FDS 310 User Manual 1
V 2.0 JMK 9 August 1996 This equipment has been tested and found to comply with the following European Standards for Electromagnetic Compatibility: Emission Specification: EN55013 (1990) (Associated equipment) Immunity Specification: EN50082/1 (1992) (RF Immunity, Fast Transients and ESD) Mains Disturbance: EN61000/3/2 (1995) For continued compliance ensure that all input and output cables are wired with cable screen connected to Pin 1 of the XLR.
Contents Contents 1.0 What is a Crossover? 5 2.0 The difference between Active and Passive Crossovers 6 3.0 Other advantages 7 4.0 The Linkwitz-Riley advantage 8 5.0 What is special about BSS Crossovers? 9 6.0 Unpacking 9 7.0 Mechanical Installation 12 8.0 Mains Power Connection 13 9.0 Input Connections 14 9.1 9.2 10.0 10.1 10.2 11.0 11.1 11.2 11.3 13.0 Using Jack Plugs. Using XLR Plugs.
Contents 16.0 16.1 16.2 17.0 LED indicators 'Signal Present' 'Peak' 21 21 Crossover Alignment Procedure: Setting the level controls 22 18.0 Using the Mute switch 24 19.0 Polarity switching and Output Polarity reversal option 25 20.0 Troubleshooting 26 21.0 Grounding/Earthing Procedures (Curing hums) 27 Service Section 28 22.0 22.1 22.2 22.3 22.4 22.5 2-Channel Sub-Woofer Operation Mono-Low/Linking switch Activating Equalisation Eliminating Hum Polarity Switching 28 28 29 30 30 23.
Crossovers 1.0 What is a Crossover? Crossovers are a necessary part of sound reinforcement systems because the loudspeaker drive-unit which can produce clear reliable high SPL (sound levels) over the full audio bandwidth has yet to be invented. All real-world drive units work best when they are driven over a limited band of frequencies, for example: Low, Mid and High.
Active and Passive Crossovers 2.0 The difference between Active and Passive Crossovers Passive crossovers divide the frequency spectrum after the signal has been raised to a high power level. They are generally heavy, bulky and inefficient. Active crossovers utilise ICs and transistors, and divide the frequency spectrum at line levels immediately ahead of the amplifiers (See Figure 2.1).
Crossover advantages 3.0 Other advantages The drive-units in sound reinforcement systems utilising active crossovers benefit because: • Steep rolloffs are readily attainable. The -24dB/OCT rolloff in the BSS FDS310 active crossover rapidly discharges out-of-band energy. At one octave below the crossover point, power received by the driver has dropped to less than ½% (or 1/200th) of full power.
Linkwitz-Riley Alignment 4.0 The Linkwitz-Riley advantage There is an additional set of advantages exclusive to active crossovers made by BSS, and other manufactures using the Linkwitz-Riley alignment (See Figure 4.1). Fig 4.1 Linkwitz-Riley filters Zero Phase difference at crossover: The phase difference between drivers operating in adjacent frequency bands is close to zero degrees at the crossover frequency. 'Phase alignment' in this manner prevents interactive effects (i.e.
BSS Crossovers Unpacking 5.0 What is special about BSS Crossovers? The FDS-310 is a condensation of over ten years experience, manufacturing the industry's most advanced active crossovers for worldwide use. The FDS310 contains all the features required for todays sound reinforcement systems in a compact enclosure: • It can be configured for 2 2-way channels, or for 3-way single channel operation. • Crossover frequencies are easily and precisely adjustable for all applications including sub-woofers.
Getting to know the FDS-310 Fig 6.1 Front Panel Fig 6.
All numbers in bubbles refer to Section numbers.
Installation 7.0 Mechanical Installation A vertical rack space of 1U (1¾" / 44.5 mm high) is required. Ventilation gaps are unnecessary (See Figure 7.1). If the FDS-310 is likely to undergo extreme vibration through extensive road trucking and touring, it is advisable to support the unit at the rear and/or sides to lessen the stress on the front mounting flange. The necessary support can generally be bought ready-built as a rack tray.
Connecting to Power 8.0 Mains Power Connection Voltage: The FDS-310 operates on either 115 or 230 volt supplies. Use the voltage selector switch to choose the required voltage setting. (See Figure 8.1). Frequency: Both 60Hz and 50Hz are acceptable. Fig 8.1 Mains fuse/ Voltage selector on rear panel. Grounding: The FDS-310 must always be connected to a 3-wire grounded ('earthed') AC outlet. The rack framework is assumed to be connected to the same grounding circuit.
Input Connections 9.0 Input Connections 9.1 Using Jack Plugs. Each jack socket accepts signal sources from a 3-pole (stereo), or 2-pole (mono), 'A' gauge phone plug (See Figure 9.1). The balanced input of the FDS-310 will accept both balanced or unbalanced signal feeds, without needing any modification. There is no internal ground connection to the 'sleeve' on the input jack socket, to avoid possible interconnection earth loops.
Output Connections 10.0 Output Connections 10.1 Using Phone Plugs Each jack socket outputs a balanced signal - symmetrical to ground and floating. The output is immune from short circuits and drives low impedances and long cable runs. Each socket accepts either 2-pole or 3-pole (stereo) ¼" 'A' gauge phone plugs. In general, these plugs will automatically provide a suitable interface with unbalanced and balanced circuits respectively (See Figure 9.1).
Setting up 2-Way 2 Channel Operation 11.0 Connection and Setup 11.1 Selecting '2Way' 2 Channel Operation In a 2-way system, the incoming full range signal is split into 2 bands. Normally the corresponding loudspeaker drive units cover Bass (LOW), Top (HIGH) frequencies, and the crossover point between them lies between 180Hz and 2000Hz (2kHz). When setup for 2-way operation, the FDS-310 handles two channels (stereo).
Setting up 3-Way Mono Operation 11.2 Selecting '3Way' Mono Operation In a 3-way system, the incoming full range signal is split into 3 bands. Normally the corresponding loudspeaker drive units cover Bass (LOW), Mid and Top (HIGH) frequencies. In this mode, the FDS-310 operates in mono and there are two crossover points. The LOW-to-MID crossover point normally lies between 180Hz and 2000Hz (2kHz). The MID-to-HIGH crossover point normally lies between 800Hz and 9000Hz (9kHz).
Setting up Schematics Fig 11.1 2- and 3-Way Setups 11.3 2-Channel Sub-Woofer Operation 18 The FDS-310 can drive sub-woofers ('Sub-Low or 'Sub-Bass' cabinets) when switched to the 2-way configuration. The Sub-woofer-to-HIGH crossover point can lie anywhere between 18Hz and 200Hz. The 'high' output is substantially a full range signal, and is normally split further into 2 or 3 bands, using a second active crossover.
Setting up 2-Channel Sub-Woofer Operation 12.0 Monaural Sub-Woofer Operation for stereo 2-way systems only Because human hearing is insensitive to the location of low-frequency sound sources below 100Hz, stereo operation is normally dispensed with when driving sub-woofers. The FDS-310 contains an internal link which can be set to sum (mix) the incoming two channel (stereo) signals, so that the two sublow outputs are identical. Meanwhile, full stereo operation is retained on the 'high' outputs.
Equalising CD Horns 14.0 How to Equalise CD Horns Todays 'Constant Directivity' (CD) horns and drivers can be used in 2-way systems with comparatively low crossover frequencies. Even so, the laws of physics dictate that the very high efficiency attained cannot be kept up all the way to 20kHz. In addition, the CD horns control of dispersion further 'thins out' the SPL at higher frequencies. As a result, response falls off progressively above 4kHz, and more rapidly above 20kHz.
Full Range Output LED Indicators 15.0 Full range Output 3-way operation only When switched on 'MONO 3-WAY' mode, the Channel 2 input ('FULL RANGE' in 3-way mode) is not wasted. Instead, it can be used as a balanced in-out line driver passing through to the adjacent 'FULL RANGE' output sockets. Follow the yellow legend for this. In combination with the remainder of the FDS-310, it shares the following facilities: • Up to +6dB of gain. • +6 to -00 gain adjustment, using the 'FULL RANGE' level trim control.
Crossover Alignment Procedure 17.0 Crossover Alignment Procedure: Setting the level controls The modern idea is to set the crossovers' level controls so the entire speaker system exhibits a uniform, flat response, independent of the rooms' own acoustic anomalies. This means that powerful T.D.S. (Time-Delay Spectrometry) equipment is needed to make speedy, reliable measurements.
If the mid output is not enough, even when the crossovers MID RANGE control is set at maximum (+6dB), check the mid-range power amplifiers sensitivity. If this cannot be altered, set the MID RANGE control at 0dB, then decrease the LOW RANGE control, until the two frequency bands fuse together to give an essentially straight line on the R.T.A display. If the response appears uneven around the LOW-to-MID crossover frequency, the drivers polarity may be reversed. Refer to section 24 to remedy this.
MUTE switch • All EQ controls throughout the sound system should be set flat before setting up the FDS-310 LEVEL controls. Any house EQ adjustments can be made later. • For a 3-way set up, set the MID RANGE control first for a comfortable level. Then bring up the LOW RANGE control until the music/vocals/speech is 'filled-out'. Next, increase the HIGH RANGE control until the vocals have a natural presence. Finally, you may want to readjust the LOW RANGE for the best balance.
POLARITY switch 19.0 Polarity switching and Output Polarity reversal option Each frequency bands' control surface includes a POLARITY switch (See Figure 6.1). Depressing it reverses the polarity ('phasing') of the signal emerging from the related output socket. It is a valuable 'instant' troubleshooting aid in complex multi-driver installations. Polarity in/out relations are factory set, so at any input and any related output: • XLR + or HOT goes to Pin 3. • Phone sockets + or HOT goes to tip.
Troubleshooting 20.0 26 Troubleshooting Problem: Solution: No Output Is the MUTE switch depressed? Is the mains power on? (See section 8). Check the connections. See Fuse failure (below). Do you have an input signal? Is the SIGNAL LED on? Check the input and output connections (See sections 9 & 10). Are the power amplifiers switched on? Problem: High Frequency signal from 'LOW' output Low Frequency signal from 'HIGH' output. Solution: Switch unit to 3-way operation.
Grounding/Earthing 21.0 Grounding/Earthing Procedures (Curing hums) The FDS-310 is supplied with the signal ground (0V) tied to chassis, which is connected in turn to: • Mains ground (earth). • Other equipment chassis' in the rack. If the FDS-310 outputs are connected to amplifiers with unbalanced inputs, it will normally be necessary to disconnect the internal ground link, to prevent ground-loop hums. Refer to section 22.
!!! CAUTION - Important Notes !!! SERVICE SECTION 22.0 Service Section 22.1 2-Channel Sub-Woofer Operation • Refer to section 11.1, first 3 bulleted points: For 'LOW', read 'Sub-Bass' Output. For 'HIGH', read 'Mainly full range signal, for further splitting'. • Before setting the crossover point, disconnect the mains power, remove the lid of the unit, and locate the slide switches SW2 and SW3 marked 'divide 10 FREQ X 1' (See Figure 22.1).
!!! CAUTION - Important Notes !!! SERVICE SECTION Fig 22.2 Locating the MONO LOW/LINKING switch 22.3 Activating Equalisation To activate the equalisation: • Disconnect the mains power and remove the top cover plate. • Locate the 3-pin programming plug on the left side of the main PCB, marked 'CD HORN EQ - OUTPUT 2', and 'CD HORN EQ - OUTPUT 4' in the centre of the PCB.
!!! CAUTION - Important Notes !!! SERVICE SECTION 22.4 Eliminating Hum • Disconnect the power and remove the top cover plate. • Locate the green wire bolted to the chassis on the right side of the toroidal transformer. Check the wire connects to the PCB terminal marked 'CHASSIS' (See figure 22.4). • Remove the tag from the chassis bolt, or alternatively unsolder its other end from the circuit board. Either way, do not leave the wire hanging loose; fold it over and sleeve for continued safety. Fig 22.
Glossary 23.0 Glossary Active Amplitude Balanced Bi-Amped Crossover Point dB Active electronic circuits are those which are capable of voltage and power gain by using transistors and integrated circuits. Refers to the voltage level or intensity of a signal, and is usually measured in voltage or decibels. A three wire connection in which two of the wires carry the signal information, and the third acts as a shield tied to chassis ground.
Glossary Equalisation Frequency The repetition of a waveform. The unit of frequency is Hz, and 1 cycle per second is equal to 1Hz. The audio band is generally restricted to frequencies of 20Hz to 20,000Hz (20kHz). Frequency Response Equipment's relative gain compared to frequency. Generally expressed as +/a certain number of dBs from 20Hz to 20kHz. Headroom The amount, in dBs, above the normal operating level that can be used before serious distortion commences.
Specifications 24.0 Specifications Input Impedance: Balanced bridging; 12k ohms Max. Input Level: +20dBm/dBu/dBv Through Gain: Input CMRR: Max. Output Level: Input to any output with level control set at 0dB: 0dB Fully adjustable from - to +6dB. (Common Mode Rejection Ratio) <-50dB at 120Hz <-50dB at 10kHz Balanced Mode: Unbalanced Mode: Min. Load Impedance: Output Impedance: +26dBv/dBu 15.5v rms +20dBv/dBu 7.
Warranty Information 25.0 Warranty Information This unit is warranted by BSS Audio to the original end user purchaser against defects in workmanship and the materials used in its manufacture for a period of one year from the date of shipment to the end user. Faults arising from misuse, unauthorised modifications or accidents are not covered under this warranty. No other warranty is expressed or implied.
Index Index Symbols L 2-Channel Sub-Woofer Operation. See Setting up 2-Way 2 Channel Operation. See Setting up 3-Way Mono Operation. See Setting up LED indicators A Active Crossovers 6 B Balanced Input. See Input Connections BSS Crossovers 9 C Constant Directivity. See Equalising CD Horns Contents 3 Crossover Alignment 22 CROSSOVER MODE SELECTOR. See Setting up Crossover Points 19 Crossovers 6 E Equalising CD Horns 20 F Front Panel Full range Output Fuses.
Index W Warranty Info. 34 Wiring Convention. See Input Connections: Output Connections X XLR Plugs. See Input Connections Z Zero Phase difference.
User Notes 37
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