CX Series USER MANUAL ▼ CX4 ▼ CX4T ▼ CX6 ▼ CX6T ▼ CX12 ▼ CX12T Rev.
Table of Contents PART 1—CX SERIES USER MANUAL I. Warning Notices ....................................................................................................................................... 2 Speaker Damage ............................................................................................................................................ 3 Speaker Output Shock Hazard .......................................................................................................................
EXPLANATION OF GRAPHICAL SYMBOLS The lightning flash with arrowhead symbol, within an equilateral triangle, is intended to alert the user to the presence of uninsulated “dangerous voltage” within the product’s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to humans.
I. Warning Notices SPEAKER DAMAGE The CX Series amplifiers are among the most powerful professional amplifiers available and are capable of producing much more power than many loudspeakers can handle. It is the user’s responsibility to use suitable speakers with the amplifier and to use them in a sensible way that will not cause damage. QSC will not be responsible for blown speakers. Consult the speaker manufacturer for power-handling recommendations.
II. Overall Description The CX Series from QSC comprises six high-efficiency professional power amplifier models, each with two independent channels. The table below lists the range’s audio power ratings.
12 1 2 4 Front features of CX4 or CX4T amplifier 13 Rear features of CX4 amplifier 9 7 8 10 7 13 9 10 11 10 11 Rear features of CX4T amplifier 7 8 7 12 1 2 3 4 5 Front features of CX6, CX6T, CX12 or CX12T amplifier 13 9 6 10 1 — Power Switch 2 — Power Indicators (Ch1, Ch2) 3 — Signal Indicators (Ch1, Ch2) 4 — Clip Indicators (Ch1, Ch2) 5 — Protect Indicators (Ch1, Ch2) 6 — Accessory Slot Cover 7 — Gain Control 8 — Detachable Input Header Rear features of CX6 or CX12 amplifier
III. Inputs CX amplifiers feature balanced inputs, connected via a Euro-style 7-terminal detachable header. Attach input signal wires as shown. If you are connecting an Loosen screw, insert wire here, then tighten screw. unbalanced signal to an input, use the non-inverting (+) input and the ground input and the ground terminal. The wire jumper will prevent a reduction in gain caused by a floating input.
If your application calls for connecting an 8-ohm speaker and a distributed line to the same amplifier channel, the CX4T, CX6T and CX12T can do that. However, since most of the audio power is drawn by the direct-connected speaker, you must derate the distributed line; the distributed line should have a total power load of no more than one-fourth the amplifier’s normal distributed line power rating. Make sure the direct-connected speaker can handle the 8-ohm power rating of the amplifier.
V. Controls & Displays LED Display for CX4 and CX4T: CX4 AND CX4T The channel attenuator controls, labeled in dB of attenuation , are located on the rear panel. They have 11 detents, adjustable from 0 dB (full gain) to × (full attenuation). The LED displays for each channel function as shown at right. CX6, CX6T, CX12, AND CX12T The channel attenuator controls, labeled in dB of attenuation , are located on the rear panel. They have 11 detents, adjustable from 0 dB (full gain) to × (full attenuation).
CX6, CX6T, CX12 and CX12T When the amplifier is first turned on, the red “PROTECT” LED on each channel will light for about two or three seconds, during which the output relays will stay open to mute the speakers. After the turn-on muting interval, the “PROTECT” LEDs turn off, the green “POWER” LEDs light, and the output relays close to enable the speaker outputs. Even during the muting interval, the yellow “SIGNAL” and red “CLIP” LEDs operate normally if there is a signal present.
• If the fan is not running at full speed, or the channel does not reset to normal after a cool-down period, the muting is probably because of a DC fault or other amplifier failure, especially if the “SIGNAL” or “CLIP” indicators are lit even with the attenuator turned all the way down. PROBLEM: Overheating • The thermal management system on a CX Series amplifier features a two-speed fan that modulates the cooling air flow over the heatsinks in response to the cooling needs.
The standard input panel installed on the CX Series amplifier has balanced Euro-style detachable header inputs, gain controls, and the Parallel-Stereo-Bridge switch. The panel’s circuit board has solder footprints for passive roll-off circuit components, input isolation transformers, and other special customizations. The MX-1 Input Expander panel may be installed in the upper panel position. It features XLR inputs and 1/4" RTS inputs. Installation instructions are included with the expansion kit.
BRIDGED-MONO MODE CAUTION: MODE BRIDGÉ MONO: ATTENTION VORSICHT BEI MONOBRÜCKENBETRIEB: PRECAUCIÓN PARA EL MODO MONO PUENTE ALL MODELS—Output voltages as high as 160 volts rms are available between the CX amplifier’s bridged terminals (200 volts at isolated outputs). TOUT LES MODÈLES— Des tensions de sorties aussi élevée que 160 volts rms sont disponible aux bornes du amplificateur CX en mode bridgé mono (200 volts aux sorties isolés).
MAXIMUM LONG-TERM OUTPUT POWER In a properly designed sound system, you can obtain the desired sound level without using the full output power of the amplifier; if the “CLIP” indicators flash once in a while, that is perfectly normal. If the amplifier is operated at extremely high power levels, it may overheat or may even damage the speakers. The amount of stress on the amplifier depends largely on the load and how hard the amplifier drives it.
HEAT EMISSIONS Essentially, a power amplifier draws electrical energy from the AC mains, converts it to DC, and then converts it again into an analog of the input signal to send out to the loudspeakers. Any AC power that enters the amplifier through the power cord and does not exit through the speaker outputs turns into heat, which the amplifier must rid itself of by exhausting it to the outside. In indoor use this may present a sizeable challenge to a building’s air conditioning system.
PROTECTION CIRCUITS The design goal in high-efficiency amplifiers such as the CX Series is to increase the amplifier’s ability to deliver peak power without increasing its size, weight, and cost. However, the higher power flow through the output components makes effective, responsive protection circuitry absolutely vital. To this end, the design of the CX series takes a comprehensive approach to protection. As in all QSC amplifiers, the inputs are resistively buffered for overload and RF protection.
VII. Specifications CX4 POWER OUTPUT Direct output, watts per channel, both channels driven 8Ω, 20 Hz–20 kHz, 0.1% THD 8Ω, 45 Hz–20 kHz, 0.1% THD** 8Ω, 1 kHz, 1% THD 4Ω, 20 Hz–20 kHz, 0.1% THD 4Ω, 45 Hz–20 kHz, 0.1% THD** 4Ω, 1 kHz, 1% THD 2Ω, 1 kHz, 1% THD* 150 170 225 270 350 Isolated outputs, watts per channel, both channels driven 70V or 100V, 45 Hz–16 kHz, 0.25% THD** 25V, 45 Hz–16 kHz, 0.25% THD** Direct Outputs, bridged mono 8Ω 20 Hz–20 kHz, 0.1% THD 8Ω, 45 Hz–20 kHz, 0.
VII. Specifications (cont.) CX4 VOLTAGE GAIN @ direct outputs: CX4T CX6 CX6T CX12 CX12T 35× (31 dB) 35× (31 dB) 40× (32 dB) 40× (32 dB) 56.5× (35 dB) 56.5× (35 dB) INPUT SENSITIVITY, VRMS for rated power, 8 ohms 0.98 0.98 1.03 1.03 1.043 1.043 INPUT IMPEDANCE 10K unbalanced, 20K balanced CONTROLS Front: AC Switch Rear: Parallel/Stereo/Bridge Switch (except CX4, CX4T) Ch.1 and Ch.
VII. Specifications (cont.) POWER CONSUMPTION (see chart on page 13) Normal operation: 1/8 power @ 4Ω per channel Worst case continuous program: 1/3 power @ 2Ω per channel Maximum: full power @ 2Ω per channel Multiply current times 0.5 for 220-240 VAC operation Model CX4, CX4T Channel Load 8Ω + 8Ω 4Ω + 4Ω 2Ω + 2Ω 25V, 70V, 100V AC Current, Full Power 5.7 A 9.2 A 13.3 A 8.7 A AC Current, 1/3 Power 3.4 A 5.2 A 7.4 A 5.0 A AC Current, 1/8 Power 2.3 A 3.5 A 4.9 A 3.3 A AC Current, Idle 0.4 A 0.4 A 0.4 A 0.
Part 2—CX Series Application Guide W ith the helpful advice and input from contractors and consultants around the world, engineers at QSC designed the CX Series amplifiers to be a versatile and reliable foundation for high-quality installed sound systems. This applications guide will help you design your sound system properly and utilize your CX amplifier(s) effectively. VIII.
IX. Designing the Distributed Sound System There are several main steps in designing a distributed sound system: • Determining loudspeaker coverage and placement • Determining power levels for each loudspeaker • Choosing the right amplifier LOUDSPEAKER COVERAGE AND PLACEMENT The goal in placing the loudspeakers in a distributed system is to acoustically cover the required area effectively but economically.
reflective surfaces—wood floors and ceiling, concrete and plaster walls, etc., the type of room that tends to make speech unintelligible—might benefit from using many low-powered loudspeakers placed throughout the room and close to the listeners, instead of using a couple high-powered, centrally-located loudspeakers. With ceiling-mounted loudspeakers, one general rule of thumb is to make the center-to-center distance between them no greater than twice the floor-to-ceiling distance.
DETERMINING POWER LEVELS After you’ve determined where to place the loudspeakers, you need to calculate the power each one requires. If the installation is in an existing facility already in use, use an SPL meter, set for slow response, to measure the A weighted ambient noise at the listener’s ear position. Try to take this measurement at the noisiest time—in a factory, 20.0 when the machines are running; in a restaurant, when it’s full 18.0 of patrons, etc.
EXAMPLE A loudspeaker (sensitivity: 94 dB @ 1W, 1 meter) in a busy office covers an area with an ambient noise of 72 dBA, measured at a seated person’s ear position at the desks. The client wants superb intelligibility, so your goal is to provide an SPL of 97 dB (72 plus 25) to the intended listeners. The ceilingmounted speaker is about 6 feet, or 1.8 meters, above the listeners’ ears. The dB figure from the inverse square law conversion guide for that distance is 5.
USING COMPONENTS WITH DIFFERENT VOLTAGES Sometimes it may be practical to use a transformer or loudspeaker/transformer combination with a different voltage system from what it was originally intended. For example, a 70-volt transformer could be used in a 25volt system, although you would have to derate the power taps similarly. Never use a transformer with a higher voltage than what it is designed for, though; i.e., you couldn’t use that same transformer on a 100- or 140-volt line.
X. How Many Speakers? How many loudspeakers can you connect to the distributed line? The amplifier itself determines the amount of audio power available to the line, and from that figure you must compensate for insertion loss in the speaker transformers and for headroom when you determine how much power is available 1.56 watts For example, let’s suppose you have an amplifier rated at 500 watts into a 70-volt …+25% for headroom.† …approx.
XI. Other Design Considerations SPEAKER TRANSFORMER SATURATION Speaker transformers tend to be fairly small, and some vary widely in quality. They tend, therefore, to be prone to core saturation at low frequencies. Saturation occurs when the magnetic field induced in the transformer’s iron core by the audio signal waveform has built up as high as the core can handle. Even if the signal voltage increases, the magnetic flux cannot increase any further, so it “clips,” in a way.
speaker, it will affect the sound level from the distributed line’s speakers also, possibly altering them from your intended levels. An alternate method is to attach an 8-ohm speaker across the 25-volt outputs. This provides up to approximately 80 watts to the speaker and makes more power available to the 70V or 100V connections: up to 75 watts for the CX4T, up to 150 watts for the CX6T; up to 400 watts for the CX12T.
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AC CURRENT CONSUMPTION A major objective in the design of the CX Series amplifiers—even the higher-powered models—is to permit their operation from readily available, standard AC power sources. “Normal conditions” in power amplifier rating means operating with a random program source (pink noise), using pink noise as a source, at an average power level equal to one-eighth of maximum power.
XII. Address & Telephone Information Address: QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, CA 92626-1468 USA Telephone Numbers: Main Number (714) 754-6175 Sales Direct Line (714) 957-7100 Sales & Marketing (800) 854-4079 (toll-free in U.S.A. only) Technical Services (714) 957-7150 (800) 772-2834 (toll-free in U.S.A. only) Facsimile Numbers: Sales & Marketing FAX (714) 754-6174 Technical Services FAX (714) 754-6173 World Wide Web: http://www.qscaudio.
1675 MacArthur Boulevard Costa Mesa, California 92626 USA PH: (714) 754-6175 FAX: (714) 754-6174 32 “QSC” and the QSC logo are registered with the U.S.
