KEF Q350

ONLINE AUTHORITY: WWW.STEREOPHILE.COM

ELECTRONICALLY REPRINTED FROM MARCH 2018

EQ UIPMENT R EPORT

HERB REICHERT

KEF Q350 LOUDSPEAKER

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uring the hour preceding my removal of the KEF LS50 loudspeakers from their spiked, rough-iron stands, I was lost in the recurring still moments, reverberating tones, and contemplative spirit of Sir John Tavener’s Eis Thanaton and Theophany, in the recording by soprano Patricia Rozario, bass Stephen Richardson, and Richard Hickox conducting the City of London Sinfonia (CD, Chandos CHAN 9440). After replacing the LS50s with the not-yet-broken-in KEF Q350s, I restarted Eis

Optimizing a loudspeaker’s radiation pattern is the Uni-Q’s raison d’être.

Thanaton. Three minutes in I was staring blankly, eyes closed, swaying slowly in my seat, astounded by how much larger and

SPECIFICATIONS Description Two-way, bass reflex, stand-mounted loudspeaker. Drive-units: a single Uni-Q coincident driver array comprising a 1" (25mm) vented aluminum-dome tweeter and 6.5" (165mm) aluminum-cone woofer. Crossover frequency: 2.5kHz with first-order slopes. Frequency response: 63Hz–

28kHz, ±3dB. Sensitivity: 87dB/2.83V/m. Impedance: 8 ohms nominal, 3.7 ohms minimum. Dimensions 14.1" (358mm) H by 8.3" (210mm) W by 12.1" (306mm) D. Weight 16.75 lbs (7.6kg). Finishes White with silver drivers, black with black drivers.

Serial numbers of units reviewed 391113, 391114. Price $649.99/pair; grilles add $39.98/pair. Approximate number of dealers: “Amazon, Best Buy Magnolia, KEFDirect, and participating local KEF dealers.” Warranty: 5 years. Manufacturer KEF, GP Acoustics (UK) Ltd.,

Ecceleston Road, Tovil, Maidstone, Kent ME15 6QP, England, UK. US distributor: GP Acoustics (US) Inc., 10 Timber Lane, Marlboro, NJ 07746. Tel: (732) 683-2356. Fax: (732) 683-2358. Web: www.kef.com.

KEF Q350

more serious every note had become. Voices, instruments, and recorded atmosphere not only felt more expansive; everything seemed more exposed, more sacred, more directly communicative, possibly even more darkly transparent. These differences in degrees of directness and exposure made me excited to be reviewing a British loudspeaker that could accomplish such things while costing only $649.99/pair.

the back of the tweeter—improving response at the bottom S S O C Iharshness.” AT E D E Q U I P M E N T andAreducing The LS50 crossover has a third-order low-pass filter and a second-order high-pass filter; the Q350 has first-order filters for the high and low passes. According to Sehdev, “The lower component count for 1st order network allows us to use better quality components for the price.”1 The Q350’s cloth grille is optional at $39.98/pair, but KEF does include concentric, two-piece foam plugs to partially or fully block the rear-firing ports when the pair are positioned near room boundaries.

Description I was first drawn to KEF’s Q350 because I wondered how a larger version of their signature Uni-Q driver than the one used in the LS50 would sound in a less expensive, vinylwrapped enclosure of larger volume and thinner walls. I’d Setup logged a lot of hours with KEF’s reference-quality LS50, Reviewing loudspeakers is plagued with uncertainty. Everyand I wondered if comparing it to its lower-priced, Q-series where I place them and every amp I connect them to makes sibling might disclose not only another high-value standa pair of speakers sound different. mounted bookshelf speaker, but also show me some things Throughout the five weeks of my listening, I never about the effects of cabinet mass and crossover slope on stopped adjusting the Q350s’ positions, but not because loudspeaker performance. they never sounded right—they sounded fundamentally The LS50 has a 5.25" Uni-Q coincident array with an aluminum-magnesium alloy midrange-bass Reviewing loudspeakers is cone, a 1" aluminum dome tweeter, and a cast-aluplagued with uncertainty. minum basket, in a 7.5-liter, 15.8-lb cabinet made of MDF and a sculpted solid molding. The Q350 has a good everywhere. I kept moving them to determine which similar, 6.5" Uni-Q array with an aluminum midrange-bass cone, a 1" aluminum dome tweeter, and a stamped-steel bas- combination of wall-to-speaker distance and port plugging worked best. In the end, I slightly preferred the Q350s 6' ket, in a 14.5-liter, 16.75-lb, generic-looking MDF box. apart, toed in just a little, 33" from the wall behind them to According to Dipin Sehdev of KEF America, the stamped their front baffles, and with their ports partially plugged. basket “is equal in rigidity to the cast one” because “We designed the chassis using Finite Element Analysis (FEA) to increase its strength. The Q350’s box material is 0.59" MDF, Listening I prefer loudspeakers with well-controlled directivity, which with a 1.34" thick front baffle. There is a single horizontal is the main reason I admire KEF’s Uni-Q concentric drivers. brace in the middle of the cabinet. The Q350 doesn’t have Optimizing a loudspeaker’s radiation pattern is the Uni-Q’s the same constrained layer damping as the LS50.” raison d’être. The Q350s generated a proper soundstage and While the motor systems of the LS50’s and Q350’s good timbres throughout my small listening room. drivers are the same, the Q350’s specified sensitivity is The last speaker I reviewed, the Totem Signature One, slightly higher: 87dB/2.83V vs the LS50’s 85dB/2.83V. The had a rear port that whistled at about 560Hz, so the very Q350’s Uni-Q driver includes a damped loading tube for its first thing I listened for with the Q350s was noise from their tweeter, which, Sehdev says, “gives a gentler termination at

MEASUREMENTS

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used DRA Labs’ MLSSA system and a calibrated DPA 4006 microphone to measure the KEF Q350’s frequency response in the farfield, and an Earthworks QTC40 for the nearfield responses. My estimate of the KEF’s sensitivity was 86.6dB(B)/2.83V/m, which is within experimental error of the specified 87dB. Though the impedance magnitude (fig.1, solid trace) drops just below 4 ohms at 180Hz and there is a combination of 5 ohms and a –39° electrical phase angle at 125Hz, the speaker is a relatively easy load for the partnering amplifier. This graph was taken with the port open, hence the twin impedance peaks in the bass, which confirm that this is a reflex design. Completely blocking the port gives a single low-fre-

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quency peak centered at 78Hz—a fairly high tuning frequency for a sealed-box woofer alignment. The traces in fig.1 have a small wrinkle between 600 and 700Hz, suggesting the presence of a cabinet resonance in that region. However, when I investigated the vibrational behavior of the enclosure panels with an accelerometer, there was nothing untoward between 600 and 700Hz. However, there was a fairly strong mode at 309Hz on all surfaces (fig.2), and a slightly less strong one at 504Hz. With the Q350’s port open, the minimum-motion notch in its woofer’s output (fig.3, green trace) indicates that the port is tuned to 45Hz, and the port’s response (blue trace) peaks between 30 and 60Hz. While some

midrange liveliness can be seen in the port’s output, this is relatively low in level and will be mitigated by the fact that the port faces to the Q350’s rear. With the port fully blocked, the woofer’s output (red trace) is down by Stereophile KEF Q350 (reflex) Impedance (ohms) & Phase (deg) vs Frequency (Hz)

Fig.1 KEF Q350, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

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KEF Q350

ports and cabinets. The port seemed quiet, but not as quiet as when it was partially or fully blocked. I also noticed a bit of “talk” from the cabinet, but only rarely did I detect any cabinet resonances in the fundamental range of human speech— approximately 200-750Hz—while listening to music. To roughly assess the maximum amplitude of the noise produced by the Q350’s enclosure, I drove the KEFs with Bel Canto Design’s e.One REF600M monoblocks ($4990/ pair) to play François Couperin’s complete works for organ, with Michel Chapuis performing on the Jean-Esprit Isnard “large organ” of the Basilica of St. Mary Magdalene, in Saint-Maximin-la-Sainte-Baume, France (LP, RCA Victrola VICS 6018). I used the powerful Bel Cantos to hear how well these little speakers could reproduce the sound of a big organ recorded in a giant cathedral. The Q350s replicated Couperin’s “Parish” and “Convent” organ masses with greater scale and finer, more intricate detail, but less forcefulness, than did the LS50s with the same amps. Imagine how I felt as I lay on the couch in my night-dark, candlelit apartment, feeling like I was surrounded by the stone walls of a Gothic cathedral begun in 1295. Imagine expansive pipe-organ notes energizing the air and echoing throughout my little room. These modest stand-mounted speakers let me feel that. At one point in my critical listening, I got up and put my hands on the sides of the Q350s’ cabinets. I could tell where the internal brace was. The vibration I felt, especially toward the bottom front of each side, was not subtle. But maybe this isn’t a bad thing? It certainly did no harm to the reproduction of this glorious organ recording. I replaced the Bel Cantos with the Pass Laboratories XA25 stereo amplifier ($4900) and listened to Robert Palmer’s Quintet for A-Clarinet, String Trio, and Piano, composed in 1952 and performed by clarinetist Arthur Bloom, violinist Kees Kooper, violist Paul Doktor, cellist Warren Lash, and pianist Mary Louise Boehm, and produced by Marc Aubort and Joanna Nickrenz (LP, Vox Turnabout TV-S 34508, now available on CD as Albany 153). The Pass Labs amp and KEF Q350s reproduced the sound of each in-

1 By the time this issue hits newsstands, we will have an interview posted to the Stereophile website where Jack Oclee-Brown, KEF’s Head of Acoustics, discusses the design of the Q350.—Ed. 2 See the February 2017 issue: www.stereophile.com/content/schiit-audioyggdrasil-da-processor. 3 See the May 2016 issue: www.stereophile.com/content/schiit-audio-ragnarokintegrated-amplifier.

pears to be tuned to be maximally flat. Higher in frequency in fig.3, the black trace shows the Q350’s farfield

response averaged across a 30° horizontal window centered on the tweeter axis. There are a slight lack of energy in the mid-treble and two small peaks between 600Hz and 1.3kHz, but the balance is otherwise even. The plot of the KEF’s lateral dispersion, normal-

Amplitude in dB

6dB at 45Hz, but offers greater lowbass output than the sum of the reflexloaded woofer and port responses (black trace below 312Hz). Note that the apparent rise in the upper bass in this graph is an artifact of the nearfield measurement technique; the KEF ap-

strument with almost pitch-perfect tone and above-average force and texture. I could sense the thicknesses of the wood of the stringed instruments. I could feel the pull and push of the players’ bows. On other selections on this LP, the flute made breathy, lifelike notes. The attacks of piano notes felt surprisingly natural. Note decays were blurry, and slightly too long. But overall, the Q350s allowed the piano to sound full-bodied and musically satisfying. Driven by Rogue Audio’s Sphinx hybrid integrated amplifier (tubes, class-D, $1299), the Q350’s sound had stout bones, especially through the bottom octaves. The midrange was clear as water. Unfortunately, there was a leanness that turned dry and flat through the uppermost octaves. The big drum in Guo YaZhi’s Sorrow of the River (CD, M•A Recordings M074A) was taut and surprisingly powerful, but YaZhi’s various Chinese wind instruments sounded annoyingly hard and two-dimensional. I’m proud of my Stereophile reviews of Schiit Audio’s Yggdrasil DAC ($2299)2 and Ragnarok integrated amplifier ($1699).3 Now, one and two years later, respectively, I’m enjoying both Schiits more than ever. Therefore, the natural-feeling energy, hip-shaking momentums, saturated colors, high-relief textures, and relaxed coherence they brought to the Q350s did not surprise me. The Ragnarok showcased the Q350’s reproduction of instrumental tones. The sound was thicker than it should be, but instruments and voices appeared more tangibly in the room than with the Rogue Sphinx. The Q350s really liked tubes, especially push-pull EL34s. With the PrimaLuna Prologue Premium stereo amplifier ($2199) and preamplifier ($2199), the modest KEFs’ bass was less taut, but they delivered a fleshy, organic-feeling midrange and elegant, delectable highs. The PrimaLuna amplification

Frequency in Hz

Fig.2 KEF Q350, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

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Fig.3 KEF Q350, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with nearfield responses of woofer with port blocked (red), port open (green), and port (blue), and the complex sum of the last two (black), respectively plotted below 312Hz, 312Hz, 1.2kHz, and 312Hz.

Fig.4 KEF Q350, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.

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KEF Q350

had a satisfying way of filling out the Q350’s tendency toward thinness. The combo made male and female voices—such as those of Furia Zanasi and Ximena Biondo of La Chimera, in their Buenos Aires Madrigal: Argentine Tangos & Italian Madrigals (CD, M•A M063A)—feel more embodied and tonally complex, more engaging. The PrimaLuna was my favorite amp with the Q350s; more than the others, it made music feel deeper, fuller, more probing, more whole. Tavener’s Eis Thanaton was most comprehensible with this amp. Erudition—Enter the KEF LS50 After a week of listening only to the Q350s, I switched back to KEF’s LS50s, driven by the PrimaLuna ProLogue Premium amplifier. The first difference I noticed was how pure, solid, and properly damped the LS50s sounded. Bass was more forceful and detailed, but not as expansive or reaching as low as with the Q350s. The firm quiet of the LS50s made the Q350s sound slightly noisy and wispy. Conversely, my weeklong familiarity with the Q350s caused me to perceive the LS50s as sounding ever so slightly thick, over-damped, and restrained. In contrast, the Q350s seemed quicker and more mercurial than the LS50s. The Q350s didn’t appear to suppress music’s inner currents as much as the LS50s did. Still, each time I reinstall the LS50s, I appreciate them more. Today, as I compared them with their lower-cost sibling, they seemed one of the most impressive bits of speaker engineering of the 21st century. After a few agreeable LP sides, I put on a CD of Tavener’s Eternity’s Sunrise, performed by the choir and orchestra of the Academy of Ancient Music, Paul Goodwin directing (CD, Harmonia Mundi 907231). This recording is dominated by two sopranos, a baritone, and, a violin. The LS50’s balanced

purity directed my attention to the precision of this recording. It served up those cavernous spaces that Tavener uses to frame his meditations. High soprano notes were attractively supple and tangible, demanding scrutiny and admiration. I switched back to the Q350s and found myself admiring something different. I was using the AMG Giro G9 turntable ($9900) with a Koetsu Rosewood Standard cartridge ($3495, review in the works) driving the Tavish Design Adagio phono stage ($1690), a Rogue RH-5 preamplifier ($2495), and Pass Labs’ ridiculously solid and transparent XA25 amplifier. I swear I could almost count the separate voices in the choir. What the Q350s did with Grayston Burgess and the Purcell Consort’s Now Make We Merthe: Medieval Carols (LP, Argo ZRG 526) was even more impressive: They put living medieval persons in front of the microphones, and made these Christmas carols from the 12th through 15th centuries seem right-here-and-now present and contemporary—not quaint, canned, or antique. I felt a little bad that I didn’t have my Linn Sondek LP12 in the system, or at least a British-made amplifier—that was how British Benjamin Britten’s anti-war opera, Owen Wingrave, based on a short story by Henry James, felt through the KEF Q350s. This spectacular 1971 recording, in which Britten himself conducts the English Chamber Orchestra (2 LPs, London OS 26224), was made near the height of the Vietnam War, and features the same cast as in the first live performance, with Dame Janet Baker and Peter Pears, and Benjamin Luxon in the title role. I enjoy this opera because it is English, and because I identify with Owen as he defies his family’s traditions and refuses to enlist in the military.

measurements, continued

In the time domain, the step response on the tweeter axis (fig.6) indicates that the tweeter is connected in inverted acoustic polarity, the woofer in positive polarity, with the tweeter’s output slightly leading the woofer’s. However, the decay of the tweeter’s step blends smoothly into the start of

Fig.5 KEF Q350, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

Fig.6 KEF Q350, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

the woofer’s step, suggesting optimal crossover design. The cumulative spectral-decay plot (fig.7) is superbly clean, especially considering that the Q350 is a relatively inexpensive loudspeaker. Its rather lively enclosure apart, KEF’s Q350 offers excellent measured performance.—John Atkinson

Data in Volts

ized to the tweeter-axis response (fig.4), shows excellent control of the speaker’s off-axis behavior, the pattern becoming more directional in an even manner as the frequency increases. The same characteristic can be seen in the plot of the speaker’s vertical dispersion (fig.5).

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Time in ms

Fig.7 KEF Q350, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

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KEF Q350

“War should be a crime!” he laments. I completely agree. His refusal to fight costs him first his inheritance, then his life. The performances and recording quality of Owen Wingrave showed me the full measure of the Q350s’ ability to open a window on the recording venue, London’s Kingsway Hall. When I switched from the LS50s to the Q350s, the dimensions of the soundstage didn’t significantly change, but the sense of air became less dense. Unfortunately, that less dense air also seemed a bit dusty, and the performers less dense and defined. Instrumental and vocal tones became less saturated. But to its credit, the Q350s’ sound felt more direct, open, and fundamentally truthful than the LS50s. A Revelation This is when, as an experiment, I replaced the massive, 24"-high Sound Anchor Signature stands I’d been using to support the Q350s with the elegant TonTräger Reference hardwood stands ($1395/pair). Skinny as sticks, the 24"-high TonTrägers weigh only 6 lbs and can be lifted with a finger.4 Guess what? The Q350s’ less-than-perfectly-clean air got a whole lot cleaner. Less dusty-foggy. Those cabinet vibrations I’d felt under my hands were reduced. Bass became purer, more effectively detailed. Music felt more relaxed, focused, and three-dimensional—even at high volumes. Opera recordings make excellent tools for assessing amps and speakers. Britten’s Owen Wingrave made easy work of showing what the Q350s could and could not do. In addition to the lower-distortion fresh-air effect, the new stands let the Q350s show just how precisely they could pinpoint the positions of singers on the stage. This improvement in the Q350s’ sound was so conspicuous that I never returned to my iron anchors. (KEF recommends using their own 24"-high, 10.3-lb Performance Speaker Stands, which sell for $399.99/pair; these were not submitted with the Q350 review samples.) LS3/5a Comparisons The three versions I have of the BBC’s classic LS3/5a minimonitor are all of the same size, weight, and construction quality, and measure as identically as any three speakers could. But they sound surprisingly different. Each in turn sat on the TonTräger stands in the same positions in my room. The Falcon LS3/5a ($2995/pair) is the most uncolored, most precise loudspeaker in my bunker collection. I own the pair of them, they’re my primary reference, and I’ll never let them go. But I hadn’t used the Falcons in a while, and had forgotten how refined, descriptive, and naturally toned they are. When I switched from the KEF Q350s to the Falcons, still using the TonTräger stands, it was as if someone had vacuumed the last vestiges of fog from the space surrounding Janet Baker’s voice. With Elvis Presley’s first-ever recording, “My Happiness,” from A Boy from Tupelo: The Complete 1953–1955 Recordings (3 CDs, RCA/Legacy 8985-41773-2), Elvis seemed even more three-dimensional. When audiophiles speak of resolution, they usually mean seeing and hearing into the performing space and down into the recording’s noise floor. This type of resolution is the Falcons’ specialty. When I compared them with the Q350s, I realized that it was also one of the KEFs’ best traits. My infatuation with the Stirling Broadcast LS3/5a V2 ($1990/pair) is based entirely on its greater fullness at the bottom and the liquid flow of its sound. It makes the stereophile.com  n  March 2018

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A S S O C I AT E D E Q U I P M E N T Analog Sources AMG Giro G9, MoFi Electronics UltraDeck turntables & tonearms; EMT TSD 75, Koetsu Rosewood Standard, Miyajima Saboten, MoFi Electronics MasterTracker cartridges. Digital Sources Mytek HiFi Manhattan II, Schiit Audio Yggdrasil DACs; Integra DPS-7.2 DVD player (used as CD transport). Preamplification Auditorium 23 (for EMT TSD 75), Bob’s Devices CineMag 1131, Dynavector SUP-200, Lounge Audio Copla JFET-MC step-up transformers; Lounge Audio LCR Mk.III RIAA, Parasound Halo JC 3+, Tavish Design Adagio phono preamplifiers; PrimaLuna ProLogue Premium, Rogue Audio RH-5 line-level preamplifiers. Power Amplifiers Bel Canto Design REF600M (monoblocks), Pass Laboratories XA25, PrimaLuna ProLogue Premium. Integrated Amplifiers Rogue Audio Sphinx, Schiit Audio Ragnarok. Loudspeakers Falcon Acoustics LS3/5a, KEF LS50, Rogers LS3/5a, Stirling Broadcast LS3/5a V2. Cables Digital: Kimber Kable D60 Data Flex Studio (coaxial). Interconnect: AudioQuest Mackenzie & Big Sur, Auditorium 23, Kimber Kable Silver Streak, TriodeWire Labs Spirit, Wireworld Silver Eclipse 7. Speaker: AudioQuest Type 4, Auditorium 23, TriodeWire American Series. Accessories Harmonic Resolution Systems M3X-1719AMG GR LF, PS Audio PerfectWave PowerBase isolation platforms; Sound Anchor Signature, TonTräger Audio Reference speaker stands; Dr. Feickert Analogue, Acoustical-Systems SmarTractor cartridge-alignment protractors; Musical Surroundings Fozgometer azimuth-range meter.

Falcon LS3/5a sound slightly dry and tipped up in comparison. Compared to both the Stirling and Falcon LS3/5a’s, my original “white badge,” 15-ohm Rogers LS3/5a seemed a little sluggish and fuzzy. But the Stirling is the most different-sounding of the three BBCs—and the one that sounded most like the KEF Q350. The Stirling LS3/5a V2 and the Q350 each produced a more relaxed warmth than the Rogers or Falcon, and, for reasons I don’t quite understand, a larger soundstage. I am a student and admirer of British boxes, but if I could keep only one, I would keep the LS50—but only when I’m an audio reviewer. The LS50 is a benchmark for accurate octave-to-octave energy balance and tonal neutrality—a reference-quality speaker if ever there was one. If I were just Herb, listening alone in my bunker, I’d keep the Stirling LS3/5a V2s because they make me forget audiophilia. If I were Herb the amp builder, I’d keep the Falcons because they’re the most revealing of whatever drives them. If I wanted only to impress other audiophiles, I’d keep my collectible 1984 Rogers. But if I lived with my romantic partner, I’d keep the KEF Q350s, because they reproduced the widest range of music—including techno, bluegrass, reggae, and pop—in a musically satisfying way. 4 The TonTräger Audio Reference stands were designed to support Harbeth’s 30.2 Anniversary Edition speakers, to be reviewed next month.

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Conclusions Early in this review process I realized that KEF’s Q350 is not the poor person’s LS50, but has a unique goodness of its own. Comparing the two KEFs became a case study in the fundamental ways speaker enclosures and crossover slopes can affect the sound character of the drivers they support. To my ears, dense, highly damped boxes and/or steep-sloped crossovers can sound subliminally thick and restrained. In

contrast, lightly damped boxes with first-order crossovers S S Oloose, C I AT E D E Q U I Pnoise M Eto Nthe T midrange— addAsome not-so-subliminal but they can also jump, sound expansive, and dance like Fred and Ginger. The KEF Q350 is a lively and open-sounding loudspeaker. It delivers appealing tone, taut and satisfying bass, excellent boogie factor, and a feeling of sophistication—all at a very low price. Highly recommended. n

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