Text preview for : sc21mancommunity.pdf part of comunity sc21 dsp (cross-over)
Back to : sc21mancommunity.pdf | Home
SYSTEM CONTROLLER
S C 21
O W N E R 'S M A N U A L
1
REFERENCE TO EC STATEMENT OF CONFORMITY
This document confirms that the range of products of Community Professional Loudspeakers bearing the CE label meet all the requirements in the EMC directive 89/336/EEC laid down by the Member States Councel for adjustment of legal requirements, furthermore the products comply to the rules and regulations referring to the electromagnetic compatibility of devices from 30 August 1995. The Community Professional Loudspeakers' products bearing the CE label comply with the following harmonised or national standards: · · · DIN EN 55013:08-1991 DIN EN 55020:05-1995 DIN EN 50082-1:03-1993
The authorized declaration and compatibility certification lie with the manufacturer and can be viewed upon request. The responsible manufacturer is the company: Community Light & Sound, Inc. 333 East 5th Street Chester, PA 19013 USA Tel: 610 876-3400 Fax: 610 874-0190
Chester, PA USA January 1996
2
TABLE OF CONTENTS - SC21 OWNER'S MANUAL
CONTENTS PAGE
Introduction and Safety Information ........................................................................................ 4 Introduction to Electronically Controlled Loudspeaker Systems ................................................ 5 Unpacking and Inspection ....................................................................................................... 6 Quick Start-Up ........................................................................................................................ 7 Front and Rear Panel Views ..................................................................................................... 8 Indicators, Controls and Connectors ...................................................................................9-10 General Description .............................................................................................................. 11 Circuit Description ........................................................................................................... 11-12 Audio Signal Chain Block Diagram: Fig. 2 .............................................................................. 13 Protection Signal Chain Block Diagram: Fig 3 ......................................................................... 14 Setup and Operation ........................................................................................................ 15-23 Internal Jumper Setting Diagrams: Figs 4,5,6 .......................................................................... 16 Connection Diagram: Fig 7 .................................................................................................... 18 RS/VBS Series - Equalization and Protection Settings: Table 1 ................................................. 21 SLS/SBS Series - Equalization and Protection Settings: Table 2 ................................................ 22 Operating Considerations ................................................................................................. 24-26 Special Operating Considerations .......................................................................................... 27 Technical Specifications ......................................................................................................... 28 In Case of Difficulty ............................................................................................................... 29 Warranty Information ....................................................................................................... 30-31 Bill of Materials................................................................................................................. 32-33 Index..................................................................................................................................... 34 DIAGRAMS and TABLES Fig 1: ...................... Fig 2: ...................... Fig 3: ...................... Fig 4: ...................... Fig 5: ...................... Fig 6: ...................... Fig 7: ...................... Table 1: .................. Table 2: .................. PAGE
Front and Rear Panel Views ..................................................................... 8 Audio Signal Chain Block Diagram ........................................................ 13 Protection Signal Chain Block Diagram .................................................. 14 Internal Jumper Setting - Sub Low High Pass .......................................... 16 Internal Jumper Setting - Full Range High Pass........................................ 16 Internal Jumper Setting - Protection Limiter threshold ............................ 16 Connection Diagram ............................................................................. 18 RS/VBS Series - Equalization and Protection Settings .............................. 21 SLS/SBS Series - Equalization and Protection Settings ............................. 22
3
MANUAL COMMUNITY SC21 SYSTEM CONTROLLER OWNER'S MANUAL
SC21 SYSTEM CONTROLLER
This manual contains information for the proper setup and operation of the Community SC21 (120 VAC) and SC21E (220-240 VAC) System Controllers for Community RS/VBS and SolutionsTM SLS/SBS loudspeaker systems. While every attempt has been made to ensure this information is correct and up to date, Community continuously incorporates worthwhile improvements to each product that may include changes and/or modifications not contained in this manual. Except for the mains input voltage, the SC21 and SC21E are identical in all other respects.
IMPORTANT SAFETY INFORMATION
The terms "Caution", "Warning", and "Danger" are used throughout this manual to alert the reader to important safety considerations. If you have any questions about any aspect of these cautions, contact your local dealer, your country's Community distributor, or Community.
CAUTION: describes an equipment operating condition or user action that may expose the equipment
or user to potential damage or danger.
WARNING: describes an operating condition or user action that will cause damage to the equipment or
injure the user.
ANGER: DANGER: describes an operating condition or user action that will immediately damage the equipment
or be extremely dangerous or possibly life-threatening to the user.
ELECTRICAL PRECAUTIONS CAUTION:
To prevent electric shock, disconnect the unit from the AC mains before opening the unit. Refer service to qualified service personnel only.
WARNING:
In order to reduce the possibility of electric shock or damage to this equipment, do not expose this device to moisture or rain.
4
ELECTRONICALL ALLY LOUDSPEAKER INTRODUCTION TO ELECTRONIC ALLY CONTROLLED LOUDSPEAKER SYSTEMS
In simple terms, an electronically controlled loudspeaker system consists of: 1. The loudspeaker components and cabinet 2. An associated electronic device that modifies the source signal in some fashion 3. The power amplifier used to drive the loudspeaker system Properly done, an electronically controlled loudspeaker system, in combination with a power amplifier of appropriate rating, will provide enhanced performance over a non-electronically-controlled loudspeaker cabinet in one or more of the following ways: · Improved frequency response · Maximized power-handling · Higher acoustic output · Lowered distortion · Protection of the loudspeaker system components All loudspeaker systems have frequency response limitations. Flat response from a system is typically attained by lowering the output in certain portions of the system's passband to match the lower output of the system at other frequencies within its passband. As a consequence the overall sensitivity of the system is lowered. Rather than modifying the system, the input signal may be modified to compensate for those areas within the system's passband where it would normally have lower output. In this way flat frequency response can be achieved while maintaining the sensitivity of the system. All loudspeaker systems have power handling limits beyond which they can be damaged. An electronic model may be developed with characteristics that help prevent exceeding the mechanical and thermal limits of the system's components. For example, suppose it can be determined with accuracy that an input signal of 20 volts to the voice coil of a driver will cause the voice coil former to strike the rear of the magnet assembly. If the electronic model for this speaker is designed into a controller so that the input signal to the driver's voice coil may never exceed 19.5 volts, then it should never be capable of bottoming out. Some other important operational characteristics may also be addressed by a controller. One is compensating for the natural characteristics of the human hearing, which does not "hear" low frequencies and high frequencies as well at lower sound pressure levels. The controller can increase the output of these frequencies at low volume (in essence, a sophisticated loudness control). The controller can then reduce the output at these frequencies as the signal level is increased. Another characteristic is providing an electronic crossover function; while yet another might be to correct for phase anomalies in the loudspeaker system. A properly-designed electronic controller will inaudibly provide the necessary equalization, compression, and limiting required for the associated loudspeaker system when the loudspeaker system is operated within its rated power constraints. Even when this boundary is exceeded, it will apply control in a manner that is audibly acceptable.
5
UNPACKING UNPACKING AND INSPECTION
The Community SC21 is inherently rugged and is carefully packed in a well-designed carton, but it is a good idea to carefully inspect the unit after it has been removed from the packaging. Sometimes there may be hidden damage due to some unfortunate incident in shipment. Please note that once the shipment has left Community (or the dealer), the responsibility for damage is borne by the freight company. This means that if there is damage, you must file a claim with the freight company. Each freight company has its own set of regulations that must be followed and forms that must be filled out. Therefore the freight company must be contacted as soon as a shipping damage problem is discovered. Save the carton and packing material because many times shipping claims will be considered invalid if these are thrown away. The Community dealer and the factory will try to help in any way possible. Remember, though, it is up to the person receiving the shipment to file a claim. It is always a good idea to keep the carton and packing material in case the unit must be shipped back to your dealer or country distributor. The shipping carton contains the following items: SC21 Controller Unit External Power Transformer Unit Owner's Manual
6
7
8
1) INDICA INDIC ATORS, CONTROLS AND CONNECTORS (See Figure 1
FRONT PANEL INDICATORS 1
IN: SIGNAL PRESENCE SUB & FULL RANGE: SIGNAL PROTECT POWER
DESCRIPTION
Green LED Indicates an input signal > -27 dBu. Two-color LED's Green = Indicates a sense signal > 8 dBu. Flashing red = Indicates the output is in protect mode. Steady red = Indicates the output is in full protection mode 1. Green LED Indicates that the SC21 is on. Note: There is no power on/off switch.
2 3 4
REAR PANEL CONTROLS 2 5
PROTECTION Three position switch for selecting the level of loudspeaker protection. Sets the limiting thresholds used for the protect mode. MIN =Highest threshold (minimum protection) MED =Moderate threshold (normal protection: 2.5 dB lower than MIN) MAX =Lowest threshold (maximum protection: 5 dB lower than MIN) Four position slide switch for selecting the corner frequency of the high-pass filter for the FULL RANGE output. Set this switch as indicated in Tables 1 and 2 for the loudspeaker system being used with the SC21. Corner Frequencies: 50 Hz, 70 Hz, 95 Hz, 130 Hz. Two position slide switch for selecting the corner frequency of the high-pass filter for the SUB LOW output. Set this switch as indicated in Tables 1 and 2 for the loudspeaker system being used with the SC21. Corner Frequencies: 38 Hz, 52 Hz. Potentiometer (marked 1 to 10) for adjusting the gain of the SUB LOW output. The gain is variable from 0 dB to +10 dB and is used to balance the subwoofer output to the output of the full-range loudspeaker.
6
F.R. HIGH PASS FREQ
7
SUB HIGH PASS FREQ
8
SUB GAIN
REAR PANEL CONNECTORS 9 10
OUTPUTS: FULL RANGE & SUB LOW
Signal outputs: 3-Pin XLR-type male connectors. Pin 1: Ground or shield Pin 2: Positive Pin 3: Negative Output impedance: < 20 ohms balanced Maximum load: 600 ohms Nominal output level: +4 dBu Maximum output levels: +22 dBu balanced +16 dBu unbalanced Signal input: 3-pin XLR-type female connector. Pin 1: Ground or shield Pin 2: Positive Pin 3: Negative Input impedance: 40k ohms, balanced 20k ohms, unbalanced Nominal input level: +4 dBu Maximum input level: +16 dBu Receptacle for the external mains transformer output cable.
11
IN
12
24VAC
9
REAR PANEL SCREW TERMINALS Connected internally to the SC21 chassis and allows an external connection 13 GROUND
to the SC21's chassis. SUB ADJUST
14
This terminal must be connected to the GROUND (terminal 1) when using 8 ohm Community subwoofers. Sense input for connection to the output of an amplifier channel fed from the SC21 FULL RANGE output. This two-terminal IntelliSenseTM input is compatible with all types of power amplifiers including mono-bridged amplifiers. Input impedance: 300k ohms, balanced, polarity insensitive. Sense input for connection to the output of an amplifier channel fed from the SC21 SUB LOW output. This two-terminal IntelliSenseTM input is compatible with all types of power amplifiers, including mono-bridged amplifiers. Input impedance: 300k ohms, balanced, polarity insensitive.
15
F.R.
16
SUB
Footnotes for Indicators, Controls and Connectors 1 Full protection mode is where the dynamic EQ and compression/limiting circuits are automatically set to operate at their maximum protection levels. When either or both the two-color LED's is steady red, it indicates one of the following: 1. A sense signal is not present or is not 10 dB more than its associated output signal. Check and correct the connections the sense inputs. Note: A sense input fault causing full protection in the FULL RANGE output will also cause the SUB output to go into full protection. However, a sense input fault causing full protection in the SUB output will not affect the FULL RANGE output. 2. The power level from the amplifier(s) is excessive. The input signal to the SC21 must be reduced to correct this condition. The rear panel controls, three slide switches and a gain control, are located behind a security cover on the rear panel. Fastened with captive screws, the cover protects these controls from tampering.
CAUTION:
2
Internal Jumpers
A jumper block on the PC board inside the SC21 can be programmed to individually disable or enable the rear panel control switches so as to fix their settings. If a control is disabled, a fixed setting must be used instead. Disabling the rear panel controls and fixing specific settings is useful when the SC21 is used in permanent installations or in rental systems where tampering with the control setting might allow damage to the loudspeaker system. Refer to Figures 4, 5 & 6 and Internal Jumpers in the Setup And Operation section to pre-program the SC21.
10
GENERAL DESCRIPTION
The SC21 System Controller is a single-channel device that provides the electronic crossover, filtering, equalization and protection functions for Community RS/SLS series full-range and VBS/SBS series subwoofer loudspeaker systems. The SC21 uses IntelliSense circuitry to monitor the output of the associated power amplifiers and provide appropriate control to the audio signal to prevent overdrive and damage to the loudspeaker systems. The front panel has illuminated indicators to inform the operator about the SC21's status, including power on, signal presence for both input and sense signals, and protect mode operation. Critical set-up controls are located behind a security cover on the rear of the unit. These controls include filter selections, protection threshold, and gain level for the subwoofer output. Settings are selected based upon the model of the loudspeaker system to be used. The removable cover is attached by captive screws, to help prevent tampering or accidental adjustment of these controls. An external power supply transformer is provided with and connects to the unit via a rear panel receptacle. The internal, regulated +/- 10V DC supply is equipped with fuseless over-voltage and over-current protection. The SC21.1 is an updated version of the SC21. It has a sense circuit that gates off the dynamically controlled HF Equalization when no signal is present. This modification was implemented to reduce high frequency background noise under no signal conditions.
CIRCUIT DESCRIPTION Audio Signal Chain (See Figure 2)
An input signal is applied to the SC21's electronically balanced input stage via a 3-pin female XLR-type connector. The input signal then goes to a voltage-controlled amplifier (VCA). This VCA is used as the gain reduction stage controlled by the compressor/limiter for overall overdrive protection. This circuit also functions as a balanced to single-ended signal conversion stage. The signal is then routed to a 27 Hz 2nd-order high-pass filter (HPF) with a Q of 0.9, followed by a second 2nd-order HPF. The second HPF functions as a voltage-controlled filter (VCF) with control voltage for gain and Q provided by the SUB limiter circuit. The filter frequency may be set to 38 Hz or 52 Hz by adjustment of the SUB HIGH PASS FREQ switch on the rear panel. A gain stage follows that provides an adjustment range of 10 dB via the SUB GAIN control potentiometer. The signal is then fed to a 130 Hz, 4th-order Linkwitz-Riley, low-pass filter (LPF). At the end of the signal chain is a line-driver circuit with 6 dB gain that provides the electronically balanced output, wired to a 3-pin male XLR-type connector. The FULL RANGE signal is derived from the output of the 27 Hz 2nd-order HPF. This signal connects to a 34 Hz 2nd-order Butterworth HPF, followed by a second 2nd order HPF. The second HPF functions as a VCF, with control voltage for gain and Q provided by the LF limiter circuit. The filter frequency may be set to 70 Hz, 95 Hz or 135 Hz by adjustment of the F.R. HIGH PASS FREQ switch on the rear panel. The signal then flows to a 2 dB/octave, 1st-order shelving filter that provides a smooth attenuation of the signal up to the higher frequencies of the lower mid band. The next stage is a 1st-order band pass filter (BPF) with a rising slope of 3 dB/Octave and a falling slope of 6 dB/Octave. This filter is controlled by the HF limiter. At the end of the signal chain is a line-driver circuit with 6 dB gain that provides the electronically balanced output, wired to a 3-pin male XLR-type connector. The integrated circuits used in the audio chain are NE5532 op-amps, with additional low noise, low distortion, high dynamic range SSM-series components from PMI/Analog Devices. The balanced output line-driver IC's (SSM2142) provide the properties of a transformer-balanced output. The output signal
11
level is absolutely the same when driving either balanced or unbalanced devices. The only difference when an unbalanced configuration is used is that maximum output level capability is 6 dB lower than when a balanced configuration is used. Capacitors up to 4700 pF are 2.5% tolerance polypropylene; capacitors from 10000 pF to 2.2µF are 5% tolerance metal-polyester. 1% tolerance metal film resistors are used. These components ensure high precision filter characteristics.
Protection Signal Chain (See Figure 3)
The protection section of the SC21 provides dynamic equalization and loudspeaker protection to prevent damage to the speaker system components due to excessive power from the amplifiers. Additionally, a compressor/limiter avoids system overdrive. A front panel LED indicates the status of the control section. A three-position switch on the rear panel permits the setting of all control thresholds for minimum, medium (normal) or maximum protection. The SC21's two sense inputs, F.R. (FULL RANGE) and SUB (SUB LOW), accept signals from the power amplifiers outputs via the sense input terminals located on the rear panel. The sense signals provide raw signal information that the SC21 processes to determine if potentially damaging signal levels are present at the output of the power amplifiers. There are four processing chains that provide control voltages for the SC21's dynamic equalization and compression/limiting. 1. SUB Limiter - Controls the VCF (Voltage Controlled Filter) for the SUB LOW output. 2. LF Limiter - Controls a VCF for low frequencies in the FULL RANGE output. A 190 Hz 1st-order LPF ensures that only lower frequencies will affect this chain. 3. HF Limiter - Controls a VCF for the high frequencies in the FULL RANGE output. A 2.26 kHz 1storder HPF ensures that only higher frequencies will affect this chain. 4. Compressor/Limiter - Controls the input VCA for overall overdrive protection. This VCA is situated at the input of the SC21 and therefore affects all outputs, thus keeping the balance between the subwoofer and full-range speakers during a limiting condition. A 160 Hz 1st-order HPF ensures that the lowest frequencies will not affect this chain. The sense inputs are high impedance (300k ohm), balanced, bridging circuits that do not affect the amplifier output in any way. Each sense circuit attenuates the output voltage returned from the power amplifier by 23.5 dB and converts it to a single-ended signal. When using 8 ohm Community subwoofers, the SUB ADJUST terminal is connected to GROUND to provide 6 dB more attenuation for the SUB LOW sense signal. A comparator circuit, that functions only at higher signal levels, will cause the SC21 to go into full protection mode if the signal level at that output is less than 10 dB above the signal at the associated sense input (16 dB for the SUB LOW when the SUB ADJUST terminal is used). This is done to protect the loudspeakers in the event there is a fault in the sense line. While a full protection condition on the FULL RANGE output will affect the SUB output, a full protection condition on the SUB output will not affect the FULL RANGE output. The sense signal is RMS rectified, processed with attack/release time-constants, and fed to a threshold level and compression ratio stage to form a compressor/peak limiter. A control voltage for filter Q and gain reduction is then generated. This voltage is summed with the comparator output (potential sense fault signal), fed to a VCF control circuit and then passed to the corresponding VCA device of the audio chain.
12
13
14
OPERATION SETUP AND OPERATION
The SC21 System Controller is a line-level electronic device used in conjunction with a power amplifier and loudspeaker system for dynamic signal equalization, signal compression/limiting, loudspeaker system transducer protection, and active crossover. Proper installation, setup and operation of the SC21 will help ensure exceptional sonic performance of the system, while reducing the possibility of transducer damage and distortion.
Internal Jumpers
Prior to installing the unit you should determine if you want to disable any or all of the rear panel switches and program the SC21 with fixed settings. This requires removal of the integral top cover/front panel that is not possible once the unit is mounted in an equipment rack. Once the unit is open, a jumper block can be accessed for this programming. The unit is shipped programmed so that all rear panel switches are enabled and therefore no settings are fixed. To program the jumper block, remove the integral top cover/front panel. This is done by removing a screw on each side of the SC21 and sliding the top cover/front panel forward about 1/2" (10 mm). Then lift the cover at the front panel and carefully hinge it back. There is a grounding wire attached to this cover that connects to the bottom chassis at the rear. Do not remove this wire. Once the unit is open, the jumper block will be seen towards the middle rear, just forward of the rear panel switches. Program the jumper block according to Figures 4, 5, and 6 for the SUB LOW, FULL RANGE and PROTECTION functions. This is done using the computer type push-on jumpers provided. Refer to Tables 1 and 2 for the recommended settings for the loudspeaker being used with the SC21. To close the cover, reverse the removal procedure, ensuring that the captive tab on the rear underside of the cover is "captured" by the lip on the rear panel, and ensuring that the LED indicators properly seat in their holes in the front panel.
CAUTION:
The SC21 will not function properly unless EITHER a hardwired setting or a switch enabled setting is programmed on the jumper block for each of the functions: SUB LOW, FULL RANGE and PROTECTION.
15
16
Location In The Audio System
The SC21 should be the last device in the signal chain before the power amplifier, with its outputs going directly to the inputs of the associated power amplifier(s). In systems that have the source processing equipment (mixer, equalizers, signal delays, etc.) located at a distance from the power amplifiers, the SC21 may be located either with this equipment, or with the power amplifiers. Since the SC21 front panel has several LED indicators, a system operator should be able to view these indicators for important information about the operation of the system. However, because of the requirement that amplifier outputs must be returned to the SC21, it may be more convenient to locate it near the power amplifiers. If system is properly gain-structured, signal level indications at the source equipment location should give the operator adequate information regarding system signal levels at the SC21.
Mounting
The SC21 is a 1U-high device, designed for mounting in a standard, 19" (482 mm) equipment rack. The front panel is designed to fully support the unit when properly mounted to the rack. Because some of the internal circuitry is unbalanced (single-ended), locate the unit away from strong AC magnetic fields, dimmers, SCR's or other interference producing equipment. See section on I NTERFERENCE - HUM AND NOISE for additional mounting considerations.
Operating Environment
The SC21 is designed to operate in environments with normal temperature and humidity. Abnormal conditions, including subjecting the SC21 to things like spilled drinks, rain, snow or hot sunlight, may very likely adversely modify its performance. As with any electronic device it is recommended that you mount the SC21 in a well-ventilated location.
Power Connections
Connect the output cable plug from the external 24 VAC transformer to the 24VAC receptacle on the rear panel of the SC21. After this connection is made, the output cable should be secured under the cable clamp located next to the receptacle. This will prevent its plug from being accidentally pulled out (or possibly vibrating out) of the receptacle. Connect the transformer input to the proper 110-120 VAC or 220-240 VAC power receptacle, depending on the transformer input rating. Note that once connected to a live power receptacle the SC21 will be powered on as there is no on/off switch.
WARNING:
The external transformer supplied with this unit is specifically designed for the SC21. Do not substitute another transformer. Doing so may damage the unit and will void the warranty.
ANGER: DANGER:
Check the AC power before connecting the SC21's transformer to the power receptacle. Use an AC circuit tester to verify that the receptacle's hot, neutral and ground wires are properly connected. If something is not correct, have a licensed electrician fix the problem.
17
Basic Connection Diagram
Figure 7 shows connections for the inputs and outputs of the SC21 for both balanced and unbalanced operation, the sense input connections, and the SUB ADJUST connection when used with the 8 ohm Community subwoofers.
18
Audio Signal Connections (See Figure 7)
Standard, twisted-pair, shielded audio cable with XLR-type connectors should be used for connecting the SC21 input to its source equipment and its outputs to the power amplifiers(s). Always use this type of cable whether the interconnections are balanced or unbalanced. Pay close attention to the output cable and connector wiring to ensure that proper signal polarity is maintained. Systems with incorrect polarity may experience reduced bass response or other less obvious but detrimental effects to the acoustical performance of the system. The SC21's input and outputs may be connected in either balanced or unbalanced modes. The mode is independent for each section meaning that the input may be balanced and the outputs unbalanced; one output may be balanced and the other unbalanced, etc. The mode is determined by the devices connected to the SC21 and the associated connector/cable wiring. If connected to a balanced device, the section will be balanced, assuming the wiring is as shown in Figure 7 "Balanced Connections". If connected to an unbalanced device, the section will be unbalanced. There are several advantages to balanced operation. Balanced lines help reject hum and noise that may be picked up in cables, particularly in long runs. The SC21 outputs have higher output voltage capability (more headroom) in the balanced mode. Most professional power amplifiers will accept balanced inputs and they should be used when available. Unbalanced interconnections should be wired as shown in Figure 7 "Unbalanced Connections", with pin 3 on SC21 always as the negative side of the signal. The shields are connected to the negative side of the signal path only at one end of the cable. This method of wiring correctly prevents the shield from conducting any audio signals. If unbalanced cable (single conductor plus shield) must be used, connect pin 3 to pin 1 in the XLR connector(s) plugged into SC21. See the section Interference - Hum And Noise for more information on connecting the SC21.
Sense Input Connections (See Figure 7)
The sense inputs must be properly connected or the SC21 will not function correctly meaning it will automatically go into a full protection mode at higher signal levels. This mode applies the maximum compression and limiting to the audio signal and cause the front panel indicators for the SUB LOW, FULL RANGE or both to be illuminated a steady red. Connect the sense input(s) on the SC21 to output of the associated amplifier(s). The sense inputs are polarity insensitive and are compatible with all types of power amplifiers, including mono-bridged amplifiers. Because only small amounts of current flow through the sense wiring, typically < 0.1 mA, #22 or #24 AWG twisted pair wire can be used. If the SC21 is located at a distance from the amplifier(s), use twisted-pair shielded audio cable for the connections. Connect the shield only to the amplifier chassis. Do not connect the other end of the shield to the SC21. If an SC21 output feeds multiple amplifiers, connect the sense line to only one amplifier output. Unless all amplifiers are set for the same voltage gain, it should be connected to the amplifier with the highest gain. This is because amplifiers with a gain higher than that of the monitored amplifier may overdrive and damage the loudspeakers connected to their outputs before the IntelliSenseTM protection circuits are activated. Conversely, loudspeakers connected to amplifiers with a gain lower than that of the monitored amplifier will be somewhat overprotected. This will do no harm except to reduce their maximum output capability proportionally.
19
Full Range Only Operation
If the SC21 is to be used only for a full-range loudspeaker, the control settings should be set as in Tables 1 and 2 for the particular loudspeaker. However, because there will be no sense input for the SUB LOW IntelliSenseTM circuitry, the SC21 will detect a sense fault at higher signal levels and cause the front panel SUB LOW indicator to be illuminated a steady red. While this will not affect the function of the SC21, it may be disturbing for the operator. To prevent this condition simply connect the sense return line from the full range amplifier in parallel to both the FULL RANGE and SUB LOW sense inputs. The front panel SUB LOW indicator will then basically track the operation of the FULL RANGE front panel indicator.
Subwoofer Only Operation
If the SC21 is to be used only for a subwoofer, the control settings should be set as in Tables 1 and 2 for the particular subwoofer. However, because of the operation of the IntelliSenseTM circuitry, the sense return line from the subwoofer amplifier must be connected in parallel to both the FULL RANGE and SUB LOW sense inputs. If this is not done, the FULL RANGE sense circuit will detect a sense fault at higher signal levels and automatically apply full protection to the FULL RANGE output. This will also cause a full protection condition on the SUB LOW output. Connecting the subwoofer sense lines to both sense inputs avoids this situation.
Grounding
Even though the SC21 uses a low voltage (24 VAC) external transformer, grounding is still a safety consideration. Ensure that a low impedance electrical connection is made from the SC21's chassis to the electrical system's safety ground. The chassis GROUND screw on the rear panel of the SC21 is provided for this purpose.
WARNING:
Failure to establish a proper ground connection to the electrical system safety ground may create a personnel safety hazard. Do not use the shield of the audio wiring as a safety ground.
Interference - Hum And Noise
The circuitry of the SC21 is quite resistant, but not entirely immune, to hum pick-up from strong magnetic fields radiated by power transformers in nearby equipment. Specifically, the power transformers in compact, high-powered amplifiers can produce significant stray magnetic fields that can induce hum in equipment mounted near to them. To avoid hum pick-up it may be necessary to locate the SC21 one or two rack spaces away from such amplifiers. The SC21 has high quality electronically balanced input and output circuitry that, when connected to other balanced equipment, can provide excellent interference rejection under most conditions. If connected to unbalanced equipment, ground loops will be formed and associated hums and buzzes may result. Likewise it is sometimes impossible avoid a situation where cables are routed next to interferenceprone signal sources such as AC power cables or other sources of high-level electro-magnetic or radiofrequency interference. Also, long runs between electronically balanced equipment may be prone to interference. This is because voltage differences between the ground reference for each unit may be too high to be effectively rejected by the limited CMRR range of electronically balanced circuits.
20
In the above cases, use of external, audio line-level transformers may be required. The input transformer to the SC21 should have a 1:1 turns ratio and be of the bridging type, 15k:15k. Output transformers should have a 1:1 turns ratio with an input and output impedance that matches or is somewhat less than the input impedance of the amplifier to which the SC21 is connected. If more than one amplifier is fed from an SC21 output, calculate and match the combined input impedance of the amplifiers. In no case should the SC21 feed a load below 600 ohms. Other turn ratios may be used but the voltage gains or loses must be accounted for in the system's gain structure. Always use quality transformers from manufacturers such as Jensen or Reichenbach. Lesser quality transformers may seriously degrade the audio quality of the system.
Setting the Rear Panel Controls
After installing the SC21, remove the rear security cover by undoing its captive screws and adjust the controls under the cover as follows. Sub Gain Control This potentiometer (marked 1 to 10) is used to adjust the gain of the SUB LOW output. The gain is variable from 0 dB to +10 dB and is used to balance the acoustic levels between the subwoofer and fullrange loudspeaker. The correct adjustment must be determined by listening tests because a subwoofer's bass response can vary significantly depending on its placement in a room. Equalization and Protection Settings Refer to Tables 1 and 2 for proper set up of the PROTECTION, F.R. HIGH PASS FREQ, and SUB HIGH PASS FREQ controls.
TO MODERATE LOW TO MODERATE POWER
FULL RANGE SYSTEM SUBWOOFER SUB POLARITY
1
2
HIGH POWER
PROTECTION PROTECTION FULL RANGE PASS HIGH PASS
3
PROTECTION PROTECTION FULL RANGE PASS HIGH PASS
SUB HIGH PASS PASS
SUB HIGH PASS PASS
RS880 RS880 RS880 RS660 RS660 RS660 RS220 RS220 RS220 RSJr RSJr RSJr RSFB(Biamp) RSFB(Biamp) RSFB(Passive)4 RSFB(Passive) RSFB(Passive)
VBS415 VBS212 None VBS415 5 VBS212 None -- VBS415 5 VBS212/112 None -- VBS415 5 VBS212/112 None -- No Add'l Sub VBS212/112 VBS415 5 VBS212/112 No Add'l Sub
5
Reverse Reverse -- Normal Reverse MED Normal Normal MED Normal Normal MAX Normal Normal Reverse Normal --
MIN MIN MIN MIN MIN 70 Hz MED MED 130 Hz MAX MAX 130 Hz MED MED MED MED MED
70 Hz 70 Hz 70 Hz-- 95 Hz 95 Hz -- 130 Hz 130 Hz -- 130 Hz 130 Hz -- 130 Hz 130 Hz 70 Hz 70 Hz 50 Hz
38 Hz 52 Hz MED 38 Hz 52 Hz MED 38 Hz 52 Hz MAX 38 Hz 52 Hz MAX 52 Hz 52 Hz 38 Hz 52 Hz --
MED MED 70 Hz MED MED 95 Hz MAX MAX 130 Hz MAX MAX 130 Hz MAX MAX MAX MAX MAX
70 Hz 70 Hz -- 95 Hz 95 Hz -- 130 Hz 130 Hz -- 130 Hz 130 Hz -- 130 Hz 130 Hz 70 Hz 70 Hz 50 Hz
38 Hz 52 Hz 38 Hz 52 Hz 38 Hz 52 Hz 38 Hz 52 Hz 52 Hz 52 Hz 38 Hz 52 Hz --
TABLE 1: Recommended Equalization And Protection Settings - RS/VBS Series
21
TO MODERATE LOW TO MODERATE POWER
FULL RANGE SYSTEM SUBWOOFER SUB POLARITY
1
2
HIGH POWER
PROTECTION PROTECTION FULL RANGE PASS HIGH PASS
3
PROTECTION PRO TECTION FULL RANGE PASS HIGH PASS
SUB HIGH PASS PASS
SUB HIGH PASS PASS
SLS980 SLS980 SLS980 SLS960 SLS960 SLS960 SLS920 SLS920 SLS920 SLS915 SLS915 SLS915 SLS918(Biamp) SLS918(Biamp) SLS918(Passive)4 SLS918(Passive) SLS918(Passive)
SBS45/25 SBS22 None SBS45/25 5 SBS22 None SBS45/25 5 SBS22/12 None SBS45/25 5 SBS22/12 None No Add'l Sub SBS22/12 SBS45/25 5 SBS22/12 No Add'l Sub
5
Reverse Reverse -- Normal Reverse -- Normal Normal -- Normal Normal -- Normal Normal Reverse Normal --
MIN MIN MIN MIN MIN MED MED MED MED MAX MAX MAX MED MED MED MED MED
70 Hz 70 Hz 70 Hz 95 Hz 95 Hz 70 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 70 Hz 70 Hz 50 Hz
38 Hz 52 Hz -- 38 Hz 52 Hz -- 38 Hz 52 Hz -- 38 Hz 52 Hz -- 52 Hz 52 Hz 38 Hz 52 Hz --
MED MED MED MED MED MED MAX MAX MAX MAX MAX MAX MAX MAX MAX MAX MAX
70 Hz 70 Hz 70 Hz 95 Hz 95 Hz 95 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 130 Hz 70 Hz 70 Hz 50 Hz
38 Hz 52 Hz -- 38 Hz 52 Hz -- 38 Hz 52 Hz -- 38 Hz 52 Hz -- 52 Hz 52 Hz 38 Hz 52 Hz --
TABLE 2: Recommended Equalization And Protection Settings - SLS/SBS Series Footnotes for Tables 1 and 2 This is the optimum subwoofer polarity when the full-range cabinet is in close proximity to the subwoofer. If the full-range cabinet and subwoofer are separated by more than a few feet, optimum polarity should be determined by listening tests. Polarity is changed by reversing the connections to pins 2 and 3 on the XLR connected to the SUB LOW output. 2 Low-to-moderate power levels are indicated by the SUB and FULL RANGE LED's on the SC21's front panel occasionally flashing red with the protection level set as indicated. 3 High power levels are indicated by the SUB and FULL RANGE LED's on the SC21's front panel flashing red more than 25% of the time with the protection level set as indicated. 4 The RSFB or SLS918 can only be used with the VBS415 or SBS45 in passive mode. In biamplified mode the 38 Hz high pass signal for the SUB LOW output could damage the 12" driver in the RSFB or SLS918. 5 Connect the SUB ADJUST (terminal 2) to GROUND (terminal 1) when using Community 8 ohm subwoofers. See section on Use Of SC21 With 8 Ohm Community Subwoofers for further information.
1
22
Indicator Lights (See Figure 1)
In Signal Presence When an input signal of greater than -27 dBu is applied to the input stage of the unit, the green LED on the front panel labeled IN - SIGNAL PRESENCE is illuminated green. Sub & Full Range Signal Protect The IntelliSenseTM circuits of the SC21 include two 2-color LED indicators on the front panel: one for the FULL RANGE section and one for the SUB LOW section. They function as both signal presence and protect indicators. The LED's are illuminated green when there is a signal level of 8 dBu or greater present on the sense inputs. The LED's turn red and blink on and off when the sense voltage input is sufficient to activate the loudspeaker protection circuits of the SC21. Each indicator provides valuable information about system operation as follows: 1. Indicator off: Normal operation but indicates the signal level is below 8 dBu (2.5V) from the associated power amplifier. 2. Blinking or steady green: Normal operation. 3. Blinking red: As system power levels approach maximum, the LED will turn from green to red and blink on and off. This indicates that the compression/limiting circuits are activated. It is normal during high level operation for this to occur. As power is increased further it will blink more often. If an indicator is blinking red more than 50% of the time, reduce the signal level to the loudspeaker.
CAUTION:
If either protection LED is blinking red constantly (over 50% of the time), the loudspeakers are probably being overpowered. The signal level should be reduced to avoid excessive distortion and possible transducer damage in the loudspeaker system. 4. Steady red condition: Indicates excessive power to the loudspeaker or indicates a fault in the sense wiring, perhaps due to a broken cable or an improper termination at either the amplifier or at the SC21. It may also indicate that the amplifier connected to the SC21 has not been turned on or that it is in a protection or failure mode.
CAUTION:
Any fault in the sense circuit may cause serious damage to the speaker system. If the LED's are steady red, the cause should be immediately investigated and the fault corrected.
Power When this front panel LED is illuminated green it indicates that the SC21 is powered on. This LED is powered from the internal minus 10 VDC supply.
23
OPERATING CONSIDERATIONS OPERATING CONSIDERATIONS Loudspeaker Protection
The dynamic equalization and compression/limiting circuits of the SC21 have filter slopes and time constants chosen to make the operation as unobtrusive as possible yet still provide a high degree of protection for the loudspeaker components. However, the SC21 cannot provide absolute protection against speaker damage under all operating conditions. It is important that reasonable care be taken in the setup and operation of the loudspeaker systems to protect them against damage due to system overload.
External Equalization
Great care must be taken when applying external equalization to Community loudspeaker systems. The SC21's dynamic equalization circuits reduce the amount of signal at the low and high frequency ends of their operating range at high power levels. If external equalization is used to boost these frequencies, already attenuated by the dynamic compression circuits, the result may defeat the SC21's protection function, possibly resulting in loudspeaker damage. If additional equalization is used, it should only be used moderately to adjust the response of the system or for equalizing against feedback.
Using With Other Loudspeakers
The SC21 incorporates frequency-dividing crossover circuits and associated outputs to drive power amplifiers for both the full-range and subwoofer systems. The crossover frequencies, slopes and dynamic control levels must be closely matched to specific speaker systems. For this reason use only the loudspeakers specified in Tables 1 and 2.
IntelliSenseTM Operation
The SC21 employs IntelliSenseTM circuitry to monitor power amplifier output voltage and frequency content and to automatically adjust equalization based on the monitored information. This dynamic control of equalization contributes significantly to the loudspeaker's capabilities at high sound pressures with both excellent sound quality and reliability. The SC21 will not function properly unless the sense inputs are correctly connected to the power amplifier outputs.
Compression/Limiting
The IntelliSenseTM circuitry also provides a full bandwidth compression/limiting function. The functions for compression (dynamic range reduction) and limiting (to maximum output signal level) are controlled by monitoring the power amplifier output similarly to the dynamic equalization function. However, the compression and limiting functions are full bandwidth, take effect only at higher output voltages and are primarily protective in nature. As the monitored amplifier approaches the loudspeaker's maximum acceptable voltage levels, the IntelliSenseTM circuitry first reduces gain in specific frequency ranges that are nearing excessive levels (dynamic equalization). If the amplifier output voltage continues rising, the compression and limiting functions are activated and the full bandwidth gain reduction is employed.
24
Outboard Compressors/Limiters
An additional, outboard compressor/limiter may also prove to be useful, particularly in systems that are used for rental or are otherwise likely to be operated by persons of limited technical knowledge. Community loudspeaker systems are well protected by the IntelliSenseTM circuits in the SC21 and the PowerSenseÔ circuits in their crossovers, but they are not immune from damage. They can be damaged by unskilled or abusive operation. A "hard" limiter with tamper-proof settings can be good extra insurance against system damage due to overpowering. If the limiter ahead of the SC21 is adjusted to a high or infinite ratio and its threshold set to a few dB beyond the initial activation of the IntelliSenseTM circuits most of the output capacity of the system will still be available but overpowering will be prevented.
Sense Line Fault Detection
During higher signal level operation, the sense input signals from the amplifiers are compared to the associated SC21 output signals. The signal from an amplifier must be 10 dB greater (16 dB for the SUB LOW if the SUB ADJUST terminal is used) than the associated output from the SC21. If not, that output will automatically go into full protection. In this sense fault mode there will be maximum compression and limiting of the signal with a substantial gain reduction and the associated protect LED will be illuminated a steady red. This is done to protect the loudspeaker in the event there is a fault in the sense lines from the amplifiers. This means that, for proper high level operation, the sense lines from the amplifier must be correctly connected and the amplifier voltage gain must be at least 10 dB (16 dB for the SUB LOW if the SUB ADJUST terminal is used), including the amplifier input level control setting. The comparator circuit does not function at low signal levels because there is little risk of loudspeaker damage due to a fault in a sense line.
Power Amplifiers
Power amplifiers used with the SC21 should be appropriate for professional use. This means that they should be able to deliver the rated power and signal bandwidth required by the loudspeaker system for extended periods of time, without distortion or signal/thermal overload. Amplifiers should have an output power rating (at the load impedance of the loudspeaker system) close to the rated program power capabilities of the loudspeaker system.
CAUTION:
Amplifiers that have significantly less output power capability than described above should be avoided. Because their maximum output voltages are lower, they can go into clipping without activating the SC21 protection circuitry. In this case the clipped signal from the power amplifier will very likely damage the transducers in the loudspeaker system. This type of damage is not covered under Community's Limited Warranty for loudspeakers.
Power Amplifier Gain
The SC21 will accommodate a wide range of power amplifiers and gain settings. Since the sense lines monitor power amplifier output voltages, the SC21 does not depend on an exact amount of amplifier gain for its operation. Very low amplifier voltage gain (below 18 dB, or 8:1) can cause the SC21's output to clip before the power amplifier does, causing unnecessary distortion or possible loudspeaker damage. High amplifier gain may lead to an undesirable level of system noise. As a general guideline, amplifier voltage gains of 20 to 33 dB (10:1 to 45:1) should give good performance.
25
Note that because of the design of the IntelliSenseTM circuit, a voltage gain of at least 10 dB (16 dB for the SUB LOW amplifier if the SUB ADJUST terminal is used) is necessary between the output of the SC21 and the output of the amplifier. The gain must include the amplifier's internal gain minus the amplifier's input attnuator setting. If this total is lower, the SC21 will automatically go into full protection mode at higher signal levels.
Multiple Amplifiers
Many system configurations use multiple power amplifiers to power multiple speaker systems. The SC21 has a low output impedance (<20 ohms) and can easily drive multiple amplifier input channels. Assuming identical input impedances, the total number of amplifiers the SC21 can drive can be calculated by dividing the input impedance of one amplifier by 600. If it is desired to drive more amplifiers than this calculation allows, use an external, unity gain, distribution amplifier or a second SC21.
Subwoofer Polarity
Optimum subwoofer polarity is affected by its relative physical position to the full-range loudspeakers. Subwoofer polarity is optimized for the best performance when the full-range cabinet is mounted directly above the subwoofer cabinet. If the subwoofer cabinet is mounted forward of, behind, or at some distance from the full-range cabinet, the polarity requirements may change, and optimum polarity may need to be determined by listening tests. Polarity is changed by reversing the pin 2 and 3 connections on the XLR connector that plugs into the SUB LOW output. Experimentation may also be required to determine proper subwoofer polarity in systems combining more than one type of Community full-range loudspeaker. See Tables 1 and 2 for detailed information.
Testing
When bench testing, the SC21 must be connected to an amplifier and the sense lines properly connected. If this is not done, the SC21 will detect a sense fault at higher signal levels. It will then enter full protection mode resulting in unexpected or inaccurate measurements.
26
OPERATING CONSIDERATIONS SPECIAL OPERATING CONSIDERATIONS
Use Of The SC21 With 8 Ohm Community Subwoofers Products affected: VBS415, SBS45 The IntelliSenseTM circuits of the SC21 are calibrated to provide protection for 4 ohm subwoofers. When using 8 ohm subwoofers with the SC21, connect the SUB ADJUST (terminal 2) to GROUND (terminal 1) on the rear panel screw terminal block as shown in Figure 7 This reduces the level of the sense signal 7. from the power amplifier driving the subwoofer. If this is not done, the IntelliSenseTM circuit will protect at an unnecessarily low power level. Use Of The SC21 With Biamplified Community Loudspeaker Systems Products affected: SLS Series (except SLS918) The SC21 is not designed to be used with these products when they are used in biamplified mode. Products affected: RSFB, SLS918 These loudspeakers are three-way systems that feature wide range response with extended low frequency capability. The low frequency driver in these systems is a true subwoofer. To take full advantage of their performance, these speaker systems are equipped with a switch to select either biamplified or passive operation. In the passive mode, their internal, three-way passive crossovers are switched on and the systems are driven by a single amplifier channel fed from the FULL RANGE output of the SC21. In the biamplified mode, the low frequency driver is switched to a separate input connector that is connected to a separate amplifier channel. This amplifier is driven by the SUB LOW output of the SC21. The midrange and high frequency sections of the system are connected to an amplifier channel driven by the FULL RANGE output of the SC21. Other than the option to bi-amplify the RSFB or SLS918 and drive the low frequency driver separately as a subwoofer, the connections, functions and operation of the SC21 are identical to that of the other electronically controlled Community loudspeaker systems. Using Additional Subwoofers With The RSFB And SLS918 In either passive or biamplified mode the subwoofer output of the SC21 may be used to operate additional subwoofers as well. See Tables 1 and 2 for more detailed information.
27
SC21 AND SC21E SYSTEM CONTROLLER TECHNIC AL SPECIFIC ATIONS TECHNICAL SPECIFICA
Note: 0 dBu = 0.775V
Gain (Level And Frequency Dependent) Distortion (THD + Noise) Full Range Output Sub Low Output Hum And Noise Full Range Output Sub Low Output Dynamic Range Full Range Output Sub Low Output Input Cmrr (Common Mode Rejection Ratio) Input Impedances Signal Sense Maximum Input Level (Reduced Depending On Control Settings) Output Impedance Maximum Output Load Maximum Output Level External Mains Transformer Input (SC21) Input (SC21E) Output Mechanical Construction And Finish Chassis and Front Panel/Top Cover Finish Labeling Dimensions (H = 1 Rack Unit) Net Weight Shipping Weight SC21 SC21E Supplied Accessories
Typically -3 dB at 1,000 Hz < 0.05% @ +14 dBu, 70-16,000 Hz < 0.02% @ +10 dBu, 40 Hz < -87 dBu, A-weighted < -97 dBu, A-weighted, 0 dB to +10 dB gain > 109 dB (balanced); > 103 dB (unbalanced) > 119 dB (balanced); > 113 dB (unbalanced) > 58 dB, 1,000 Hz > 46 dB @ 20,000 Hz 40k ohms (balanced); 20k ohms (unbalanced) 300k ohms (balanced, polarity insensitive) +16 dBu, 100-12,000 Hz < 20 ohms 600 ohms +22 dBm (balanced) +16 dBm (unbalanced) 120 VAC, 60 Hz, 7W maximum 220-240 VAC, 50-60 Hz, 6W maximum 24 VAC Sheet steel Black powder-coat paint White screen-printed, yellow accents 19 in. (482 mm) W 1.75 in. (44 mm) H 3.94 in. (100 mm) D 3.2 lbs (1.45 kg), excluding mains transformer 6.2 lbs (2.8 kg) 6.4 lbs (2.9 kg) External mains transformer Operating manual
28
Should you have a problem with the SC21, find the symptom and follow the associated "What To Do" instructions. Please refer to appropriate sections in this manual if you need more detailed information.
SYMPTOM SYMPTOM
Bass is weak. of the owner's manual. Bass is weak. Distortion from the loudspeaker at higher volume levels. FULL RANGE and/or SUB LOW indicators are blinking from green to red. FULL RANGE and/or SUB LOW indicators are steady red. FULL RANGE and/or SUB LOW indicators are steady red. FULL RANGE and/or SUB LOW indicators do not illuminate green or red. FULL RANGE or SUB LOW indicators go to steady red when testing the system FULL RANGE and/or SUB LOW indicators stay red longer than the audible sound peak. Hum from the loudspeaker. Noise from the loudspeaker (hum and/or buzzes) No Sound No sound
CASE DIFFICULTY IN C ASE OF DIFFICULTY
CAUSE PROBABLE CAUSE
Incorrect subwoofer polarity. SUB LOW gain is set too low. Too little amplifier power.
WHAT TO WHAT TO DO
Verify polarity is set as recommended in Tables 1 & 2 Increase the SUB LOW gain. If the power rating of the amplifier(s) being used is too low, it will clip before the SC21 can do its job. Either set the protection to MAX or use a more powerful amplifier. It is normal for these indicators to blink red when operating at high volume levels. Unless one or both indicators are steady red, the blinking indicates the SC21 is doing what it is supposed to do. Check the sense connections between the amplifier output(s) and the SC21. Amplifier gain must be at least 10 dB including the input attenuator setting. Subwoofer amplifier gain must be 16 dB if SUB ADJUST terminal is used. The output of the amplifier(s) must be at least 2 volts to illuminate the indicators The sense circuitry in the SC21 is dynamic and expects dynamic signals such as music and voice. Test tones, pink noise or similar signals may cause the SC21 to "overprotect". These LED's have a peak-hold circuit that keeps them illuminated red for a few milliseconds every time they light even if the signal peak is much shorter. This is to make them more visible. Physically move unit in relation to nearby electrical or electronic equipment. If hum changes, relocate to minimize the hum. Check the signal connections for the SC21 input and outputs. If connecting to unbalanced equipment you may need a signal isolation Check that amplifier and SC21 are turned on and that loudspeaker is on or loudspeaker properly connected to the amplifier. Check that SC21 has an audio signal (input signal presence should be green if input is over 35 mV) and that audio is going from the SC21 to the amplifier input. Make sure external transformer is the proper voltage for the AC mains Check that the external transformer is plugged into the AC mains and into the 24 VAC receptacle on the rear panel. Check that SUB LOW sense is also connected to the FULL RANGE sense. This prevents the FULL RANGE from detecting a sense fault. A sense fault FULL RANGE will cause the SUB LOW to go to full protection. If using an 8 ohm Community subwoofer, the SUB ADJUST terminal must be connected to the GROUND terminal. If not, the SC21 will "over protect" the subwoofer. This terminal is not used with 4 ohm subwoofers. Check the sense connections between the subwoofer amplifier output and the SC21. Amplifier gains must be at least 10 dB including the input attenuator setting. Subwoofer amplifier must be 16 dB if SUB ADJUST terminal is used. Check the sense connections between the amplifier output(s) and the SC21.
SC21 is protecting the loudspeaker(s) Sense line to the output of the amplifier(s) is not connected or is faulty. Amplifier gain is too low.
Amplifier output too low.
Sine wave or noise test signal is being used. The indicators have a peak-hold circuit. Unit may be in an AC magnetic field. Incorrect connections or ground loop. transformer. SC21 or amplifier is not disconnected No audio signal
POWER light is not illuminated. POWER light is not illuminated. SC21 is used only for a subwoofer and there is a sudden drop in bass volume as the signal is increased. SUB LOW is going into protect mode at too low a volume.
Incorrect external transformer. being used: 120V or 220-240V. No input voltage to the SC21. FULL RANGE output is going to sense fault mode. This affects the SUB LOW output. 8 ohm subwoofer is being used.
Sudden drop in bass volume as the signal is increased. Sudden drop in overall volume as the signal level is increased. Sudden drop in volume as the signal level is increased.
Sense line for the SUB LOW is not connected or is faulty Amplifier gain is too low. Sense line from the output of the amplifier(s) is not connected or is faulty.
29
INFORMATION WARRANTY INFORMATION AND SERVICE FOR THE USA
Transferable Warranty (Limited) - valid in the USA only The Community SC21 Electronic System Controller is warranted in the USA to be free from defects in materials and workmanship for a period of two years, as determined by one of the following two methods, whichever is longer: 1. Starting from the date of retail purchase, as noted on the sales receipt from an authorized Community dealer, OR 2. Starting from the date of manufacture, determined by the serial number, if the sales receipt is not available. This warranty applies to the product; therefore, the remainder of the warranty period will be automatically transferred to any subsequent owner. This warranty applies only to failure of a Community SC21 caused by defects in materials and workmanship during the stated warranty period. It does not apply to a unit that has been subjected to abuse, accident, modification, improper handling/installation, or repairs made without factory authorization or by anyone other than authorized Community Field Service Stations. This warranty is void if the serial number has been defaced, altered or removed. Products covered by this warranty will be repaired or replaced at the option of Community, without charge for materials or labor, provided all the terms of this warranty have been met. Obtaining Warranty Service Warranty service may be obtained from the factory, or from an authorized Field Service Station. To obtain factory or field warranty service for products purchased in the United States, return the product for inspection to the address below, freight prepaid, in the original packaging. If the original packaging is not available, call or write Community Warranty Service to obtain proper packaging materials or hand carry the product to the nearest Field Service Station. Factory Service Center: Community Warranty Service 333 East 5th Street Chester, PA. 19013-4511 Field Service Station: Call (610) 876-3400 for the nearest Authorized Field Service Station
For factory service, please call (610) 876-3400 for a Return Authorization (R/A) number before shipping. If the product is shipped, the following information must be included in the package: 1. Owner's complete name, daytime phone number, return street address and return authorization number. 2. The serial number of the product being returned and copy of the retail sales receipt, if possible. 3. A complete description of the problem(s) experienced, including a brief description of how the equipment is being used and with what brand, model and output power of amplifier.
30
Upon receipt, the service center will determine if the problem is covered under warranty. If covered under this warranty, the product will be repaired or replaced, at Community's option, and returned to the owner freight prepaid. If the problem is not covered under this warranty, the owner will be notified of the problem with an estimate of the repair costs. Consequential and Incidental Damages: Community shall not be liable for any consequential or incidental damages including, without limitation, injury to persons, property, or loss of use. Some states do not allow the exclusion or limitations of consequential or incidental damages, so the above limitations and exclusions may not apply. This Community warranty is not extended by the length of time which an owner is deprived of the use of the product. Repairs and replacement parts provided under the terms of this warranty shall carry only the remaining portion of the warranty. Community reserves the right to change the design of any product from time to time, without notice and with no obligation to make corresponding changes in products previously manufactured. While this warranty gives specific legal rights, there may also be other rights that vary from state to state. No action to enforce this warranty shall be permitted ninety days after expiration of the warranty period. THIS STATEMENT OF WARRANTY SUPERSEDES ANY PREVIOUS WARRANTY STATEMENTS FOR COMMUNITY ELECTRONIC PRODUCTS.
INFORMATION WARRANTY INFORMATION AND SERVICE FOR COUNTRIES OTHER THAN THE USA
To obtain specific warranty information and available service locations for countries other than the United States of America, contact the authorized Community Distributor for your specific country or region.
31
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56
Quantity 3 2 7 4 4 10 6 3 3 1 1 8 6 14 6 4 4 4 4 4 7 1 1 1 2 1 1 2 1 2 1 1 1 1 1 2 1 1 1 1 1 1 1 1 4 4 2 1 2 1 3 1 1 1 6 6
Schematic Reference
SC21 BILL OF MATERIALS MATERIALS
7 Feb 96 Revision: 1.5 Feb Part Number 0m47 MKS-2 100p CerCo 220p CerCo 0m47 Alu_E 6p8 CerCo 0m1 CerCo 0m33 MKS-2 0m1 MKS-2 0m22 MKS-2 2200p FKP-2 0m01 MKS-2 *opt 1% 100k 1% 20k 1% 10k 1% 5M6 1% 510k 1% 25k Trimpot PT6v 1M Trimpot PT6v 4k7 1% 1k 1% 33k 1% 18k 1% 36k 1% 12k 1% 5k6 1% 3k3 1% 8k2 1% 7k5 1% 56k 1% 3k 1% 150k 1% 5k Trimpot PT10Lh 1k3 1% 1k8 1% 2k7 1% 220R 1% 22k 1% 30k 1% 47k 1% 6k2 1% MFP2220 Slide-Switch MFP2420 Slide-Switch MFP2320 Slide-Switch NE5532N Amp SM2018P VCA SSM2142P Line driver NC3FKH XLR NC3MKH XLR PFL2X13 Preset terminal 0m1 MKS-2 0m01 MKS-2 1500p FKP-2 0m033 MKS-2 4m7 Alu_E 0m1 CerCo
C101, C102, C120 C103, C107 C104, C122, C125, C131, C134, C139, C142 C105, C123, C132, C140 C106, C124, C133, C141 C108, C109, C118, C119, C127, C128, C135, C136, C143, C144 C110, C111, C112, C113, C129, C130 C114, C115, C117 C116, C137, C138 C121 C126 R001, R002, R003, R004, R005, R006, R007, R008 R101, R102, R114, R138, R151, R169 R103, R104, R108, R109, R120, R128, R130, R131, R132, R133, R145, R146, R163, R164 R105, R106, R107, R117, R119, R129 R110, R134, R146, R165 R111, R135, R148, R166 R112, R135, R149, R167 R113, R137, R150, R1