d&b SL-GSUB: wiring, INFRA and alignment with J8

Check the channel pair, loudspeaker setup and all four cable conductors. The SL-GSUB has two front-facing 21-inch drivers and one rear-facing driver. Both sections need separate amplification and processing to create the cardioid pattern. Bass from the front does not establish that the rear section is connected.

Manual 1.5 recommends D90/D80 and specifies one cabinet per channel pair. The steps below apply to a D80 with NL4 outputs; if the rack uses another output or adapters, verify the complete path before connecting.

1. Save the amplifier configuration and note the input, channel pair, setup and INFRA state. Reduce the source level and MUTE the affected outputs before changing mode, setup or wiring. Check the cabinet label: SL-GSUB and SL-SUB have different mounting applications.
2. In Device setup → Output on the D80, select 2-Way Active for A/B or C/D to match the patch. Confirm with Back or Home: this activates the mode and mutes that pair. In Speaker, check the SL-SUB setup specified for SL-GSUB. The SL-SUB AP row in the manual applies to SL-SUB; do not apply it to this cabinet because the names overlap.
3. At the cabinet, the NLT4 F connector carries the front section on 1+/1− and the rear section on 2+/2−. Check that the cable, panel and adapters carry both pairs without swapping them. A two-conductor cable can leave the rear section unpowered. For continuity checks, disconnect the cable from both devices; never probe or handle contacts on an energized amplifier output.
4. In 2-Way Active, the D80 NL4 connectors A and B carry the same two sections; C and D do the same for their pair. Two available connectors do not permit two SL-GSUBs in parallel: the loudspeaker table allows one cabinet per pair. Do not connect the cabinet directly to the central NL8 4 CHANNEL OUTPUT; that port requires a panel or breakout with verified pin assignments.
5. Check the pair’s Input routing and source signal. ISP indicates input signal presence; it does not check the loudspeaker cable or individual drivers. With the correct patch, resume the test at low level. If replacing only the cable with a verified one changes the fault, follow that section of the path. If it persists, retain observations of both sections and refer the cabinet or amplifier to technical service. Do not compensate for a missing section with more level or EQ.

First check that both sections work with the correct setup and that the cabinet has the clearances specified in the manual. The SL-GSUB already includes a rear section to reduce energy behind the system; it does not need another reversed cabinet to produce its factory cardioid pattern. That reduction does not guarantee silence across the stage.

1. Check the model and orientation against the installation plan. SL-GSUB is for ground stacking and does not include SL-SUB flying hardware. Check support stability and the documentation for the actual accessories before moving or stacking cabinets; this guide does not specify stack heights or loads.
2. Leave at least 60 cm between adjacent columns of cabinets and between a subwoofer and a side wall. At a rear wall, the manual specifies at least 10 cm between the rear panel and the wall; the original wheels maintain that distance. Measure the actual gap if the assembly has changed. The 60 cm side clearance and 10 cm rear clearance apply to different situations.
3. Check that panels, fabric or objects do not obstruct the rear section’s output, and compare the wiring and setup with the first question. Keep the processing specified for the cabinet; do not add a polarity reversal or delay only to the rear section to correct what you hear on stage.
4. During rehearsal, use the same material and level with other bass sources isolated. Record positions in front of and behind the cabinet at equal distance and height where possible, without approaching the drivers at high level. If distances differ, do not attribute the whole level difference to the cardioid pattern. Include audience and musician positions to locate the problem.
5. If both sections and their connections are correct, review cabinet distribution, other bass sources and room reflections. Model the actual positions in ArrayCalc and compare them with measurements at the installation. Change one variable at a time; if audience coverage or stage monitoring worsens, return to the recorded configuration. No single delay or extra spacing solves every room.

Choose the combination according to which system will reproduce the programme’s low frequencies. SL-SUB/SL-GSUB manual 1.5 describes standard mode with compatible d&b systems in CUT, and INFRA to supplement compatible systems running full range. At −5 dB, SL-GSUB changes from 33–84 Hz in standard mode to 30–65 Hz in INFRA: both the low-frequency extension and the upper range change.

TI 385 edition 10.4 allows SL-SUB to be used with other d&b line arrays and point-source systems, and identifies SL-GSUB as acoustically identical. Its SL crossover plots show GSL/KSL examples; they do not specify a delay or cabinet ratio for J8. J8/J12 manual 2.2 describes CUT for J-SUB/J-INFRA. Check the J8 and SL-GSUB combination in ArrayCalc and verify it on site before considering the system aligned.

1. Save the project and note the J8 setup, CUT, CPL, SL-GSUB mode, levels and starting delays. Confirm the actual cabinet models, counts and positions. Matching device names in R1 do not establish that the patch and physical layout match the plan.
2. If the design assigns the low range to the subwoofers and uses J8 in CUT, assess SL-GSUB standard mode as the starting combination. If it uses the J8 full-range response and needs lower extension, assess SL-GSUB in INFRA. Do not select INFRA just because the name suggests more bass: its specified upper range is lower too, and leaving J8 in CUT can produce a different balance from the intended design.
3. During rehearsal, check the tops and subs separately and together with the same programme excerpt and reference level. If one system lacks bass on its own, trace the input, mute, setup and both sections. If the loss appears when they are combined, check alignment and signal-chain latency before adding EQ. Compare several positions; if the change worsens the combined result, restore the saved state and review the design.

No. They are published response limits at −5 dB, not filter settings to copy. J8/J12 manual 2.2 specifies 48 Hz–17 kHz in standard mode and 85 Hz–17 kHz in CUT. SL-SUB/SL-GSUB manual 1.5 specifies 33–84 Hz in standard mode and 30–65 Hz in INFRA at −5 dB.

The SL-GSUB manual also gives ranges at −10 dB under IEC 60268: 30–120 Hz in standard mode and 27–90 Hz in INFRA. Response continues to roll off beyond the −5 dB limits rather than stopping abruptly. Comparing 84 with 85, or 65 with 85, therefore cannot establish a gap, a correct overlap or the need for another crossover.

1. Record the edition, operating mode and dB criterion for each specification you compare. Use the table below to distinguish the two SL-GSUB response specifications; do not treat a −5 dB range and a −10 dB range as equivalent.
2. Check whether the console or an upstream processor already applies high-pass or low-pass filters, EQ or delay to those outputs. Record frequency, slope and enabled state before changing anything. An additional filter changes the system relative to its preset response; do not add one merely to match the numbers in the specifications.
3. With the configuration documented, measure or listen to each system and their sum at reference positions. A loss that appears only when they combine also calls for checking arrival time and phase; response limits do not determine that adjustment. If an external-filter comparison is agreed, do it during rehearsal, retain captures and repeat the positions. Restore the earlier state if summation worsens or the improvement does not hold across the audience area.