Bss FDS366T User Manual
FDS-366T OMNIDRIVE
™
User Manual
Connect here first...
ZM10019 issue 4 CB/PW/DN/DP/JWK
Software version 2.00
IMPORTANT SAFETY INFORMATION
DO NOT REMOVE COVERS.
NO USER SERVICABLE 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 PRACTISE OF BSS AUDIO AND WILL
RENDER ANY EMC OR SAFETY CERTIFICATION VOID.
REGULATORY INFORMATION
FDS-366T
This equipment has been tested and found to comply with the following European and International Standards
for Electromagnetic Compatibility and Electrical Safety:
Emmissions (EU): EN55013+A12+A13 (1990)
Generic Immunity (EU): EN50082-1 (1992)
Mains Harmonics (EU) EN61000-3-2 (1995)
Voltage Fluctuations (EU) EN61000-3-3 (1995)
Electrical Safety (EU): EN60065+A11 (1993)
Electrical Safety (USA): UL813/ETL (1996)
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.
The input XLR Pin 1 is connected to the chassis via a low value capacitor, providing high immunity from ground
loops whilst ensuring good EMC performance.
The FDS-366T Omnidrive was designed and developed by BSS Audio, Hertfordshire, UK.
In keeping with our policy of continued improvement, BSS Audio reserves the right to alter specifications
without prior notice.
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FDS-366T
Contents
FDS-366T Omnidrive compact plus
1.0 Primary Checks ......................................................................................... 8
2.0 Installation ................................................................................................. 8
3.0 Warranty Information ............................................................................... 9
About the FDS-366T Omnidrive Compact Plus...............................10
4.0 Introduction ............................................................................................ 11
5.0 Features .................................................................................................... 12
What is DEQ? ................................................................................................. 16
6.0 Dynamic Equalisation .............................................................................. 16
Notes and Uses ..................................................................................................................17
7.0 Crossover Shapes and Frequencies .......................................................... 19
Thiele Crossover ................................................................................................................21
Crossover comparison chart ............................................................................................... 22
Phase Compensation .......................................................................................................... 23
Stereo 3-Way with mono sub-bass. ................................................................ 24
8.0 Typical Applications ................................................................................. 24
6-Way zoning distribution .............................................................................. 25
LCR cinema systems (3x2-way)....................................................................... 25
Triple Bi-amp (Stage monitors) ........................................................................ 25
Mono 6-way ................................................................................................... 26
Stereo 6-way (example) .................................................................................. 26
9.0 Front Panel ............................................................................................... 27
10.0 Rear panel .............................................................................................. 29
Using the FDS-366T Omnidrive Compact Plus ............................... 30
Voltage setting ................................................................................................ 31
11.0 Connections - Mains Power .................................................................. 31
AC Power fusing ............................................................................................ 32
Connections - Audio...................................................................................... 33
Balanced wiring.................................................................................................................. 33
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FDS-366T
Unbalanced wiring ............................................................................................................. 34
MIDI ................................................................................................................................... 35
RS232 Serial ....................................................................................................................... 35
RS485 Serial ....................................................................................................................... 35
Program Select Port.............................................................................................................36
12.0 Navigation.............................................................................................. 37
The Navipad ................................................................................................... 37
The Rotary Encoder ........................................................................................ 37
13.0 Default Screen ....................................................................................... 38
14.0 Quick Start Guide .................................................................................. 39
Keep relative delays while delaying a group ....................................................................... 44
Name a band .....................................................................................................................44
15.0 Quick Reference - How to ... ................................................................. 44
Use delays for driver alignment .......................................................................................... 44
Make a band full range ...................................................................................................... 45
Add EQ for Constant Directivity horns................................................................................ 45
Load custom logos ............................................................................................................. 45
Programming functions in depth ..................................................... 46
Recalling a Program ........................................................................................................... 47
16.0 Program Functions - Recall .................................................................... 47
Storing a Program ...............................................................................................................48
Program Functions - Store.............................................................................. 48
Store Lock .......................................................................................................................... 48
Program lock ...................................................................................................................... 49
Store Type .......................................................................................................................... 49
Delete Program ..................................................................................................................50
Card types .......................................................................................................................... 51
Compatible Cards .............................................................................................................. 51
Storage life ......................................................................................................................... 51
PC Card format ..................................................................................................................51
17.0 PC Card Usage ....................................................................................... 51
FDS-355 compatibility ....................................................................................................... 52
Computer compatibility...................................................................................................... 53
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FDS-366T
18.0 Utilities .................................................................................................. 53
1. Configuration.................................................................................................................. 54
2. Stereo Link...................................................................................................................... 54
3. Sum Type........................................................................................................................ 54
5. Phase Comp ...................................................................................................................55
4. Xover Adjust ................................................................................................................... 55
6. Alignment Assistant ......................................................................................................... 56
Method .............................................................................................................................. 56
Microphone placement and connection .............................................................................. 56
Procedure........................................................................................................................... 57
Selecting bands to measure ................................................................................................. 57
Adjusting the stimulus level ................................................................................................. 58
Notes ................................................................................................................................. 58
7. Delay Corrn (Correction) ................................................................................................. 60
8. Temperature .................................................................................................................... 61
9. Limit units ....................................................................................................................... 61
10. Delay units ................................................................................................................... 61
11. Brightness ..................................................................................................................... 61
12. Contrast ........................................................................................................................ 61
14. Owner lock ..................................................................................................................62
13. Lock out ....................................................................................................................... 63
Setting up 'Owner' Locks .................................................................................................... 63
Storing Owner Programs ..................................................................................................... 64
Adding further locks...........................................................................................................64
15. OEM Lock ....................................................................................................................65
Storing OEM Programs ........................................................................................................ 66
Adding further locks...........................................................................................................66
OEM & Owner Locks .......................................................................................................... 67
Configuration parameter note.............................................................................................. 67
Lockable Utilities ................................................................................................................ 67
17. Serial Port ..................................................................................................................... 68
18. MIDI Mode ...................................................................................................................68
16. Input A/AES .................................................................................................................. 68
19. MIDI Channel ............................................................................................................... 69
20. MIDI Dump .................................................................................................................. 69
23. Delete Program ............................................................................................................. 70
21. Backup & Swap ............................................................................................................ 70
22. Store Gain Trims ............................................................................................................70
24. Format Card.................................................................................................................. 70
19.0 Input Channels ....................................................................................... 71
2. Delay ............................................................................................................................. 72
3. EQ Bypass ...................................................................................................................... 72
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FDS-366T
4. Dynamic EQ ...................................................................................................................72
1. Gain ............................................................................................................................... 72
DEQ................................................................................................................................... 73
Thr (Threshold) ................................................................................................................... 73
Ratio .................................................................................................................................. 73
Attack and Release ............................................................................................................. 74
Atk (Attack) ......................................................................................................................... 74
Rel (Release) ....................................................................................................................... 74
20.0 Output Channels .................................................................................... 75
1. Name ............................................................................................................................. 76
2. Source............................................................................................................................ 76
3. Low Shape ..................................................................................................................... 77
Low Freq/Xover ..................................................................................................................77
4. High shape..................................................................................................................... 77
High Freq/Xover .................................................................................................................77
6. Band gain....................................................................................................................... 78
5. Phase ............................................................................................................................. 79
Polarity .............................................................................................................................. 79
7. Limiter ........................................................................................................................... 79
Over (Overshoot) ............................................................................................................... 79
Thr (Threshold)................................................................................................................... 79
Rel (Release) ...................................................................................................................... 79
Atk (Attack) ........................................................................................................................ 79
Delay ................................................................................................................................. 80
EQ Bypass....................................................................................................... 80
Delay link .......................................................................................................................... 80
DEQ................................................................................................................................... 81
Thr (Threshold)................................................................................................................... 81
Ratio .................................................................................................................................. 81
Attack and Release ............................................................................................................. 82
Atk (Attack) ........................................................................................................................ 82
Rel (Release) ...................................................................................................................... 82
Outputs - EQ .................................................................................................. 83
EQ shape ........................................................................................................................... 84
Frequency .......................................................................................................................... 85
Width................................................................................................................................. 85
Cut/Boost ........................................................................................................................... 85
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FDS-366T
Reference Section ...........................................................................86
21.0 Serial Communications ......................................................................... 87
MIDI ................................................................................................................................... 87
MIDI with PC Control.......................................................................................................... 88
Synchronous Control .......................................................................................................... 88
RS232 ................................................................................................................................ 89
RS485 & Multidrop ............................................................................................................. 90
22.0 Troubleshooting ..................................................................................... 94
23.0 FDS-366T Omnidrive MIDI Implementation ....................................... 95
A.1 FDS-366T MIDI Implementation ............................................................ 95
24.0 Default Configuration Settings ............................................................... 96
25.0 Filter Allocations .................................................................................... 98
26.0 Specifications and Block Diagram ......................................................... 99
27.0 Block Diagram ..................................................................................... 101
28.0 User Notes ........................................................................................... 102
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FDS-366T
1.0 Primary Checks
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.
Please fill in the warranty details on the form opposite for future reference.
2.0 Installation
✓
Fig 3.1 Unit
dimensions.
Fig 3.2 Rack
dimensions.
Note all dimension in mm
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FDS-366T
3.0 Warranty Infor mation
When sold to an end user by BSS Audio or a BSS Audio Authorised Reseller,
this unit is warranted by the seller to the purchaser against defects in
workmanship and the materials used in its manufacture for a period of one
year from the date of sale.
Faults arising from misuse, unauthorised modifications or accidents are not
covered under this warranty. No other warranty is expressed or implied.
If the unit is faulty it should be sent to the seller of the equipment, in its original
packaging with shipping prepaid. The unit will be returned to you when the
repair has been completed. If the unit was purchased in the European Union,
you may, as an alternative, return the unit to any other BSS distributor in the
European Union.
You should include a statement listing the faults found. The unit’s serial
number must be quoted in all correspondence relating to a claim.
IMPORTANT
We recommend that you record your purchase information here for future
reference.
Unit Serial Number:
Dealer Name:
✍
+
Dealer Address:
Post/Zip Code:
Dealer Phone Number:
Dealer Contact Name:
Invoice/Receipt Number:
Date of Purchase:
Comments or questions regarding the FDS-366T or other BSS products? Contact
us at this address:
BSS Audio
Cranborne House
Cranborne Road
Potter Bar
Herfordshire
EN6 3JN
England
✆
Phone (+44) (0)1707 660667. Fax (+44) (0)1707 660742.
Web site, www.bss.co.uk
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FDS-366T
About the
FDS-366T
Omnidrive
Compact
Plus
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4.0 Introduction
Introducing the BSS Audio FDS-366T Omndrive Compact Plus, an incredibly
powerful loudspeaker management system in only 1U of rackspace! Based on
BSS Audio's many years of experience building analogue processing devices
for the live sound and installed markets, the FDS-366T Omnidrive is an 'all in
one' solution for system crossover assignment, EQ, delay and dynamics
control.
Processing power
Using custom designed digital signal processing (DSP) technologies BSS Audio
are able to deliver far more capabilities in one box than was realisable from a
whole rack of analogue equipment only a few years ago. Also as all the
processing on the audio signal is kept in the digital domain added noise and
phase anomalies usually expected with analogue equivalents are virtually
eliminated. The signals are processed at 24bit, 96kHz resolution to achieve a
dynamic range greater than 112dB to ensure the best possible audio quality for
your system.
Security
Moreover, the comprehensive security features included in the FDS-366T
enable the unit to be set up with varying degrees of access to its functionality
applied and protected by passwords. Indeed the whole unit can be locked
totally to prevent tampering, in installed applications for example.
FDS-366T
Routing
An arrangement of 3 inputs and 6 outputs and an additional internal sum of
inputs A&B, A+B+C, pre or post input EQ can be matrixed in various
combinations to provide a complete loudspeaker management system with
integral crossovers, delays, dynamic EQ, and protection limiters.
Applications
The flexibility of the FDS-366T enables it to be employed for many system
uses, such as complete 3 way stereo setups or a 2 way LCR combination.
Equally FDS-366T Omnidrives can be stacked to run larger 5 and 6 way
systems and more.
In stage monitor systems the FDS-366T can function as a triple bi-amp
crossover with delay, limiters and EQ. On-stage 'hotspots' caused by monitors
with identical signals can be eliminated by applying small delays between
wedges.
Furthermore, the FDS-366T can function as a distribution unit to multizone
systems where crossovers may be passive or local to the loudspeaker. In this
case, the provision of delays and EQ can radically enhance such a system
while reducing both processing costs and required rack space.
Upgradeable operating system
The system operating software is held in flash EPROM, which means that
upgrading to new software is easy - either via PC card or from a PC via the
MIDI or RS-232 ports.
Memorising Setups
60 internal program locations are available to the user for storing system
setups, which may be generic system programs or complete venue settings.
These memories may be stored onto a PC card for backup or archiving.
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5.0 Features
FDS-366T
✓ Individual keys to select input and output channels for editing.
✓ Crossover slopes of 6,12, 18, 24 or 48dB per octave.
Filter types:Butterworth, Bessel, Linkwitz-Riley and WHISEWORKSNTM*.
✓ Comprehensive output limiters on each band (mid-filter).
✓ Equalisers and 'dynamic' equalisers on each input and output.
✓ High resolution input and output delays up to 2.6 seconds in
approximately 11 microsecond steps.
✓ Input LED metering, showing signals from -12dB to clip level, and SIG.
✓ Output LED metering, showing signals from -20dB to +6dB over limit
threshold, and SIG.
✓ Front panel output level trims and mutes.
✓ Polarity reverse on each output.
✓ Phase adjustment for each crossover point, and phase compensation
defeat.
✓ PC card port for storage and recall of program settings
✓ Electronically balanced inputs and outputs with transformer output
option.
✓ MIDI, RS-232, RS-485 and program change ports on rear panel.
✓ 96kHz sample rate and 24bit encoding/decoding for audio excellence.
✓ AES/EBU digital input for direct digital feeds into Omnidrive.
✓ Alignment Assistant for setting up cabinet driver alignments.
✓ Comprehensive system security with control lock out, programmable
'Owner' and 'OEM' locks, and 'Safe' mode available for complete
system lock out.
✓ Temperature based delay correction.
If you are familiar with the FDS-355 Omnidrive then look at the extra benefits
that the FDS-366T brings, an extra output channel, dynamic equalisation,
Thiele crossover shape and 96kHz audio quality to start with!
* The words "WHISEWORKS", "Neville Thiele Method" and NTM logotype are
trademarks of Precision Audio Pty. Ltd (registration pending). Manufactured
under license from Precision Audio Pty. Ltd. International Patents Pending.
- 12 -
Features
FDS-366T
Some of the features are explained in greater detail here.
• 96kHz Sample rate
The FDS-366T operates the A-D and D-A converters and the Digital
Signal Processing (DSP) at a sample rate of 96kHz. The use of a higher
Nyquist frequency enables the audio bandwidth to extend all the way
up to 40kHz. With this extra frequency response we have also been
able to incorporate more accurate filter sets for a more natural, open
sound.
There is also benefit from the improved filter response shapes when the
nyquist frequency (the maximum frequency of which the DSP can
correctly process the signal), moves up from 24kHz to 48kHz. Low-pass
filters and bell filters then retain their magnitude and phase response
shapes more accurately.
• AES/EBU digital input
The FDS-366T is equipped as standard with a stereo AES/EBU digital
audio input which will accept sample rates of 44.1, 48, 88.2 and 96kHz.
44.1 and 48kHz modes are sample-rate converted and the waveform
interpolated to 88.2 and 96kHz respectively within the FDS-366T so
that all of the filtering is done at the higher rate to get more of the
benefits of the increased sample rate. Using the AES input the
realisable dynamic range is increased to greater than 117dB.
• Phase matching
This feature maintains the inter-band phase relationship true to the
crossover type selected (Bessel, Butterworth, L-R etc), regardless of any
interference from far-end crossover filtering.
In 2-way crossovers, this is not an issue since each band has just one
high-pass or low-pass filter. Three or more bands however, cause at least
one band to have both low-pass and high-pass filters which react with
one another, so disturbing the correct phase relationship at the crossover
point. This can result in poor combining of adjacent crossover bands,
resulting in an irregular frequency response and non-uniform polar
characteristics.
The Phase Matching technique used in the FDS-366T eliminates this
problem by compensating for these phase anomalies. The phase
compensation can be bypassed if not required.
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Features
@
FDS-366T
• Alignment Assistant
The Alignment Assistant is an advanced loudspeaker measurement
function built-in to the FDS-366T for directly measuring the delay and
phase relationships between drivers (using a measurement microphone),
and automatically adjusting the settings to accommodate these.
The Alignment Assistant has the ability to ‘see’ past the crossover filters,
and is thus able to compensate for the drivers and enclosures
themselves, leaving the crossovers to do exactly what they were
intended to do - presenting a precisely aligned acoustic wavefront.
The Alignment Assistant can measure and compensate for:
- Physical alignment of drivers within an enclosure.
- Driver or enclosure phase anomalies near the crossover point.
- Relative distance correction of arrayed boxes.
• Advanced Limiters
Driver protection limiters have always been a balance between
protection, transparency and the preservation of maximum power. The
all-new limiter algorithm in the FDS-366T not only allows the user the
freedom to change the way the compromises are balanced, but
introduces several new features which enable the requirements to be
met with less sacrifice.
- Feed-forward design for better stability.
- Adaptive attack, so that attack time is reduced the further over
threshold the signal strays. This helps to preserve transparency for
light overshoots, but acts more aggressively if the signal strays too
far.
- Adaptive release, so that short-term overshoots do not reduce the
average power output, whilst keeping distortion low on sustained
over-threshold signals.
- Adjustable attack speed (fast/med/slow/dual) - but still related to
the high-pass crossover frequency.
- Adjustable release speed (fast/med/slow) - but still related to the
high-pass crossover frequency.
- Brickwall overshoot limiter. This is actually a soft-clipper which
constrains signals which overshoot during the attack phase. The
user has adjustable ‘overshoot’ from 1 to 12dB (and off).
- Dual time-constant mode for giving simultaneous protection
against short-term mechanical damage or clipping, and longer
term thermal damage.
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Features
FDS-366T
• Safe mode
The FDS-366T has a hidden function called 'Safe'. 'Safe' mode is intended to
be used as a complete lock-out for installations or as the ultimate protection
for hire systems etc.
When SAFE mode is switched on, all controls are disabled, the screen blanks
and the backlight is dimmed. The input and output meters will still display the
existence of signal being processed through the unit but no one can change
any values within the unit.
! Any adjustments made to the gain controls whilst in 'Safe' mode will not be
heard until 'Safe' is turned off.
! As the 'Safe' mode is intended for ultimate security, the details of its use
cannot be published here. Please consult your dealer for further information
on Safe mode.
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FDS-366T
6.0 Typical Applications
The FDS-366T has three inputs: A, B, C. An internal mono sum of inputs is also
available for routing to any of the outputs. Many combination of routing inputs
to outputs is available, and the FDS-366T can be configured as a stereo or
mono device. The basic configurations are selected in the Utilities and the
following examples are based upon these as possible likely setups.
Stereo 3-Way with
mono sub-bass.
Systems can be run in one of two stereo 3-way modes.
LLMMHH allows compatability with the 355, now having two low outputs.
j
LMHLMH set up is an alternative, allowing users to choose the setup they are
most familiar with.
Stereo Link "On" mode allows the same parameters on the left and right
channels to be adjusted simultaneously, and any edits made whilst unlinked
preserve the left/right difference as an offset.
Note: The stereo pairs change appropriately for LLMMHH and LMHLMH
modes.
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FDS-366T
Typical Applications
Triple Bi-amp
(Stage monitors)
The FDS-366T can provide 3 channels of bi-amp crossover for monitor racks
with EQ, delays, and limiters. With so much EQ available in the FDS-366T, it
is easy to assign 12 bands of EQ to the input, as well as EQ to the output
bands, saving the need for external EQ.
In LHLHLH mode by default, input A feeds outputs 1 and 2, input B feeds
outputs 3 and 4, and input C feeds outputs 5 and 6.
In this mode, it is possible to remove ‘hot spots’ on stage. Where the same mix
is sent to a number of performers, interaction between wedges can create lobes
of high intensity sound causing confusion. Using a fine delay to shift wedge
feeds can move these 'hot-spots' to less sensitive areas on stage.
j
LCR cinema
systems (3x2-way)
6-Way zoning
distribution
A similar configuration to the triple 2-way setup above.
The FDS-366T can be also be used as a zone distribution system, without
using any of its crossover facilities. Using this mode, a common input signal
can be routed to up to 6 separate outputs, each with delays, EQ and limiters.
Typical uses for this mode would include feeding a number of under-balcony
loudspeakers with integral passive crossovers, using the delays of the FDS366T for time correction, and EQ for tuning response.
For this application set the configuration to Mono and each output should be
full range (unless you particularly want to band restrict the outputs). Use the
'Xover Freq' screens in the output channel to set each band edge to be 'OUT'.
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FDS-366T
Typical Applications
Mono 6-way
Stereo 6-way
(example)
In the mono mode, the FDS-366T can provide a full 6-way system. It can also
function as a 5-way system fed from input A, with an independent sub-bass
output fed from the sum of inputs A & B or input C.
Two FDS-366Ts working in this mode can form a stereo 6-way system. For
example purposes only, in the diagram below the first FDS-366T is running a 5
way system with the mono sub bass derived from the sum of inputs A and B.
The second FDS-366T has its mono sub bass output fed from a dedicated
output on the desk running into input C.
j
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7.0 Crossover Shapes and Frequencies
It is not possible to provide one loudspeaker driver to cover all audible
frequencies. Even if the frequency response could be achieved, the large size
of the driver required to shift enough air at low frequencies would offer an
impossibly directional beam at high frequencies because at small wavelengths,
the differing path lengths from the extremities of the diaphragm to the listener
would cause cancellations off-axis. Therefore, it is necessary to use more than
one driver and to split the bands with an electrical filter or crossover. This
filtering can be done by passive, active or digital means, external to or within
the loudspeaker cabinet.
Ideally, the filtering is done so that when acoustically combined, the drivers
produce a constant output across the required range of frequencies.
Additionally, the signal phase behavior with frequency should offer smooth
transitions across all the drivers to achieve a constant group delay. Another
important consideration is that the crossover should control the beaming
properties, also known as the polar response, so that listeners off-axis do not
hear anomalies in the sound range. Many crossover filter designs do not
achieve these goals.
Finally, the signal should be quickly attenuated outside the optimum band of
operation for each driver to avoid driver anomalies such as resonance and
over-excursion distortion at low frequencies. In these instances some crossover
shapes have limitations.
FDS-366T
The FDS-366T allows full control over each high and low pass filter of a
crossover segment in shape, slope and frequency. Graphically these
parameters are labelled as below.
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Filter Edge Identification
FDS-366T
5
5
Crossover Shapes and Frequencies
The graphs on this page show the filter slope curves with associated crossover points in order to aid the sound
technician in the choice of filter shape to use for the desired result between speaker drivers of differing
specifications and characteristics.
5.0000
0.0
-5.000
-10.00
-15.00
-20.00
-25.00
-30.00
-35.00
-40.00
-45.00
-50.00
20 100 1k 10k 20k
Butterworth 6, 12, 18, 24 & 48dB/Octave Slopes.
The even order Butterworth crossovers (12, 24,
48dB/octave) exhibit a symmetrical polar response
due to identical phase responses in the Hi and Lo
bands. There is an issue with a 3dB peak in the
amplitude response at the crossover frequency but
this can be corrected with equalisation. In
contrast, the odd order Butterworths (6 & 18dB/
octave) sum to a flat amplitude response but suffer
asymmetry in their polar response that changes as
the signal moves through the crossover point. This
'tilt' can produce colouration and is dependant on
the listening position. These also require polarity
inversion for correct response.
Linkwitz-Riley 12, 24 & 48dB/Octave Slopes.
For many years Linkwitz-Riley crossovers have
been the 'industry standard' as they offered the
best compromise between the parameters
discussed earlier. They retain good polar
response, sum to a flat amplitude response and
retain correct polarity across the 24dB/octave and
48dB/octave slopes. The 12dB/octave variant
generally needs a polarity inversion to achieve the
required results. They have been the usual choice
for most applications.
Bessel 12 & 24dB/Octave Slopes.
Standard Bessel filters when used for crossover
duties do not provide immediately acceptable
results due to deficiencies in their amplitude
response. Due to this only 4th and 2nd order (Bes
24 & 12) alignments were considered to be
acceptable for inclusion. The 12dB/octave
version will require a polarity inversion of one
band for proper summation.
0
0
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-
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- 20 -
Crossover Shapes and Frequencies
FDS-366T
10
0
10
20
dB
30
40
50
100 1.10
WHISEWORKS-NTM
Crossover
Thiele 4 rolloff
3
Hz
1.10
4
The WHISEWORKS-Neville Thiele Method (NTM) crossover filter is a new
type of electrical/acoustical filter offering significant performance advantages
over all previous crossover filter types in audio applications. The filter was
developed by Neville Thiele (pronounced “Teel”).
This filter uses a unique notched response to achieve a very steep roll-off rate
outside the passband. There are two choices of NTM crossover included in
the FDS-366T; a 4th order (NTM 36) and an 8th order (NTM52). The 4th order
shape offers exceptional group delay flatness with a roll-off of at least 36dB/
octave. The 8th order version offers the steepest roll-off rate of all.
WHISEWORKS-NTM Crossover Filter advantages:
1. It sums to give constant output against frequency.
2. It has a well defined phase response.
3. It keeps the phase difference between adjacent drivers at zero degrees
throughout the crossover region to prevent beam shifting.
4. It has the highest known rate of attenuation in the stop band of all
conventional analogue or analogue-equivalent filters of similar order.
The faster roll-off rates realised by the NTM filter shape enable lower
distortion that is particularly valuable in applications where space is at a
premium as smaller drivers may be used. Driver and cabinet design
constraints are also eased since designers can work ‘closer to the edge’ where
resonance, breakup, or other anomalies may normally occur with more gentle
slopes.
The new Neville Thiele Method crossover shapes now represent the optimal
combination of characteristics for most applications and listening tests seem
to bear this out! We feel that this shape could topple the Linkwitz-Riley as
the new 'industry standard', particularly as the nearest Linkwitz-Riley
equivalent (L-R 48) has attained a reputation for a "hard sound", this doesn't
appear to be the case using the NTM shapes.
- 21 -
Crossover Shapes and Frequencies
FDS-366T
Crossover
comparison chart
Below is a chart comparing the different crossover filter types that are
provided in the FDS-366T Omnidrive. This table should help to ascertain the
particular choice of filter dependant on application. Shapes marked with an
asterisk * will require polarity inversion.
Key:
= Worst
•
••••••
BUT = Butterworth
BES = Bessel
L-R = Linkwitz-Riley
NTM = Neville Thiele
Method
= Best
Amplitude response flatness: also known as 'frequency response', a measure of
the flatness of the amplitude with differing frequencies. Choosing a crossover
alignment that sums to a flat amplitude response is usually desirable because
such a system will require less equalisation.
Group delay flatness: a measure of how different frequencies are delayed
throughout the crossover region. Although it is unlikely that all frequencies
can be delayed equally, a smooth group delay response that lacks peakiness is
desirable.
Polar response: a qualification of the lobing effect due to the distance between
any pair of drivers involved in the crossover. The main lobe needs to be onaxis so that listeners on-axis do not hear dips in the amplitude response
through the crossover region.
Roll-off rate: A measure of how quickly the slope of the filter drops off to a
much lower amplitude. A steeper slope is generally required to maximise the
potential of driver frequency response and to narrow the frequency range that
is affected by the crossover operation.
- 22 -
Crossover Shapes and Frequencies
FDS-366T
Phase
Compensation
Phase compensation to active crossovers was introduced in the classic FDS355 Omnidrive Compact Loudspeaker Management System. The FDS-366T
Omnidrive includes this feature, freeing the user of worry about phase
alignment between bands.
More info about Phase Compensation:
A properly designed 2 way crossover always exhibits the inter-band phase
relationships that are characteristic of the chosen crossover shape. For
example, the Linkwitz-Riley filter shape, with its low-pass filter for the low
band, and high-pass filter for the high band, will maintain zero phase
difference between these bands at all frequencies, which means that the
acoustic outputs from the drivers will sum to a flat response, free of any shifting
in polar response.
In 3 way (or more) systems, things can start to go wrong. The mid band in a 3
way system for example, has not one filter, but two (high-pass, and low-pass).
The low-pass filter, set at the mid-high crossover frequency will produce some
phase disturbance at the low-mid crossover frequency, causing the low-mid
crossover filter pair to be misaligned. The same is true of the high-pass filter,
which may affect the mid-high crossover filter pair. This misalignment causes
incorrect acoustic summing, which results in a non-flat response, and a polar
response which shifts with frequency, causing further response problems in
some listening positions. Although these effects may be subtle when the
crossover frequencies are well separated, 4 and 5 way systems particularly can
produce significant errors.
The phase compensation scheme employed in Omnidrive analyses these phase
anomalies whenever adjustments are made, and automatically introduces
phase adjustment into certain bands so that the phase difference between
adjacent bands is always close to zero degrees. Intentional phase differences
can be introduced using the Delay and Phase parameters.
Omnidrive will not attempt to apply phase compensation if the high and low
frequencies or shapes of the adjacent bands do not match, on the assumption
that the user does not expect to produce a standard crossover alignment.
By default the FDS-366T applies phase compensation to crossover setups
where there are 3 bands, or more, in use on a channel and where the
crossover filter shapes are identical. In general the application of this feature
is desirable to maintain the correct phase relationships between bands but, in
certain circumstances phase compensation may need to be defeated to avoid
phase inconsistencies between separated speaker installations, such as side or
under fills and certain monitoring applications. The facility to do this is called
'Phase Comp' and is found in the Utilities.
- 23 -
8.0 Dynamic Equalisation
FDS-366T
What is DEQ?
The BSS DPR-901 Analogue Dynamic Equaliser was a revolutionary way of
dealing with equalisation, and was made possible by the subtractive
progressive knee technique developed for the industry-standard DPR-402
Analogue Compressor. The very same techniques are used in the FDS-366T to
give you dynamic control of equalisation, or indeed for conventional full-range
compression on every input and every output.
The compressor used in the FDS-366T Dynamic Equaliser uses the audibly
transparent ‘subtractive VCA' (Voltage Controlled Amplifier) technology used
in all other BSS compressors, and results in substantially better performance
than other methods. There is clearly no VCA in use in the FDS-366T, as it is a
digital device, but the DSP (Digital Signal Processing) models the effect using
algorithms developed by our crack team of audio systems experts.
The subtractive ‘VCA’ also allows the realisation of a completely different type
of compression that BSS have named parametric compression. This enables
selective compression to be applied to only certain frequencies in a signal, as
displayed by a conventional looking parametric filter control window. When
the selected frequencies are encountered, the Dynamic Equaliser starts to
compress only those signals at a rate determined by the ratio and threshold
controls.
The Dynamic Equaliser operates in two very different ways depending on
whether the parametric equaliser is set to boost or cut:
In boost mode, the parametric equaliser is allowed to impose its
response on the signal when below threshold, but the effect of the
equaliser is ‘flattened out’ as the signal starts to exceed threshold.
Dynamic EQ boost at -15dB threshold
In cut mode however, the equaliser only has effect above threshold, and
is flattened out as the signal reduces below threshold.
Dynamic EQ cut at -15dB threshold
- 24 -
Dynamic Equalisation
FDS-366T
Notes and Uses
Frequency selective compressing
Conventional compressors affect the whole audible band of frequencies
equally. Some compressors can be configured to only start compression when
they encounter given frequencies, however, once they start compressing they
compress the whole audio band. This is quite distinct from the type of
compression available in the FDS-366T DEQ.
The DEQ can be set up so that when it encounters a given band of frequencies
it compresses only that band, this is a very different technique from simple
equalisation and is vastly more powerful for both corrective applications and
creative manipulation.
To use Dynamic EQ as a wide band compressor, use high pass (i.e low
shelving) with a low frequency or vice versa.
Use with Stereo sources
To avoid 'image shift' when stereo sources are compressed the input DEQs
have their sidechains linked when the Stereo Link parameter is set to "On" .
Control of horn distortion
Above a certain critical sound level output, horn loaded speakers often start to
produce distortion. This is due to the irregular movement of air in the horn
throat and is usually a problem over a restricted range of frequencies. The band
of frequencies affected is dependent on the dimensions of the horn.
The DEQ can be used to reduce the energy in the frequency band that
aggravates the horn, resulting in both a much-improved sound and the
possibility of higher sound levels.
To do this:
1 With some program material playing, set the EQ shape of the DEQ to
Bell with some boost.
2 Manipulate the sound system level, DEQ frequency and width
parameters to find the frequency band that is causing problems.
3 Make this band as narrow as possible using the width parameter,
ensuring that the DEQ is initially set to "Off".
4 Set the EQ to cut and increase the system sound level until there is
unacceptable distortion.
5 Adjust the threshold ("Thr") parameter until the distortion is diminished.
6 Try different ratio and filter settings to achieve the best response.
- 25 -
Dynamic Equalisation
Dynamic bass and treble enhancement
The bass and treble content of the program can be made to appear louder
without increasing the overall sound level if the middle frequencies of the
program are reduced when the sound level approaches the limit. This can be
especially useful to squeeze the last few dB of perceived headroom out of a
PA.
The parametric equaliser associated with the Dynamic Equaliser is much like
the other EQs in the FDS-366T (and may in fact be used as a conventional
equaliser if DEQ is set to "Off".
As the sidechain of the compressor is fed from the equaliser, this endows the
DEQ with the unique ability to select a portion of the audio band and
compress only that band.
To do this:
1 Set the EQ parameters to boost at the appropriate frequencies, using
either BELL filter shape, or probably more aptly, LO-SHELF for the LF
end or HI-SHELF for the HF end.
FDS-366T
2 Set the threshold ("Thr") parameter so that the boost/cut bargraph starts
to go upward at the desired level.
3 Adjust the ratio control for the correct amount of compression.
For more information on setting Dynamic Equalisation please refer to the DEQ
descriptions in the Input and Output sections of this manual.
- 26 -
FDS-366T
The Rear Panel
and Connections
- 27 -
9.0 Rear panel
A Mains power input
The power inlet for the FDS-366T. Note that there is no On/Off switch
for the unit. Accepted voltage range: 90-240V AC 50/60Hz,
autosensing.
B Fuse
In the event of failure due to mains overload only replace with T1A fuse
as stated on the unit.
C,D RS-485 connectors
Serial connection to a PC on a multi-drop network.
FDS-366T
E RS-232 connector
Serial connection to either a PC or to connect to another FDS-366T.
Provides an easy way to upload new software.
F Program select connector
Use to select programs 1-8 with external switches or buttons or can also
be connected to Soundweb's control port logic outputs.
G MIDI OUT connector
H MIDI IN connector
For connection to other FDS-366T units in order to perform simultaneous
program changes, backup or control functions.
J Band outputs (6)
The FDS-366T audio outputs are electronically balanced and floating.
Pin 1 Shield/Ground
Pin 2 Signal Hot (+)
Pin 3 Signal Cold (-)
K Channel inputs (3)
The FDS-366T audio inputs are electronically balanced. Transformer
balancing is available as a retrofit option.
Pin 1 Open circuit
Pin 2 Signal Hot (+)
Pin 3 Signal Cold (-)
- 28 -
FDS-366T
10.0 Connections - Mains Power
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
If the colours of the wires in the mains lead do not correspond with the
identifying markings on the terminals in your plug refer to the following:
The wire that is coloured Green & Yellow or Green must be connected to
the terminal which is marked with the letter ‘E’ or by the Earth symbol
or which is coloured Green & Yellow or Green.
The wire that is coloured Blue must be connected to the terminal labelled
‘N’ or coloured Black or Blue.
The wire that is coloured Brown must be connected to the terminal labelled
‘L’ or coloured Red or Brown.
,
Voltage setting
WARNING! THIS APPLIANCE MUST BE EARTHED.
The Green and Yellow wire of the mains cord must always be connected to
an installation safety earth or ground. The earth is essential for personal
safety as well as the correct operation of the system, and is internally
connected to all exposed metal surfaces. Any rack framework into which this
unit may be mounted is assumed to be connected to the same grounding
circuit.
” Units supplied to the North American market will have a moulded 3 pin
connector that is provided to satisfy required local standards.
The FDS-366T uses a switch mode power supply which offers high efficiency
and low heat generation. This power supply accepts universal AC power input
voltages in the range 100V AC to 240V AC (nominal), and requires no setting
adjustment for AC power voltages in this range. Minimum AC input voltage is
90 Volts, and the maximum is 264 volts.
Outside these ranges the unit will not work satisfactorily, if at all. Voltages in
excess of the maximum will probably cause damage. Voltages below the
minimum will cause complete system shutdown. The flash memory in the unit
should preserve all data in the event of a power failure.
- 29 -
FDS-366T
Connections - Mains Power
AC Power fusing
The incoming mains power is protected within the FDS-366T by a fuse in the
holder mounted on the rear panel.
In the event that a mains fault occurs and blows this fuse always replace with
an identical 20mm x 5mm 'T' fuse, rated at 1A for continued protection from
equipment damage and fire.
Spare fuses of the correct rating are supplied with the unit.
It is most important for continued safety that this specification is strictly
adhered to.
,
Location of mains fuse on rear panel.
- 30 -
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