Floor Loudspeaker Reviews

Looking back at our September 2014 issue, I think my review of the Triangle Signature Delta loudspeaker marked something of a watershed in the evolution of my taste in loudspeaker sound quality. For decades I have been a devotee of what might be called "British" sound: low coloration and, overall, a rather polite presentation, coupled with low sensitivity. The Triangle speaker opened my ears to what could be achieved with a very different approach: still-low coloration but high sensitivity, impressive clarity, and a hefty dose of what the late J. Gordon Holt called "jump factor," in which the leading edges of transients are neither smeared nor tamed. So when, last September, on a visit to Dallas and The Sound Organisation, the US distributor of Danish Audiophile Loudspeaker Industries (DALI), I encountered DALI's Rubicon 8 speaker (footnote 1), which had benefited from a low-loss design philosophy similar to the Triangle's, I asked for a pair for review.

Across the Rubicon
At $7995/pair, the DALI Rubicon 8 is priced the same as Triangle's Signature Delta, and is also a slim, floorstanding design that loads each of its woofers with a separate ported chamber. There the similarities end. Where the three-way Triangle combines a horn-loaded tweeter with a midrange unit and two woofers, the DALI uses the unique combination of a larger-than-usual (1.15") soft-dome tweeter mounted below a small ribbon supertweeter and below that, three 6.5" woofers. However, only the topmost woofer continues its upper-frequency output to 2.5kHz, where it's crossed over to the dome tweeter. The middle woofer is rolled off earlier than the top one, and the bottom woofer earlier still. All three woofers operate in the bass, where the increased surface area will be necessary but the radiating area shrinks as the frequency rises. DALI calls this "2½+½+½-way construction."

All five of the Rubicon 8's drive-units are made by DALI. The tweeter and supertweeter are constructed on one chassis: a reworked version of the hybrid tweeter module that first appeared in DALI's flagship Epicon series. The ribbon tweeter operates above 14kHz, and is intended to widen the horizontal radiation pattern in the top octaves, to give a wider range of seating positions at which listeners can hear a full high-frequency balance.

The three 6.5" woofers are technically sophisticated, having been designed to minimize both harmonic distortion and stored energy. A problem with all magnets is that they suffer from hysteresis, in which the magnetization and demagnetization that result from the electrical drive to the voice-coil do not happen at the same speed. It takes longer to demagnetize than to magnetize the iron, which results in distortion. If a magnet could be made from a material that is highly susceptible to magnetization but is also an electrical insulator, the hysteresis and the resultant distortion would be very much reduced. What DALI calls their Soft Magnetic Compound (SMC) in the pole pieces is just such a material. SMC is formed from individual particles of iron—think dust—that are each coated with an insulating material. So while SMC is very highly magnetically conductive, it has a very low electrical conductivity: about 1?10,000 that of iron, dramatically reducing hysteresis.

The woofer's pole piece is therefore constructed from SMC, surrounded with a copper cap, and energized by a large ferrite magnet. The copper ring minimizes the modulation of the magnetic field by the current fed to the voice coil. As in earlier DALI speakers, the woofer cone is formed from a matrix of wood fibers and terminated in a soft, low-loss rubber surround.

The Rubicon's cabinet is constructed from MDF, with the front baffle and rear panel gently radiused. The three ports on the rear panel are flared to minimize wind noise, and electrical connection is via two pairs of high-quality binding posts at the base of the rear panel. The lightweight, black-cloth grille is constructed on a plastic frame, but as the Rubicon 8s look extremely elegant without the grilles, I left them off for my listening.

Listening
The Rubicon 8s were set up in my room as recommended by The Sound Organisation's David Carr: firing straight head (not toed in to the listening seat), and a little farther out from the wall behind them than I usually place speakers: 94" measured from the front baffles. This placed each tweeter 99" from my head, to describe an almost perfect equilateral triangle. My room is slightly asymmetrical, so the most-even transition from midbass to midrange was also achieved in a slightly asymmetrical manner: the dustcaps of the right speaker's woofers were 44" from the books that line the adjacent sidewall; the left speaker's woofers were 41" from the books and LPs that line that sidewall.

With my Editor's Choice (CD, Stereophile STPH016-2), the low-frequency, 1/3-octave warble tones were reproduced with full weight down to the 32Hz band. While the 40Hz tone was a little suppressed, as always with speakers with extended lows, the 32Hz warble tone was boosted by the lowest-frequency mode in my room. The 25Hz warble tone was just audible at normal listening levels, but the 20Hz was missing in action. But I was impressed by how clean the low-frequency tones sounded—this DALI woofer is indeed a low-distortion design. With the half-step–spaced toneburst track on Editor's Choice, the tones were reproduced cleanly from the midbass through the mid-treble, with less of the aliasing-like ghost tones audible than I usually hear.

It was time for some music. After watching the TV documentary on current-day musicians building songs on half-century-old lyrics by a younger Bob Dylan, I picked up a copy of The New Basement Tapes: Lost on the River (CD, Harvest 02537 95014). The overcooked, chromium-plated modern sound was a disappointment, as was hearing the backing instruments fighting both each other and the voices. However, the music is terrific, and when the mix was more open—as in "Kansas City," with music by Mumford & Sons' Marcus Mumford and Dawes's Taylor Goldsmith—I could appreciate the way the DALIs reproduced the driving rhythm of the drums. But the bass guitar in this track was overripe, as were the bass and kick drum in "When I Get My Hands on You," another gem from Mumford and Goldsmith.

Was this the speaker or the recording? As I write above, the Rubicon 8s were being helped out below 40Hz by the lowest-frequency room mode. When Eberhard Weber drops down to the bottom register on the E and A strings of his double bass on his Endless Days (CD, ECM 1748), the modest-sized Rubicon 8s reproduced his instrument with excellent body to the sound but also superb definition. And Rainer Brüninghaus's synthesizer-bass notes on this album sounded superbly clean, if a little on the rich side.

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Footnote 1: See February 2015, p.22.