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QSC K-SUB Active Sub Woofer

The K-Sub is a professional active PA subwoofer with dual 12" drivers and 1000w of RMS power.

Key Features:

  • Dual 12" dual subwoofer drivers
  • Lightweight portable powered speaker
  • 1000-watt continuous Class D power
  • Extensive DSP
  • Speaker mounting pole included
  • 3 + 3 year warranty
  • 6 year warranty

      Product Code: 400020940

      Pre-Order from our next delivery

      Regular Price: £1,100.00

      Special Price £869.00

      The QSC K-Sub is a dual-12 bandpass design, constructed of premium birch and includes high-quality, low-noise casters. The subwoofer features a threaded pole receptacle for a positive, wobble free connection to a threaded speaker pole (included).
      K Series  
      Configuration 4th Order Bandpass


      2 x 12" cone transducers
      Frequency Response (-6 dB) 48 Hz - 134 Hz
      Frequency Range (-10 dB) 44 Hz - 148 Hz
      Maximum SPL (1 meter) 130 dB peak
      Power Output 1000 W Class D (2x500 W)
      Input Impedance (ohms) XLR / ¼": 40k balanced / 20k unbalanced
      Controls Power, Gain, LF Mode (Normal/DEEP™), Polarity (Normal/Reverse), Front LED (On/Off/Limit)
      Indicators Power, Signal, Standby, Limit
      Connectors Dual balanced female XLR/¼" line
      level input, Dual Balanced male XLR full range line level out, Remote gain control, Locking IEC power connector
      Cooling On demand, 50 mm variable speed fan
      Amplifier Protection Thermal limiting, output overcurrent, overtemperature muting, GuardRail™
      Transducer Protection Thermal limiting, excursion limiting
      AC Power Input Universal power supply 85 - 265 VAC, 50 - 60 Hz
      AC Power Consumption

      (1/8 Power)
      100 VAC, 2.3 A

      120 VAC, 2.01 A

      230 VAC, 1.13 A
      Material Painted birch plywood
      Finish Black textured paint 
      Weight (Net) 74 lb / 33.6 kg
      Available Accessories KSub COVER 

      Dimensions (HWD)

      26" × 14" × 28.1" (including casters)
      665 mm × 356 mm × 714 mm


      • Lightweight portable powered speakers with legendary QSC amplifier power and reliability
      • 1000 watt Class D power modules in all models
      • Extensive DSP enhances system performance
      • Attractive and professional appearance
      • Tour-grade 18 gauge steel grilles
      • Ergonomic handles with comfortable, non-slip grip
      • 35 mm pole sockets with Tilt-Direct™ (fullrange models)
      • M10 rigging points for suspended installation (fullrange models)

      Extensive DSP

      • DMT™ (Directivity Matched Transition) provides for matched LF and HF coverage across the entire listening area, eliminating unnatural "dead" or "hot" frequency zones.
      • Intrinsic Correction™, first featured in our high-end line-array products maps 65-75 spacially-averaged measurements to IIR and FIR filters that actively adjust time, frequency and amplitude response to a maximally flat bandpass target. The result is a speaker that behaves equally well across the entire sound field.
      • DEEP™ and excursion limiting allow for extended low-frequency response by actively managing low-frequency transients without degradation of the underlying signal or adjacent frequencies.
      • GuardRail™ protection, first introduced on our GX Series amplifiers protects both the amplifier module and your performance from unnatural and destructive clipping.


      DEEP (Digital Extension and Excursion Processing) is an exclusive QSC process that allows a K Series loudspeaker to deliver far more undistorted low-frequency output than could be produced by conventional means.

      DEEP begins by applying an equalization boost at low frequency. Certainly many loudspeaker systems do the same thing (there´s nothing new about this). Some even take the next step and apply limiting to reduce the amount of EQ boost as the amplifier approaches overload. The effect may be better than nothing at all, but this process does create audible "pumping" and unnatural high frequency reductions at higher performance volume.

      DEEP employs sophisticated digital signal processing to identify and reduce only those brief, transient low-frequency peaks that can cause woofer over-excursion or amplifier clipping. Reduction of the transient peaks is nearly inaudible and allows the average low-frequency output to remain high. The result is an astonishing amount of low-frequency output, previously impossible to achieve from compact, smaller-format speaker systems.

      1000 Watts

      Loudspeaker manufacturers typically have two separate amplifiers in their powered speakers. Although they share a common power supply, the amplifiers operate very differently and output different power levels. While this approach can make for a streamlined, efficient design, it usually results in a less capable high frequency amp. As a result, the amplifier is easily over-driven if the operator pushes the system hard. The resulting high-frequency distortion is audible and may destroy the compression driver.

      The QSC kilowatt amplifier defines another key difference between K Series and traditional powered speaker systems. All K Series models, regardless of woofer diameter use the same kilowatt power module. Only the input circuitry and DSP programming differ from model to model. No longer does a smaller-format powered loudspeaker have to be equated with lower power and less total performance.

      Energy Management

      When the K Series DSP doesn´t sense input to the amplifier module for 5 minutes, it automatically enters standby mode - effectively shutting down the amplifier, conserving energy and extending the life of the product. Once signal is restored, the processor instantly turns the amplifier back on without any noticeable audio delay. In this manner, the energy-conscious operator is able to conserve resources without taking any additional measures, regardless of the number of K Series loudspeakers in the system.

      Conical Wave Guide

      There are a few basic concepts that guided the design of the K Series waveguides and helped achieve its overall impressive sound quality. First is the understanding that the best, most natural performance in a horn is achieved by avoiding parallel surfaces and abrupt changes in contour. Either will cause phase and acoustical impedance problems that lead to erratic frequency response.

      Second, while a waveguide with a large difference between horizontal and vertical coverage angles may be needed for specific applications, it will necessarily exhibit compromised audio performance. For K Series, the horizontal and vertical coverage angles are identical.

      Finally, the mouth (opening) of the waveguide should be approximately the same diameter as the woofer. In speakers where that isn´t the case, it´s likely that either the crossover frequency is too high or the waveguide isn´t really controlling the pattern all the way down to the crossover frequency. Either of the above will lead to lack of pattern control in the critical mid-range.

      By keeping these concepts in mind, QSC created the large, well-behaved, conical waveguide found on K Series. The sonic benefits, both on and off axis will be clear when you listen for yourself.

      LED Operation

      Located on the front of each K Series loudspealer is a blue LED that´s more than just a simple power indicator. A switch on the rear panel allows the user their choice of three ways to utilize the light.

      In the default (PWR) position, the LED will illuminate and stay on as long as the speaker is powered on. For instances when a bright blue light may not be aesthetically consistent with the venue or the event, moving the switch to the (OFF) position defeats the front LED operation entirely but doesn´t affect the status of the amplifier module. In (LIMIT) mode, the front LED indicates the onset of system limiting, allowing the operator to monitor the well being of the system from in front of the box.

      Remote Control

      A unique, yet highly beneficial function for many users of a product in this class is the K Series remote gain control. By way of a three pin block connector, a potentiometer (pot) can be wired to the K Series from a remote location. This pot will then act as an attenuator allowing volume adjustment from a remote location. Multiple speakers can also be wired to a single control knob - a particularly handy benefit when K Series speakers are suspended in out-of-reach locations within a venue. Combined with the Energy Management function, this capability presents a compelling solution for many venues.

      Locking IEC Power Cable

      Every K Series loudspeaker is equipped with a locking IEC power connector and cable. With a simple "click" the AC cord creates a positive lock with the amp module all but eliminating accidental disconnect during a performance.

      This feature is especially useful when using either the K10 or K12 as a floor monitor. If damaged or lost, the locking cable can be easily replaced with a standard widely available IEC cable.

      Threaded Pole

      The K Sub features a threaded pole socket which accommodates a 31" positive-fit speaker pole (included). Unlike typical open-cup designs that can cause a speaker to wobble or tilt in the subwoofer receptacle, the K Series threaded mounting system assures a snug, safe fit.

      At the top of the pole, a 35mm circular end cap inserts into any K Series or other fullrange enclosure outfitted with a standard pole receptacle.

      Rugged Construction

      Unlike typical molded loudspeakers, K Series fullrange models are made with ABS (Acrylonitrile Butadiene Styrene) which is harder and more rigid than most traditional plastics. Used for high-pressure or high-impact applications, ABS can withstand greater temperature extremes, resist impact and stay rigid against high pressure fluctuations far better than polypropylene, polystyrene, or polyurethane. ABS is used in golf club heads, very high pressure plumbing, car body parts, helmets and other products requiring robust physical performance.

      Not only is ABS tough, it also delivers acoustic benefits. An ABS enclosure will vibrate less with low frequency audio energy resulting in more and tighter bass. The stability of ABS also makes it ideal for a molded enclosure that is going to be suspended for installation applications.

      Additionally, all K Series speakers are designed to withstand a rigorous series of drop tests and other abuses that make the wear and tear typically encountered by years of real-world use seem tame. Solid cast aluminum handles and an 18 gauge steel grille round out the K Series road-ready design.

      The K Series is capable of connecting to just about any audio source - a microphone, iPod™ or other MP3/CD player, a musical instrument or mixing console. Inputs can also be combined and mixed at the K Series rear-panel. For instance, a microphone and CD player can be combined for background music with announcements. Or, a musical instrument, MP3 player and microphone can all be combined for solo entertainer applications. Neutrik™ Combo XLR/1/4" and RCA inputs are featured, as well as XLR outputs for either daisy-chaining multiple K Series speakers or providing a mixed output to an amplifier, mixer or other audio device. 

      Class D

      K Series features a state of the art, QSC-designed Class-D amplifier module. The benefits of Class D technology in a powered loudspeaker are many. First, because the power supply is much smaller than other amplifier designs, there is a significant weight savings (The K Series module weighs a mere 6 pounds). Also, because Class D amplifiers generate far less heat, they don´t need bulky heatsinks, further reducing the amp´s weight.

      And while amplifier performance in typical designs relies greatly on access to a sturdy, steady AC power source, Class D amplifiers operate with far greater efficiency, drawing less current from the power source.

      Basic linear amplifiers see significant power losses due to heat generated as they cycle between the positive and negative voltage rails. But an ideal semi conductor wants to be either "fully on" or "fully off" in order to maximize efficiency and minimize loss due to heat.

      The basic principle of Class D is to utilize fully-on and fully-off "switches" that operate at a frequency much higher than the audio range so the resulting pulses can be filtered and smoothed out, leaving only the desired audio signal. The result is nearly loss-free operation and far less heat build up when the amplifier is driven continuously at high operating levels.


      K Series is one of the most robust and trouble free systems available anywhere. First, it benefits from the closed design of an active loudspeaker system, offering more protection of both the amplifier and the transducers than would typically be possible with a component system.

      Next, K Series features QSC Guardrail™ technology, originally introduced on our GX Series amplifiers, which prevents destructive clipping distortion and woofer over excursion.

      Heat dispersion is managed by a number of thermal protections including a virtually silent internal fan that engages on-demand during periods when the amp senses high temperatures and turns off when no additional cooling is necessary.

      There is also discreet signal limiting technology to prevent overheating of the amplifier and transducers as well as DC and short-circuit protection such as is found on all rugged, reliable QSC amplifiers.


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