al-4SB Flying Subwoofer System



The al-4SB subwoofer is designed specifically for use with the al-4 Subcompact Line Array System. Benefitting from the same advanced isobaric loading found in our formidable as-418 subwoofer, the al-4SB extracts exceptional low-frequency output from a very compact package. When combined with an al-4 line array system, the al-4SB delivers powerful and well-defined low-frequency reproduction down to 45 Hz. The al-4SB can also be used along with additional ground stacked VUE subwoofers to further extend low-frequency response and increase overall system output. The al-4SB is equipped with hardware for ground stacking small arrays of al-4’s (using the SP-24 speaker pole).


  • Integrated flypoints and optional flybars allow al-4SB systems to be flown above or behind al-4 acoustic elements, as well as in a stand-alone LF system
  • Skids and versatile hardware allow for easy ground stacking with al-4 acoustic elements
  • Integrated M20 thread accepts optional SP-24 speaker pole enabling use with VUE full range systems in a variety of portable applications
  • Optimal performance when used with VUEDrive™ Systems Engines


Advanced Isobaric Design

Isobaric-diagram-01At the heart of the al-4SB are two powerful, precision-engineered 15-inch transducers that feature neodymium magnets and large 4-inch (100 mm) diameter voice coils for high power handling and reduced power compression. These two powerful transducers are placed in a front-to-front, isobaric (push-pull) configuration. The unique qualities of the isobaric design allow the tightly coupled woofers to work as if they were a single unit in a vented box with double the internal volume. The net result is dramatic increase in output and low-end frequency response—all from an enclosure that’s significantly smaller than a conventional dual 15-inch design.

Rugged Flyable Enclosure

The al-4SB enclosure is constructed of top quality birch plywood, coated in the same durable 12-step Dura-Coat LX finish as the al-4 acoustic elements. Extensive interior bracing ensures resonant-free low-frequency performance. The machined, powder-coated steel grill with acoustically transparent lining provides ample driver protection while completing the top-quality al-Class aesthetic.

Integrated suspencion hardware ensures that the al-4SB is perfectly configured for use in any al-4 Line Array System in both flown as well as ground stacked configurations. Recessed handles, skids, and a top-mounted 20 mm socket even allow the al-4SB to be used in portable configurations. Recessed, rear-mounted Neutrik® Speakon sockets provide easy input and output connection.

The VUEDrive™ Advantage

Ultimate performance is achieved when the al-4SB is used with one of VUE’s VUEDrive™ Systems Engines. Custom al-4SB settings are available to optimize the powerful processors inside the V4 and V6 units specifically for the al-4SB.  In addition, VUEDrive™ amplifiers provide ample power for two al-4SB systems with the V4, and up to four al-4SB systems with the V6.




DESCRIPTION Subcompact Line Array Subwoofer
Frequency Response (+- 3 dB) 45 Hz – 200 Hz
Frequency Range (-10 dB) 38 Hz – 300 hz
Sensitivity (1 W/1 m) 96 dB
Power Long Term Sine Wave Before Protection LF: 800 watts
Power Burst (6 dB crest before clip) LF: 2000 watts
Max Peak SPL †(band limited pink noise 6 dB crest factor) 125 dB SPL
Max SPL Long Term (AVG SPL @1 band limited pink noise 6 dB crest factor)) 119 dB SPL
Coverage Horizontal 360 degrees – 6 dB
Coverage Vertical 360 degrees – 6 dB
LF Driver Description Two 15-inch Neodymium long travel woofers in isobaric configuration
Impedance 8 Ohms
Connectors Neutrik NL4 Speakon In and Loop
Cabinet Material Multi-ply birch hardwood
Cabinet Surface Dura-Coat LX – an elastomer synthetic resin chemical coating
Handles: Two Metal
Dimensions (H x W x D) 20.51 x 18.90 x 19.69 in (521 x 480 x 500 mm)
Weight Net: 97.3 lbs (44.13 kg) / Shipped: 108.3 lbs (49.12 kg)
al-4SBFB al-4SB End-fire array Fly bar
al-4SB-fc2x Flight case for two al-4SB subwoofers
† Measured Max SPL is recommended for system design purposes and represents the average peak output before protection and after power compression. In accordance with common industry

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