ESX QM-FOUR-PP

The ESX QUANTUM QM-FOUR-PP is a compact 4-channel digital amplifier designed specifically to enhance the sound quality of factory-installed audio systems. Thanks to modern Class D technology, the amplifier delivers high output power while taking up minimal space, making it ideal for retrofitting existing car audio systems.

The plug-and-play version comes with a 5-meter adapter harness for compatible car stereos with a Power Quadlock connection. This allows the amplifier to be integrated into the existing speaker system without the need for time-consuming re-routing of the original speaker wires. Only the separate power supply needs to be connected properly.

With up to 4 × 90 watts RMS at 2 ohms, the QM-FOUR-PP offers sufficient power reserves to drive front and rear speakers with plenty of power. Alternatively, two channels can be bridged at a time, providing up to 2 × 180 watts RMS at 4 ohms.

For customized sound tuning, separately adjustable high-pass and low-pass filters are available for both channel pairs, as well as a switchable bass boost. The integrated high-level inputs with the ESX Error Protection System (EPS®), the automatic power-on function, and start-stop compatibility facilitate integration into modern vehicles.

The sturdy die-cast aluminum housing ensures efficient heat dissipation. With a length of just 216 mm, the amplifier can be installed even in tight spaces.

Technical Specifications

General Characteristics

• Manufacturer: ESX

• Model: QM-FOUR-PP

• Series: QUANTUM QM

• Amplifier Type: 4-Channel Digital Amplifier

• Amplifier Technology: Class D

• Number of channels: 4

• Operating modes: 4-channel, 3-channel, or 2-channel bridged

• Efficiency: Up to 86%

• Housing: Die-cast aluminum

• Dimensions (L × W × H): 216 × 84 × 39 mm
  
  

RMS Output Power

• 4 × 52 watts RMS at 4 ohms

• 4 × 90 watts RMS at 2 ohms

• 2 × 180 watts RMS bridged at 4 ohms
  
  

Crossover Networks and Sound Settings

• High-pass filter (HPF) Channel 1/2: 40–4,000 Hz

• Low-pass filter (LPF) Channel 1/2: 40–4,000 Hz

• High-pass filter (HPF) Channel 3/4: 40–4,000 Hz

• Low-pass filter (LPF) Channel 3/4: 40–4,000 Hz

• Bass Boost Channel 1/2: 0 / +6 / +12 dB

• Bass Boost Channels 3/4: 0 / +6 / +12 dB

• Bass boost center frequency: 45 Hz (according to an independent test report)

• Input selector switch: 2CH / 4CH
  
  

Connections and Features

• High-level inputs: Yes

• Error Protection System (EPS®): Yes

• RCA inputs: Yes, via cable connectors

• RCA outputs: Yes, via cable connectors

• Automatic power-on function: Yes

• Automatic power-on via DC offset: Yes

• Start-Stop Compatibility: Yes

• Clipping Indicator: LED

• Plug-and-Play Connection: Power Quadlock

• Adapter wiring harness: 5 meters

• Power Supply: Separate +12-V connection via FULL POWER INPUT

• Speaker connection: Via the included wiring harness
  
  

Additional measurement results from the independent test report

• Measured output power at 4 ohms: 4 × 47 watts

• Measured output power at 2 ohms: 4 × 83 watts

• Measured bridge power at 4 ohms: 2 × 166 watts

• Input sensitivity: approx. 0.22–5.7 V

• Signal-to-noise ratio: 89 dB(A)

• THD+N at 5 watts: 0.034%

• THD+N at half power: 0.150%

• Damping factor at 20 Hz: 78

• Damping factor at 80 Hz: 77

• Damping factor at 400 Hz: 76

• Damping factor at 1 kHz: 71

The additional measurements come from a test conducted by the trade magazine *Car & Hifi* and are not official manufacturer specifications. 

What's Included

• ESX QM-FOUR-PP 4-Channel Digital Amplifier

• 5-meter plug-and-play adapter wiring harness for Power Quadlock connectors