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The Thunder-KMT21P is a high-performance passive subwoofer designed with a powerful peak output of 136 dB to provide high-quality audio in the low frequency range for use in mid to large applications. The KMT21P features a 1800 W 21" drive unit with magnet structure and suspension engineered for maximum linear excursion.

The Thunder-KMT21P is ideal for medium throw applications, like theaters, concert halls, and AV installations.

More information about the Thunder line

Unique Performance-to-Size Ratio

Produces an impressive high-power performance by producing a high SPL from a small frame.


Color Customizable

We have the ability to customize your project by color matching your system to any RAL code to help you to better integrate the speakers into a wide variety of venues.



We created a portfolio complete with lightweight products that are easy to transportation and quick to setup optimizing logistics, space, labor costs and time.



Four-Corner Port Configuration

The unique four-corner port configuration provides symmetrical back loading to the speakers, for extended bass response with very low distortion.


Dante Compatible

With the dedicated K-dante accessory, this solution can be integrated into a Dante network making it interoperable with other devices.




  • Type Passive subwoofer
  • Transducers 21" neodymium magnet woofer
  • Frequency Response (1) 35 Hz – 150 Hz (-6 dB)
  • Maximum SPL (2) 136 dB (peak)
  • Rated Power 2800 W
  • Coverage Omni
  • Connectors speakOn NL4 1+ 1- (signal); 2+ 2- (through)
  • Nominal Impedance 4 Ω

Handling and Finishes

  • Dimensions (W x H x D) (3) 555 x 572 x 763 mm (21.8 x 22.5 x 30 in)
  • Weight 40 kg (82.2 lb)
  • Material Wood
  • Color Black, White, Custom RAL


  • IP Rating IP43
  • Notes for data:
    (1) With dedicated preset
    (2) Maximum SPL is calculated using a signal with crest factor 4 (12dB) measured at 1 m.
    (3) Included 17 mm (0.7 in) removable rubber feet

    Passive loudspeakers require dedicated presets loaded on K-array amplifiers.
    New materials and designs are introduced into existing products without previous notice.

Customers Applications

Thunder-KMT21P can be successfully used in a range of different settings and events.

Discover all the projects where Thunder-KMT21P products have been used