Harbeth Super HL5plus Loudspeaker

British and Beautiful

Equipment report
Harbeth Super HL5 plus
Harbeth Super HL5plus Loudspeaker

Put simply, Alan Shaw’s new Harbeth SuperHL5plus is one of the most beautiful-sounding speaker systems I’ve heard since the original Quad electrostatic. The comparison is not stated lightly: This transducer has the same musical authority, naturalness, midrange beauty, and really extraordinary top-to-bottom coherence that I’ve heard from very few dynamic speakers of any type, persuasion, or expense. The SuperHL5plus may lack the Quad’s ultimate transparency, but so do most speakers; yet it’s as transparent as just about anything I’ve heard this side of Quads, and it more than compensates with superior top- and bottom-end extension and dynamic range. Allow me to anticipate my conclusion: If I were closing up shop tomorrow as a reviewer, the only speakers I’d be inclined to add to my Quads (57s and 2805s) would be these new Harbeths because of how they make almost anything played through them sound gorgeous in a way that is completely musically natural.

At a time when each month seems to bring products trumpeting this or that breakthrough, the 5plus is commendably unprepossessing, even modest in presentation and appearance. As the photograph shows, it’s a two-cubic-foot box with a bass/midrange, a tweeter, and a supertweeter mounted on the front baffle. Apart from its wood veneering, which is handsome and flawlessly matched within each pair, there would be no reason why it would stand out from any number of other similar-looking boxes. But it would be a mistake to underestimate the depth and sophistication of thinking, science, research, engineering, and technology that has gone into this and other Harbeths. Shaw was trained in the ways of the British Broadcasting Corporation and he is proud to be one of the very last speaker manufacturers whose designs both uphold and extend that tradition. What this translates into is original and innovative thinking; formidable knowledge of drivers, driver behavior, crossovers, and materials both theoretically and practically; scrupulous laboratory work, including live-versus-recorded comparisons; and fanatical measurements and record keeping. To these Shaw adds extensive use of computer-generated models and simulations; genuinely groundbreaking work with new materials; and quality control that is second to none and equaled by only a few (the sample-to-sample uniformity and consistency of Harbeth speakers are nearly legendary—once again, the comparison to Quads suggests itself). After all the laboratory work is completed, the final voicing of the speakers involves live-versus-recorded comparison of speaking voices he knows intimately—those of his immediate family. He is wary of using only music because he believes there are far too many uncontrollable variables, including everything from one’s emotional associations with it, to not being able to know the sound at the source of recordings. And he performs the final listening evaluations of every design in stereo because the “tweaking of the crossovers has to be in stereo and in the final cabinets.” (See The Absolute Sound’s Illustrated History of High-End Audio: Loudspeakers for a brief history of the BBC monitor [pp. 293-94] and for more about Shaw’s philosophy and methods of speaker design [pp. 147-48].)

The SuperHL5plus has one of the longest lineages, if not the longest of any speaker in the Harbeth lineup—indeed, I can think of few current models from any manufacturer that can boast one that’s lengthier or has been improved more consistently. It’s the ninth generation of the HL Monitor, the loudspeaker with which Dudley Harwood launched the inaugural Harbeth upon his departure from the BBC in 1977. Ten years later, when Shaw bought the company from Harwood, the speaker was in its fourth iteration, the relatively short-lived HL Monitor Mk4; before long, he introduced the HL5, which has encompassed five models, including this latest one, introduced in 2014. Although among American audiophiles Harbeth is better known for its consumer versions of its professional monitors, Shaw informed me that the several versions of the SHL5 have consistently been the company’s best sellers—and worldwide, the new version is flying off the shelves so fast that some reviewers have been unable to get speakers because the company can’t spare them. Of any speaker he has ever authored, remarks he has made suggest this may be considered a statement offering.

According to Shaw, the 5plus is a complete, ground-up redesign, with particular emphasis upon the bass/midrange-to-tweeter crossover, “made possible,” he told me, “by a little serendipitous luck in hitting upon a combination of components that I’d not tried before and recognizing immediately that a genuine step forward in sonics had become possible.” Also pertinent here is a newer version of the company’s innovative RADIAL polymer material for the bass/midrange driver—now called RADIAL2—but Shaw credits the new crossover with really “opening up the sound of the 5plus.” The tweeter and supertweeter remain constant from the previous versions, as does the cabinet.                                          

Speaking of the cabinet, also preserved from the previous models, and a hallmark of all Harbeths, are the thin walls of half-inch MDF. When Harwood was at the BBC in the Sixties, he initiated considerable research on materials and construction using an accelerometer. His research revealed that large, heavy, extremely rigid cabinets were not the only path to reproduction free from the resonant contributions of the enclosures—and perhaps not even the best way. No matter the materials involved, play something loud enough and enclosures will resonate—the trick is to control them. Harwood’s findings indicated that multiple very low-level or inaudible resonances at lower frequencies, where the effects are benign, are preferable to (or at least as desirable as) pronounced, i.e., high-Q resonances in a narrow band or even at a single frequency, especially at higher frequencies above the bass range. The danger of the latter approach, according to Shaw, “is that only a tiny amount of energy in the music can set off a high-Q resonance. We know from resonant systems that the higher and purer the peak, the longer it takes the resonance, once excited, to decay. But when resonances are pushed downwards in level and, critically, downwards in frequency, the ear cannot identify them as bass tones from the music, the cabinet, or the woofer: it becomes a homogeneity, and inaudible means inaudible. So yes, we still use that method because the cabinet’s midband contribution—which is where the ear really can pick out box resonances if they exist—is so clean.” The proof is in both measurements and listening: All Harbeths are outstandingly clean, clear, and high-resolution—and the new 5plus is no exception. Even at uncomfortably loud playback levels—too loud to listen for very long—in my 2600-cubic-foot listening room, the speaker remained unperturbed, the reproduction superlatively clean, composed, and controlled.

Setup is straightforward, requiring stand-mounting with the tweeter (not the supertweeter) at ear level. A pair of superb dedicated stands by the Canadian company Skylan was used for the review. The flattest, most uniform response is on-axis; though dispersion is good enough that head-in-a-vise syndrome is avoided. Sensitivity is 86dB, impedance an easy-to-drive 6 ohms, and recommended minimum power 25 watts (though considerably more, i.e., 100 watts or greater, is preferable, especially in larger rooms). In common with all Harbeths, the 5plus proves in use to be a straightforward, uncomplicated speaker. This is because Shaw does such a thorough job voicing them for real-world, in-room performance. Put them on sturdy stands at the recommended height; get them out from the walls a few feet; and they just work without a lot of hair-pulling, tweaking, fussing, or agonizing.

When I singled out the speaker’s coherence in my opening paragraph, I was referring not only to the integration of the three drivers, which makes the presentation appear as if it’s coming from a single source, but also to the way the drivers themselves, though of different materials, seem to speak with one voice. I’ve heard more than a few box speakers with multiple drivers that sound coherent in the sense of producing what sounds like a solid wave-front, while at the same time the drivers in those same speakers each have audibly different sonic signatures. This doesn’t happen with the 5plus. Shaw is known for selecting his drivers very carefully, and his RADIAL ones are all made in-house, so this gives him a tremendous leg up when it comes to coordinating the individual drivers within a loudspeaker. Although the 5plus is technically a three-way owing to the supertweeter, in a practical sense it functions more like a two-way with top-most octave augmentation—extension would be a more accurate word—from the supertweeter. The Harbeth’s eight-inch driver handles bass (the -3dB point is 40Hz), midrange, and lower-treble frequencies, crossing over to the tweeter at 3.3kHz, which is augmented by the supertweeter above 12kHz. The supertweeter thus serves to confer a subtle sense of airiness and definition in the uppermost octave without calling any undue attention to itself. On the contrary, the top end here is as smooth and as detailed as you please without any apparent rise, peakiness, or raggedness. That indeed characterizes the response of the 5plus all across the spectrum. It’s an exceptionally well-behaved speaker system.

This includes the very bottom end, even below 40Hz, where room reinforcement provides a bit of oomph down into the high thirties. As loud as I cared to listen, including even some very extended organ recordings, such as Kei Koito’s Bach program on the Claves label (the best organ recording I know), I was unable to push the RADIAL2 cone into doubling or make the port chuff. But people who really enjoy deep, deep bass with a strength equivalent to what you’d hear in a church or concert hall will want to add a subwoofer (I’d recommend an REL because they mate so well with BBC-type speakers).