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Behringer Multifex • Ultrafex • Bassfex • Multiband Enhancers

Wilf Smarties assesses three Behringer enhancement systems, all designed to make your mixes sound larger than life.

The harmonic enhancer has become a mainstay of studio processing in recent years and Behringer have several products that address the desire to make a mix sound brighter, wider and deeper. Reviewed here are three of Behringer's current processors, starting with the very attractively priced Multifex EX2200.


Like Behringer's existing Dualfex, the new Multifex is a 1U, rackmounting stereo enhancer, but unlike the former it works over two frequency ranges, enabling it to enhance both extremes of the audio spectrum simultaneously. The high-frequency harmonics used to augment the existing top end are derived from a high-pass filter tunable from 1 to 8KHz, while a low band filter, switchable between 50 and 100Hz, takes care of the deep bass. The high-pass filter feeds into a harmonic generator, which produces new high-frequency harmonics which are musically related to the existing signal, but which extend to the limits of human hearing.

Each channel is equipped with two switches: (Process) In/Out and Shift (50/100Hz). There are pots for Process (amount), (Low Band) Mix, and (High Band) Tune and Mix. A four-stage horizontal LED ladder monitors the Drive level, while another LED lets you know the unit is active. Between the twin channels lies a Solo button, which defeats the dry portion of the signal, enabling the unit to be connected via the aux sends like any other time-domain processor. This is useful if you want to add different levels of enhancement to different sounds in a mix, but unless you have stereo aux sends, you're likely to find the stereo imaging badly messed up unless you're very careful.

Connections at the rear include two input and two output quarter-inch jack sockets. These are balanced, but they also work with mono, unbalanced jacks. Note that there's no need for a bulky external power supply — emerging from the rear of the Multifex is a captive mains lead.


In testing, I found it virtually impossible to drive the Multifex into distortion, and the high-frequency enhancement worked every bit as well as on Behringer's existing Dualfex, adding brightness and transparency without fizziness. Grungy drum-loop hi-hats can often be renovated beyond the processing ability of any EQ, while complete mixes take on an extra sense of space and clarity.

Turning to the bass enhancer, I tried to duplicate the effect of applying full-on bass processing at 100Hz with an equaliser similarly tuned. Though the observed level increase on a VU meter was set to be the same for both EQ and EX, I couldn't achieve the same degree of low-end firmness with the EQ, especially on bass sounds and kick drum signals. I found I was able to tighten up a mix simply by rolling off some of the bass using EQ and then putting it back in with the Multifex. The 50Hz cut-off was not well tuned to my home monitoring setup, due to the limited bandwidth of domestic speakers, and program material intended for CD release might be better served by selecting the 100Hz band. The 50Hz setting might be more applicable to dance music intended to be played predominantly in a club setting, where the extra bass could be accommodated by a decent sound system.

The first examples of the Multifex I received had faulty mains transformers which I felt were also unsatisfactorily mounted, by means of a single retaining bolt, onto the large PCB. This has, apparently, been rectified, though I haven't seen an updated Multifex to check this. However, Behringer's Pre-Q, which suffered the same problem, has certainly been improved in this respect.


In addition to top and bottom end enhancement, which seems to be based on the same systems used in the Multifex, the Ultrafex incorporates balanced XLR connections, a switchable stereo width enhancer, and single-ended noise reduction. The latter is monitored by one 8-stage LED meter per channel, and is applied only to the enhanced component of the signal so that side effects are kept to an absolute minimum. Depending on the threshold setting, the noise reduction can be used to effectively eliminate any build-up in quiescent noise, the filter only opening as far as the frequency/energy of the input signal-requires. An enhancer circuit, by its very nature, does emphasise noise, and I found the noise reduction useful when passing DAT mixes through the unit for enhancement, though low-level signals can cause a degree of audible noise pumping; to be fair, the manual warns of this. Whether it merits such weight on the crowded front panel is another story; I would have preferred to see a knob for adjusting the amount of width enhancement applied instead of the existing on/off button!

Even so, the width enhancement really works, and can be quite startling. Minor riffs that were submerged suddenly jump out of the mix, while the overall stereo panorama is greatly widened. The process seems to work best for signals which already have a stereo (as opposed to mono or panned mono) image — in other words, true stereo tracks or samples, or those which have a stereo or cross-panned effect applied. I felt that formerly hard-panned, dry signals appeared closer to the image centre, and slightly less positionally focused — the effect can be somewhat unpredictable, so try a few mixes to get used to it.

Though no technical details are provided on the width enhancement, I get the impression that it works by feeding out-of-phase signals from the left channel into the right and vice versa, rather like the Wide button on a ghetto blaster. This process tends to push back any mono sounds that are panned to the centre of the mix, (because stereo sounds increase in level slightly) and despite the fact that the result is massive in stereo (on both headphones and speakers), mono-only signals are entirely unaffected, assuring 100% mono compatibility. Again the effect can be solo'd, isolating the process-only signal and allowing use via an aux send, though because exciters rely on the phase relationship between the dry and treated signal, a lot depends on the phase integrity of your mixer if you work in this way.


I have to confess that I'd already decided to swop my Dualfex for a Multifex when the Ultrafex arrived at Brookside Nurseries and changed my mind. No question, this is the one for me — it does a lot of things and it does them rather well. I shall be taking it out on the road soon, where I hope it will give an edge to our sound in the clubs, so it's not just a studio tool. More often than not I found myself using all four functions simultaneously when bouncing older mixes through it. I'm convinced.


This unit bears the first occurrence of the word 'digital' in a Behringer product, yet it sports the simplest front panel of any of their units. Essentially, the Bassfex is a tunable sub-harmonic synthesizer which sports only three knobs: a 'Tuner', which is legended Low to Ultralow; a process Level control; and a Threshold for the onboard limiter, included to try to keep your speaker cones intact. Two switches are marked In/Out and High Pass respectively, and there are LEDs indicating Mode and Activity, the latter relating to limiting and sub-harmonic generation. No manual came with this unit so I'll just tell you what it appears to do.

A tunable sub-harmonic generator boosts the bottom end drastically from about 100Hz downwards, by creating new harmonics an octave below the original low-frequency components of the sound. In this respect, I imagine the process to be something like a digital equivalent of the dbx Boom Box, though it may rely on pitch-shifting techniques rather than simple harmonic division. Hitting the Hi Pass button routes the processed sound away from the main left and right output jacks and into a single summed subwoofer output, simultaneously applying a high-pass filter at (I'd guess) around 150-200Hz to the main monitors, effectively subtracting the natural bass end from the music. Used live, it could doubtless provide extra bass punch from a house PA (using an active sub-bass speaker system), though in my home setup I was unable to test out this thesis due to the more conservative nature of my monitoring — though I did feed the left and right outputs and the subwoofer output into three mixer channels to better audition what was going on.


Remixer Phil Kelsey once described solo-ing the dbx Boom Box as being like standing outside a club, and that's exactly how I'd describe listening to the subwoofer output. The limiter was definitely needed to preserve the speakers. At low-frequency boost I thought I could hear some sort of digitisation of the sound going on — though it could just have been my cones flapping!

Despite its tunability, I could get no better-sounding bass enhancement out of this beast in my domestic listening environment than I could with the simpler devices installed in the Multifex and Ultrafex. This isn't surprising, as the harmonics generated by this system are well below the cut-off point of domestic monitors, but I can see that the device would come in useful for processing club mixes, with the proviso that you have a large enough monitoring system to enable you to hear what you're actually doing to the sound. I think the watchword here is — use with caution.


Aside from the teething trouble with the transformers, these are all nicely built, neatly styled units that represent excellent value for money. All dispatch their respective tasks admirably, though it must be pretty obvious that the Ultrafex is my personal favourite. Though it costs more than the Multifex, I feel the addition of a single-ended noise reduction system and a stereo width enhancer make it well worth the extra.

The Bassfex is unusual in that there is no direct equivalent, the nearest thing being the dbx Boom Box, which is analogue rather than digital. Any sub-harmonic processor has to be used with extreme care, as most small monitoring systems are simply unable to reproduce the very low frequencies generated by these devices; because of this fact, which is governed entirely by the laws of physics, the use of such devices may be more suitable for live PA/club music system processing or for tweaking dance recordings being mixed over a proper full-range monitor system.

Though there are other enhancers on the market, some being arguably more sophisticated in certain areas, the Behringer range is very capable, easy to use and attractively priced. As with any enhancement process, the user needs to exercise a degree of restraint, but used sensibly, all the above units can be used to make some or all aspects of a mix that bit larger than life. If you feel your life is lacking that certain something, check them out.

Further Information

Multifex £199; Ultrafex £278; Bassfex £278. Prices include VAT.

Shuttlesound, (Contact Details).


Not prone to distortion.
Adds brightness and transparency without fizziness.
Bass enhancement useful.

50Hz setting not really applicable in a home setup.

A very able enhancer at a more than reasonable price.


Built-in noise reduction.
Effective width enhancement feature.
Great for beefing up old and new mixes.

Putting low-level signals through the noise reduction can cause 'pumping' - though this is true of noise reduction in general.

The one to go for if you've a bit more money to spend. An all-round audio sweetener with possible applications live as well as in the studio.


Dedicated bass enhancement could make a real difference to dance mixes.
Built-in limiter.
Could be used live with a house PA.

Not so well suited to home use unless you have a decent full-range monitoring system.

A dedicated bass enhancer with very little competition, since there are few such units on the market. Probably best suited to dance music mixing and live use.

Previous Article in this issue

Robo Bop

Next article in this issue

Sound Bites

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Oct 1993

Review by Wilf Smarties

Previous article in this issue:

> Robo Bop

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> Sound Bites

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