L-Acoustics Sb28 Subwoofer User Manual

USER MANUAL

SB28 SUBWOOFER USER MANUAL VERSION 3.0

SAFETY INSTRUCTIONS

1. Read this manual

2. Heed all SAFETY INSTRUCTIONS as well as DANGER and OBLIGATION warnings

3.  Never incorporate equipment or accessories not approved by L-ACOUSTICS®

4. Read all the related PRODUCT INFORMATION documents before exploiting the system
   The product information document is included in the shipping carton of the related system component.

5. Read the RIGGING MANUAL before installing the product
   Use the rigging elements described in the rigging manual and follow the associated procedures.

6. Beware of sound levels
   Do not stay within close proximity of loudspeakers in operation and consider wearing earplugs.
   Loudspeaker systems are capable of producing very high sound pressure levels (SPL) which can instantaneously
   lead to permanent hearing damage to performers, production crew and audience members. Hearing damage can
   also occur with prolonged exposure to sound: 8 h at 90 dB(A), 30 min at 110 dB(A), less than 4 min at 130 dB(A).

SYMBOLS
The following symbols are used in this document

DANGER
This symbol indicates a potential risk of harm to an individual or damage to the product.
It can also notify the user about instructions that must be strictly followed to ensure safe installation or
operation of the product.

OBLIGATION
This symbol notifies the user about instructions that must be strictly followed to ensure proper installation or
operation of the product.

INFORMATION
This symbol notifies the user about complementary information or optional instructions.

WELCOME TO L-ACOUSTICS®
Thank you for choosing the L-ACOUSTICS® SB28 subwoofer enclosure.
This document contains essential information on using the system properly. Carefully read this document in order to
become familiar with the system.
As part of a continuous evolution of techniques and standards, L-ACOUSTICS® reserves the right to
change the specifications of its products and the content of its documents without prior notice.
Please check the L-ACOUSTICS® web site on a regular basis to download latest updates for documents and software:
www.l-acoustics.com.

1 SB28 HIGH POWER SUBWOOFER
The SB28 contains two 18’’ direct radiating LF transducers integrated into a bass-reflex tuned enclosure. The specially
designed 18’’ transducers provide an exceptional cone excursion capability combined with low thermal compression
even at the very highest operating levels. The progressive profile of vents allows laminar airflow and reduces turbulence
noise. The combination of these characteristics provides a greatly improved +5 dB peak SPL output compared to the
previous standards. The SB28 enclosure is made of first grade Baltic birch plywood to ensure maximum acoustical and
mechanical integrity. The SB28 enclosure is exclusively driven and amplified by the LA8 amplified controller. This one
ensures linearization, protection and optimization for the loudspeaker system in the different operating modes of the
SB18, cardioid included.

2 SYSTEM COMPONENTS
The system approach developed by L-ACOUSTICS® consists in offering a global solution that guarantee the highest and
most predictable level of performance at any step of loudspeaker system deployment: modeling, installation and
operation. A complete L-ACOUSTICS® system includes enclosures, amplified controllers, cables, rigging system and
software applications. The main components of an L-ACOUSTICS® system that includes the SB28 subwoofer are:

2.1 Powering and driving system

LA8            Amplified controller with DSP library and networking capabilities
LA-RAK    Touring rack containing three LA8, for mains, audio signals and network distribution

Operating instructions
Refer to the LA8 and the LA-RAK user manual.

2.2 Loudspeaker cables

DO cables (DO.7, DO10, DO25)| 8-point PA-COM® loudspeaker cables
respective lengths of 0.7m/2.3ft,10m/32.8ft, and 25m/82ft
---|---
DO3WFILL| Breakout cable for one 2-way active enclosure and two passive enclosures
PA-COM® < 3 x SpeakON®
DOSUB-LA8| Breakout cable for four passive enclosures
PA-COM® < 4 x SpeakON®
SP cables (SP.7, SP5, SP10, SP25)| 4-point SpeakON® loudspeaker cables,
respective lengths of 0.7m/2.3ft, 5m/16.4ft, 10m/32.8ft and 25m/82ft
SP-Y1| Breakout cable for two passive enclosure
SpeakON® < 2 x SpeakON®

Information about the connection of the enclosures to the LA amplifiers is given in this document.
Refer to the LA8 and the LA-RAK user manual for detailed instructions about the whole cabling scheme,
including modulation cables and network.

2.3 Software

Using L-ACOUSTICS® software,
Refer to the SOUNDVISON user manual and the LA NETWORK MANAGER tutorial.

L-ACOUSTICS® system components for SB28
(excluding main systems, rigging elements and modulation cables)

3 OPERATING MODES

3.1 STANDARD mode

In STANDARD mode, a subwoofer system operates with an omni-directional directivity pattern.
It corresponds to the use of SB subwoofers as single elements or as an array in standard configuration.
The SB28 subwoofers are driven by the LA8 amplified controller with a choice of two factory presets, each one offering
a distinct upper frequency limit in order to optimize the acoustic coupling between the subwoofer system and a main
full-range system.

3.2 CARDIOID mode

In CARDIOID mode, a subwoofer system produces a rear SPL rejection.
It corresponds to the use of an array of four SB enclosures with one reversed element, i.e. turned towards the rear.
The SB28 subwoofers are driven by the LA8 amplified controller with a choice of two different factory presets, each
one offering a distinct upper frequency limit, in order to optimize the acoustic coupling between the subwoofer system
and a main full-range system. Both presets feature delay settings optimized for SB28 arrays in cardioid configuration.

Delay settings
When combining a line source with subwoofers, delays may have to be added to the presets.
Refer to the LA8 PRESET LIBRARY user manual to obtain the pre-alignment delay values.

Grouping subwoofers
Place the subwoofer enclosures side by side. If not possible, the maximum distance between two adjacent
acoustic centers must be 2.8 m or 1.7 m whether the upper frequency limit of the subwoofer system is 60 Hz
or 100 Hz, respectively.

4  LOUDSPEAKER CONNECTION
The SB28 subwoofer is equipped with one 4-point SpeakON® connector.

Internal pinout for SB28 subwoofers

The SB28 is exclusively amplified by the L-ACOUSTICS® LA8 amplified controller.
To cable SB28 subwoofers with the LA8, three options are available:

Option A:

• Connect a DO cable (DO.7, DO10 or DO25) to the PA-COM® connector of the LA8 and use the DOSUB-LA8 to
  split the audio signals into four channels, each one feeding one subwoofer.

Option B:

• Connect an SP cable (SP.7, SP5, SP10 or SP25) to one of the SpeakON® connectors of the LA8, and use the SP-Y1
  cable to split the audio signals into two channels, each one feeding one subwoofer. The CC4FP adaptor allows
  interfacing the SP and SP-Y1 cables. Apply the same cabling scheme with the other LA8 SpeakON® connector.

Option C:

• Connect a DO cable (DO.7, DO10 or DO25) to the PA-COM® connector of the LA8 and use the DO3WFILL to
  split the audio signals into one channel pair, feeding one two-way enclosure, and two single channels, each one feeding
  one SB28 subwoofer. This cabling scheme needs a dedicated custom preset.

Maximum of 4 SB28 subwoofers per LA8
1 SB28 subwoofer can be connected to each output channel on the LA8.

PA-COM® standard
Using cable other than specified in this document to connect a subwoofer via the PA-COM® connector of the
LA8 may affect the acoustic results. Refer to the LA8 PACOM CABLES technical bulletin.

CARDIOID mode
By connecting the reversed subwoofer to OUT 1, Option A and Option B allow using the cardioid preset

Impedance load
4 Ω for1 SB28.

Connecting four SB28 to one LA8 with the DOSUB-LA8 (Option A)

APPENDIX A: PRESET DESCRIPTION

The latest version of each PRESET LIBRARY and the corresponding user manuals are downloadable from
the L-ACOUSTICS® web site.

[SB28_60] and [SB28_100]: standard subwoofer

To use SB28 subwoofers in STANDARD mode, as single elements or as an array in standard configuration.

[SB28_60_C] and [SB28_100_C]: cardioid subwoofer

To use SB28 subwoofers in CARDIOID mode, as an array in cardioid configuration.

APPENDIX B: SPECIFICATIONS FOR LOUDSPEAKER CABLES

Cable quality and resistance
Only use high-quality fully insulated speaker cables made of stranded copper wire.
Use cables of gauge offering low resistance per unit length and keep the cables as short as possible.

The following table provides the recommended maximum length depending on the cable cross-section and on the
impedance load connected to the amplifier.

APPENDIX C: SPECIFICATIONS

SB28

L-Acoustics, an L-Group Company

L-Acoustics Sb28 SubwooferManual Optimized

L-Acoustics Sb28 SubwooferManual Original

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