein.
SMART Devices, Inc. makes no warranties, express or implied, including warranties of merchantability or fitness for a particular purpose.
RETURN POLICY: Factory authorization MUST be obtained before returning any product. A 15%
restocking charge will be issued on unused equipment (in original box) that is returned for credit.
Credit is issued to the dealers account. The credit may be used against future purchases and no
cash transactions are offered. All returns must be shipped freight prepaid by the dealer. Equipment returned without a factory RA (Return Authorization) will be refused.
TCX924 Three Way Electronic Time Delayed Crossover
from the midrange band arrives
at the same time at the listener’s
ear, the tones combine acoustically in phase and produce a
clear , transparent sound. J umpers
have been provided in the
circuitry of the TCX924 to align
most of the common stage speakers by varying the
SECTION 1
INTRODUCTION
delay. Figure 2 shows mechanical misalignment of the
a 3 way speaker arrangement.
The TCX924 T hree Way T ime-Corrected Electronic
Crossover is a multi-channel electronic crossover
designed specifically for cinema use. This product
contains features not found in other products of its type.
The TCX924 contains three identical crossover channels
for the stage speakers, along with its own AC power
supply that can operate from 110-120 V A C or 220240VAC 50/60 Hz line voltages. Each channel has its
own adjustment for time correction of the high frequency/horn driver and the low frequency woofer(s) to
align acoustically relative to the midrange speaker.
Although it is desirable to use identical stage speakers
for stereo in an auditorium, non-similar types can be
accommodated and the time correction for each
channel can be individually adjusted.
Three Way Electronic Crossover.
divides an audio signal into three frequency bands: 300
Hz and lower , 300 to 2500 Hz, and 2500 Hz and higher.
Alternate "Crossover points" are available upon request
from the SMART factory. The crossover slopes are 24 dB
per octave (utilizing 4 pole active filters) to provide a
smooth blend of sounds from the low , mid and high
frequency components. The steep 24 dB slope also
provides maximum protection for the high frequency
driver during loud sound passages.
Time Correction.
note at (or near) the crossover frequency, both the HF
and LF speakers are working at that frequency. Because the HF driver cannot be physically aligned with
the LF woofer, the HF sound arrives at the listener’s ears
slightly behind the sound created by the LF woofer. This
creates a muddy, confused sound in the overlap frequencies where misaligned pressure fronts of the
corresponding frequencies cancel each other out. For
example, if a 2.5 kHz tone is electrically delayed in
the high frequency band so that the corresponding tone
When a 2-way speaker reproduces a
T he standard TCX924
CD horn compensation.
8“
6“
Figure 2. Acoustically
unaligned 3 way speaker
system.
over a bigger and appear not to be as loud as their
lower counterparts. T he TCX924 has CD horn compensation built in. The smooth high frequency boost is up
12 dB at 10kHz from the Crossover frequency of 2.5
kHz. This high frequency boost is valuable for movie
theatres because of screen attenuation losses at high
frequencies. Equalization is easier and smoother with
the CD horn correction added.
new constant directivity horns
offered by most major loudspeaker manufacturers hold
their published dispersion
patterns very nicely. Early
design horns used in cinemas
until the early 1960’s were very
directional at higher frequencies. A horn may have a 90degree by 40-degree pattern at
the crossover frequency, but as
the frequency tone went up, the
pattern could narrow as low as
10 degrees. You could only
hear all tones directly on-axis of
the horn.
New CD horns can hold their
pattern throughout the high
audio frequency range. Because the pattern is so wide, the
higher frequencies are spread
SECTION 2
The
INSTALLA TION
Mount the TCX924 in the equipment rack where it is in
proximity to the power amplifiers. An ideal location is
where the TCX924 output leads can easily reach the
Figure 1. The TCX924 Front panel with Security Cover removed.
2
INSTALLATION AND OPERATION
inputs of the power amplifiers with a minimum run of
cable.
Wire the outputs to the respective inputs of each power
amplifier making sure the LF outputs arrive at the LF
amplifier inputs. Mixing the LF, MF, and HF signals
can cause damage to the drivers.
Wire each stereo processor channel to its respective
input at the TCX924. All connections are made to the
Phoenix brand connector on the back of the chassis.
Keep all wiring from this connector away from the AC
lines and speaker output lines from the power amplifiers.
The TCX924 has unbalanced outputs. Wire the inputs of
the power amplifiers for this mode.
Allow ventilation space for the electronic crossover. It
is not good practice to wedge the crossover between
two power amplifiers without the vent panels separating
the units.
SECTION 3
CALIBRA TION
Remove the front security cover with the allen wrench
provided with the product.
Make sure the power switch is in the ON position. The
OFF position is also the bypass mode that allows the
audio signals from each channel to pass to the amplifiers. A special protection circuit is included in the
bypass circuits to protect the MF and HF drivers from
damage from low frequency energy. The LF woofers
will receive full range audio when the TCX924 is in the
bypass mode. This is not a problem because the
woofers will not reproduce HF audio very well.
With pink noise playing adjust the MF and HF level
controls for the smoothest crossover while observing the
response on the real time analyzer set up to monitor the
auditorium. The levels should be set to match at the
crossover frequencies of 300 Hz and 2.5 kHz. Do not
be concerned with the level of the other parts of the
audio spectrum at this time.
With a ruler, measure the distance from the point where
the voice coil of the woofer is to the voice coil/diaphragm of the MF driver. This is the acoustic difference
between the two components. Also measure the distance between the coil/diaphragms of the MF driver
and the HF driver. The TCX924 is configured so that the
HF and LF may be positioned behind the MF driver.
Refer to the following CROSSOVER DELAY chart to
determine the best setting of the jumper “shunts” for
each channel and each delay of the TCX924 (See figure
3 for diagram of front panel shunt positions). You may
wish to reposition the mechanical alignment of the
horn/HF driver before securing it to the enclosure for an
even multiple of 2.5". For example, if the horn/HF
driver is 11 inches behind the MF woofer voice coil,
slide the HF assembly back 1.5 inch so that it is an
even 12.5 inches difference. Secure the horn/HF driver
assembly to the main enclosure.
CROSSOVER DELAY
2.5 kHz High Frequency Delay
Position Acoustic Distance
10"
2 2.5"
35"
4 7.5"
5 10"
6 12.5"
300 Hz Low Frequency Delay
Position Acoustic Distance
10"
26"
3 12"
4 18"
5 24"
6 30"
Some manufacturers of cinema loudspeaker stage
systems recommend reversing the HF driver connections when using a 24 dB 4-pole filter crossover. Observe your real time analyzer response to determine the
best wiring scheme.
Figure 3. Front Panel LOW and HI delay positions and MID and
HI level control. NOTE: A jumper must be installed in one of the
six delay positions or no sound will reach the output.
All channels should be set to the same time correction
setting when using identical model speakers.
Leave the security cover off the TCX924 until you have
completed your room equalization. This will allow you
to make minor adjustments to the HF level setting as
you continue to tune for the flattest response.
3
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