BSS Audio FDS-318 Manuale utente
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FDS-318
User Manual
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This equipment has been tested and found to comply with the following European and
international Standards for Electromagnetic Compatibility and Electrical Safety:
Radiated Emissions (EU): EN55013 (1990) Associated Equipment
RF Immunity (EU): EN50082/1 (1992) RF Immunity, Fast Transients ESD
Mains Disturbance (EU): EN61000/3/2 (1995)
Electrical Safety (EU): EN60065 (1993)
Radiated Emissions (USA): FCC part 15 Class B
Electrical Safety (USA): UL813/ETL (1996) Commercial Audio Equipment
Electrical Safety (CAN): UL813/ETLc (1996) Commercial Audio Equipment
IMPORTANT SAFETY INFORMATION
DO NOT REMOVE COVERS. NO USER SERVICEABLE PARTS INSIDE, REFER SERVICING TO QUALIFIED
SERVICE PERSONNEL. THIS EQUIPMENT MUST BE EARTHED.
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. The input XLR Pin 1
and the side-chain input jack socket sleeve are connected to the chassis via a low value capacitor, providing
high immunity from ground loops whilst ensuring good EMC performance.
V 2.1 JMK 21st December 1999
Please read
We have written this manual with the aim of helping installers, sound engineers and musicians alike to get the
most out of the FDS-318. We recommend that you read this manual, particularly the section on installation,
before attempting to operate the unit.
The manual is split into two main sections. The first deals with quick reference information, regarding the
functions and operation of the unit, while the second covers a more general background to use and application
of the FDS-318.
We welcome any comments or questions regarding the FDS-318 or other BSS products, and you may contact us
at the address or World Wide Web site given in the warranty section.
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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
8.1 Mains Power 13
8.2 Voltage Setting 13
8.3 AC Power Fusing 14
8.4 Powering up 14
9.0 Audio Connections 15
9.1 Wiring convention 15
9.2 Balanced wiring 15
9.3 Unbalanced wiring 15
9.4 Ground loop control 16
10.0 Controls and connections 17
10.1 Crossover frequency adjustment
control 17
10.2 Output level control 17
10.3 Polarity reverse switch 17
10.4 Mute switch 17
10.5 Signal level indicators 18
10.6 Select mode LED 18
10.7 Rear panel switch LEDs 18
10.8 Mains power fuse 18
10.9 Main power switch 19
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Contents
10.10 Voltage selector switch 19
10.11 Output connections 19
10.12 Input connections 19
10.13 MONO LOW switch 20
10.14 CD EQ switch 20
10.15 SELECT MODE switch 20
11.0 Using the FDS-318 22
11.1 Selecting modes 22
11.2 Crossover frequency adjustment 25
11.3 Output level alignment 25
11.4 Output MUTE selector 25
11.5 Output polarity reverse selector 25
11.6 Output signal level indicators 26
11.7 CD Horn equalisation selector 26
11.8 MONO LO selector 26
12.0 Service Section 27
12.1 Chassis/0V Removal 27
12.2 Transient Suppressor Replacement 28
13.0 Specifications 29
14.0 Warranty Information 30
Index
User Notes
Spare Parts Information
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1.0 What is a Crossover?
Crossovers
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.
Any crossover aims to provide the division of the audio band necessary, so
each drive unit receives only the frequencies it is designed to handle. In a high
power, high performance sound system, the crossover should also reject
unsuitable frequencies to avoid damage and poor quality sound.
Fig 1.1 Stereo 2-way
Crossover set-up
Fig 1.2 Mono 3-way
Crossover set-up
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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). An active
crossover does the same job as a passive crossover, but with more precision,
flexibility, efficiency, and quality.
Fig 2.1
Active and Passive Crossovers
Some advantages of active crossovers are:
• Crossover frequencies can be more readily altered to suit different driver-
horn combinations.
• The level balance between the 2 or 3 frequency bands (brought on by
differences in driver and amplifier sensitivity) can be readily trimmed.
• Inside an active crossover unit, line-driving, signal summing, driver
equalisation, system muting and polarity ('phase') reversal facilities can all be
incorporated at small extra cost.
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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 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. The result: Bad sound resulting from out-
of-band resonances is effectively masked immediately beyond the crossover
frequency (See Figure 3.1). This contrasts markedly with passive crossovers,
where slopes in excess of -12dB/OCT are rarely achieved, and power rolloff is
4 times less rapid per octave.
• If one frequency range is driven into clip, drive-units and horns in other
frequency ranges are protected from damage, and distortion is kept to a
minimum.
• Direct connection of drive-units to the power amplifier cut out loss of
damping factor, normally inevitable, thanks to the appreciable resistance of the
inductors in passive crossovers.
Amplifiers benefit too from the use of active crossovers. As they do not handle
a full-range signal, clipping produces far less harmonic and intermodulation
distortion. The results: Momentary overdrive sounds less harsh. Also the
amplifiers' dynamic headroom is generally higher, and heatsink temperatures
can run lower.
Fig 3.1 Crossover
Terminology
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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 4.2 Radiation
Pattern Frequency
showing excellent on-
axis symmetry
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.: High and
Low drivers 'fighting' each other) over the narrow band of frequencies around
the crossover point, which is where the units from two adjacent frequency
ranges are contributing near equal amounts of sound pressure.
More predictable sound dispersion: By providing in-phase summation at the
crossover point(s), the Linkwitz-Riley alignment provides for more coherent
sound dispersion - it provides on-axis symmetrical radiation patterns. (See
Figure 4.2).
'Invisible' slopes: The absence of electrical phase difference close to the
crossover frequency helps to make the steep -24dB/OCT slope effectively
inaudible. Response peaks and dips are negligible and inaudible given the
correct polarity ('phasing') of the speaker connections. The same is not true of
the shallower (-6, -12 or -18dB/OCT) rates or rolloff, in other crossovers.
Fig 4.1 Linkwitz-Riley
filters
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BSS Crossovers
5.0 What is special about BSS Crossovers?
The FDS-318 is an electronic crossover offering many modes of operation to
suit professional sound systems, and also to support equipment rental
companies in reducing crossover inventory by having an easily re-configurable
loudspeaker system controller.
The FDS-318 fully supports stereo 3-way, stereo 4-way, or four separate
channels of 2-way operation, all in a 1U package. The internal switching of
circuitry is automatically controlled by information held within a digital PROM
memory device, such that the operator needs no additional knowledge other
than the mode the currently required. As with other BSS crossover products,
output sections not used within a given configuration are always available as
full range buffer drivers. 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. These filters are fully
sweepable by accurate front panel controls, which are also automatically
reconfigured depedant upon the mode of operation selected.
Some of the features available within the FDS-318 are:
• Stereo 4-way, stereo 3-way, four channels of 2-way in a 1U unit.
• Linkwitz-Riley fourth order filters with sweepable frequency selection.
• Digitally controlled mode selection, offering extended range selection and
features.
• Electronically balanced inputs and floating balanced outputs.
• Constant directivity equalisation externally selectable for all HIGH outputs.
• Polarity reverse, mute selection and signal LED indication for each output.
• MONO LOW selection for all stereo modes.
• Comprehensive mode selection indication, identifying the function of each
control.
• Full range buffer outputs on all non-used section.
As part of BSS' system of quality control, this product is carefully inspected
before packing to ensure flawless appearance.
After unpacking the unit, please inspect for any physical damage and retain the
shipping carton and ALL relevant packing materials for use should the unit
need returning.
In the event that damage has occurred, please notify your dealer immediately,
so that a written claim to cover the damages can be initiated. See Section 14.
6.0 Unpacking
Unpacking
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Getting to know the FDS-318
Fig 6.1 Front Panel
Fig 6.2 Rear Panel
Indice
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