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Behringer FBQ2496

Feedback Destroyer Pro
Published June 2006
By Mike Crofts

Behringer FBQ2496Photo: Mark Ewing

Given its more than respectable range of facilities and 24-bit/96kHz operation, the low price of this feedback processor seems far too good to be true. We find out whether it is...

The FBQ2496 is the latest model from Behringer and represents a higher-tech approach to the art of feedback suppression — but still keeping within the realms of budget gear. This device, which works either in stereo or as two independent channels, functions as an automatic feedback eliminator and also as a manually operated digital equaliser. It's claimed to be faster in operation than its predecessors and, as the model number suggests, incorporates 96kHz, 24-bit technology. With a modest price tag of little more than £100, if it does what it's supposed to do it should represent very good value.

First Impressions

The FBQ2496's general appearance and styling are very much in line with the general look for the Behringer range of rack processors — the 1U black-and-silver face-plate is very familiar — but this model is blessed with a distinctive layout for the displays and control groupings, which, for some reason, lean to the right of the panel, a bit like handwriting that slopes forward. It does look slightly strange (to me) straight out of the box, but overall the styling is neat and businesslike.

The rear panel of any rack gear generally gives a good idea of what it does, so let's start there. There are inputs and outputs grouped together for left and right channels, and each channel is provided with a set of balanced XLR and TRS (stereo jack) connections, plus a level-setting switch that selects between -10dB and +4dB operation, for compatibility with your other system components. There are three MIDI connectors, too — In, Out and Thru — which are used to receive, pass and transmit various control instructions and may also be used for future operating-system updates. As with all Behringer gear, the mains power supply is internal and can accept anything from 110V to 240V, at either 50Hz or 60Hz.

Turning to the logically arranged front panel, the controls are mainly push-buttons and are arranged in two banks of six either side of the main filter-status display, which occupies the centre of the panel. To the right is an LED numeric indicator and a rotary setting control, and at the far left-hand end is a stereo input-level meter featuring three-colour vertical LED ladders with an input clip indicator at the top of each. Finally, we have a recessed power switch, always a welcome inclusion on the front of any outboard gear, in my opinion.

Functionality

I'm a big fan of automatic feedback suppressors for general-purpose live work; indeed, they've got me out of trouble on several occasions. The various models available are all quite similar, in that they automatically detect feedback frequencies and assign a suitable width and depth of digital filter to knock out the offending one(s). As technology has progressed, the filters have become narrower, thus having a less detrimental effect on overall signal quality, and the devices have also become much faster at detecting and removing unwanted feedback. Differences between devices are more apparent in the method of operation, particularly in how the user sets them up. This new Behringer machine takes the technology a stage further, by introducing an interesting and rather different setting-up method (the 'auto learn' function), which is completely automatic.

In addition to its feedback-suppression capabilities, the FBQ2496 also functions as a fully configurable parametric equaliser, and it can actually perform both functions at the same time, by simply assigning a number of filters to each task. In normal use, the 40 available digital filters are assigned 20 to each channel, and you can programme them to act as Single-shot (fixed) or Automatic (roving/dynamic) feedback filters, or as Parametric EQ filters in any combination.

As with earlier Behringer feedback eliminators, the FBQ2496 starts working as soon as it is powered up and detects signal passing through, and will always assign the automatic filters to any feedback frequencies it can detect, up to the maximum number of available filters (ie. those which have not been assigned to either Single-shot or Parametric EQ duties).

On Display

Obviously, we need to feed in a signal for the FBQ2496 to do anything; the dual vertical LED meters on the front panel indicate input level. There are eight LEDs per channel, left and right, and the clip level represents the maximum input level before digital clipping will occur. As mentioned earlier, the reference input level can be set at either -10dB or +4dB, to match your other equipment.

In the centre of the front panel is the main filter-status display. Each channel has a horizontal arrangement of 20 red LED indicators that represent all the filters available. An LED will light either if that particular feedback filter has been deployed or if a manually-set Parametric EQ filter is active. When an individual Parametric EQ filter is being adjusted, its corresponding LED will flash.

A third display shows parameter values and works in conjunction with the rotary controller knob. The three-digit LED display shows actual values and the small LEDs below will light up to indicate what the displayed value means — for example, Hz, dB, minutes, and so on.

The display side of things is very well covered by these three sections, and the LEDs themselves are bright and easy to read from a few feet away. The main display is also used when you're setting the filter types (Auto, Single-shot or PEQ) and a quick press of the appropriate button will light up the corresponding number of filters of that type, which is a useful check.

The Knobs

Apart from the rotary control, which is used for parameter adjustments, all the remaining controls are simple push-button types. They need only a light touch but operate with a positive and audible click. There are a few combination operations that involve two buttons being pressed simultaneously, but all the most basic functions are accessed via individual buttons, which keeps life nice and simple. Some functions have two-stage access, depending on whether the button is pressed briefly or held for a second or so. Some of the buttons access a function that's obvious from their label — for example, pressing the one marked Speech will make the unit operate in a less discerning way than for more critical music applications, and will apply more vigorous attenuation at a lower feedback level.

The FBQ's rear panel. The FBQ's rear panel. Photo: Mark EwingThe button labelled Reset is pretty straightforward, too, but it has the two aforementioned levels of operation: a short press will erase and reset all automatically set filters, leaving the preset or single-shot filters alone, but a longer press will clear the whole lot.

The Freeze button is pretty handy: whenever a combination of filter settings is working really well and you don't want any more automatic adjustments to be made, pressing this button will store and deploy all current filter settings, until the Freeze mode is cancelled with another single press. As far as I can tell, the unit always clears the filters (but not the filter types) when it is powered down, unless the Freeze facility has been used to store the settings.

Once an Automatic feedback filter has been deployed, how long it remains in place can be adjusted via the 'filter lift' button. The available settings range from 'off', which means that the filter won't ever release until manually reset, to anything between one and 60 minutes.

The Clever Automatic Bits

Of particular interest are two buttons marked Learn and Panic. The Panic button (the red one) is used if everything gets out of control during a performance and will, if pressed for more than one second, re-assess the feedback situation and deploy filters as necessary, to automatically remove any feedback that's present. It's useful as a get-out-of-jail-free card, but with any luck it won't be needed very often!

The Learn functions give access to the setup procedure for the Single-shot filters only, which can be set in one of two ways. Assuming that the PA system is up and running, a brief press of the Learn button will begin the automatic process of detecting feedback and assigning appropriate Single-shot filters. This can be done in the (by now) traditional way, by slowly increasing system gain (with open microphones) until feedback occurs at various frequencies, which will then be quickly detected and suppressed. If you don't have time to perform this routine the FBQ2496 will just find the frequencies as they occur, and this can be done even after the performance has begun if there is no other way — although you do run the risk of, for example, sustained keyboard notes being interpreted as feedback. You can always press the Panic button later, anyway....

Additional Controls

On the right of the front panel are additional controls that can be used to manage the Parametric EQ and its individual filter properties — frequency, gain and bandwidth. The centre frequency of a parametric EQ filter can be adjusted to anywhere between 20Hz and 20kHz, while its gain can be set between +/- 15dB in 0.5dB steps and down to -36dB in 1dB steps. Filter bandwidth — again, individually managed for each filter — can be selected between 1/60 octave and 10 octaves.

The button labelled 'Left/Right' is used to link the left and right channels for stereo operation, or to apply settings to left or right channels individually. Finally, the Bypass control applies a true hard bypass from input to output, by means of a relay. This is a useful feature, especially if the unit is in a rack and you don't want to be switching the power on and off. Personally, I'd make this button the red one, because you can imagine the consequences of hitting it by mistake in the middle of a performance! All in all, this is a comprehensive control set that provides relatively straightforward and intuitive user access to all the important settings.

It's worth noting that the individual filter settings can only be manually adjusted when filters are in PEQ mode: when the filters are used as feedback filters, these characteristics are set automatically by the unit's processing circuits and cannot be altered, other than by specific user settings such as Speech mode (see main text).

The Really Clever Bits

If the Learn button is pressed and held, the FBQ2496 goes into 'auto learn' mode, which employs a rather different method of finding and eliminating feedback in the system. As soon as the button is held for a second, the numeric display counts down from 16 to zero in seconds, during which time a number of sharp pulses at -15dB are produced from the output. Throughout this process the FBQ2496 steadily and automatically increases its gain by 15dB. The pulses will provoke feedback at various frequencies. The 'worst' frequency will be kicked into feedback first (i.e by the first pulse and at the lowest gain setting) and the remaining pulses will excite feedback at subsequent frequencies, as the gain is increased, until all the Single-shot filters have been assigned.

This is a strange process to listen to, as you don't hear much of the ringing frequencies before the machine captures and eliminates them, but it's much quicker than gingerly pushing up a fader yourself and hoping the device will work before your speakers or audience start to suffer. All you hear is a sharp 'tick' followed by the start of a ringing frequency, followed by the next tick, and so on, until the process is complete and the gain is returned to the original setting, but without the feedback. It's totally automatic: all you have to do is press the button!

Using It

The FBQ2496 is very simple to connect and set up. It's always useful to have the choice of TRS or balanced XLR connectors, and the operating-level switch means that this unit can be interfaced with virtually any system.

Once you've decided what mix of filter types you need and have tweaked any parametric equaliser filters, the feedback setup is completely automatic and the end result is precisely what you'd want: more gain from your system before feedback starts to happen. With 24-bit, 96kHz operation, audio quality at this price point is beyond any criticism in my book, and with its automatic setup process I think this is an interesting and effective product. The 1/60 octave filters don't, for me, have any detrimental effect on the overall sound, and they're extremely fast in operation.

As with all gear for the road, only time will tell if it's exactly right for you, or me, but my first impressions are definitely favourable and I'll be using the FBQ2496 as much as possible until they take it off me! 

Published June 2006