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Communications Systems | LBB 1968/00 Plena Feedback Suppressor
LBB 1968/00 Plena Feedback Suppressor
The Plena feedback suppressor uses a powerful DSP with
a patented algorithm to suppress acoustic feedback. It
actively filters out unwanted room reverberations using an
echo-cancellation and de-reverberation algorithm. By
adding masked (inaudible) noise to the output signal or by
shifting the frequency of the output signal by five hertz,
the Plena feedback suppressor is able to detect the
reverb component of the signal and remove it before
feedback occurs. This leaves the original signal intact.
Functions
The adaptive filter can be switched between fast mode
and accurate mode. The fast mode is for situations where
the microphone position changes over time, such as in a
discussion system with multiple switching microphones.
The accurate mode is for situations with a fixed
microphone position, such as on a pulpit where the
acoustical environment is more stable. The adaptive filter
is allowed to converge more slowly, suppressing
reverberation components even more effectively.
Depending on the acoustical environment and the chosen
mode of operation, up to 12dB of additional gain is
possible before acoustic feedback occurs.
▶ Patented feedback suppression algorithm
▶ Suppresses feedback before it occurs
▶ Automatically adapts to the acoustical situation
▶ Up to 12 dB additional gain before feedback occurs
▶ Balanced line or microphone input with phantom
supply
▶ Second microphone input with automatic mixer
The Plena feedback suppressor also features a built-in
automatic mixer for the two microphone inputs. In many
situations, such as on a rostrum, a pulpit or a conference
table, two microphones are used to capture the voice of a
moving speaker better, even though this increases the risk
of acoustic feedback. To counter this, the automatic mixer
in the Plena feedback suppressor reduces the gain of the
microphone with the lowest signal input and increases the
gain of the microphone with the highest signal input. This
way, it tracks the moving speaker for optimum speech
intelligibility, while maintaining a maximum feedback
margin by keeping the combined gain constant. The
automatic mixer function remains operational even when
the feedback suppressor is deactivated.
Certifications and Approvals
Region
Certification
Europe
CE
Declaration of Conformity
Safety
acc. to EN 60065
Immunity
acc. to EN 55103-2
Emission
acc. to EN 55103-1
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Summary of Contents for Bosch LBB 1968/00
- Page 1 Communications Systems | LBB 1968/00 Plena Feedback Suppressor LBB 1968/00 Plena Feedback Suppressor ▶ Patented feedback suppression algorithm ▶ Suppresses feedback before it occurs ▶ Automatically adapts to the acoustical situation ▶ Up to 12 dB additional gain before feedback occurs ▶...
- Page 2 2 | LBB 1968/00 Plena Feedback Suppressor Installation/Configuration Notes Mains power supply Mic input Connectors 3-pin XLR, 5-pin DIN, balanced Max level -18 / -30 / -42 dBV Impedance 2 kohm Phantom power 16 V (switchable) Priority control Loop-through of pin 4 and 5 of DIN...
- Page 3 Plena Feedback Suppressor Installation and Operating Manual LBB 1968...
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Page 4: Important Safeguards
This is a safety feature. If you are unable to insert the plug into the outlet, contact your electrician to replace your obsolete outlet. Do not defeat the safety purpose of the grounding-type lug. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 5: Safety Precautions
Do not open the unit when it is connected to the mains. The unit contains non-insulated parts, which can cause electric shock. Caution There are no user-serviceable parts inside the unit. Service must be done by qualified personnel. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 6: Table Of Contents
Switching ON ................................20 Calibration ................................21 General recommendations to prevent feedback ....................21 5 Technical data ..................................22 Electrical ..................................22 Performance ................................22 Inputs ..................................22 Outputs ..................................23 Controls and indicators ............................23 Environmental conditions ............................23 General ..................................23 Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 7: About The Equipment
'tracks' the moving speaker for optimum speech intelligibility, and the maximum feedback margin is maintained by keeping the summed gain constant. Even if the feedback processor is switched to bypass this automatic mixer is still operating. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 8: Controls And Indicators (Front)
The LED lights up to indicate a fast calibration cycle after pressing the calibrate button (9). 9 Calibrate button Upon pressing the calibrate button, random noise at -6 dBr is generated for a few seconds to allow the feedback suppression algorithm to calibrate quickly. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 9: Controls And Connections (Rear)
Switch that enables and disables phantom power on Microphone 1/Line input (1 and 2) and Microphone 2 input (4 and 5). When the line input is selected with the help of the Mic/Line switch (3), phantom power is disabled for this input. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 10: Installation In Rack
Remove the 4 feet from the bottom of the unit. Without the feet, the unit is 1U high. • Ensure that the ambient temperature of the unit in the rack does not exceed 55 °C. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 11: External Settings And Connections
24VDC In Mic/Line Mic/Line 100/70V/ 8Ω0 100/70 V 0 100/70 V 0 100/70 V 0 100/70 V 0 Chime Warning This apparatus must be earthed figure 3. 1 : Announcement set-up Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 12: 3.1.2 Live Performance Set-Up And Conference Set-Up
Rated input S/N. Design & Quality Power: 50VA The Netherlands Mic/Line T500L250V Signal Level Phantom Mic 1+2 Warning 1 2 3 4 This apparatus must be earthed figure 3.2: Live performance set-up Bosch Security Systems | 2003-11 | 9922 141 81681en... - Page 13 UTILISER UN FUSIBLE DE RECHANGE DE MEME TYPE Multi Link Rec. Line Trunk Port 1 COMMERCIAL AUDIO EQUIPMENT LISTED 9R88 Port 2 2A 250V Made in Holland Symmetrical figure 3.3: Conference set-up Bosch Security Systems | 2003-11 | 9922 141 81681en...
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Page 14: 3.1.3 Presentation Set-Up And Set-Up In Churches, Mosques, Houses Of Worship, Etc
Zone 2 Call Only Mix Only Call/Mix 24VDC In Mic/Line Mic/Line 100/70V/ 8Ω0 100/70 V 0 100/70 V 0 100/70 V 0 100/70 V 0 Chime Warning This apparatus must be earthed figure 3.4: Presentation set-up Bosch Security Systems | 2003-11 | 9922 141 81681en... - Page 15 100/70V/ 8Ω0 100/70 V 0 100/70 V 0 100/70 V 0 100/70 V 0 Chime Warning This apparatus must be earthed figure 3.5: Set-up in churches, mosques, houses of worship, etc. Bosch Security Systems | 2003-11 | 9922 141 81681en...
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Page 16: 3.1.4 Signal Level
+12 dBV Output level -12 dBV 0 dBV +12 dBV table 3.2: Mic in High Input level -42 dBV -30 dBV -18 dBV Output level 0 dBV 0 dBV 0 dBV Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 17: Setting The Options Switches
The 'Bass lift' option is provided to correct this phenomenon. Bosch Security Systems | 2003-11 | 9922 141 81681en... - Page 18 Fast filter mode set-up Presentation Speech mode Dual input voice Any position Fast filter mode set-up tracking Churches, houses Music mode Dual input voice Any position Accurate filter mode of worship set-up tracking Bosch Security Systems | 2003-11 | 9922 141 81681en...
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Page 19: Mains Connection
Use the supplied mains cord to connect the system to the mains supply. Note If necessary set the mains voltage selection switch (14) to the required voltage using a sharp object, e.g. a small screwdriver. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 20: Operation Of The Feedback Suppressor
Note Keep in mind that, contrary to traditional feedback reduction systems, the Plena Feedback Suppressor suppresses feedback before it occurs. Consequently, deactivating the suppression algorithm may lead to immediate feedback. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 21: Calibration
Improve poor and reverberating room acoustics, e.g. by covering highly reflective (tiled) walls and floors with curtains or carpets. • Never use loudspeakers above their rated power. Due to power compression of the loudspeakers, the feedback margin is reduced. Try to ensure enough headroom. Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 22: Technical Data
Loopthrough of pin 4 and 5 of DIN (for microphones with priority switch) Line input 3, Line (Cinch, unbalanced) Max. input level 18 / 6 / -6 dBV (Hi / Med / Lo level) Impedance 20 kOhm Bosch Security Systems | 2003-11 | 9922 141 81681en... -
Page 23: Outputs
EN 55103-2 Dimensions 56 x 430 x 270 mm (with feet, without mounting brackets) 19”, 1U high (with mounting brackets, without feet) Weight approx. 3 kg 19” mounting brackets included Bosch Security Systems | 2003-11 | 9922 141 81681en...