AUTOCOM PRO MDX1400
4.1.1 The AUTOCOM PRO In Digital Recording And Sampling
In an analog recording, too low recording levels lead to an increased noise level, whereas too high levels will cause a compressed and “squashed” sound. In extreme cases, it will cause distortion due to tape saturation. In contrast to analog, side effects in the digital field always become extremely audible: with decreasing level, a tape previously recorded with insufficient level loses resolution: the recording sounds “hard” and loses “atmosphere”. With excessive level, the recording sounds harsh and heavily distorted. In order to avoid these effects, the AUTOCOM PRO as a limiter should be placed before for example a sampler. As a result of this process, a digital recording or a sampling event can be optimally set in level without any problem.
4.1.2 The AUTOCOM PRO In Mastering
The mastering process is one of the most critical processing steps in recording. In this production step, it is the goal to achieve a “maximum level” copy of the recording, without any noise or distortion. In many applications it is further required to produce a high average volume. In the field of commercial media for example, this is apparent especially with records and cassettes which are processed with high average volumes. Quite often in these cases, dynamics suffer drastically, because the program material has been compressed and limited too heavily. Using the Compressor section of the AUTOCOM PRO as a limiter allows you to drastically increase the overall volume, without audibly affecting the dynamics.
Proceed as follows:
Limit the dynamics of the program material by 6 dB using the AUTOCOM PRO as a Peak Limiter (Ratio 1:oo). By softly clipping just the transients, the real audio signal will not be limited, resulting in a higher headroom. The overall gain can now be increased by 6 dB, which leads to a higher volume. More than 6 dB should not be limited, otherwise side effects could become audible.
This effect is particularly noticeable with DAT recorders, whose level indicators achieve a response time of less than 1 ms. Set the DAT recorder at unity and now reduce the LEVEL control of the peak limiter until a gain reduction of 6 dB is indicated. The “cut” signal peaks cause a reduced recording level of about 6 dB, which is visible on the level indicators of the DAT recorder. Now increase the recording level of the recorder back to unity. The result is a clearly louder recording without any loss of sound.
4.2 The AUTOCOM PRO As A Protective Device
Sound system distortion is usually a result of amplifiers and loudspeakers being driven beyond their limitations by signals clipping. The signal limitations that occur lead to unpleasant distortion that is dangerous to the speakers.
A speaker diaphragm is required to accelerate, slow down, smoothly change direction and accelerate again in normal operation. Distorted operation (clipping) leads to instant acceleration, instant stop, change of direction and instant acceleration again. Since speaker diaphragms are subject to the laws of physics, they will not take this kind of punishment for long: the diaphragm will either break up or its voice coil may overheat.
In addition to the damage caused by sustained overload, the speaker may also be damaged by an occasional high level overload, e.g. the sound of a microphone falling onto a hard floor. Even if this type of transient does not destroy a speaker outright, it may damage the speaker surround in such a way, as to cause mechanical abrasion and future failure. It is recommended that you use the Behringer AUTOCOM PRO in order to protect the speaker. “Brick Wall” peak limiters are not normally necessary for PA systems, as amplifiers and loudspeakers are tolerant of short signal peaks.
Nevertheless, conventional limiters have to be generally driven far beyond the headroom limit of an amplifier, in order to limit the level and length of the transients responsible for overloading the system. The disadvantage of this principle is that the unit’s full range cannot be completely used. If an increase in the average level of up to 3 dB is attained with the AUTOCOM PRO as a Limiter, this means that you effectively double the power amplification. The AUTOCOM PRO can act in this way to convert a PA system of 5,000 Watts into a distortion free 10,000 Watts system. The following instructions will help you to integrate the unit into your system.
4.2.1 Protection Of A System With A Passive Crossover
If your sound system incorporates a passive crossover network (included in the loudspeaker case), insert the BEHRINGER AUTOCOM PRO between your mixing console output and the power amplifier input. It is used as the last link in the chain preceding the power amp. Thus, you can effectively avoid the “technical knockout” of
18 | 4. SPECIAL APPLICATIONS |
