Behringer Shark FBQ100 User Manual

SHARK FBQ100 User Manual

Monitoring

P.A.

+4 dBu

Line

Monitor 

Out

Master Out

Fig. 2.4: Two SHARKs in the monitor path

2.1.5  The SHARK used in single channels and subgroups
Whenever you want to make sure that wanted feedback such as the feedback 

sounds produced by a guitar won’t be removed, you should insert one or several 

FBQ100 into “feedback-prone” single channels (e.g. vocals) or subgroups of your 

mixing console! Route all channels that are susceptible to feedback (e.g. all vocal 

mics) to one or several subgroups, in which you insert one or several SHARKs. 

In this way, all channels that are less liable to produce feedback (e.g. those 

carrying line-level signals, or instrumental microphones with lower volumes) 

can pass the console unaltered, while only critical microphone channels are 

controlled by the FBQ100. Thus, you can protect your sound reinforcement system 

against feedback and still use wanted feedback sounds.

Mixer

Insert Point

Send

Return

Out

Return

Send

Ground

Ground

+4 

dBu

Line 

In

Fig. 2.5: The SHARK in the insert path

2.1.6  Automatic “tuning in” of P.A. and monitor systems
With the FBQ100 you can improve the protection against feedback even before 

a concert begins, simply by “tuning in” your sound reinforcement system: 

once the system has been installed and set up, open all microphone channels 

and monitor paths, then enable FILTER LEARN mode on your FBQ100. The SHARK 

generates short feedback-causing signals, which are then sent back to its input 

and suppressed by the filters. These filters are permanently assigned and can 

be reconfigured as free searching filters only by means of a RESET. Without the 

SHARK you could raise the overall volume level only until the first feedback 

occurs. But with the FBQ100 you’ve got considerably more headroom! Please note 

that the FILTER LEARN mode is limited to about 15 seconds.

If you are using not just one FBQ100 for the monitor path, you should employ 

some additional units to safeguard critical signal paths. Experience has shown 

that during a concert the musicians on stage usually want their instruments 

made louder in the monitors. With the SHARK you can raise the volume without 

running the risk of feedback. When the concert begins the FBQ100 automatically 

tracks and removes varying feedback signals produced by “moving” 

vocal microphones.

The SHARK identifies feedback by splitting the entire frequency spectrum 

(20 Hz to 20 kHz) into sections of 1/60 of an octave and determining the level 

of each of these bands. The values calculated are then referenced to the level 

of the overall signal. The resulting level difference determines whether or not 

a filter is set. The SHARK allows you to adapt these decisive parameter to your 

needs: within a range from 1 through 100 you can edit the feedback detection 

sensitivity. The standard setting is 50, which ensures the best possible detection 

of feedback for the majority of applications. For speech-only applications you can 

raise the feedback detection threshold towards 100, which enables the algorithm 

to detect and remove feedback even more quickly. Vice versa, lower values 

provide for a more stable feedback suppression responding less to wanted 

feedback-like signal portions produced by guitars or keyboards.
In FILTER LEARN mode, feedback is generated and suppressed automatically. 

Whenever it detects feedback, the FBQ100 selects the filter parameters 

automatically to efficiently remove the feedback. As the filter is set to the 

frequency detected, this mode is ideally suitable for suppressing constant 

feedback frequencies produced by “fixed” microphones, e.g. those used on 

drums. Once set, the filters automatically enters lock mode, i.e. the frequency 

remains fixed but width and depth of the filter are still being adapted to the 

signal. The filter width is enlarged whenever the feedback frequency shifts 

slightly. If feedback persists, gain is reduced even more and kept low to prevent 

feedback from recurring.
All microphones that are moved during a performance (e.g. hand-held 

vocal microphones) are usually susceptible to varying feedback frequencies, 

which should be suppressed in automatic search mode (entered when you 

power up the SHARK). Much like in FILTER LEARN mode, a filter automatically 

determines the ideal settings for all parameters, in order to suppress feedback. 

However, once all filters have been set, the filter first activated gets reset to 

automatic search mode. Thus, the SHARK makes sure that there is always one free 

filter to identify and remove new feedback frequencies. If your music contains 

wanted feedback elements (e.g. guitar feedback), the SHARK will suppress these 

too, because it is impossible from a physical point of view to distinguish wanted 

from unwanted feedback. Section 2.1.6 provides some information on how to get 

around this physical problem.

In addition to speakers on or near the stage, major-scale installations often 

have speaker groups positioned at a distance to the stage or flown above the 

audience, in order to provide listeners away from the stage with direct sound. 

However, since sound needs some time to travel around (343.6 m/sec at 20°C, 

accelerates by 0.6 m/sec per °C), it reaches the audience not simultaneously 

but gets delayed by a certain amount. To make up for the different run times 

between stage and remote speakers, the latter must be provided with an 

electronically delayed signal, which is usually done by means of special-purpose 

Delay devices. You won’t need them, however, when you’ve got a SHARK, 

as the FBQ100 integrates a Delay Line circuit giving you the same convenience 

of operation as dedicated devices. Simply measure the distance between the 

various speaker groups and enter this value (in meters or feet). Chapter 2.1.3 

shows you how to wire the FBQ100 in this type of application.