Raising the performance bar that additional centimeter can be difficult in the case of a speaker that had already set a high standard. After all, the original Helicon 400, released some seven years ago, had garnered its share of accolades including our own 2005 Mid-Priced Loudspeaker of the Year award. DALI’s CEO and chief designer, Lars Worre, explained that because of its loyal following there was little incentive for a major update and that only a few improvements have been implemented in the Mk2 version under review, chiefly as a result of customer feedback. First, and most obvious, is what Lars refers to a “facial” change—improved finish quality. And there’s no question that the 400 MkII’s lacquered-veneer finish and curvaceous cabinet will have a high wife acceptance factor. The 6.5-inch mid/woofers are manufactured to DALI’s specs by Scan Speak in Denmark. It’s a natural partnership says Lars, as Scan Speak is located less than 100 miles from DALI’s headquarters. The Mk2 woofers feature slightly increased magnetic flux density for better bass damping and improved pole-piece saturation. The rest has to do with improved parts quality: a new binding-post-terminal assembly and a higher-grade capacitor in the woofer network for reduced distortion and enhanced clarity.
On the surface, this appears to be a conventional four-driver, three-way design. But, in fact, things are not quite what they seem to be. At its core this is a two-way design. The upper woofer is crossed over conventionally at around 3kHz to a 1-inch silk-dome tweeter. However, the lower woofer rolls in gently below 700Hz, the Helicon’s baffle-step frequency. This is where the radiation pattern transitions from half space to full space as the wavelength wraps around the front baffle. The expected or theoretical result would be a 6dB-per-octave rolloff, though that is counteracted to some extent by room gain. The lower woofer attempts to mirror-image the baffle step in order to maintain tonal neutrality through the lower midrange and upper bass range.
Does this strategy succeed? Definitely, no doubt about it! Rarely have I failed to complain about tonal balance issues, specifically a lean lower midrange or an anemic upper bass—the octaves spanning the range of 120 to 440 \Hz. This is where the perception of full-bodied, big-tone sound originates. Vincent Salmon, as far back as 1947, may have been the first to offer a comprehensive set of descriptors, terms suggestive of the sensations experienced by a listener. For example, he hit the spot with the words Lean, Thin, and Tinny, listed in order of increasing severity, to describe a balance deficient in this region. A moderate excess, on the other hand, may be communicated by terms such as Punch, Body, Mellow, and Thick. These terms are not to be confused with Tubby and Boomy which he reserved for the midbass.
Tonal balance is paramount on my list of priorities and helps explain why conventional mini-monitors don’t cut it for me. They’re terminally neutered in the upper bass/lower midrange and can’t even be fixed by the addition of a subwoofer. Even floorstanders haven’t generally fared too well. That’s why I was pleasantly surprised to discover that the Helicon fit my listening room live a glove with a satisfying sense of body and punch. Now, that’s what I call getting off to great start! I was even more ecstatic about its potential when I discovered that its in-room bass extension reached down to about 30Hz. Of course, it’s not all about bass extension, a major consideration being bass quality—especially in a bass-reflex design. And this is apparently a priority at DALI, to tune bass-reflex speakers to obtain bass quality approaching that of aperiodic or non-resonant systems. Still, as with other bass-reflex designs, you’ll need a power amp with a decent damping factor to properly control bass lines. I’m not suggesting that a solid-state amp with a damping factor of 100 is mandatory. On the contrary, I obtained very decent results even with Audio by Van Alstine’s Ultravalve tube amp. So maybe a damping factor under 10 is O.K., too. Either way, bass lines were well delineated with excellent pitch definition and minimal intrusion from cabinet resonances.
At the other end of the frequency spectrum, the 1-inch silk dome is augmented at 13kHz by a quasi-ribbon tweeter (thin aluminum conductor over a polymer base). A total of six rod magnets are used to generate the magnetic flux density; three ferrite magnets in back of the diaphragm and three neodymium types in front. There’s plenty of good engineering in evidence here. The ribbon is well protected by a third-order high-pass network, while the dome tweeter is crossed over a good two octaves above its free-air resonance. Both tweeters are bolted to a die-cast aluminum faceplate, which is recessed on the back side at different depths, to align their acoustic centers and minimize off-axis interference effects. An acoustic lens is used to improve the ribbon’s horizontal dispersion.
Unfortunately, the overlap between the tweeters around 13kHz results in a peak of about +6dB (relative to the response at 1kHz) when measured (without the grilles) at one meter on the ribbon’s axis. That’s why I preferred not to toe-in the cabinets toward the listening seat and ended up firing the tweeters straight ahead for the most natural treble balance. And sure enough, the owner’s manual recommends not pointing the speakers directly at the listening seat. Even so, without any toe-in the treble emphasis did not disappear completely due to the Helicon’s excellent horizontal dispersion; at the listening seat I still measured about a +3dB SPL peak relative to 1kHz. With proper setup, the residual treble bump is a minor effect, but one that is potentially audible as a slightly brittle character when reproducing cymbals and brass. Not surprisingly, the Helicon sounded its best when partnered with power amps lacking an assertive treble range.
Right out of the box, a touch of roughness and sibilance permeated the upper midrange. Since the mid/woofer is pushed well into the upper midrange, I was hoping that things would smooth out as the woofers broke in. Like a fine wine, the Helicon continued to improve over the first couple of weeks of break-in, finally settling down to a satisfactory level of textural silkiness.
Goldilocks would be pleased. The Helicon’s presentation consistently felt just right. It is the only speaker I’ve auditioned to date at this price point that I find suitable for realistic reproduction of orchestral music. It lays down a solid orchestral foundation without cheating the orchestral power range of 100Hz to 400Hz. Despite the modest woofer size, it was able to generate a reasonable sense of slam and satisfying levels of lower-midrange punch. And despite the array of drivers on the front baffle, there was plenty of imaging magic on display. The soundstage was deep and spacious, populated by robust image outlines, though the speakers didn’t disappear as easily as did the Esoteric MG20 or the recently reviewed Salk Sound SongTower. Harmonic textures were plush and vivid, especially when the Helicon was driven by tube amplification.
Another major priority of mine is emotional expressiveness, the ability of a speaker to communicate the music’s drama and passion. I found the Helicon to be quite engaging emotionally and capable of plenty of boogie factor. And there was plenty of detail to behold, including transient decay into the noise floor of the recording. But note that the Helicon is not an analytical-sounding speaker. I didn’t feel inundated with low-level information, as I do sometimes when listening to an electrostatic midrange. OK, so it’s not the most revealing or transparent speaker on the market, but it really hangs well together. It is quite capable of reproducing the wholeness, the gestalt of the musical experience, and to that extent it transcends the typical audiophile speaker.
While the Helicon’s design does not attempt to nudge the state of the art forward, it aims high enough to create an exceptionally satisfying speaker. It’s not the kind of speaker that will necessarily wow you during a quick audition. It lacks the sort of attention-grabbing hyped-up balance that some audiophiles are attracted to like moths to a flame. You know, like a response bump in the presence region, around 4-to-6kHz, that makes female vocals jump out of the mix with surreal clarity. The test of any great speaker is long-term satisfaction, being able to live with it, day in and day out, without any significant reservations. The Helicon is that sort of speaker.
Listening to the Helicon I have no worries about missing out on a particular aspect of the reproduced sound. I just kick back and enjoy the music. You may have been seduced by various speakers over the years, had your fling, only to wake up the morning after with nagging doubts. The DALI Helicon 400 Mk 2 is a speaker you can “marry” for life. A two-thumbs up enthusiastic recommendation!
SPECS & PRICING
Frequency response: 32Hz–27kHz +/-3dB
Sensitivity (2.83V/1m): 88dB
Nominal impedance: 4 ohm
Maximum SPL: 111dB
Recommended amplifier power: 50–300Wpc
Crossover frequencies: 700Hz/3kHz/13kHz
Drivers: 1mm x 10mm x 55mm ribbon, 1mm x 25mm soft textile dome, two 6½” wood-fiber cone
Enclosure type: Bass-reflex
Bass-reflex tuning frequency: 32Hz
Input connections: Bi-wire
Dimensions: 40.6”x 10.6” x 19.9”
Loudspeaker weight: 70.5 lbs.
THE SOUND ORGANISATION (U.S. DISTRIBUTOR)
159 Leslie Street
Dallas, TX 75207
Kuzma Reference turntable; Kuzma Stogi Reference 313 VTA tonearm; Symphonic Line RG-8 Gold MC phono cartridge; Air Tight ATE-2 phonostage; SoundTradition Live! MC-10 step-up; Weiss Engineering Jason transport and Medea DAC, Sony XA5400 SACD player; Concert Fidelity DAC-040 DAC, PrimaLuna ProLogue Eight CD player; Concert Fidelity CF-080, Accustic Arts Tube Hybrid II, and Mystère CA21 line preamps; Pass Labs XA30.5, Lamm Industries M1.2 Reference monoblocks, Audio by Van Alstine Ultra valve, and Mystère CA21 power amps; Bybee Speaker Bullets; FMS Nexus 2 interconnects and FMS speaker cable