BSS Audio FDS 360 User manual

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FDS 360
User Manual

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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. The input XLR Pin 1 on BSS equipment is generally connected to chassis via a capacitor to
prevent ground loops whilst ensuring good EMC compatibility.
V3.0 JMK 14October1996
We have written this manual with the aim of helping installers, sound engineers and consultants alike get to
grips with the FDS-360 and obtain its maximum capability.
If you are new to BSS products, we recommend that you begin at the start of the manual. If, however, you are
already familiar with the intended application, and just want to get the unit installed without delay, then
follow the highlighted sections.
We welcome any comments or questions regarding the FDS-360 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
9.0 Input Connections 14
9.1 XLR Plugs. 14
10.0 Output Connections 14
10.1 XLR Plugs 14
11.0 Controls 16
11.1 Mode Switch 16
11.2 Level Control 16
11.3 Mute Switch 16
11.4 Polarity Switch 17
11.5 Mono Low Switch 17
11.6 Phase Control 17
11.7 Limiter Threshold Switch 18
11.8 Signal LEDs 18
12.0 Frequency Cards 19
Card Location for Four Way System 19
Card Location for Three Way System 19
Card Location for Stereo Two Way System 19
13.0 Rear Barrier Strip 20
13.1 Limiter Cancel 20
13.2 Auto Mute Cancel 20
13.3 Limiter Threshold Reference 20
13.4 Band Insertion Points 20

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Contents
14.0 Modes of Operation 21
14.1 Mono Three Way with Extra Full Range
Buffered Output 21
14.2 Operating a Sub-Woofer system from an
Effects Send 21
14.3 Mono Low between separate units 21
15.0 Limiter Adjustment 22
Adjustment for A 22
Adjustment for B 22
16.0 Phase Adjustment 24
17.0 System Diagrams and Descriptions25
17.1 Full unit 25
17.2 15Hz Subsonic Filter Change 25
18.0 Filters and Frequency Tables 27
18.1 Standard Filters 27
18.2 Full Range Frequency Card 27
19.0 BSS Supported Options 30
19.1 Output Balancing 30
19.2 Security Cover 30
20.0 FDS-360 Equalisation Options 31
20.1 Introduction 31
20.2 FDS-360D Installation 31
20.3 Circuit Description 31
20.4 Filter Design 33
20.5 Application Notes 35
20.6 Application of the FDS-360D to a system 36
20.7 FDS-360 E Installation 38
21.0 Electronic/Chassis Earth Link 39
22.0 Transient Suppressor Replacement 39
23.0 Troubleshooting 40
24.0 Glossary 41
25.0 Specifications 44
26.0 Warranty Information 45
Index 49
User Notes 51
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
level) 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 setup
Fig 1.2 Mono 3-way
Crossover setup

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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
• Crossover frequencies can be more readily altered to suit different driver-
horncombinations.
• 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-
360 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 are 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.
Fig 3.1 Crossover
Terminology
• 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 cuts 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. Because 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.

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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; this 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 cogent
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-360 is an electronic crossover system, and incorporates all the latest
technology and facilities that are required for todays high powered
loudspeaker systems. This frequency dividing system (FDS) is substantially
more than a basic crossover, combining a high degree of sophistication which
enables accurate control of loudspeaker power, dispersion and acoustical
summation around the critical crossover region.
The FDS-360 features the following:
• Stereo two-way mode, or switchable three/four way mono mode.
• Separate frequency band limiters matched to the precise band of
frequencies controlled.
• Separate polarity switching for each band.
• LED signal level monitoring.
• Band insertion points for interfacing external equalisation and time delay
units.
• Band-edge phase adjustment allowing 360 degrees of control.
• Crossover filter programming via plug-in frequency cards allowing any
frequency, choice of 12/18/24dB/OCT slopes and filter responses to be
specified. 24dB/OCT Linkwitz-Riley responses are supplied as standard.
• Internal equalisation option.
Every FDS-360 is manufactured to the highest professional standards with a
robust steel case, high quality circuit boards and ICs, and high quality
components to provide reliable performance under the most demanding
conditions of the global sound-reinforcement environment. In common with
all other BSS equipment, the FDS-360 is subject to stringent quality control
procedures throughout the manufacturing process. Components are tested
against demanding acceptance criteria. Every completed unit is tested both
by measurement and in a listening test carried out by trained audio
professionals. To positively ensure reliability, all units are burnt-in for fifty
hours, before being tested.
Unpacking
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 26.
6.0 Unpacking

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Getting to know the FDS-360
11.2
11.411.5
11.8
Fig 6.1 Front Panel
Fig 6.2 Rear Panel
FUSE
5x20mm
240
.5 1
ON
OFF W
A
.5 1
ON
OFF W
A
10.0
8.0 11.1

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11.3
11.6
All numbers in bubbles refer to Section numbers.
.51248dB
ON
OFF WATS560B 4H
.51248dB
ON
OFF WATS560B 4H
.51248dB
ON
OFF WATS560B 4H
.51248dB
ON
OFF WATS560B 4H
11.7 13.0
9.0

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7.0 Mechanical Installation
A vertical rack space of 1U (1¾" / 10½mm) deep is required. Ventilation gaps
are unnecessary (See Figure 7.1).
If the FDS-360 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. As with any low-level signal
processing electronics, it is best to avoid mounting the unit next to a strong
source of magnetic radiation, (for example, a high power amplifier), to help
keep residual noise levels in the system to a minimum.
Installation
Fig 7.1 Unit dimensions.
Fig 7.2 Rack
dimensions.

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Connecting to Power
8.0 Mains Power Connection
Voltage: The FDS-360 operates on supply voltages between 95 and 125V AC.
It must not be plugged into 220, 230 and 240V AC outlets. If the unit is
accidentally connected to an AC supply giving in excess of 132V AC, refer to
section 23, (See Figure 8.1).
Frequency: Both 60Hz and 50Hz are acceptable.
Fig 8.1 Mains fuse on
rear panel.
FUSE
5x20mm
240
Grounding: The FDS-360 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. The unit must NOT be operated unless the power
cables ground ('earth') wire is properly terminated - it is important for personal
safety, as well as for proper control over the system grounding. If the
electronic 0V has to be separated from the chassis and mains power earth,
refer to section 23.
Connections: The AC power cable has a moulded 3-pin utility plug attached
to the free end to facilitate the correct and proper connections.
AC Power Fusing: The incoming line power passes through a 200mA (for 240V
only) anti-surge ('T') fuse, accessible from the rear panel (The fuse is rated at
250mA for 120V). If the fuse blows without good reason, refer to section 23.
Always replace with an identical 20mm x 5mm T rated fuse for continued
protection from equipment damage and fire. Also see section 22 for
information on replacing blown transient suppressors (if applicable).
Power ON: Before turning on the power, it is worth checking that the three
frequency cards are installed correctly. Loosen the captive screw securing the
small cover plate on the lid of the unit, and inspect the cards. The slope and
frequency information is recorded on each of these cards, and it must be
ensured that all cards are fitted, regardless of whether they are required. Refer
to sections 12 & 18 for more information concerning these cards.
The FDS-360 outputs are instantaneously muted at power OFF. At switch on, a
delay prevents turn-off thumps propagating through the sound system.

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Input Connections
9.0 Input Connections
The two input signals are 10k ohm active balanced on a standard 3 pin
'female' XLR which will accept levels up to +20dBv. The wiring convention is
as follows: (See Figure 9.1a):
Pin 1: No connection (the shield of the drain wire can be terminated
here if desired).
Pin 2: Signal '-', out of phase or 'COLD'.
Pin 3: Signal '+', in phase or 'HOT'.
For unbalanced sources (See figure 9.1b):
Pin 1: Leave open, or link to pin 2.
Pin 2: Shield, braid, or screen wire.
Pin 3: Signal '+' or 'HOT' (inner core).
There is no internal ground connection to Pin 1 of the female XLR to avoid
possible interconnection earth loops. The input signal cable shield must
therefore be tied to ground, or signal 0V, at the source end.
9.1 XLR Plugs.
Fig 9.1 XLR Plug Wiring
10.0 Output Connections
10.1 XLR Plugs The four signal outputs are DC blocked low impedance unbalanced from a
standard 3 pin male XLR and are designed to drive up to +20dBv into 600
ohms or greater. The wiring convention is as follows:
Pin 1: Connects to shield, screen or drain wire.
Pin 2: '-', cold or 'out of phase' output.
Pin 3: '+', hot or 'in phase' output.
If the amplifiers you are feeding have unbalanced (single ended) inputs, but
are fed from standard pin to pin XLR cables (See above), simply link the cable
at the crossover end as follows:
Pin 1: Connects to shield or screen wire.
Pin 2: Link to Pin 1.
Pin 3: Connects to the inner 'hot' or live core.
Unbalanced transmission is not recommended for connections to distant
equipment, but is generally acceptable for local connections within the rack,
or to an adjacent rack.

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Output Connections
Technicians note: As with a traditional transformer balanced output, either
output phase (+ or -, hot or cold) can be linked to ground to 'unbalance the
line' without upsetting the operation of the unit. As with a transformer, output
level remains the same in the unbalanced mode.

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240
.5
ON
OFF
.5
ON
OFF
Controls
11.0 Controls
11.1 Mode Switch
These four controls have a momentary action and allow the operator to mute
each band individually. Pressing once will activate the mute function, and
pressing again will de-mute. In addition, to protect the following speaker
system from DC power thumps, logic circuits ensure that all band outputs are
automatically muted when power is first switched on, or if a DC fault occurs
internally to the unit. This will be noted when first powering up, as the four
mute LEDs will remain on. Refer to section 13.2 for further details.
11.3 Mute Switch
11.2 Level Control
The four front panel controls adjust the level of the program in each of the
frequency bands, and is set to give a precise restricted range of ±6dB. In their
fully anticlockwise position they do not reduce the level to zero.
These controls are designed to allow the operator to carefully balance the
respective bands in relation to each other, and do not interfere with the
crossover networks, or the limiter threshold settings.
The mode switch is located at the rear of the unit and sets the internal
architecture for either the stereo 2-way, the mono 3-way, or mono 4-way
mode. In the mono modes, the channel 1 input connector is used. Refer to
section 14 for other possibilities.
This selector switch also operates the front panel 'band' LEDs, to give a visual
indication of the function of each of the four frequency bands.

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11.4 Polarity Switch
These four latching switched allow 180 degree phase reversal of the signal
output for each band individually. Refer to section 16 for more information.
11.5 Mono Low
Switch
When operating the FDS-360 in the stereo 2-way mode, this switch will sum
together the signal information in bands 1 and 3 so that the outputs of these
bands are equal, regardless of input stereo image. This gives a mono low
signal feed which is often desirable for low frequency information. Refer to
section 14.3 for more information regarding mono low linking.
11.6 Phase Control
These three controls will adjust the relative phase between adjacent band
outputs at the crossover region. The phase circuitry is programmed by the
frequency cards to give precise control regardless of the crossover frequency.
When these controls are used in conjunction with the polarity switch the
operator has a full 360 degree of adjustment. Refer to section 16 for further
information.

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.51248dB
ON
OFF WATS560B
4H
.51248dB
ON
OFF WATS560B
4H
.51248dB
ON
OFF WATS560B
4H
.51248dB
ON
OFF WATS560B
4H
Controls
11.7 Limiter
Threshold Switch
These four switch blocks on the rear panel allow the individual band limiter
thresholds to be set. With all switches in the 'out' position, the threshold will
be either +10dBv or +4dBv depending on the barrier strip link.
Binary addition of the switches will then subtract from this reference to give a
specific threshold adjustable in 0.5dB steps. (The centre switch position should
not be used and is provided for manufacturing reasons only). Refer to section
13.1 & 15 for further information.
11.8 Signal LEDs
Each band has associated with it three LEDs which monitor the signal level.
The lower green LED gives an indication that signal is present at a level -15dB
below the limiter threshold setting. The middle orange LED indicates that the
signal has reached the limiter threshold setting, and the upper red LED
indicates 6dB of limiting.

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FC1 FC2 FC3
MONO 4-WAY
FC1
STEREO 2-WAY CHANNEL ONE
FC1 FC2
MONO 3-WAY
FC3
STEREO 2-WAY CHANNEL TWO
Frequency Cards
12.0 Frequency Cards
The frequency programming cards for the FDS-360 are located underneath the
small panel on the top cover of the unit. Access to them is obtained by
loosening the captive screw and then removing the cover. Each frequency
card contains the components required for one low pass filter, one high pass
filter, the limiter dynamics setting and phase control setting. The relevant
frequency, slope and response type is recorded on a label attached to the
respective card.
When fitting the frequency cards take care that they are correctly orientated
and positioned in their edge connectors, and that the foam underneath the
metal cover is locating properly on the edge of the cards to provide correct
support.
The card located in position FC1 is for the first break point, that in position
FC2 is for the second break point, and that in position FC3 is for the third
break point.
Card Location for
Four Way System
The card located in position FC1 is for the first break point, and that in
position FC2 is for the second break point. The card in position FC3 will not
be used, so its value is not important. However, a card MUST be fitted to
prevent damage to the unit.
Card Location for
Three Way System
The card located in position FC1 is for channel 1, and that in position FC3 is
for channel 2. The card in position FC2 is not used so its value is not
important. A card MUST be fitted in order to prevent damage to the unit.
Card Location for
Stereo Two Way
System Refer to section 11 for information on component values for various
frequencies. All standard cards supplied are of the Linkwitz-Riley response
type. Please refer to your dealer who can supply you with cards for other filter
types, as well as frequencies not shown in the tables.

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Rear Barrier Strip
13.0 Rear Barrier Strip
The barrier strip located on the rear of the FDS-360 provides for a number of
facilities specific to the BSS FDS-360, to give the operator greater flexibility.
By adding a wire link between the two marked terminals all four limiters can
be cancelled and taken out of circuit. Simultaneously the four red LEDs
marked 'over' on the front panel will illuminate, regardless of the level of the
input signal, to give a warning to the operator that the limiters have been
cancelled.
13.1 Limiter Cancel
As mentioned in section 11.1, 'Mode Switch', when the unit is switched on all
four mute circuits will operate to protect the following equipment from
potentially dangerous DC thumps. To commence using the FDS-360 the mutes
will then have to be operated via the respective mute switches. In certain
fixed installations where access to the FDS-360 is not possible by the operator,
it will be necessary to activate the auto-mute cancel facility by adding a wire
link between the two marked terminals. Once activated, the FDS-360 will
still power-up in the mute mode, thus maintaining protection, but after
approximately 20 seconds will automatically un-mute itself to allow full
operation to commence.
13.2 Auto Mute
Cancel
As mentioned in section 11.7, 'Limiter Threshold Switch', the limiter threshold
reference is +10dBv. Should a threshold below -5dBv be required, adding a
wire link between the two marked terminals will reduce the reference to
+4dBv, thus allowing a lower threshold point of -11dBv. This operates on all
four limiters together. However, the adjustable range of 15.5dB down from the
reference level allows sufficient adjustment for each individual limiter for
correct speaker protection. Refer to section 15 for further information.
13.3 Limiter
Threshold
Reference
13.4 Band Insertion
Points The barrier strip provides 'send' and 'return' points for each of the four bands
individually. This allows the operator to connect external equipment such as
equalisers and digital time delays into the particular frequency band required.
The send or input to the external equipment or return to the FDS-360 is taken
to the appropriate BAND IN terminal. The factory provided wire link should
obviously be removed. Both the inputs and outputs from the barrier strip are
unbalanced and work at line level with a headroom of +20dBv.