JBL LSR 6312SP
Linear Spatial Reference Powered Studio Subwoofer System

The JBL LSR6312SP powered studio subwoofer is designed to provide low frequency extension and sophisticated bass management capabilities in stereo and multi-channel applications where exceptional spectral accuracy and high-SPL are required. The system includes JBL's RMC room mode correction circuit.

The system is designed around JBL's 252F 12" LF transducer, which uses dual voice coils and a powerful neodymium magnet. With the patented Neodymium Differential Drive NDD technology, power compression is kept to a minimum.

An additional third coil located between the two drive coils acts as a dynamic brake to limit excess excursion and reduce audible distortion at the highest operating levels. The cone is made of a carbon fiber polypropylene composite forming a rigid piston area supported by a soft butyl rubber surround.

A 250-watt continuous power amplifier is integrated into the LSR6312SP system and provides correct drive levels for optimized frequency response. Amplification is class A-B in an all discrete topology.

The subwoofer derives its feed from a combination of Left, Center, Right and Direct LFE inputs. Subwoofer signals can be selectively derived from the front channels or from the Direct input alone using a simple Remote Bypass contact closure switch. User-selectable settings are provided for -10 dBv, +4 and +8 dBu sensitivity. For calibration and level matching of the system, an Input Trim control can be inserted into the circuit for continuously variable attenuation of the system input. Additionally, the Direct input has a dedicated Input Trim. The LSR6312SP includes Left, Center and Right channel outputs to feed external satellite speakers. The LCR outputs are high-passed at 80 Hz. A ¼" jack allows connection of a Remote LCR Bypass contact closure switch. When the switch is used, full-range signals are sent to the Left, Center and Right satellite speakers and the subwoofer derives its feed from the Direct input only.

Subwoofer low pass filtering uses steep 5th order low pass sections to minimize the possibility of localization of the subwoofer's acoustic output. High pass filtering for Left, Center and Right outputs is 12 dB/octave. For convenience, input receptacles are Neutrik "Combi" type, which accommodate both XLR and ¼" connectors.

Six DIP switches on the input panel allow the user to precisely adjust the gain and response of the system. DIP switch one inserts a variable attenuator inserted into the circuit allowing the level to be trimmed from 0 to -13dB. The Left, Center, Right and Direct inputs default to -10 dBv sensitivity. Using DIP switches 2 & 3 the user can set input sensitivity for all inputs to +4 dBu, +8 dBu or +12 dBu. A signal to any input will drive the output level of the LSR6312SP to 96 dB SPL at 1 meter.

Switch 4 inverts the signal polarity of the subwoofer feed. This is used to correct for placement mismatch between the subwoofer and satellite spacing. Due to the varied placement options available in audio production environments, it is suggested that this switch be adjusted after the final placement of the system has been determined.

Switch 5 adjusts the low frequency spectrum to compensate for the boundary conditions that exist when a subwoofer is placed against a wall or in a corner. Switch 5 reduces the output level below 50 Hz by 2 dB.

Discrete and bypass operation of the subwoofer can be switched via a remote control plugged into a ¼" jack on the rear of the enclosure. Shorting the ring and tip will remove highpass filtering from the left, center, and right inputs, thus sourcing the subwoofer from the direct input only.

For compatibility with film industry playback standards, +10 dB LFE sensitivity is provided and engaged by a push-on/push-off switch on the rear electronics panel. This operates only on the Direct input, and its purpose is to restore proper level to the LF effects channel, which may have been previously attenuated by 10 dB during program processing.

The LSR6312SP includes JBL's exclusive RMC Room Mode Compensation circuitry for final matching of the system response to the room's acoustics. RMC consists of a single parametric cut-only equalizer that is individually tuned to attenuate to the dominant room mode peak in the system's response, thus making the overall room response linear. A kit including a small sound level meter, test CD and a Q template, and a remote bypass switch accompanies each system. Switch 6 defeats the RMC function. The remote bypass switch is connected to the LSR6312SP RMC remote bypass ¼" jack via a 2-conductor cable.

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