Behringer SUPER-X PRO CX2310 Manual - Page 8

8 SUPER-X PRO CX2310 User Manual 3. Applications You will need some tools to help set up the SUPER-X PRO to its optimal configuration. To set up the crossover frequency you need to know which frequency range a loudspeaker stack covers, over which range the sound energy is linearly transmitted, and where reductions or increases in the frequency response occur. In addition, every room has different size and quality characteristics. These strongly influence the sound response, since resonances and reflections in the different frequency ranges can also lead to reductions or increases in the sound picture. You will need suitable equipment in order to be able to recognize and compensate for these features. 3.1 Tools You will need a high-grade microphone for making measurements. This should have a frequency response that should be as linear as possible (e.g. the BEHRINGER measurement microphone ECM8000) and at least linear over the range from 90 Hz and 15 kHz. Place the microphone about 5 m. in front of the speaker system and between the diaphragms of the two frequency bands you wish to measure. When using a measuring microphone to set the levels for the individual frequency bands and the crossover frequencies, you should only operate one loudspeaker stack. For optimal settings you will usually need to reposition the microphone between two successive measurements. When used in combination with a measuring microphone and a generator producing pink noise via an input into the P.A. mixing console, an analyzer will show the sound energy distribution over the individual frequency bands (usually in 1/3 of an octave). The BEHRINGER ULTRA-CURVE PRO DSP8024 equalizer/analyzer is the ideal tool for this application. When listening 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, without however 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 desired results with your own ears. ◊ BEHRINGER accepts no responsibility for any damage or destruction of loudspeakers arising from improper or incorrect use of the SUPER-X PRO and in particular from actions which are in contravention with the clearly stated procedures given in this manual. 3.2 Setting the input and output levels Both inputs offer a gain or loss of up to 12 dB. Normally, the output level on the mixing console and the input sensitivity of the amplifiers are identical, i.e. 0 dB at the mixing console corresponds with 0 dB at the amplifiers. This means that there is full control over the amplifiers. In this case the SUPER-X PRO should have no effect on the system level and all input and output level settings should be set at 0 dB. Where e.g. a home recording or disco console is being used with an operating level of -10 dBV but the amplifiers need +4 dBu for complete control, then an additional gain of 12 dB must be provided between them. In this case the INPUT control of the SUPER-X PRO should be set to the maximum. 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. To check the crossover frequencies and levels, mute all outputs except for one, and play back pink noise over the system at an appropriate volume level. When you now 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. 3.3 Correcting problems 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. To achieve this, you need an equalizer such as the ULTRA-CURVE PRO DSP8024 or the ULTRA-GRAPH GEQ3102. Look for drop-outs around the crossover frequencies! If the frequency response is very irregular, then it can make sense to grade adjust it using the frequency crossover, before using an equalizer (EQ). The errors in the crossover frequency must then be as far as possible corrected using the EQ. If the loudspeaker diaphragms in a multi-way system are not exactly aligned along a vertical axis, the varying distances between the sound source and the listener result in phase errors and cancellations (also known as the "comb filter effect"). Particularly in the higher frequencies it is important, due to the shorter wavelengths, to position the diaphragms above each other and not next to each other. The various types of construction used in individual systems (horns, bass reflex cabinets etc.) still give rise to run time differences, even where the front sides of all systems are aligned vertically above each other. In this case a run time correction must be made by electronic means. This can be done by using a delay function. Run time differences can be compensated by delaying the frequency bands over a range of milliseconds. This helps avoid loss of sound quality, particularly in the high tone ranges. ◊ Runtime correction is not the same as phase correction. If a speaker system has the same run times then it also has the same phases (unless the polarity of a cable has been reversed). However the opposite is not necessarily true. 3.4 Setting the crossover frequencies The frequency range from which the crossover frequencies can be selected, can be one of two ranges-from 44 to 930 Hz and from 440 Hz to 9.3 kHz. To set the crossover frequencies, please first read the manufacturers' specifications for the individual loudspeaker components. To use the capacity of your system at its best you should set up the crossover frequencies in accordance with the frequency diagrams on the individual loudspeaker boxes. Further, the crossovers should not lie on peaks or drop-outs. Look for a range with the flattest possible curve. If folded bass horns are being used, then the length of the horn path must also be taken into account, since the run time displacements arising from differing long paths can also have a negative effect on the frequency development (see chapter 3.3). ◊ Never operate loudspeakers or horn drivers below the limiting frequency specified by the manufacturer! 3.5 SUBWOOFER output To achieve a very loud and deep bass playback the SUPER-X PRO has an additional mono subwoofer output for 2-way and 3-way operation. In this sense the CX2310 is a stereo 2-way + mono 1-way or mono 4-way frequency crossover. The subwoofer signal is mono, since people cannot sense the location of lower frequencies. Another reason is that combining all bass signals into a single signal produces an excellent effect. This is because two bass speaker boxes combined together produce 3 dB more sound pressure than if they were separated from each other by a small distance. The increased pressure is due to the speakers producing a single wave front. With four loudspeaker boxes the increase is 6 dB. The reason here is the spherical shape of the expanding low-frequency sound waves. Bass boxes which are separate from each other can mutually disrupt each other where their sound waves meet (what happens here can be easily imagined if you throw two stones into water-first separately and then stuck together).