Q Acoustics Concept 50 loudspeaker

Given how crowded the loudspeaker manufacturing space has always been, I am always surprised when a new brand not only springs into being but does so with new speakers that sound and measure well. Take the UK's Q Acoustics, for example. The company didn't exist before 2006 and didn't have a presence in the US until 2018. However, two of its designs have already received very favorable coverage in Stereophile: the Concept 500 tower ($5999.99/pair), which Tom Norton reviewed in March 2019, and the Concept 300 standmount ($4499.99/pair, including stands), which I reviewed in January 2020.

Q Acoustics' new Concept 50 floorstanding loudspeaker ($2995/ pair) is the top model in a new series of loudspeakers that uses technology trickled down from the earlier Concepts. Because my experience with the Concept 300 was so positive, I readily agreed to review the 50.

The Concept 50
Like the Concept 500, the Concept 50 uses a vertical D'Appolito drive-unit configuration, the 0.9" fabric-dome tweeter positioned between two 5" plastic-cone woofers. The proprietary drivers are mounted on a 0.12"-thick aluminum sub-baffle at the top of the enclosure with pretensioned studs, and the tweeter is mechanically isolated from the front baffle to minimize mechanical interference from the woofers. The crossover is set to 2.1kHz, a lower frequency than is usual for a tweeter this size, which Q Acoustics says is possible because the unit's resonant frequency is at 700Hz. The crossover itself is mounted on the speaker's sprung base plate to keep it as far away as possible from the magnetic fields associated with the drive-unit motors.


A sprung base plate? Q Acoustics has paid a lot of attention to addressing the cabinet's vibrational behavior. The Concept 50's enclosure features the company's proprietary Gelcore construction, which is intended to reduce higher-frequency noise. Each panel consists of two MDF layers separated by a compliant layer. To address lower-frequency cabinet noise, Q Acoustics used Finite Element Analysis to determine where to add internal braces, called P2P (point-to-point) bracing, at strategic positions. And to eliminate low-frequency cabinet noise, the Concept 50's base comprises two plates. The upper plate is fixed to the enclosure and isolated from a lower plate with 14 compliant spheres. The lower plate sits on two carpet-piercing spikes at the front and on a gently curved stabilizer bar fitted with two more spikes at the rear. (Ball-end feet are also supplied.) This suspension made the speaker a bit wobbly to the touch but not to the point where it was unstable. (One of our cats, who likes to sit on the tops of the speakers I am reviewing, will vouch for that.)

The woofers each use a relatively large voice-coil with a 30.5mm diameter, wound from low-mass, copper-clad aluminum wire on a fiberglass former. According to a Q Acoustics white paper, Finite Element Analysis was used to optimize the design of the surround and Nomex spider to give a symmetric compliance characteristic. The woofers are reflex loaded with a flared port 2" in diameter placed a quarter of the way up the rear panel, and an internal vertical pipe, which Q Acoustics calls a HPE (Helmholtz Pressure Equalizer), is said to reduce internal pressure and standing waves.

Electrical connection is via four (two sets) high-quality binding posts at the bottom of the rear panel. With its gloss-painted finish, the Concept 50 has an elegant appearance.

Setting up
The main source of music was my Roon Nucleus+ feeding audio data over my network to an MBL N31 CD player/DAC, which was connected to a pair of Parasound Halo JC 1+ monoblocks. The Q Acoustics speakers were single wired with AudioQuest Robin Hood cable. I later used the Concept 50s with my Mark Levinson No.30.6 D/A processor to prepare my review of the WiiM Mini Wi-Fi streamer for this issue.

Like the JansZen Valentina P8 loudspeaker I reviewed in the June issue, it quickly became apparent that even with their ports open, the Concept 50s needed to be closer to the wall behind them than was possible in my room. (This is due to a short flight of stairs behind the right-hand speaker that runs up to the vestibule.) I therefore experimented with the distance of each speaker from its closest sidewall to give the most even midbass and upper bass balance.


With the Concept 50s sitting on their spikes, the tweeters were 32" from the floor, which is a few inches below my ear height. However, listening to the dual-mono pink noise track on my Editor's Choice CD (Stereophile STPH016-2), I didn't hear any significant change in tonal balance if I slouched or sat up straight.


With their ports open, the Concept 50s cleanly reproduced the 1/3-octave warble tones on the Editor's Choice CD down to the 50Hz band, with the 80Hz and 50Hz warbles a little lower in level than those at either side. The 40Hz warble was reproduced higher in level than the one at 50Hz, and the 32Hz tone was reinforced by the lowest room mode. The 25Hz and 20Hz tones were inaudible. The warble tones sounded very clean, with no "doubling" (adding second-harmonic distortion). The half-step–spaced tonebursts on Editor's Choice spoke cleanly down to 100Hz, with those lower in frequency suppressed a little and those around 1kHz slightly accentuated. Listening to the enclosure's wall with a stethoscope while the tonebursts played, I could hear a narrow band of liveliness between 500Hz and 600Hz, particularly on the rear panel a few inches above the port.

Q Acoustics
Unit 2, Woodside
Bishop's Stortford CM23 5RG
England, UK
(855) 279-5070