Name: SX218+
Rating: 4.7 (23 reviews)

The SX218+ delivers very high output levels and superb transient performance with minimal distortion, making it ideal for the most demanding applications. With an operating range of 38 Hz–100 Hz ± 3 dB, it houses dual 18 in (460 mm) long‑excursion drivers with 4 in (100 mm) voice coils, water‑resistant cones and triple‑roll surrounds. Each driver is rated to handle 1500 watts AES and has a magnet structure and suspension engineered for maximum linear excursion.

Features

Dual-driver, direct radiating reflex-loaded subwoofer
2 x 18” (460mm) long-excursion drivers, 4” (100mm) voice coils, neodymium motors, waterproof cones
Very high output capability
Tour-grade plywood enclosure with M10 mounting points

Applications

Touring sound reinforcement for small and medium-size venues
Fixed installations in concert halls, theatres, ballrooms and houses of worship
Sports stadiums, arenas and corporate AV events
Restaurants, bars and hotel entertainment areas
Concourses and theme parks

The enclosure is constructed from multi‑laminate birch ply and finished with a durable polyurethane coating. Eight reflex ports provide a large frontal area to reduce turbulent air noise, and a perforated steel grille protects the drivers from damage. The internal port geometry promotes laminar airflow.

The SX218+ features an M20 pole‑mount insert for mounting point‑source speakers. Cabinet wheels and a transit cover are available as accessories.

Compared with the SX218, the SX218+ [Shipping Q2 2026] is an all‑new design with enhanced performance and features. It is slightly deeper, so it uses a new transit cover, and it includes new drivers and an improved cabinet. Unlike the SX218, which required two 8 ohm amplifier channels, the SX218+ uses a single 4 ohm amplifier channel.

The SX218+ adds a third NL4 input connector on the front to improve cabling for subwoofers used in cardioid configurations. For outdoor use, you no longer need a WRKIT, but you must seal all three NL4 sockets. Use the correct cable connectors (NLT4FX or NLT4FX‑BAG) for connected sockets and install a Martin Audio weatherproof NL4 sealing plug in any unused socket.

The SX218+ adds a channel crossover on the link output, letting you run two cabinets from independent amplifier channels down a single four core cable. The SX218+ has two LED indicators, one on the front and one on the back, which you can illuminate via Vu‑Net software to identify each enclosure on the circuit. The rear LED is intended for use in cardioid setups.

Links

User guide Brochure Datasheet Settings [v2.2]

Specification

TYPE	Dual driver, direct radiating reflex-loaded subwoofer
FREQUENCY RESPONSE (1)	38Hz – 100Hz ±3dB, -10dB @ 31Hz
DRIVER	2 x 18 in (460 mm) long-excursion drivers with 4 in (100 mm) aluminium voice coils, neodymium motors with T-poles and demodulation rings, waterproof cones
RATED POWER (2)	3000W AES, 12000W peak
RECOMMENDED AMPLIFIER	iK42 bridged for full output
	For details, see SX218+ User Guide
SENSITIVITY (3)	102.5 dB
MAXIMUM SPL (2)(3)	137dB continuous, 143dB peak
	149dB peak with crest factor 4
NOMINAL IMPEDANCE	4 ohms
DISPERSION (-6dB)	Omni-directional or cardioid when paired
ENCLOSURE	Multi-laminate birch ply
FINISH	Textured black or white paint
PROTECTIVE GRILLE	Black or white perforated stainless steel
Environmental Testing (for details click here)	IP rating IP21 MIL-STD-810H ISO 4892-2 Solar Radiation ISO 12944-6 Category C3 Corrosion resistance
LED INDICATORS	Two LEDs: one front, one rear (rear LED for cardioid subs)
CONNECTORS	3 x NLT4MPXX-BAG (one front, two rear)
	IP54 weather-resistant seal with NLT4FX, NLT4FX-BAG or weatherproof NL4 sealing plug
PIN CONNECTIONS (INPUT ON FRONT)	1+/1-
PIN CONNECTIONS (INPUT ON REAR)	1+/1-
PIN CONNECTIONS (LINK ON REAR)	1+/1- linked to 2+/2- 2+/2- linked to 1+/1-
FITTINGS	Two skids on base, with mating channels on top M20 thread plate on right side for pole mounting with sub in portrait 24 x M10 mounting points, 6 on top, 6 on bottom, 4 on left, 4 on right, 4 on back 4 x bar handles, two on each side 16 x M8 inserts for optional castors
DIMENSIONS (INCL SKIDS)	(W) 1084 mm × (H) 530 mm × (D) 799 mm (927 mm with castors, transit-cover brackets add 28 mm) (W) 42.7 in × (H) 20.9 in × (D) 31.5 in (36.5 in with castors, transit-cover brackets add 1.1 in)
WEIGHT	82.3 kg (181 lb), 85.5 kg (189 lb) with castors
ACCESSORIES	Pack of four castors WHEELKIT M10 eye bolt HTKCT06 Weatherproof NL4 sealing plug Install flying frame SX218GRID Flying kit SX218FKIT Transit Cover SX218+TC

Architectural Specs

SX218+

The loudspeaker shall be a dual‑driver, direct‑radiating, reflex‑loaded subwoofer consisting of two 18‑inch (460 mm) long‑excursion low‑frequency transducers. The on‑axis frequency response shall be 38 Hz–100 Hz ±3 dB, with a –10 dB point at 31 Hz. The loudspeaker shall produce a maximum SPL of 143 dB peak or 149 dB peak with crest factor 4.

Power handling shall be 3000 W AES, 12 000 W peak, and the rated impedance shall be 4 ohms. The loudspeaker shall be fitted with three NL4 connectors (one front, two rear). The loudspeaker shall be operated in conjunction with a dedicated controller amplifier. The enclosure shall be constructed from multi‑laminate birch plywood with a textured black (RAL 9005) or white (RAL 9016) paint finish.

The drivers shall be protected by a perforated stainless‑steel grille. The enclosure shall be fitted with two skids on the base with mating channels on the top, an M20 thread plate on the right side for pole‑mounting, 24 M10 mounting points, bar handles and inserts for optional castors. Two LED indicators, one on the front and one on the rear, shall allow enclosure identification via Vu‑Net, with the rear LED intended for cardioid operation.

Dimensions including skids, excluding castors (W × H × D) shall be 1084 mm × 530 mm × 799 mm (42.7 in × 20.9 in × 31.5 in). Dimensions including castors shall be 1084 mm × 530 mm × 927 mm (42.7 in × 20.9 in × 36.5 in). Weight shall be 82.3 kg (181 lb), or 85.5 kg (189 lb) with castors.

The loudspeaker shall be the Martin Audio SX218+.

Technical Drawings & 3D Models