Behringer SUPER-X PRO, CX3400 Manual

1. INPUT control. This control adjusts the input gain from +12 to -12 dB (see control 16).
2. LOW CUT button. This button activates the 25 Hz highpass filter protecting the woofers against low-frequency signals.
3. LOW/HIGH XOVER FREQ. control. This control governs the crossover frequency between the Low and High bands. When the XOVER FREQUENCY button on the rear of the unit is pressed, the frequency range is multiplied by the factor 10.

5. DELAY control. This control delays the Low signal by as much as 2 ms, which is useful to align the speaker systems in phase.
6. LOW OUTPUT control. Controls the output level of the Low band from +6 to -6 dB.
7. LOW PHASE INVERT button. This button reverses the polarity of the Low output.
8. LOW MUTE button. Mutes the Low band.

12. HIGH OUTPUT control. Controls the output level of the High band from +6 to -6 dB.
13. HIGH PHASE INVERT button. This button reverses the polarity of the High output.
14. HIGH MUTE button. Mutes the High band.
15. CD HORN button. This button provides a special form of frequency correction in the High band for constant-directivity horns.

30. THRESHOLD control. This control determines the limiter threshold.
31. LIMITER button. This button activates all limiters. Whenever the signal surpasses the limiter threshold, the LIM-LEDs above the Gain control light up, signaling that the CX3400 cuts back the output level.

1. Use the enclosed power cord to connect the unit to the mains.
2. FUSE HOLDER / VOLTAGE SELECTOR. Please make sure that your local voltage matches the voltage indicated on the unit, before you attempt to connect and operate the CX3400. Blown fuses may only be replaced by fuses of the same type and rating. Some models allow for inserting the fuse holder in two different positions, in order to switch over from 230 V to 115 V operation, and vice versa. Please note that for 115 V operation outside Europe, you need to use a fuse of a higher rating (see chapter "INSTALLATION").
3. and 10 HIGH OUTPUT connector. Output for the High band signal.
   5 and 12 LOW (LF SUM) OUTPUT connector. Output for the Low band signal.
   6 and 13 XOVER FREQ. button. This button serves to switch over the control range of the front-panel LOW/HIGH OVER FREQ. control from 44 to 930 Hz or 440 Hz to 9.3 kHz.
   
   Always switch off the entire system before you press this button, as it produces heavy interference noise that could damage your speakers and/or other equipment.

30. THRESHOLD control. This control determines the limiter threshold.
31. LIMITER button. This button activates all limiters. Whenever the signal surpasses the limiter threshold, the LIM-LEDs above the Gain control light up, signaling that the CX3400 cuts back the output level.

Fig. 2.8: Proper selection of the two MODE switches for mono 4-way operation

Subsequently, the LEDs above the active controls on the front panel light up, signaling which controls are active in the operating mode you just selected. The functions of these controls can be seen from the first strip label.

Fig. 2.9: Active control elements on the front panel of the SUPER-X PRO for mono 4-way operation

1. INPUT control. This control adjusts the input gain from +12 to -12 dB.
2. LOW CUT button. This button activates the 25 Hz highpass filter protecting the woofers against low-frequency signals.
3. LOW/LOW-MID XOVER FREQ. control. This control governs the crossover frequency between the Low and Low-Mid bands. When the XOVER FREQUENCY button on the rear of the unit is pressed, the frequency range is multiplied by the factor 10.
4. LOW-MID/HIGH-MID XOVER FREQ. control. This control governs the crossover frequency between the Low-Mid and High-Mid bands.
5. DELAY control. This control delays the Low signal by as much as 2 ms, which is useful to align the speaker systems in phase.

Fig. 2.10: Active control elements on the rear panel of the SUPER-X PRO for mono 4-way operation

APPLICATION

Tools

The following tools are indispensable for a perfect system alignment. You should by all means try to obtain the speaker specifications from the manufacturer, in order to operate the systems in their proper frequency and level ranges. Use the manufacturer's documentation to adjust the operating mode and crossover frequencies.

BEHRINGER does not assume any responsibility for speaker damage caused by improper handling of the SUPER-X PRO.

Measuring microphone
For making measurements you need a high-grade microphone with a frequency response that should be as linear as possible over the entire frequency range (e.g. BEHRINGER measuring microphone ECM8000), or at least between 90 Hz and 15 kHz. Place the microphone about 5 m in front of the speaker system to be measured, in a height where it is on axis with the drivers of the two frequency bands you wish to measure. When setting the levels for the individual frequency bands, delay times and crossover frequencies by means of a measuring microphone, you should operate only one speaker stack each. Usually, the measuring microphone needs to be repositioned between two specific measurements.

Generator/Analyzer
In combination with a measuring microphone and a generator producing pink noise that is fed into a channel of your P.A. console, an analyzer gives you a graph that shows how the acoustic energy is distributed among the various frequency bands (usually 1/3 of an octave). The equalizer/analyzer BEHRINGER ULTRA-CURVE PRO DSP8024 is the ideal tool for this application.

Your ears
When you listen to the overall sound of your system, you should walk around in the audience area and try to detect resonance frequencies or cancellations. The sound should be optimized for the position where most of the audience will be gathered, however, without neglecting other areas. This often means that the system must be operated in mono. Whenever you use technical aids such as analyzers, measuring microphones, etc., you should check the results with your ears.

Setting the input levels

Both inputs provide a gain boost/cut of up to 12 dB. Normally, the output level of the mixing console and the input sensitivity of the power amp are the same, i.e. 0 dB in the console correspond to 0 dB in the amplifier. In this case, the power amp is fully driven and the SUPER-X PRO should have no influence on the system level, as all input/output controls are set to 0 dB. However, in a home recording or discotheque environment using operating levels of -10 dBV, the power amp would still need +4 dBu, which requires some additional gain of 12 dB. If so, the SUPER-X PRO's INPUT control must be set to maximum.

Setting the output levels

The output levels of the single bands can be raised/lowered by as much as 6 dB. To achieve a linear frequency response in the system, all output levels should be adjusted with the help of an analyzer. Then, mute all outputs except for one to check the crossover frequencies and levels, play back pink noise over the system at an appropriate volume level. Now, when you switch on the adjacent band, the level measured around the crossover frequency should go up by 3 dB. Repeat this process for all crossover frequencies.

Finding "drop-outs" in the frequency response
Check the entire frequency response of the system. Rooms have quite an impact on the frequency response of speaker systems, due to resonance and various reflections. So, you cannot expect to achieve a linear frequency response right from the start. Use an equalizer such as our ULTRA-CURVE PRO DSP8024 or ULTRA-GRAPH GEQ3102. Look for drop-outs around the crossover frequencies (there should be none, if the output levels have been set properly)!
However, if the frequency response shows some irregularities, it can prove useful to correct it by means of the crossover network, before using an equalizer (EQ). Subsequently, the crossover frequencies must be corrected with an EQ as far as this is possible.

Setting the crossover frequencies

The use of extremely high-grade potentiometers made it unnecessary to install fixed-frequency plug-in modules. Thus, you have a wide range of setting options available that even more expensive crossover networks hardly give you.
The CX3400 works in two specific frequency ranges: 44 though 930 Hz and 440 Hz through 9.3 kHz. The Linkwitz-Riley filters employed in the SUPER-X PRO feature a slope of 24 dB/octave. High-grade components such as 1%-tolerance metal-film resistors ensure a perfect phase and amplitude response at all crossover frequencies.
Please consult the manufacturer's specifications of the various speaker components to set the crossover frequencies. When polar plots of specific speakers or horns are available, use them too. Don't set the crossover frequencies around peaks or drop-outs in the frequency response, but try to find a range that is largely linear. When folded woofer horns are used, you also need to take the horn length into account (see chapter "Runtime Correction").

Never operate speaker/horn drivers below the frequency range specified by the manufacturer!

Runtime Correction

Background
The ideal transducer would be a point source of sound, i.e. a speaker of infinitely small dimension, which could still reproduce the entire frequency spectrum. Unfortunately, such a sound source is impossible in reality, so that we have to accept some compromises.
If the drivers in a multi-way system (i.e. the diaphragm set in motion by the voice coil, but not e.g. the opening of a horn) are not exactly aligned on a vertical axis, the varying distances between sound source and listener result in phase errors and cancellations (also called "comb filter effect"). In particular, in the high-frequency range it is imperative, due to the shorter wavelengths, that the drivers be positioned one above the other, not side by side. The old-fashioned horizontal rows of radiators follow this principle: while the speaker power is summed up in the horizontal plane, the signals cancel each other on a vertical axis. Thus, unwanted reflections from the ceiling can be reduced.
Consequently, a speaker stack whose systems radiate towards the same area should have all speakers arranged in a vertical line. And even if the front sides of all systems are perfectly aligned, runtime differences still occur due to the different speaker designs (horns, bass reflex cabinet, etc.).
The BEHRINGER SUPER-X PRO allows you to delay the Low bands by up to 2 milliseconds. In this way, you can virtually push back a specific speaker cabinet by as much as 68.6 cm (which is quite useful, for example, when you place a constant-directivity horn (CD) on top of a closed speaker cabinet).

Runtime correction is not the same as phase correction. Speaker systems that have the same run times are also in phase (unless, the polarity of one speaker is reversed). However, the opposite is not true.

Basics of electronic runtime correction
It is important to know how the dimensions of time and space are connected with each other, e.g. by using a tape measure and a pocket calculator.
Example: a delay of 2 ms corresponds to a distance of 68.6 cm; when you measure an offset of 30 cm you can calculate the necessary delay as follows: 2 ms x 30 / 68.6 = 0.87 ms.
If it is impossible to measure the offset with an accuracy of at least 1 cm, you can perform the runtime correction with the help of a measuring microphone and tunable sine generator, using the SUPER-X PRO's feature of variably adjustable crossover frequencies. More on this below.
The speed of sound is 343 m/s or 34.3 cm/ms approximately (hence, 2 ms of delay correspond to a virtual speaker offset of 68.6 cm). Frequency is measured in oscillations per second (1/s); the unit of measurement is Hertz (Hz).
For example, when you adjust a crossover frequency of 3 kHz between the horn and midrange systems, the wavelength l is calculated as follows: l = c / f (c = speed of sound; f = frequency). So, the wavelength at 3 kHz is:

With a virtual distance of 68.6 cm, the control range of the potentiometer will provide at least six positions that ensure phase coincidence. Perhaps none of these positions will correct the runtime differences completely, for example, if the offset between the drivers is greater than 68.6 cm. Is that important? It is, because only a system whose runtime differences have been corrected will be capable of:

1. reproducing pulse peaks correctly.
2. maintaining phase coincidence when the signal frequency moves away from the crossover frequency.

Runtime correction in a P.A. system using the SUPER-X PRO
Midrange/high midrange/tweeter range Before you perform the following steps to correct both runtime and phase, you should measure the offset between the drivers in cm and move the cabinets (or delay their bands), until you think they are aligned correctly. This will save you a lot of time later on. Now, do the fine adjustment as follows:

Using an analyzer

• Use pink noise as your sound source and connect the measuring microphone to the measuring input of the analyzer.
• Adjust the bands below/above the crossover frequency so that each one alone produces a 0 dB reading at the crossover frequency; mute the remaining bands. If both bands together produce a +3 dB reading, they can be considered in phase.
• Now, raise the crossover frequency by a factor of 1.5 and perform the same steps as above. Here, too, the analyzer should read +3 dB.
• Finally, check your setting by raising the crossover frequency by a factor of 1.4.
• Here, too, you can temporarily reverse the phase of one of the bands and check the sound for cancellations.

If no runtime correction is achieved

• Check whether the distance between the two drivers is or could be greater than 68.6 cm. If so, try to correct it by moving the speaker cabinets.
• If this still doesn't solve the problem, one of the bands could be reversed in polarity. Experiment with the front-panel PHASE INVERT button.

Subwoofer/woofer/midrange
It is often claimed that phase or runtime correction below 150 Hz is unnecessary, because the sound waves feature a spherical dispersion pattern at such low frequencies. We disagree with this view.
Modern systems often use bass reflex cabinets for their woofer or subwoofer systems. Consequently, when stacking the cabinets, the drivers are usually aligned along the vertical axis of the speaker front, or can at least be aligned using the available control range of the SUPER-X PRO. Here, runtime correction follows the same principle as in midrange/high-midrange/tweeter systems. Problems will be encountered only with unconventional setups (e.g. when the woofers are placed underneath the stage, while the midrange/tweeter systems are flown above it) or when long woofer horns are used. The latter are the subject of the following discussion.
First, measure the horn length. In the case of folded woofer horns this is anything but easy. Use a design drawing or open the cabinet (usually, a flap or cabinet side wall can be opened easily, for instance, to replace a defective speaker).
We use a horn length of 1 m as an example. It will make no sense to delay the signal, because the woofer signal arrives with a 3-ms delay at the "mouth" of the horn. So, you cannot achieve a correct runtime, unless you would delay the runtime of the remaining systems in the stack. The pulse response (the main reason for runtime correction), however, is mainly determined by the mid and tweeter ranges. What you can – and should – achieve though is phase coincidence at the crossover frequency. Which is exactly what the SUPER-X PRO gives you: free adjustability of the crossover frequency.
Calculate the frequency whose wavelength corresponds to twice the horn length. At this frequency the output signal will be reversed by 180° in phase when it comes out from the horn.
The frequency can be calculated as follows:

Use the known values (speed of sound in m/s; horn length in m) to calculate the frequency:

Now, using a crossover frequency of 171.5 Hz and reversing the polarity of the woofer output will result in an approximate phase correction, which can be fine-adjusted by applying some delay or shifting the crossover frequency a bit.

General remarks on runtime correction
Only one speaker stack each should be measured and corrected. Begin with the highest crossover frequency and work your way downward.

Once you have completed the runtime correction procedure, please make a note of the relative positions of the speaker, the adjusted crossover frequencies, delay times, etc. as well as of all level settings (limiters included). The next time you set up your system, you can start from these settings and with a bit of luck you will need to make just a few fine adjustments, before you can turn to the EQs.

Never drive different speakers from the same output! The distances which the sound waves travel before they reach the listener will very likely be different and unavoidably lead to phase shifts. Additionally, the built-in drivers may have different efficiencies, impedance characteristics or even reversed polarities.
When the speaker offset is greater than 68.6 cm you can only move the speaker cabinets. Runtime correction is not the same as the signal delay applied to offset groups of speakers. Here, the entire signal must be delayed by a much greater amount (a suitable delay circuit is included, for example, in the BEHRINGER ULTRA-CURVE DSP8024).

The limiters of the SUPER-X PRO

Limiting the signal in the crossover network is the last resort to protect the system against overloading. Otherwise, improper handling by the user could lead to serious damage in several drivers.
Each frequency requires its own limiter/compressor control times. The higher the frequency, the shorter the control times. In the SUPER-X PRO, the control times for the single bands have been determined after long listening tests, in order to achieve inaudible gain adaptation instead of hard limiting.
The limiter threshold can be set from -6 dB to OFF and acts on all six limiters at the same time. Still, each limiter band works independently, with the LIM-LEDs lighting up as soon as the associated limiter is activated.

Please note that the limiters in the SUPER-X PRO are no "hard ratio" limiters, i.e. signal peaks can surpass the adjusted threshold by as much as 6 dB. Please make sure that your system provides enough headroom.

Limiter setup
On condition that you are using power amps and speakers that are compatible in terms of power rating, you should drive your amps under full load (i.e. 0 dB). Use pink noise from your analyzer as a sound source, turn the limiter THRESHOLD control to maximum and press the LIMITER button. Then, gradually cut back the threshold until just a few LIM-LEDs start flashing. Now, the entire system gain is limited to 0 dB.

LOW SUM function

To produce a very loud and deep bass response, the lowest band should be summed in a mono signal, while the remaining bands remain in stereo (the human ear cannot locate the source of low frequencies). By combining all woofer cabinets in one single cluster (the closer, the better) you can optimize their efficiency. Two woofer cabinets positioned next to each other produce an SPL that is 3 dB higher than that of two cabinets placed at a certain distance. Four cabinet give you as much as 6 dB, because low-frequency sound waves feature a spherical dispersion pattern. When the cabinets are positioned separately, the sound waves they radiate interfere with each other, while cabinets placed next to each other create one common wave front (compare two stones that are thrown into the water, either separately or together).
In stereo mode, the SUPER-X PRO can be switched to mono bass mode using the LOW SUM button.
When the LOW SUM button is pressed, the low-frequency signal portions in the left and right channels are summed up. The output signal is routed to the Low output of channel 1, from where it can be used to drive, for instance, a subwoofer cabinet.

CD HORN function

When a driver radiates into open space via a horn, its efficiency increases. Over the past few years, so-called constant-directivity horns have gained widespread popularity, as they offer the advantage of producing a very regular dispersion pattern over their frequency range; however, the higher the frequency, the lower their efficiency. To make up for this drawback, the SUPER-X PRO includes a switchable pre-EQ for CD horns that ensures a flat frequency response even before equalization is applied. This pre-EQ raises the signal gain by 3 dB at 3.5 kHz, which then increases by 6 dB/oct. up to 22.5 kHz.

INSTALLATION

Your SUPER-X PRO CX3400 was carefully packed in the factory and the packaging was designed to protect the unit from rough handling. Nevertheless, we recommend that you carefully examine the packaging and its contents for any signs of physical damage, which may have occurred in transit.

If the unit is damaged, please do not return it to us, but notify your dealer and the shipping company immediately, otherwise claims for damage or replacement may not be granted. Shipping claims must be made by the consignee.

Rack mounting

The BEHRINGER SUPER-X PRO fits into one standard 19" rack unit of space. Please allow at least an additional 4" depth for the connectors on the back panel.
Be sure that there is enough air space around the unit for cooling and please do not place the CX3400 on high-temperature devices such as power amps, etc. to avoid overheating.

Mains connection

Before you connect your SUPER-X PRO to the mains, please make sure that your local voltage matches the voltage required by the unit! The fuse holder on the female mains connector has 3 triangular markers, with two of these triangles opposing each other. Your CX3400 is set to the operating voltage printed next to these markers, and can be set to another voltage by turning the fuse holder by 180°.

this instruction does not apply to export models exclusively designed, e.g. for 115 V operation!
The mains connection of the CX3400 is made by using the enclosed mains cable and a standard IEC receptacle. It meets all of the international safety certification requirements.

Please make sure that all units have a proper ground connection. For your own safety, never remove or disable the ground conductor of the unit or of the AC power cable.

Audio connections

As a standard, the BEHRINGER SUPER-X PRO CX3400 is equipped with electronically servo-balanced inputs and outputs. The circuit design features automatic hum and noise reduction for balanced signals and thus allows for trouble-free operation, even at highest operating levels. Externally induced mains hum, etc. will be effectively suppressed. The automatic servo-function recognizes the presence of unbalanced connectors and adjusts the nominal level internally to avoid level differences between the input and output signals (6-dB correction).

Please ensure that only qualified persons install and operate the CX3400. During installation and operation the user must have sufficient electrical contact to earth. Electrostatic charges might affect the operation of the SUPER-X PRO.

Fig. 4.1: Compensation of interference with balanced connections

Fig. 4.2: Different plug types

BEHRINGER is constantly striving to maintain the highest professional standards. As a result of these efforts, modifications may be made from time to time to existing products without prior notice. Specifications and appearance may differ from those listed or illustrated.

To reduce the risk of electrical shock, do not remove the cover (or back). No user serviceable parts inside; refer servicing to qualified personnel.

To reduce the risk of fire or electrical shock, do not expose this appliance to rain or moisture.

This symbol, wherever it appears, alerts you to the presence of uninsulated dangerous voltage inside the enclosure - voltage that may be sufficient to constitute a risk of shock.
This symbol, wherever it appears, alerts you to important operating and maintenance instructions in the accompanying literature. Read the manual.