PSI Audio A21-M Active Studio Monitors, Red (Pair)

PSI Audio A21-M Active Studio Monitors, Red (Pair)

Product code: psia21mrpr

The PSI Audio A21-M Red are a pair of high power near/mid-field precision monitors, perfect for near, mid-field and surround sound applications.

  • PSI Audio A21-M Active Studio Monitors, Red (Pair)

    The PSI Audio A21-M Red are a pair of high power near/mid-field precision monitors, perfect for near, mid-field and surround sound applications.

    Main Features

    • 120 + 50W RMS output
    • 170mm woofer, 25mm tweeter
    • Adaptive Output Impedance technology reduces any possible coloration
    • Compensated Phase Response technology corrects phase shifts and group delays in crossovers
    • Phantom Standby Control for remote on/off switching
    • Class G amplification provides the linearity of Class‑AB with much improved efficiency
    • Sold as a pair
    Read More

    The A21-M high power near/mid-field precision monitor covers a broad frequency spectrum, allowing the user to be in full control of their audio production. Its unique and highly optimised assets make it perfect for near, mid-field and surround sound applications where ultimate precision is required.

    The powerful bi-amplified output stages features the unique 'AOI' output stages and has a protection circuit, which can be monitored via the red LED on the front panel.
    The active crossover, with integrated 'CPR', gives the A21-M unprecedented impulse behaviour - with excellent stereo imaging. The crossover is also optimised for maximum phase coherence, projecting a wide horizontal and vertical ideal listening area. The electronics are housed in a unit mechanically isolated from the speaker cabinet to avoid resonance at high sound pressure levels.

    Designed to work in harmony with the full range of A series monitors the A21-M also makes ideal front speakers in a surround sound setup, or can be developed in to a more powerful system by adding the A225-M sub - thus protecting your investment.

    Additional features include:

    Very high SPL in a compact cabinet
    Flat frequency response
    Optimised directivity by phase coherency
    Class G low temperature amplifier stage
    Compatible with industry standard mouting systems
    Amplifier unit acoustically uncoupled from speaker cabinet
    Protection circuits with overload indicator
    Real balanced input
    Designed for stereo and multichannel monitoring
    Magnetically shielded for use close to video monitors
    ALG Technology


    Power RMS: 120 + 50W
    Program Power: 170W
    Input Impedance: Sym, 10k Ohms
    Sensivity for 100 dB @ 1m: 0.775 V
    Signal to Noise Ratio: 96 dBA
    Continuous Max [email protected]: 108 dB (single)
    Input Overload: 24 Vpp
    Program Max [email protected]: 119 dB (pair)
    Response at -6dB: 38 - 23000 Hz
    Tolerances: ±2 dB (44Hz - 20kHz)
    Distortion THD: less than 1.4% (90Hz-12kHz)
    Phase tolerances: ±45° (190Hz - 20kHz)
    Dispersion (P.N. 4 - 16 kHz) at -6 dB: 90° x 90° (H x V)
    System: 2 Way(s)
    Crossover frequency: 2.4 kHz
    Woofer's dim. Ext. / Diaphragm: Ø217 mm / Ø170 mm
    Tweeter's dim. Ext. / Diaphragm: Ø100 mm / Ø25 mm
    Connectors: 1 x XLR F / 3P
    Signal input: 1=GND, 2=(+), 3=(-)
    Material: MDF
    Dimensions (WxHxD): 250 x 400 x 300mm
    Gross / Net Weight: 14.8 / 13.4 kg
    Voltage: 115/230V (50-60Hz)
    Consumption (Standby/Quiescent/Max): 1.2 / 5 / 150 W
    Mean / Max Humidity: less than 75% / less than 90%
    External Temperature: 5 - 40°C

    AOI: Adaptive Output Impedance System
    In low frequencies a loudspeaker behaves like a high-pass filter, therefore the damping depends on its mass, on compliances (mechanical and acoustical suspension) and of the source resistance. In high frequencies, the resonances correspond to the deformations of the membranes. The masses in movement are parts of the mobile mass. Compliances depend on the elasticity of the material. The resistances are the internal damping and the source resistance. For an ideal damping in a wide area of frequency, the source impedance must be adapted to every range of frequency for every transducer.

    The AOI system is constituted by a detection of the movement of the membrane and the moving coil, as well as by a counter reaction filtering. Therefore the damping rate is continuously ideally adjusted according to the frequency. The AOI system allows the reproduction of sound without transducer coloring over the whole frequency range.

    The PSI Audio speakers featuring the AOI system have much superior impulse behavior to traditional amplifier designs. Whilst the transducer travels to its intended position the AOI circuitry seamlessly adapts the amplifiers output impedance to insure ideal acceleration of the membrane to reproduce the desired impulse. Once the transducer reaches the end of the impulse the AOI circuitry provides a break in order to act against an overshooting of the transducer. The AOI circuitry is almost capable of reproducing a square wave and therefore increases accuracy by marring the transducer and the amplifier in to a perfect couple. A nice side effect of the AOI system is that the membranes of a PSI speaker do not produce parasite sounds when other speaker systems in the room are in use. When air pressure is produced by other sources than the PSI speakers the AOI will detect this and tighten the damping of its transducers in order not to produce parasite sounds not originating by the speaker system in use.

    In today's times where much more importance is given to the low end reproduction of sounds especially when using sub woofer technology in surround sound systems the importance of a monitoring system that has an accurate and not a flattering reproduction becomes essential. The result of the AOI featured PSI Audio speaker range is a speaker family with a highly accurate impulse behavior with a minimum of transducer coloration.

    CPR: Compensated Phase Response
    In a multi-way speaker system, the crossover filters as well as the transducers introduce distortion of phase and by consequence of the variations of group delays.

    The group delays in low frequencies are more important than in high frequency's. They provoke a time related separation of the low and high frequencies which then is responsible for the hollow sound of multi-way speaker systems.

    In a limited frequency range, an all pass filter allows to intervene on the phase without influencing the amplitude.

    The CPR system consists of several all pass filters who each act in a specific range of frequency in order to obtain a wide area of Compensated Phase Response. This then provides a constant group delay.

    Thanks to the CPR system the placement of sound in the actual sound space is highly accurate. This technology allows designing of surround sound systems with different types of PSI Audio speakers while maintaining an accurate phase response.

    The human ear is very sensitive to group delays or phase irregularities of sounds. The human brain detects such irregularities easily and processes them in to space related information's like the positioning of a sound source.

    All traditionally designed speaker systems suffer to a certain degree of such irregularities.

    These irregularities are the reason why some speakers produce a wider and deeper room perception hence a better-weaker reproduction of the sound image.

    Such phase irregularities are desirable on creative tools like equalizers, compressors, reverbs and delay units when creating a certain desired sound, whilst being an important part of the creative process of sound engineering.

    But as the speaker system represents the reference tool of every sound engineer, these irregularities represent a highly disturbing factor and should certainly not be present in the reference tool when trying to design specific sound or its positioning in the sound image.

    As a sound recording tends go through various processes (recording, mixing and mastering) in which maybe various people, locations and therefore speaker systems will be involved, it may well occur that corrections will be applied, due to phase irregularities, that may not even be present on the actual recording.

    The PSI Audio speakers feature the unique CPR system that provides a Compensated Phase Response that removes such irregularities and therefore provides a much more accurate reference tool to the sound engineer. The stereo image and the projected room are of an extreme accuracy and therefore provide a more precise working tool.

    PSC: Phantom Standby Control

    PSC enables to remote the standby mode of your loudspeakers through the signal cable. This command is generated by pulling up simultaneously the voltage of two parts of the XLR. A voltage of +5 to 25V DC referenced to the ground is necessary to control the standby mode.

    The front panel LED is slightly lit in red during the standing mode.

  • This product will be ordered in from our suppliers as required. Please contact us for availability.

    This item is normally sent to Mainland UK addresses by DPD who generally provide a one-hour window of delivery on the morning of delivery by email or text message. If you need this item faster, please upgrade to a Before 12 service at checkout.

    FREE delivery within mainland UK

    UK Non-Mainland: £ 12

    Rep. of Ireland and Mainland Europe: from £ 15 (calculated at checkout).

    Order this item before 4pm and receive it on the next working day ( Mon-Fri excluding bank holidays ), mainland UK only*

  • Additional Information

    On demo in store No
    Brand PSI
    Condition New
    Power 101-200W
    Specifications No