Bosch LA3-VARI-BH Vari Base Unit HF, 130Hz-18kHz Frequency Range, 89/92dB Sound Pressure Level, Gray

The Bosch LA3-VARI-BH Gray base unit HF is a comprehensive set of array loudspeakers to address people with clear intelligible messages in large reverberant spaces. These active units utilize integrated digital signal processing and high efficiency class-D amplifiers. Using a PC configuration program the array can be adapted to the venue where it is used and its sound output optimally aimed at the audience, creating a maximum direct to ambient sound ratio, for best intelligibility given the circumstances. The modular concept allows for three different array lengths for small to large areas. Using separate array elements makes transport easy and upgrading to a longer array possible.

Special built-in provisions make these arrays compliant to the world's emergency sound system standards. The units are suited for both background music and speech. Although these loudspeaker arrays are very sophisticated and offer unrivalled sound in difficult acoustical environments, the advanced configuration software makes setup quick and easy.

Functions

Advanced beam steering
The Bosch LA3-VARI-BHH provides a very good direct to reverberant sound ratio. Firstly, it radiates more direct sound to the audience and secondly, it induces less ceiling reflections. The increased direct sound is also due to a lower rate of decay of the sound level with distance compared to a traditional loudspeaker acting as a point source. Instead of mechanically aiming the complete loudspeaker column to the listeners, the Bosch LA3-VARI-BH is capable of virtually aiming the loudspeaker array by electronic means.

It drives the loudspeakers of the array individually with differently delayed signals, virtually moving the loudspeakers. Now the array can be positioned vertically against a wall or even recessed into the wall. This is esthetically more pleasing and as a bonus also reduces disturbing incoherent reflections from the wall. Furthermore, the Bosch LA3-VARI-BH uses very advanced beam steering techniques to achieve a beam shape that provides an equal level for all frequencies in the range of interest at all listening positions. Only then, listeners will get a balanced sound.

Another important factor is the loudness of the signal, which should be almost the same for all listening positions, avoiding hot spots. To create an even sound level in a large area, the shape of the beam should be optimized to the listening plane (ear level). Solving these challenges requires that for every audio frequency in the range of interest the level of each individual loudspeaker should be carefully controlled.

It performs this combination of frequency response and delay tailoring in the digital domain using a DSP and subsequent multi-channel amplification. Then a very consistent SPL from front to rear can be attained in the listening plane, with a minimum of side lobes. But the Bosch arrays excel in two additional ways. In the first place it is able to deal with non-flat audience planes, for instance theaters and auditoriums. Secondly, it does not solely try to maximize the direct output to the listening plane, but also to minimize the output to unwanted areas. Due to physical limitations of a loudspeaker array every practical array will have side lobes. The configuration of the Vari-directional Array uses an advanced optimization algorithm that allows for minimization of the most harmful side-lobes, to achieve the best possible coverage combined with a maximum direct to reverberant ratio.

Easy installation and setup
The Bosch LA3-VARI-BH makes installation and configuration fairly easy for the installer and sound engineer. The majority of the applications can be described in a rather straightforward way, where the configuration can be selected from a database of pre-optimized setups. Selection is quick and interactively by entering some key parameters of the room, the position of the array and the listening plane. The configuration program then shows graphically the realized direct SPL coverage.

The Vari Configuration Set includes the configuration software and a USB to RS485 converter to connect a PC's USB port to one or more (networked) Vari units, even across longer distances. Using the optional CobraNet module it is even possible to configure and monitor multiple units across an Ethernet network.

Modular approach
The base unit contains the controller, the DSP, the power supply and 8 power amplifiers and Loudspeakers. The Bosch LA3-VARI-BH, with its full steel cabinet and grill, powder coated silver gray, blends easily with contemporary and traditional interiors and exteriors. Since front-cooling is applied, even flush mounting is possible. Swivel-wall mounting brackets come with the units as standard.

CobraNet connectivity
The Bosch LA3-VARI-BH offers the possibility to equip the base unit with a small CobraNet module that allows the array to be connected to an Ethernet network via a CAT-5 cable connection. This way the audio signal to the array is delivered in a digital format to the array with low latency and a high degree of routing flexibility. Furthermore the array can be configured via Ethernet, its operation can be supervised and logged.

Use of standard Ethernet wiring reduces costs. CobraNet technology allows for the co-existence of audio and data traffic over existing standard Ethernet infrastructure resulting in substantial savings in design and installation. CobraNet is a technology that is owned by Cirrus Logic and is used by many professional audio manufacturers as the technology of choice in digital audio networking.

Emergency sound
Emergency warning and information systems are very much a part of life these days. They are mandatory for most commercial buildings and public spaces and must comply with very specific standards, such as IEC60849, BS5839-8 and EN54-16. The system elements of the Bosch LA3-VARI-BH have been designed for compliancy to these standards, right from the start. Therefore the array cannot only be used for business announcements and background music, but also as part of an emergency sound system, e.g. in combination with the Bosch Praesideo system, one of the most sophisticated emergency sound systems available, with thousands of installations worldwide.

The Bosch LA3-VARI-BH is a perfect loudspeaker system for making voice alarms in case of emergencies, when clear, intelligible and unambiguous announcements are needed most.

Automatic Volume Control (AVC)
In certain environments, such as sports stadiums and passenger terminals, the background noise level fluctuates constantly. This may seriously affect the intelligibility of spoken messages. The Bosch LA3-VARI-BH has a built-in noise level sensor that can be configured to control the gain of the amplifiers to constantly adjust the sound level. This automatic volume control (AVC) keeps the audio level comfortably above the background noise level for improved intelligibility without becoming unnecessarily loud.

Sound-processing
Large halls or platforms may need multiple arrays at different locations. The audio output of these arrays should be time-aligned to avoid echoes at the audience position. The Bosch LA3-VARI-BH provides a built-in high resolution delay adjustment. An 8-section parametric equalizer is present for adjustment of the array to the acoustical environment, e.g. to increase the margin before acoustic feedback occurs. Separate 4-section equalizers at the inputs enable separate frequency responses for e.g. background music and announcements.