Reflex Loaded Subwoofer


Large format flyable reflex subwoofer

Large format touring-oriented subwoofer
Four-point touring flying system
2 x 18″ neodymium high-excursion LF drive units
The ST-218 is a high power touring subwoofer system intended to support the large format HALO-A line array. ST-218 subwoofers are inherently scaleable – they can be used as single units, or in large numbers for filling arena or stadium shows. The substantial enclosure houses a pair of reflex-loaded 4.5” voice coil 18” neodymium LF cone drive units. As with all EM Acoustics products headroom is key: peak-to-peak linear cone travel is 28mm, meaning large amounts of low frequency energy can be accurately produced by a surprisingly small and lightweight subwoofer enclosure.
  • Ideal subwoofer solution for large-scale events
  • Impact and weather resistant black textured finish as standard
  • RAL colour and weather protection options
  • Various transport, protection and flying accessories available

The ST-218 is a large format touring subwoofer, and whilst it is designed to be mechanically and acoustically compatible with the HALO-A system, it is a standalone product in its own right and can be used to support any EM Acoustics product – either in a flown or ground stack configuration.

The compact enclosure houses a pair of 4.5” voice coil, 18” (457mm) neodymium drive units, in a reflex design with a single low-velocity port to minimise distortion. The drive units’ high motor strength gives the ST-218 excellent transient response, and the moving area of the two high-excursion 18” drive units generate significant low frequency extension and overall output. The enclosure is symmetrical, so in both flown and ground stacked configurations one enclosure in every three can be rotated to create a cardioid array. Such arrays offer exceptional low frequency directivity control and significantly reduce the energy radiating to the rear.

The robust enclosure is constructed from premium 18mm (¾”) multi-laminate Birch plywood – rebated, screwed and glued together for maximum strength. The enclosure is finished in a rugged black textured polyurethane finish or white textured paint as standard, however RAL colour matching and weather-protected outdoor installation options are also available. Input is provided by a single NLT4MP connector on the rear.

The flying hardware has been built with touring flexibility and reliability in mind. The ST-218 uses a 4-point system, and all rigging components retract flush for transit and ground stack use. Ultra-high tensile steel parts form the core of the 4-point system, meaning arrays of up to 12 elements can be safely assembled with above-regulation safety factors. The mechanical package is completed by a mesh-backed steel grille, eight recessed bar handles (four per side), protective stacking runners and mating recesses and attachment points for the optional castors on the rear.

The ST-218 requires external active high/low pass filters and a single amplifier channel to function correctly – as such it is recommended to be used with the DQ20 advanced system amplifier.

Optional accessories include castor sets, multi-enclosure touring wheel-carts, flying grids and padded covers for both single enclosures and multi-enclosure carts.

Enclosure Type High power reflex subwoofer
Components 2 x 18″ (457mm) high excursion neodymium LF drive units
Dimensions (HxWxD), mm/(ins)  580 (21.7) x 1300 (51.2) x 850 (33.5)
Net/Shipping Weight 111/118kg (224/259.6lbs)
Frequency Response 28Hz – 150Hz ± 3dB
Maximum SPL 137dB continuous, 143dB peak
Loudspeakers per amplifier DQ6*: 1 per channel, DQ10*: 1 per channel, DQ20: 1 per channel
Power Handling 2500W RMS, 5000W program
Nominal Impedance 2 ohms

* Whilst the DQ6 and DQ10 will operate the ST-218, they will not allow the subwoofer to reach its full potential and as such should only be used in low SPL environments.










Case Studies using this Product

Case Studies using this Product