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Ultra Low-Frequency Enclosure

Single 21", Low Q band-pass subwoofer system that adds extension and weight for applications where you want to feel, as well as hear, very high definition audio Working down to 23Hz with efficiency for two boxes of 102dB, it shares the same footprint as the other VHD subwoofers in a compact lightweight easily transported package. Alongside the VHD2.16, it forms part of a remarkable five-way active system.


  • Professional, Baltic birch construction with a highly resistant polymer coating

  • Very High Definition ultra low-frequency reproduction

  • 135dB sustained output / 137dB peak (using two units of VHD1.21)

  • Large-chamber bass reflex low Q bandpass design

  • Single 21" low-frequency driver with 4" (100 mm) inside/outside, epoxy baked, high-temperature voice coil assembly, and carbon fiber reinforced cone assembly.

  • Proprietary side handles (6) for simplified handling and carrying

  • High impact low friction feet, allowing lock-into other VHD cabinets and easy cabinet movement

  • Front locking aluminum VHD wheel boards with wraparound hardwood bumpers

  • Weatherproofing option and special paint finishes available on request


Specifically designed to add extreme low-frequency extension to the VHD2.0 and VHD1.0 in conjunction with other VHD subwoofers

  • Live performance

  • Fixed installation

  • Cinema

  • Theatre

System Acoustic Performance

Max SPL Long-term: 135dB (2x VHD1.21)

Max SPL Peak: 138dB (2 x VHD1.21)

-3dB Response: 29Hz to 185Hz

-10dB Response: 23Hz to 245Hz

Impedance: 8Ω

Crossover Point: 70Hz to 120Hz

Low-Frequency Section

Acoustic Design: Large chamber low Q bandpass

Low-Frequency Amplifier Requirement: 800W /1 x VHD1.21 (VHD 3200 amp.)

Woofer Size / Voice Coil Diameter / Design: 21" / 4" Inside Outside

Diaphragm Material: Epoxy Reinforced Cellulose

Magnet Type: Neodymium

Speaker Input

Speaker Input: AP4 male

Speaker Output

Speaker Output: AP4 female


Cabinet Material: Baltic birch

Handles: 6

Color: Black (wear-resistant polymer coating)

Physical Dimensions

Height: 700 mm (27.55")

Width: 700 mm (27.55")

Depth: 750 mm (29.52")

Weight: 60 kg (132.0lbs)

Product code

  • KVV 987 080 - VHD1.21

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