




Alpha Sub 428 S
Twin 18" Passive Subwoofer


Product at a Glance
The British Acoustics Alpha Sub 428 S is a robust twin 18-inch passive subwoofer crafted to provide immense low-frequency performance for professional audio systems. Featuring dual 18-inch long-excursion drivers, each with a 4-inch copper voice coil, this subwoofer delivers a continuous AES power of 1200W and an impressive peak power of 4800W. It ensures omni-directional coverage and includes cardioid presets for enhanced flexibility in live events, concerts, and installations.
Built for durability, the Alpha Sub 428 S features a marine-grade birch plywood enclosure coated with scratch-resistant polyurea paint. Its perforated black steel grills offer added protection and a sleek, professional appearance. The IP42-rated housing provides essential protection against dust and splashes, making it suitable for controlled indoor environments. Integrated handles and M10 flying inserts enhance portability and ease of setup, while optional accessories like castor wheels and subwoofer pole mounts expand its versatility. With its superior build quality and exceptional bass output, the Alpha Sub 428 S is a preferred choice for audio professionals.
CRAFTSMANSHIP
Painstakingly Perfect Production

Over the years, craftsmanship has been closely linked with small scale individualistic production. Back in 1972, we started the same way. As we grew in scale & size, it was difficult to build each speaker individually, but quality control was of utmost importance as so switching to a general assembly line was simply not an option. So we wrote up a code, one quite like enigma, to ensure quality control. We selected the right partners, got the right tools, and in cases where those weren't available, we invented them. We grew slower than most as our aim was to last longer than most.
TECHNICAL SPECIFICATIONS
ACOUSTICAL SPECIFICATIONS
• Freq. Response (-3 dB) :32 Hz - 190 Hz
• Freq. Range (-10 dB) : 37 Hz - 200 kHz
• Rated Power : 2400W AES, 9600W Peak
• Omni-Directional Coverage
• Cardioid presets available
• Nominal Impedance : 4 Ω
• Crossover : 80 - 120 Hz Active
• Max Output: Cont 136 dB, Peak 142 dB
• 2 x Speak-On Sockets, Input & Thru
SYSTEM SPECIFICATIONS
• Recommended System Control : Delta Drive
DSP Control Systems
• Recommended Amplifiers : See Amplifier
load calculation chart
LF TRANSDUCER
• 18" Low Frequency Long Excursion Driver
• 1200W AES, 4800W Peak
• 2 Drivers connected in parallel
• 4" Copper Voice Coil - Ferrite Magnet
• 3L Resistance Coating
• Minimal Power Compression with optimised
air-paths
• Aluminum Demodulation Ring for reduced
distortion
HOUSING
• Marine Birchply Enclosure
• Granular Scratch Free Polyurea Paint
• Perforated Black, Pressed Steel Grills
• Integrated Handles on Either Side
• Includes a set of round bottom feet for
secure and stable stacking
• Sloped Input Plates
• M10 Flying inserts
• Installation brackets : Alpha Throne (H),
Alpha Throne (V), Alpha Yoke B410
AESTHETIC SPECIFICATIONS
• British Acoustics Signature Umber Brown
Tone
• Blue Decals on Grills for better Aesthetics
• Available in a RAL code of your choice (24
nos, minimum)
OPERATING PARAMETERS
• Operating positions: Can be used
horizontally or vertically and can be used as
a stack of subs
• Maximum permitted ambient temperature
(Ta max) 55° C (124° F)
• Minimum permitted ambient temperature
(Ta min): -20° C (-4° F)
IP SPECIFICATIONS
• Standard Version : IP 42 - Offers basic
protection against dust & splashes
OPTIONAL ACCESSORIES
• See system chart for the System Accessories
SIZE
• Product: 508 x 1198 x 762 mm (H x W x D)
• Product: 20x 47.2x 30 inch (H x W x D)
• Packed individually
WEIGHT
• Net : 82 Kgs
• Net : 180 Lbs
SHIPPING INFORMATION
• Carton Size
583 x 1273 x 837 mm (H x W x D)
23 x 50 x 33 inch (H x W x D)
• Gross Weight : 86.1 Kgs / 189.8 Lbs
• Packed : Individually