Q Acoustics Concept 300 loudspeaker

When I performed the measurements of the Q Acoustics Concept 500 loudspeaker to accompany Thomas J. Norton’s review in March 2019, I was impressed by what I found. The floorstanding Concept 500 offers a high level of audio engineering excellence for its price of $5999.99/pair. When I attended a Q Acoustics press briefing a few months back, where the English company announced the US availability of their stand-mounted Concept 300, I didn’t hesitate to ask for a pair to review.

The Concept 300 costs $4499.99/pair, including a pair of unique stands: skeletal, 26″-tall Tensegrity supports, each with three tubular stainless-steel legs, pretensioned with wires. A small platform at the top of the tripod formed by the legs engages with a sprung plate in the speaker’s base; more on that later.

The Concept 300 is a fairly large two-way design, deeper than it is high. A 1.1″ (28mm) tweeter, using a dome fabricated from “super-fine strands of coated microfiber,” is mounted above a 6.5″ (165mm) woofer, this featuring an impregnated/coated paper cone, a rubber surround, and a glass-fiber voice-coil. The tweeter is mounted to the baffle with a rubber gasket to isolate it from vibrations from the woofer, and its front plate has a shallow waveguide profile. Both drive-units are fastened from behind, using spring-tensioned retaining bolts. The woofer is reflex-loaded with a large flared port, 7″ deep and 2″ in diameter, on the enclosure’s rear panel. Foam plugs are provided, to convert the speaker into a sealed box, for use in rooms with low-frequency problems.

The third-order crossover uses premium parts, including polypropylene capacitors. Electrical connection is via two pairs of terminals to allow biwiring or biamping. Three 4mm sockets accommodate a jumper to allow the tweeter level to be raised or lowered by 0.5dB.

The enclosure, with its radiused sidewall edges and a combination of two different wood veneers finished in a high-gloss lacquer, looks elegant in the extreme. As it says on the Q Acoustics website, “The Concept 300 is a high-end, high-performance loudspeaker that’s respectfully sophisticated and able to interact discreetly with any interior design vocabulary.” Couldn’t have said it better myself!

The elegance extends inside the cabinet. The enclosure walls are constructed from three layers of MDF, each separated by a gel that absorbs and dissipates any high-frequency vibrations. Lower-frequency vibrations are handled by strategically placed internal bracing. A large sprung plate on the enclosure’s base, which Q Acoustics calls the “isolation base suspension system,” couples to the top plate of the Tensegrity stand, creating a low-pass filter that isolates the stand and floor from the speaker, and vice versa.

No grilles were provided with the review samples, nor did the package include the typically supplied foam port plugs (“foam bungs” in Brit-speak). From the look of the packaging, these samples were much-traveled.

After some experimentation, I ended up placing the Q Acoustics Concept 300s close to the positions where small speakers have consistently worked well in my room: 75″ from the wall behind them, 122″ from the listening position, with the left speaker 29″ from the LPs that line the left sidewall, the right speaker 46″ from the books that line that sidewall. (All distances were measured from the front baffles; the asymmetry is due to there being two stairs up to a small platform behind the right-hand speaker.)

The Concept 300s looked top-heavy on their spindly tripod stands and seemed too wobbly for comfort with their sprung bases sitting on top of the stands’ top plates; as we have three cats, two of which occasionally jump on to loudspeakers, I rocked the Concept 300s back and forth and side to side on the stands, and they appeared too stable to topple. The speakers were toed-in to the listening position.

To use the Vandersteen M5-HPA power amplifiers with the Q Acoustics speakers, I set the Vandersteens’ high-pass filters to their lowest frequency, 20Hz (see fig.4, red trace, here). The amplifier’s response is down by 3dB at 20Hz, and 1dB at 38Hz, which is below the tuning frequency of the Concept’s port—see “Measurements” sidebar—so its lower limit should not have an appreciable effect on the loudspeaker’s low-frequency performance. Although I left the loudspeakers’ rear-panel jumpers in the Normal (flat) position when I used the Vandersteen and Lamm M1.2 amplifiers, I reduced the tweeter levels by 0.5dB for best sound with the NAD M10 streaming integrated amplifier. (See my review elsewhere in this issue.)

I started my auditioning of the Concept 300s with the test tracks I created for the magazine’s Editor’s Choice CD (Stereophile STPH016-2, footnote 1), driving the speakers with the NAD M10. The Concept 300s reproduced the 1/3-octave warble tones with full weight down to the 40Hz band, with a slight reduction in level for the 50Hz band. The 32Hz tone was boosted by the lowest-frequency mode in my room, the 25Hz warble was faintly audible, and I couldn’t hear the 20Hz tone at my normal listening level. There was no audible wind noise from the port with these lowest-frequency tones. The half-step–spaced low-frequency tonebursts on Editor’s Choice spoke cleanly down to 32Hz, with no emphasis of any of the tones. When I listened to the cabinet walls of both speakers with a stethoscope while these tones played, I could hear some liveliness just below 500Hz.

The dual-mono pink noise track on Editor’s Choice sounded uncolored unless I sat so high that I could see the tops of the loudspeakers. The image of the noise was precisely placed in the center of the stereo image and very narrow, with no “splashing” to the sides at any frequency.

The stable, accurate imaging of the Concept 300s with recordings of music rather than test tones impressed me from the outset. Lindsey Buckingham’s double-tracked vocal on “Never Going Back” from Rumours (24/96k ALAC file, ripped from DVD-A, Warner Bros.) was reproduced as an impressively stable central image between the multiple acoustic guitars that were spread across the stereo stage. And when the backing vocals occasionally came in to the left of center, it was as though I could hear a tunnel of reverberation behind them. The Q Acoustics pair deliciously decoded recorded spatial information, with zero ambiguity in the soundstage positions of acoustic objects at all frequencies.

Provoked by Richard Lehnert’s 1981 interview with Keith Jarrett, recently posted on the magazine’s website, I streamed the pianist’s “Kyoto, November 5, 1976” from The Sun Bear Concerts (16/44.1k ECM/Tidal stream) with the NAD M10. The somewhat forward sound of the piano in this live recording was solidly set within a delicate dome of ambience. The Q Acoustics speakers stepped out of the way of Jarrett’s improvising, leaving me marveling at the depth and breadth of his creativity. Every live concert is different, the man never seeming to repeat himself.

Footnote 1: I created the test signals on this CD to make it easier for audiophiles to optimize the setup of their loudspeakers. See here.