d&b audiotechnik J-SUB

Use standard J-SUB with J8/J12 in CUT when the design prioritizes low-frequency headroom. If the design keeps J8/J12 full range, without CUT, d&b provides for J-SUB in INFRA. INFRA lowers the upper operating limit from 100 to 70 Hz; it does not turn the cabinet into a J-INFRA.

The combination is documented in TI 385, edition 10.4 en, §3.2. Choose the mode for the actual system and its design. J-SUB INFRA mode is not a different subwoofer model.

1. Save the starting configuration and record the top models, CUT for each group and INFRA status on the J-SUBs. If the system mixes models, verify that combination before changing modes.
2. Compare tops alone, subs alone and both together at agreed positions, using a known signal and test level. Listen to or measure the crossover: a dip when combining both systems also calls for checking polarity, timing and signal path; changing INFRA alone does not confirm the cause.
3. If the change worsens an area or conflicts with the design, restore the saved configuration and review the setting with the system technician.

HCD changes the dispersion from cardioid to hypercardioid. In standard mode, maximum rejection is behind the cabinet; with HCD it shifts to the rear sides. It does not remove bass throughout the stage. The manual provides for HCD with subs on both sides of the stage and in front of walls.

The minimum 60 cm applies between adjacent columns, including with HCD. For a rear wall, the manual describes the minimum spacing provided by the rear wheels of the J-SUB. Do not treat those 60 cm as wall clearance or apply the wheel guidance to another cabinet or a modified enclosure.

1. Record cabinet positions, spacing and other active subs. Confirm both sections are working before assessing the pattern.
2. Keep geometry, signal and level unchanged while comparing standard and HCD, if the design permits that test. Repeat observations in front, behind and at the rear sides; one position behind the cabinet does not describe the entire stage.
3. If the disturbance persists, check walls, obstacles and contributions from other systems. Return to the intended mode when the comparison does not justify a change; do not compensate for an unknown configuration by raising the level.

It uses a pair in 2-Way Active; the table permits one J-SUB per pair in both J-SUB and J-SUB AP. The front drivers and the rear driver have separate feeds.

Check setup, connector variant and cabling before sending a signal. Do not treat the two channels as independent subwoofer outputs.

First check the J-SUB or J-SUB AP setup, 2-Way Active mode and the path of both channels to the cabinet. J-SUB has two front drivers and one rear driver, powered by separate sections. Hearing bass in front does not establish that the rear section is receiving its signal.

Do not disconnect the rear section to free a channel: the processing and directivity require both sections. Do not connect the cabinet to D80 central NL8 4 CHANNEL OUTPUT either; that output requires the appropriate rack panel, multicore or breakout.

1. Save the amplifier state and record the pair, outputs, cable and every adapter. With J-SUB AP, also check that project data matches that cabinet; do not replace AP with another setup just to listen.
2. Turn off amplifiers before changing power-output connections. With the cable disconnected at both ends, a qualified technician can check continuity and contact assignment against the cabinet table. Do not measure continuity on an energized output or bridge amplifier pins.
3. If you find an open conductor or an adapter with a different assignment, remove it from service and repeat the check with a verified compatible cable. If cabling matches and the section still does not respond during a controlled test, stop troubleshooting and refer the cabinet and amplifier for service; this guide does not cover internal repairs.