Behringer MDX2200 Composer Pro

Multi-function Dynamics Processor

Published in SOS May 1999
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Reviews : Processor

The latest version of Behringer's Composer dynamics processor appears to provide all the facilities anyone could ask for, with a separate expander/gate, compressor and limiter for each of its two channels. Hugh Robjohns checks it out.

Dynamic control is one of the most important but often overlooked aspects of recording. Good as modern recording technology is, it still can not quite achieve the 140dB dynamic range of human hearing. The best mic preamplifiers might be capable of about 125dB dynamic range, and the best power amplifiers and loudspeakers maybe 110dB. Even then, no one at home or in their car is going to want (or be able to cope with) real-life dynamics, so it is inevitable that the dynamic range of recorded music has to be reduced and controlled.

Dynamic control can be performed in many ways. You can modify your performance to restrict the range between your loudest and quietest passages, or 'ride' the faders in anticipation of loud or quiet sections either at the time of the recording or during the subsequent mixdown or mastering. Alternatively, some form of automatic controller can be used to raise quiet sections or reduce louder ones -- enter the compressor and limiter.

Sometimes, it is also desirable to actually increase the dynamic range of a recorded signal. This might typically be when there is a relatively high level of unwanted background noise which is effectively masked during the music but becomes obtrusive in the breaks. By increasing the dynamic range downwards, low-level noises can be pushed down to inaudibility -- enter the expander and gate. The Behringer Composer Pro offers all these tools in a neat, easy-to-use, but powerful package.

Technical Overview

The Composer Pro MDX2200 is a modest 1U rackmounting unit measuring a minuscule 190mm front to back. The front panel is polished aluminium with white-on-black screen printing and the controls are laid out in a very clear and logical manner. With the exception of the large power button, all function switches are illuminated, and each channel sports its own input/output level bargraph meter as well as a gain-reduction meter and traffic-light threshold indicators for each of the separate dynamics sections.

BEHRINGER COMPOSER PRO £182
pros
Extensive dynamics functionality.
Soft-knee curve options on both compression and expansion.
Sounds commendably clean and quiet.
Comprehensive interfacing.
Flexible side-chain access.
Good value for money.
cons
Auto attack/release feature too fast.
Distracting internal light spill to buttons.
summary
A flexible general-purpose dynamics processor which performs well. The Composer Pro sounds clean and quiet and is very easy to use. There are a couple of minor niggles, but given the price, they pale into insignificance!

The rear panel is comprehensively equipped with both TRS quarter-inch jack sockets and XLRs for the inputs and outputs (all electronically balanced), as well as a pair of tip-sleeve unbalanced jack sockets for side-chain send/receive connections. Rear-panel push buttons independently select +4dBu or -10dBV operating levels for each channel, and power is provided through a standard IEC mains inlet.

Front-Panel Controls

The two channels are equipped with identical sets of controls consisting of eight knobs (all with 41 light detents), eight illuminated push buttons, three threshold indicators and two bargraph meters. The first two rotary controls adjust the threshold and ratio of the expander/gate stage. The threshold ranges between +15dB and Off (below about -70dB) relative to the selected operating level, and the ratio can be set anywhere between 1:1 and 1:8. There are no attack or release controls, although the release time can be switched from fast to slow (via an illuminated button between the two knobs), and there is also no depth (or range) facility.

The compressor/limiter stage is far more generously appointed, with threshold, ratio, attack, release and output controls. Threshold extends between -40 and +20dB (relative to the selected operating level), ratio from 1:1 to infinity:1, attack between 1 and 150 milliseconds, release from 0.05 to 5 seconds, and output level between -20 and +20dB. The separate peak limiter section consists of a single control scaled between 0dB and Off (in excess of +20dB relative to the selected operating level).

Between the Threshold and Ratio controls, an illuminated push button engages the IKA soft-knee mode if required (see the 'Special Features' box on page 62). Three other buttons (two to the left and the third below the IKA switch) are associated with the compressor side-chain. A high-pass filter can be introduced into the side-chain to help reduce the compressor's sensitivity to loud low frequency signals such as kick drums and bass guitars. No specifications are given for this filter, but I would estimate it to reduce signals quite dramatically below about 100Hz. The other (illuminated) buttons activate the external side-chain return path, and allow the returned signal to be auditioned on the main programme output. This facility is very useful when tuning an external side-chain equaliser, perhaps for de-essing duties, but is obviously dangerous from an operational point of view, so the illuminated button flashes when it is engaged.

Between the attack and release controls, another illuminated button provides an automatic, programme-dependent attack/release mode. Finally, to the right of the Output level control, a button bypasses the entire compression signal path, providing a direct relay connection between the input and output connectors. A second button switches the audio level meter bargraph between the input and output signals. It is not entirely obvious which condition is which in normal operation so, for the record, with the button depressed and illuminated, the metering displays the input signal.

Across the top of all of these operational controls are a number of LED meters and indicators. The expander/gate section is accompanied by a pair of 'traffic-light' LEDs to show when the signal is above (red) or below (green) the threshold. A similar facility is provided for the compressor but a third (yellow) LED is also provided to show, if the IKA mode is activated, when the signal is in the soft-knee area. The limiter section is provided with a single red LED to indicate when the limiter/clipper stage is active.

The gain-reduction meter consists of red LEDs which extend from right to left, with the top few representing 1, 2, 4, and 6dB reduction, thereafter continuing in 3dB steps to -30dB. The input/output meter extends from left to right in green LEDs scaled from -30 to +18dB (relative to the selected operating level).

Between the control sections for the two channels of the Composer Pro, a single illuminated button provides a stereo-linking facility. This sums the inputs from both channels to generate an accurate RMS control signal which is then applied equally to both side-chains. In stereo mode, only channel 1's operational controls are active for setting the thresholds, ratios, attack and release times of both channels. However, each channel retains independent control of the input/output meter selection, channel bypass, and all side-chain switching functions.

In Use

The Composer Pro is easy to connect up, since it offers both TRS jacks and XLRs. However, I experienced some problems with grounding when connecting to unbalanced signal paths -- a low-level mains-related buzzing which was extremely hard to remove. In a pukka balanced system everything worked fine, fortunately, with very quiet background noise consisting of low-level hiss and no hums or buzzes whatsoever.

The first thing I noticed when starting to set the unit up was the way the buttons became partially illuminated, and even flashed, due to light spilling from the bargraph meters and threshold indicators. It would seem that light is escaping from the rear of these metering LEDs and finding its way into the clear plastic buttons. I would have thought it perfectly possible to install a black plastic screen of some sort separating the metering displays from the buttons. Indeed, I would urge Behringer to do so as this light spill creates a poor impression and can be highly distracting.

Setting the machine up is very straightforward, as the three sections -- expander/gate, compressor and limiter -- all have clearly delineated functionality. The expander/gate is a little basic, without separate attack and release times, a hold delay or a range control. However, it can still be used effectively to reduce background noise if care is given to setting the threshold and ratio parameters. Modest expansion seemed to give far better results than heavy gating in most applications (special effects excepted!). In general I also found the fast release setting the most usable, although with very gentle ratios the slower release time proved less audible.

  Special Features  
  Behringer have included a number of 'special features' in the Composer Pro, most of which have been granted acronyms. For example, the compressor boasts an 'interactive' soft knee called IKA -- Interactive Knee Adaptation -- whereby the 10dB zone around the set threshold follows a soft-knee slope before reaching the set compression ratio. The expander/gate has a similar facility called IRC or Interactive Ratio Control, which provides a more gentle transition from the linear slope above the threshold, to the expanded slope below it.

Finally, in the limiter section there is IGC, or Interactive Gain Control. Simply put, this is a feature which reduces the gain of the limiter section if it finds it is applying peak clipping for longer than 20mS at a stretch (ie. if there is excessive peak limiting being applied, it lowers the gain for a second or so along the lines of more conventional program limiters).

 

The compressor functioned much as expected and was extremely controllable. The soft-knee function (see box above) gave a much more gentle sound to the compressor, although there are obviously applications where a hard switch from linear to compressed sounds might be preferred. However, with small ratios and the IKA system active the Composer Pro provided very subtle dynamic control indeed.

I was rather disappointed with the automatic time constant setting. This disables both the attack and release controls, altering time constants according to the programme material. In general, I found that whilst the attack time seemed to be well controlled, the release time was almost always too fast, resulting in obvious noise pumping when there was any noticeable background noise. Most compressor 'auto' settings provide a two-stage release, with a fast recovery from short peak transients of high gain reduction and a much slower recovery from the last 4 or 6dB of gain reduction (so as to minimise any tendency to noise pumping). The Composer Pro did not appear to work in this way, or if it did, the difference between fast and slow modes was not terribly obvious. Consequently, I found I could obtain better results by manually setting the release time by ear to suit the material.

On a far more positive note, the side-chain facilities are extremely good, and endow the MDX2200 with a wealth of flexibility. With any bass-heavy material, inserting the side-chain filter allowed far more effective compression where improving perceived loudness was the aim. Being able to switch the side-chain external input in and out was also very useful, as was the ability to monitor the side-chain signal directly. I tried all the usual tricks such as inserting an equaliser for frequency-conscious compression (de-essing), and using an external voice signal to auto-duck music passing through the compressor, and these all worked very well with a small amount of fiddling to optimise the signal levels and thresholds.

The peak limiter could sound a little harsh if driven hard but, as a purely protective device, served its function well enough, as did the LGC function (see box above).

Stereo linking works fine; the peak levels of both channels are taken into account and the RMS sum used to control the dynamic processors in both channels equally. Only Channel 1's controls operate in this mode, so setting the unit up is fast and easy, and as I was unable to detect any instability in the stereo imaging, it must have been working!

Conclusions

Overall, I was quite impressed with the MDX2200, especially considering its very attractive price. The machine is perhaps not the most transparent or creative-sounding compressor on the planet, but it does a workmanlike job perfectly well. It is easy to use, flexible, and capable of good results if used with care. Extreme settings can also produce some pretty wacky-sounding results which might well find applications somewhere... If you are considering purchasing a general-purpose compressor/limiter with the added benefits of comprehensive side-chain access and an expander/gate facility, this is certainly one to try out.

 information
Recommended UK price
£182 including VAT.
Behringer
+44 (0)1932 588826.
0049 2154 920 665.
www.behringer.de

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