12SUPER-X PRO CX3400 User Manual

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:

c= f (see chapter 3.5.2)

λ

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

343 m/s

= 171, 5 1/s = 171, 5 Hz

2 x 1 m

 

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).

3.6 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.

3.6.1 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.

3.7 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.

3.8 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.