BSS Audio FDS 310 Manuale utente
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FDS 310
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.
V 2.0 JMK 9 August 1996
We have written this manual with the aim of helping installers, sound engineers and musicians to get to grips
with the FDS-310 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-310 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 Using Jack Plugs. 14
9.2 Using XLR Plugs. 14
10.0 Output Connections 15
10.1 Using Phone Plugs 15
10.2 Using XLR Plugs 15
11.0 Connection and Setup 16
11.1 Selecting '2-Way' 2 Channel Operation 16
11.2 Selecting '3-Way' Mono Operation 17
11.3 2-Channel Sub-Woofer Operation 18
13.0 Unusual Crossover Points -
for 3-way systems only 19
12.0 Monaural Sub-Woofer Operation -
for stereo 2-way systems only 19
14.0 How to Equalise CD Horns 20
15.0 Full range Output -
3-way operation only 21
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Contents
16.0 LED indicators 21
16.1 'Signal Present' 21
16.2 'Peak' 21
17.0 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
22.0 Service Section 28
22.1 2-Channel Sub-Woofer Operation 28
22.2 Mono-Low/Linking switch 28
22.3 Activating Equalisation 29
22.4 Eliminating Hum 30
22.5 Polarity Switching 30
23.0 Glossary 31
24.0 Specifications 33
25.0 Warranty Information 34
Index 35
User Notes 37
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-
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-
310 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-310 is a condensation of over ten years experience, manufacturing
the industry's most advanced active crossovers for worldwide use. The FDS-
310 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. ANY frequency between 180Hz and 9kHz can be
selected at the turn of a knob. Additional crossover frequencies down to 18Hz
can be selected by activating internal, tamper-free switches.
• Stereo signals can be summed for driving sub-woofers in mono.
• Equalisation suiting 'industry standard' HF CD (Constant Directivity) horn/
driver combinations is factory fitted and can be immediately activated.
• All inputs and outputs are balanced for ease of system installation and
interconnection, without hums and buzzes. Additionally, for each frequency
band:
• A green LED confirms signal present.
• A red LED warns of peak clipping (overdrive).
• A MUTE switch allows each frequency band to be switched in/out as an aid
to diagnosis and setting-up.
• A calibrated LEVEL CONTROL accommodates wide variations in the
sensitivity of adjacent frequency bands.
• A POLARITY switch enables each bands' polarity (or absolute 'phase') to be
reversed (or 'inverted').
• Additional, optional internal settings are confirmed by panel LEDs.
Every FDS-310 is manufactured to the highest professional standards, with a
robust steel case, high quality circuit boards, 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-310 is subject to stringent quality control
procedures throughout the manufacturing process. Components are tested
against demanding acceptance criteria. Each 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.
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 25.
6.0 Unpacking
Unpacking
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Getting to know the FDS-310
Fig 6.1 Front Panel
Fig 6.2 Rear Panel
Indice
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