IT SHOULD NOT BE NECESSARY TO REMOVE ANY PROTECTIVE EARTH OR SIGNAL CABLE SHIELD CONNECTIONS TO PREVENT GROUND LOOPS. ANY SUCH DISCONNECTIONS ARE OUTSIDE THE RECOMMENDED PRACTICE OF BSS AUDIO AND WILL RENDER ANY EMC OR SAFETY CERTIFICATION VOID. For continued compliance with international EMC legislation ensure that all input and output cables are wired with the cable screen connected to Pin 1 of the XLR connectors and/or the jack plug sleeve.
Contents Contents What is a Crossover? The difference between Active and Passive Crossovers Other advantages The Linkwitz-Riley advantage What is special about BSS Crossovers? Unpacking Mechanical Installation Mains Power Connection Mains Power Voltage Setting AC Power Fusing Powering up Audio Connections Wiring convention Balanced wiring Unbalanced wiring...
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Contents 10.10 Voltage selector switch 10.11 Output connections 10.12 Input connections 10.13 MONO LOW switch 10.14 CD EQ switch 10.15 SELECT MODE switch 11.0 Using the FDS-318 11.1 Selecting modes 11.2 Crossover frequency adjustment 11.3 Output level alignment 11.4 Output MUTE selector 11.5 Output polarity reverse selector 11.6...
Crossovers 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 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 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 FDS- 318 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 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.
An important part of any electronic crossover is the filter type, and todays industry standard series Butterworth filters, pioneered by BSS Audio since 1979, is available in the FDS-318 in the form of the fourth order Linkwitz-Riley design. These provide the necessary in-phase outputs and steep 24dB/Oct slopes required to give the best constant voltage summation and minimal lobing for non-coincidental drivers.
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Getting to know the FDS-318 Fig 6.1 Front Panel Fig 6.2 Rear Panel...
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All numbers in bubbles refer to Section numbers.
Installation 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-318 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.
Connecting to Power Mains Power Connection WARNING! THIS APPLIANCE MUST BE EARTHED. 8.1 Mains Power IMPORTANT: The wires in the mains lead are colour coded in accordance with the following code. Green and Yellow..Earth Blue..Neutral Brown..Live As the colours of the wires in the mains lead may not correspond with the markings identifying the terminals in your plug, proceed as follows.
Connecting to power Fig 8.1 Mains fuse on rear panel. 8.3 AC Power The incoming mains power is fused within the FDS-318 by the fuse holder mounted on the rear panel (See figure 8.1). If it needs to be replaced it should Fusing be properly rated as: 20mm 250V, T200mA for 240V voltage setting or T250mA for 120V voltage setting.
3 pin XLR connectors is the same. As is common with all other BSS Audio equipment of this type, we follow the convention of 'ground goes forward with the signal'. Input cabling screening therefore needs to be derived from the signal source end as Pin 1 is ground lifted for the inputs.
Audio connections 9.4 Ground loop Strict adherence to the wiring conventions noted above within a fully balanced signal system will give the best possible results with none of the problems control normally associated with interconnected audio equipment. Wherever possible, cable screens should not be connected to any signal pin, but rather left to perform a cable shielding function only.
Controls and connections 10.0 Controls and connections 10.1 Crossover frequency adjustment control Left and right hand channels are adjustable separately. The frequency scaling LEDs, marked as x10 and /10, indicates whether the printed frequency scale needs to be multiplied or divided by 10 for the correct value. The control of this is determined by the SELECT MODE switch on the rear panel.
Controls and connections 10.5 Signal level indicators The SIG LED indicated that a signal is being received within that band, and the PEAK LED warns of the possible onset of system overload. The SIG LED will not light for signals below peak level of -20dB, and the PEAK LED lights for signals in excess of +10dB.
10.9 Main power switch Turns the FDS-318 on or off. 10.10 Voltage selector switch Located on the side of the unit, this switch allows operation in the following regions: 96-132V or 192-264V, 50-60Hz AC. 10.11 Output connections The outputs are electronically balanced and floating. Maximum output is +20dBu into 600 ohms or greater.
Controls and connections 10.13 MONO LOW switch The MONO LOW switch operates in all stereo modes of operation and actively sums the signal information together on the LOW outputs. Both left and right LOW outputs will then contain the summed LOW signal. 10.14 CD EQ switch The CD EQ switch inserts constant directivity equalisation on all relevant outputs, dependant on the mode selected.
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2-way MID: Four channels of 2 non overlapping frequency bands with the frequency control configured to operate over a 200Hz to 2kHz sweep range. 2-way LO: Four channels of 2 non overlapping frequency bands with the frequency control configured to operate over a 20Hz to 200Hz sweep range.
Using the FDS-318 11.0 Using the FDS-318 11.1 Selecting The appropriate mode should be selected with the rear panel switch, and this will be confirmed by the LED indicators on the front panel. The table in figure modes 11.1 indicates the functions applicable to each front panel control. 4-way: Use this mode for a conventional stereo four way speaker system, where each of the four bands operate over different, non overlapping frequency ranges.
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3-way: Use this mode for a conventional stereo 3-way speaker system where each of the three bands operate over different, non overlapping frequency ranges. The extra two (stereo pair) outputs which do not form part of the crossover system are available as a full range buffer output operating over the whole frequency range of 20Hz to 20kHz.
Using the FDS-318 11.2 Crossover The large control knobs on the left hand side of the front panel adjust the frequency of the fourth order Linkwitz-Riley crossover filters. They are frequency arranged in stereo pairs to aid the setting up of like values on each channel. In adjustment the 2- and 3-way modes, the last two control knobs remain non functional.
Using the FDS-318 11.6 Output signal Each output has two LED indicators showing the level of signal within each band at the output connector. The lower SIG LED operates to show that a level indicators signal is being received . Steady illumination means high drive levels and periodic flashing indicates a moderate drive level.
XLR Pin 1 connections to chassis. Under no circumstances is it recommended that this link is removed. !!! WARNING - Refer all servicing to qualified service personnel !!! Risk of electric shock if the unit is opened. BSS Audio accepts no responsibility for injury subsequent to opening of the unit.
The unit should be disconnected from the mains supply before the lid is removed. !!! WARNING - Refer all servicing to qualified service personnel !!! Risk of electric shock if the unit is opened. BSS Audio accepts no responsibility for injury subsequent to opening of the unit.
Specifications 13.0 Specifications Input section 12k ohms electronically balanced, +20dBu maximum input level via XLR 3-31 or equivalent. Input CMMR better than -50dB, 50Hz to 15kHz. Output section Electronically balanced and floating, capable of driving +26dBu into 600 ohms (+26dBm) or greater via XLR 3- 32 or equivalent.
14.0 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.
Index Index Balanced wiring rear panel switch select mode Linkwitz-Riley CD EQ switch CD Horn equalisation switch Chassis/0V Removal Connections Main power switch audio Mains fuse input Mains power output requirements Controls Modes crossover frequency 2-way HI, 2-way MID, adjustment 2-way LO Mute switch 3-way...
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Index MONO LO 20, 26 Output MUTE Output polarity reverse select mode Voltage selector Transient Suppressor Replacement Unbalanced wiring Unpacking User Notes Voltage selector switch Voltage settings Warranty Info. Wiring convention Zero Phase difference...
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