Q Acoustics Concept 50 Loudspeaker Lab Report

Lab Report

The three-layer cabinet walls employed by Q Acoustics, together with its internal Helmholtz resonators, have successfully created a very inert enclosure, as evidenced by the CSD waterfall [see Graph 2] which shows its transient output falling sharply away, also largely free of any HF driver modes. The forward response, meanwhile, reveals a similar presence band depression – made more irregular with the grille in place [blue trace, Graph 1] – and emphasised midrange and extreme treble (+7.6dB/23.3kHz re. 10kHz) to that seen in the Concept 500 [HFN Jul '17]. While this informs the ±3.5dB and ±3.7dB response errors [see Graph 1], and influences the loudspeaker's 'mild' tonality, it also skews its sensitivity. Hence the 90.7dB/1kHz figure accords rather more closely with Q Acoustics' 90.5dB rating than the 89.8dB from 500Hz-8kHz. Either way, the pair matching of our samples proved to be an impressively tight 0.8dB up to 10kHz (1.15dB up to 20kHz) while distortion was held to a low ~0.1% (re. 90dB SPL) through the midrange.

Diffraction-corrected nearfield measurements reveal a 68Hz-875Hz/–6dB bandpass from the matched bass/midrange units augmented by the 36Hz tuning of the rear port to yield a bass extension of 40Hz (–6dB re. 200Hz). Bass output rolls away very steeply below this point [green shaded area, Graph 1]. Otherwise, this combination of high sensitivity with a modest bass output has not been won by challenging the amplifier with an especially tough load – the 3.8ohm minimum occurs at a high 4kHz while the most demanding impedance appears at 124Hz with a combination of 6.3ohm and phase angle of –41°. PM


Response inc. nearfield summed driver/port [green], freefield corrected to 1m at 2.83V [yellow], ultrasonic [pink]. Left, black; right, red; w grille, blue


Cabinet modes are well suppressed leaving mild resonances associated with the bass/mid drivers

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 90.7dB / 89.8dB / 87.0dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 3.8ohm @ 4.0kHz, 34ohm @ 78Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –57° @ 93Hz, +42° @ 27Hz
Pair matching/Resp. error (200Hz–20kHz) 1.1dB/ ±3.5dB/±3.7dB
LF/HF extension (–6dB ref 200Hz/10kHz) 40Hz / 40.3kHz/38.1kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.3% / 0.1% / 0.8%
Dimensions (HWD) / Weight (each) 1025x418x319mm / 23kg
Price £1999

Q Acoustics (Armour Home Electronics)
Supplied by: Armour Home Electronics Ltd, Herts, UK
01279 501111