Setting the crossover frequencies | Behringer CX3400 manual

3.3.1 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, as described in paragraph 3.3)!

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.

3.4 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: 45 though 960 Hz and 450 Hz through 9.6 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 3.5 “Runtime Correction”).

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

3.5 Runtime Correction

3.5.1 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.

3. APPLICATION

CX3400 specifications

The Behringer CX3400 is a versatile and highly regarded crossover that has become a staple in professional audio setups. This unit is designed to ensure optimal sound quality by efficiently distributing frequencies to appropriate loudspeakers, making it an essential component in sound reinforcement systems, PA setups, and live performances.

One of the standout features of the CX3400 is its three-way or four-way crossover topology, which allows the user to manage sound frequencies with precision. It’s equipped with independent adjustable output controls for each of its outputs, enabling users to tailor the audio experience to fit the specific requirements of any venue or application. The ability to adjust the crossover frequency range from 50 Hz to 6 kHz makes it suitable for various configurations, whether for subwoofers or high-frequency drivers.

Another significant aspect of the CX3400 is its built-in low-pass and high-pass filters. This functionality ensures that low frequencies are directed to subwoofers while high frequencies are sent to tweeters, thus maximizing the efficiency and clarity of each speaker in the system. The filters operate at a steep 24 dB per octave slope, which aids in maintaining the integrity of sound reproduction and minimizes overlap that can lead to distortion.

In terms of technology, the CX3400 features independent audio signal processing capabilities, allowing for more refined control over the audio output. The unit includes a high-quality 24-bit A/D converter and a 24-bit D/A converter, which significantly contribute to the overall audio fidelity and dynamic range. The CX3400 also features balanced XLR inputs and outputs, ensuring that the audio signal is transmitted with minimal interference and noise.

The build quality of the Behringer CX3400 is also noteworthy. It’s designed to withstand the rigors of live performance environments, with a durable chassis that ensures reliability. The user interface is straightforward, with clear, intuitive controls that make it easy to set the desired parameters quickly.

In summary, the Behringer CX3400 crossover is a powerful tool for audio professionals, offering precise frequency distribution, advanced filtering technologies, and solid construction. Its combination of versatility, performance, and user-friendly design makes it an excellent choice for those looking to enhance their sound systems, whether in live settings or recorded applications. The CX3400 continues to be a trusted device for audio engineers, ensuring that every musical element reaches its full potential.