JBL LSR Owner's Manual

Contents

11Section 5. - LSR12P ACTIVE SUBWOOFERThe LSR12P Active Subwoofer consists of a high powered Differential Drive® 12” neodymium wooferintegrated with a powerful 250 watt continuous power output amplifier. The active drive circuitry has beendeveloped to maximize the acoustic output power while maintaining overall low distortion and high transientperformance. The enclosure is manufactured with a carbon fiber composite baffle and rigidly braced MDFenclosure for low resonance and minimal box lose. The Linear Dynamics Aperture (LDA) Port design mini-mizes port noise and eliminates bass robbing port compression.Active crossover electronics supply 4th-order electroacoustic slopes to the low pass subwoofer transi-tion to reduce the possibility of localization of the subwoofer. This allows a greater flexibility in placement foroptimum operation in a wide variety of rooms. Since low frequency energy supplied by the LSR12P is essential-ly omnidirectional, placement of the unit(s) is more dependent upon room acoustics and interactions thanlocalization issues.Also included with the active electronics are switchable high pass filters for the front satellite speak-ers. This option is used when it is desired to filter out low frequency information from the front speakers andredirect this information to the subwoofer. This is usually the case when the front speakers are small nearfields that cannot handle extended low frequency information at the desired sound pressure level.Alternatively, if the front channels are operated in full range, the bypass function can be enabledallowing the subwoofer to be muted at the close of a switch contact to compare the different combinations dur-ing mixing.5.1 Audio Connections:There are several ways to connect the LSR12P into a monitoring system including stereo and multi-channel formats such as Dolby ProLogic, AC-3, DTS, MPEG and others. The bass management system in theLSR12P provides the flexibility to switch between configurations.In a Stereo Configuration, it is typical to feed the LSR12P with the left and right channels and takethe left and right outputs from the LSR12P and feed them to the satellites. The high pass filters on the outputsremove the low frequency energy below 85 Hz from the satellites. This energy is redirected to the subwoofer.The ProLogic format from Dolby uses a similar connection scheme to the one above. The Left, Cen-ter and Right channels route to the Left, Center and Right inputs of the LSR12P and through the respectiveoutputs to the satellites. Energy below 85 Hz is filtered out of the satellites and sent to the subwoofer.Other multichannel formats such as Dolby AC-3, DTS, MPEGII include six discrete channels, Left,Center, Right, Left Surround, Right Surround and Subwoofer. These are termed 5.1 for five main channels anda dedicated subwoofer channel, which is also called the Low Frequency Effects or LFE channel. Not all materi-al uses all channels and engineers have the discretion to use the subwoofer.