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Behringer SX3040 & SU9920

Enhancement Processors
Published January 2008
By Tom Flint

Behringer SX3040 & SU9920Photo: Mike Cameron

Behringer offer highly affordable excitement in the shape of two new sub-£100 rack processors.

Behringer have introduced two new low-cost stereo enhancers intended for use both in the studio and live. Although the SX3040 Sonic Exciter and SU9920 Sonic Ultramizer both do broadly the same job, the way they process audio differs somewhat.

Behringer's labelling of the SX3040 (and, for that matter, the SU9920), boldly claims that the product is the "ultimate stereo sound enhancement processor" — a statement that may be a little misleading, given that the product is very much a low-cost alternative to Aphex's 204 Aural Exciter and Optical Big Bottom, and the Vitalizer range of processors by SPL.

The SU9920 resembles BBE's Sonic Maximizer, although, once again, it has been manufactured to sell at a lower price point. I'll take a closer look at how that one works later in the review.

SX3040 Sonic Exciter

The SX3040 has two identical, independently operated channels that can be used in unison on stereo signals or separately for mono sound sources. They also have their own In/Out buttons so that processing can be bypassed if necessary. Each channel houses two fairly distinct processors, one dedicated to the high end and the other the bass.

The Bass Processor section appears to be a parallel compressor, applying processing to a duplicate signal that is mixed with the original to achieve the desired enhancement effect. The process is able to increase the apparent weight and clarity of bass without significantly hiking up the output signal level. It's worth noting that this method differs from that used by bass enhancers such as Waves' Maxxbass, which adds harmonic distortion to achieve a bass sound with more impact.

The SX3040 Sonic Exciter has two identical, independently operated channels. Each is divided into two sections: the first filters off and processes the bass (using compression and automatic phase-shifting); while the second is used to enhance the higher frequencies by adding extra harmonics.The SX3040 Sonic Exciter has two identical, independently operated channels. Each is divided into two sections: the first filters off and processes the bass (using compression and automatic phase-shifting); while the second is used to enhance the higher frequencies by adding extra harmonics.Photo: Mike CameronThe Bass Processor has just three knobs, labelled Drive, Tune and Mix. The Tune knob determines what range of bass frequencies will be filtered off for processing. Like all the knobs, it is only labelled with a Min to Max range, but the specification shows that the range is actually 50Hz to 160Hz. This annexed portion of the signal is fed into a compressor, where it is compressed to a degree specified by the position of the Drive control. There are no attack, sustain and release parameters to worry about, as these are automatically adjusted in reaction to the input material, but a green LED near the Drive knob lights up to indicate when the compression is being applied.

The compressed bass is automatically phase-shifted to correctly align it with the unprocessed signal, after which it is ready to be mixed back in, via the helpfully labelled Mix knob. When this knob is set at minimum (dry) none of the parallel signal is heard, while at maximum (wet) none of the unprocessed signal remains (useful if you're using it in a send/return effects loop).

It's the Sonic Exciter-branded part of the processor that's entrusted with the task of enhancing the high end. It does that by creating distortion, which allows it to synthesize harmonics related to the input signal. These can then be mixed back in with the original signal, increasing the high-end content of the output, but without significantly changing overall level. It therefore operates on a slightly different principle from the Bass Processor.

Like the bass section, the exciter is blessed with just three simple control knobs per channel. It does not compress, so there's no Drive dial, but the Mix control and the Tune control (with a Tune range of 1.3kHz to 10kHz) are there, and perform the same functions as on the Bass Processor. The middle knob increases the amount of harmonics added as it is turned to the right.

The rear panel is sparse and simple. Each channel has balanced inputs and outputs in both XLR and quarter-inch TRS jack formats. Surprisingly, considering its low price, the product has an internal mains transformer, so the rear panel also hosts an IEC socket for the mains connection.

Build Quality

Given the extremely low cost of these two Behringer products, many potential buyers will be wondering if the build quality has been sacrificed to save money. Actually, both units seem to be constructed reasonably well. All the inputs and outputs are securely attached to the metal chassis, so even the most vigorous plugging and unplugging of leads is unlikely to damage the more fragile circuit-board inside, and the rack ears are formed from 3mm-thick metal, which is more than adequate for the job.

Both products feel very light when you consider that they house mains transformers and have predominantly steel chassis. I removed the top panel of the SX3040 to look inside, and discovered that their lightness is because there is very little inside. In all, there are just two circuit boards mounted vertically, each measuring about an inch in height. The longest one is positioned just behind the front-panel controls, the other, a short board of less than 18cm in length, sits at the back behind the I/O. Other than that there is just a small mains transformer at one end, fixed midway between the IEC input on the back and the power switch at the front. The other end is completely empty, so there is plenty of room for air to circulate and keep components cool even when the unit is in a rack.

The only weakness in the design is that the control pots are supported by their fixing to the front vertical circuit-board, as far as I can tell, and simply poke through the metalwork instead of being secured on the chassis itself. This means that they flex easily and are not as resistant to knocks as the I/O.0

In Use

Operating the SX3040 is far easier than remembering its product name and should not pose a problem for anyone. All you really need to remember is that when the In/Out buttons are red, the processing is out of circuit and when they are blue, stuff is happening! These buttons are great for comparing the effected signal with the clean one — a process that's very important when assessing the benefits of the processing on a sound source. From there on it's just a matter of twiddling the knobs until everything sounds right.

All the knobs are lightly notched and can be felt to click from one position to another as they are turned. I counted 20 positions, and it is this design that enables the user to match the value of the two channels for stereo use. There is no stereo link button, so matching the two does have to be done manually.

The exciter, like all such devices, is best used moderately if harsh-sounding mixes are to be avoided. Certainly, when it is mixed in at low levels it has a subjectively beneficial effect on a lot of material, adding a little sparkle and energy where needed. Getting the setting right is a matter of finding the frequency sweet spot with the Tune knob. This is easily done by starting with the effect mixed high and then sweeping the Tune position until it grabs hold of the right bunch of frequencies.

Other than the labelling denoting the model, the rear panels of both these processors are identical, with the usual power in socket, and balanced input and outputs presented on both jack and XLR. Other than the labelling denoting the model, the rear panels of both these processors are identical, with the usual power in socket, and balanced input and outputs presented on both jack and XLR. Photo: Mike CameronThe bass processor I really liked. For my money, it is a more appealing effect than bass-harmonic-generating designs created to give the impression of more bass on smaller speaker systems. When I've tried to use Wave's MaxxBass during mixing, for example, I've usually ended up turning it off, finding that the way it coloured the sound didn't necessarily benefit my mixes. Behringer's processor is more akin to Aphex's Big Bottom design, and manages to beef up the bass very cleanly and naturally when applied sensibly.

Interestingly, it also enhances mixes in other, less predictable, ways. In particular it seems to boost the effect of reverbs and other low-level detail, thereby increasing the apparent depth of a mix and enabling the listener to experience hitherto hidden subtleties. Other reviews have said similar things about SPL and Aphex products, so the SX3040 offers a chance for those on a budget to get a taste of what they've been missing.

The only real issue, for me, is the lack of a high-pass shelving filter, which would be ideal for cleaning away those boomy sub-bass frequencies that get out of hand during processing. Clubs and certain dance mix engineers might not worry too much about this, but in general, having too much energy in the very low-frequency range detracts from the important parts of a mix. I tested this by severely filtering out the lower end on the stereo buss feeding the SX3040 and found that the sound cleaned up nicely.

Of course, the processor can be used on individual sources as well as mixes, but it would be easy to overdo things in isolation. Obviously, not everything can be super-energetic and up-front in a mix.

The overall operation is pretty idiot-proof. High drive settings usually require a moderate mix setting, and vice versa. The Tune control, when set at its minimum position, provides fairly unappealing sub rumbling, and it begins to interfere with the guts of a track when turned all the way up. Between those extremes the active bass frequencies are located and can usually be enhanced rather nicely.

SU9920 Sonic Ultramizer

Like the SX3040, the SU9920 processes both the high end and low end of a signal, but it takes a slightly different approach — in fact, it does not add any harmonic distortion at all. Exactly what it does to the audio, in technical terms, remains uncertain, as the manual notes are brief but, as Behringer explain, its brief is to do the processing without damaging "the relationship between the fundamental tone and the harmonics," which can often occur through equalisation. Simply put, it enables the user to increase the impact of the bass and treble frequencies without adversely changing the character of the audio. As mentioned earlier, the concept and design is similar to BBE's Sonic Maximizer, which splits audio signals into several frequency bands for dynamic equalisation processing. It then delays each band by a differing amount, in order to maintain their relative phase relationships, resulting in a psychoacoustic effect that makes the processed signal appear louder, clearer and more detailed. It seems that Behringer's Ultramizer is doing roughly the same thing, according to the specification sheet, which describes the enhancer section as a three-band phase delay and dynamic filter.


The SX3040 has undoubtedly been inspired by Aphex's 204 Aural Exciter and Optical Big Bottom, which has the same number of controls, all labelled with the same names. The Aphex offers two channels, each with an exciter for enhancing the high end and a parallel compressor for improving the punch of the lower frequencies. Behringer's product shares almost exactly the same I/O connections too, but it lacks the operating level switching. It is also significantly less expensive.

SPL are renowned for their numerous Vitalizer products and, although they are more expensive than these Behringer units and generally offer a slightly different set of features, they are well worth auditioning to get a perspective on this market niche.

In the last few years Phonic have also pitched in with their T8300 enhancer, which differs in that it is a 2U valve processor. Like the rest of the alternatives, it costs more than Behringer's products. Phonic's A6100 is closer still, though the latest model appears to be discontinued.

The SU9920 is most obviously in competition with BBE's Sonic Maximizer. BBE actually have four current Maximizer products on sale, several of which are slight modifications of well-established members of the range. Of the current batch it is the semi-pro 428i model which is closest in terms of its features and position in the market. On the face of it, the features are very similar, but the BBE has been designed with particularly high-quality components, as is reflected in its higher price.

Feature Set

The rear panel is identical to that of the SX3040, as is the design of the knobs and the style of the chassis screen-printing, and, although it is even cheaper than its stablemate, it too has an internal power transformer. There are only four controls on the front panel, not including the global processor In/out button and, of course, the power switch.

Each channel has a knob labelled Process and another labelled Low Contour. The Process knob might have been better titled High Frequency Processor, as it is the control responsible for adjusting the upper part of the audio spectrum. More specifically, it applies up to 12dB boost at 5kHz. The more informatively titled Low Contour knob provides up to 12dB at 50Hz (although the manual claims it operates at 50kHz!).

To keep a check on levels, each channel has been given a horizontal meter comprising five LEDs. The range begins at -20 dBu and goes up to +10, before reaching the red Clip level, which presumably lights at +20. Apparently, the red LED illuminates 3dB before clipping occurs, but 0dB is the optimal output level.

In Use

Operating the Ultramizer is as simple as it can possibly be and requires no explanation, really. The only slight stumbling block is that the controls are reversed on each channel, like a mirror image of each other — it would, in my opinion, be easier to operate if they were in the same order on each side, as is the case with the SX3040.

The processor is surprisingly good at adding more bass and top without making a mess of things or somehow altering the fundamental character of the material, but it is best used in moderation. It's easy to get carried away and find yourself dialling in more bass and more high-end sizzle, and producing a brutally fatiguing mix. Describing the Ultramizer's character is tricky, because by its very nature it manipulates the source signal rather than adding anything of its own. What can be said, though, is that it seems to work in a way that traditional EQ does not, managing to boost the selected frequency range without drastically changing the balance of the piece of music.

Even more so than the Sonic Exciter, the Ultramizer is primarily intended for using as a stereo processor, as is evident from the single processor In/Out button governing both channels. For dual-channel use it would really be handy to have a stereo link button, so that the two sides are forced to adopt the same settings. On the plus side, having the two independent from one another does allow separate mono sound sources to be processed simultaneously using the one box.

Time To Get Excited?

At such ridiculously low prices, the SX3040 and SU9920 are well worth buying just for the sake of having them to hand for when that extra something is required. I can't imagine both being needed on a mix, but obviously they can also be used in the channel inserts or effect-send path of a mixing desk, or as a tool in the effects rack of guitarists and keyboard players.

Of the two, the slightly more expensive SX3040 is the more flexible and interesting. As a mix processor it can be used to improve lacklustre recordings, but it really shines when the source material contains something for it to get its teeth into. At this price it would be ridiculous to form many criticisms, but I would like to have an adjustable high-pass filter available in the circuit to eradicate troublesome low frequencies. A higher-end product of this kind should offer switchblade -10dBV/+4dBU operating levels, plus a more refined enhancer sound, but for a lot of jobs this Sonic Exciter will be just the ticket. The SX3040 is quite literally a cheap trick — but my goodness it does work!

As for the SU9920, I can see it finding a home in a large number of racks, particularly in small venues and other live spaces, where a quick tweak is needed to suit the environment. I think many people will use it to process instrument feeds, as it is ideal for speedily spicing up keyboard and synth parts, or even flat-sounding guitar rigs. Clearly, it also has its place in the studio as a mix problem-solver. Jobbing producers, for example, might find it very useful when their non-technical clients say, "Yeah, that's great but can you just make it sound better?" Tweak the knobs and hey presto, everything instantly sounds better!

As it is not particularly flexible, the Ultramizer is not a total mix-mastering solution, but it could be used as a component in the signal path for home mastering. The processor does not seem to degrade the signal with the addition of noise or any other kind of distortion, so there is no reason why it shouldn't be used across a whole mix — although it's worth remembering that mastering houses will undoubtedly be able to achieve a similar result using a more sophisticated bit of kit. 

Published January 2008