Behringer Composer MDX 2000/2100
"If you're into the lower end of the pro audio market, you might be aware of the distinction between old Behringer gear, which was supposedly OK, and new stuff, which is regarded as "Pro" in name only. Having owned a number of units from both eras, I can say that this is only a general guideline, but it does apply when it comes to the compressors, where the MDX 2000/2100 Composers (the review is for both units, since they're in most respects very similar) do seem to outperform the later Composer Pros."
"The first clue that the Behringer Composer might be a decent compressor is the build quality, which is very solid. The front panel is made out of machined aluminium, the rest of the chassis is made out of steel, the knobs feel sturdy, and while the jack sockets are soldered directly onto the PCB, I haven't had any failed or intermittent connections with the three units that I've had. It's also quite well-specified: it's got an expander/gate with variable release time, an auto mode, and a limiter. The feature that I was most impressed, however, was the failsafe relay operation meaning that if something goes wrong with the compressor, the audio still gets passed through, which is something even some much more expensive and revered units can't boast, and which, together with the reliability that I have experienced, makes the Composer perfectly viable for less demanding live tasks."
"The main reason why the Composer can't take centre stage either in live or in studio work is, to put it bluntly, its second-rate sonic performance. Neither the MDX 2000 nor the 2100 are able to cope with signals that either have strong transients or a lot of bass, let alone those combining the two, e.g. kick drums. Given its reputation, some people wouldn't use it on anything, but I felt that with a bit of care, it was very transparent on vocals and acoustic guitar, though it has to be said that the Really Nice Compressor comfortably outperforms it on both as soon as ratios beyond 5:1 are required. Still, the price difference between the two is significant and if you need several channels of non-critical compression, you might appreciate what the Composer can do for you at some 20 euros per channel (and it does dual mono, which the RNC doesn't)."
"In fact, the MDX 2000 is rather better at dual mono operation since there is a documented but rarely mentioned bug in its stereo link implementation. The problem is that the left channel truly is the master channel, not only for the controls but also for the internal sidechain. In other words, the right-channel signal doesn't affect the compression at all, which is a serious oversight that can be downright dangerous under unpredictable circumstances. You could be having deafening amounts of feedback on the right channel but as long as the left channel wasn't affected, the MDX 2000 wouldn't act upon it. The only way to get around this is to sacrifice an aux send to do a mix of both channels and use it as the external sidechain control, which is obviously a bit of a bummer."
"The MDX 2100 isn't without design flaws, either. For some reason, its headroom is significantly lower than the MDX 2000's, which means that even with the limiter turned off completely, it will use the compression circuit to auto-limit the incoming signal. There is no way to prevent this, not even with switching to external keying, which should in theory completely divorce the program from the control path. I tested this when I was trying to use the MDX 2100 as a bass ducker to make some room for the kick, but instead, it began to compress the bass. When I switched back to the MDX 2000, the problem was gone (and yes, I checked the -10/+4 input setting)."
"The feature speaking strongest in favour of the Behringer Composer today is the price. They rarely sell for over 50 Euros, and if you know what you're getting them for, you can't really do much better than that. The old Composers can definitely match the Samsons, the Phonics, the Alesis 3630, and Behringer's own later offerings, and even surpass them in certain regards, such as transparency."
If the MDX2100 has a design flaw that compromises it's ability to duck a bass to make room for a kick drum... then I'm leaning MDX2000 too.