Green Mountain Audio Diamante loudspeaker Manufacturer's Comment
Editor: I was very pleased that Steven Stone and John Atkinson were impressed with the Diamante. They heard what our many owners and retailers report: that this is a product which does not call attention to itself. My primary design goal is to be true to the music—our speakers must be revealing, yet always enjoyable. After several months of living with our loudspeaker, Steve reported that the Diamante "allows the music to come through, with very little editorializing." Some of the factors that make this possible are dynamic accuracy, dispersion, time coherence, and a lack of enclosure resonance. A deficiency in any one area will color the music in ways that can make a speaker less forgiving of recordings, electronics, or even the listener's position.
Designing an overall "good" sound into any speaker is difficult because of the complexity of moving energy between the two worlds of electromagnetism and mechanics. While the infinity of the hearing process will prevent a complete set of tests from ever being developed, what I find curious is how best to interpret numbers which give mixed results. The Diamante's highs in some measurements can appear mellow, but, as Steve reported, still have good top-end extension. Here is where our first-order circuit, with its phase-coherent behavior, begins to defy conventional, close-range measurements.
Phase error has been around in speakers for so long that most of us have learned to tune it out and get on with enjoying the music. Higher-order crossovers create phase shift and, depending on the portion of the sound spectrum they affect, can add forwardness, brashness, sizzle, or other unwanted artifacts. They also alter depth, as an instrument is "stretched" from front to rear by the effects of phase error.
My first-order design was developed in the predecessors to our reference loudspeaker, the Imago (favorably reported on by Peter Mitchell in Stereophile's coverage of the 1991 WCES in Las Vegas). What is really unique about this circuit is that I was able to implement it with only a handful of parts. Most other designs that attempt first-order response add many "corrective" elements and "traps" to compensate for a poor choice of drivers or cabinet design. This is hard on an amplifier and obscures detail. As a result of our minimalist approach, the Diamante has earned a reputation for being exceptionally musical when coupled with relatively low-powered (35–40Wpc) tube electronics. Yet, as Steve experienced, the Diamante will respond faithfully to high-powered demands.
Although at first glance the Diamante may appear to circumvent the established norms of loudspeaker measurement, there is still significant information revealed in John's tests that correlates well with the listening experience. For example, the test at 45" in fig.9 shows exemplary synchronization between woofer, midrange, and tweeter. All three deliver their energy at one instant (ie, very little phase shift), which preserves the harmonic structure, or timbre, and the attack and rhythm of instruments. But at this close distance, the microphone is so far off-angle from the tweeter that the treble appears much too soft, which is not the case, as indicated by fig.6's reading of a gentle rolloff. This is exactly how an exposed dome tweeter in a slender enclosure will average across a wide "window."
Uniting measurements with listening is difficult, but I am glad that John and Steve appreciated the Diamante more for being an accurate producer of a real musical experience than a portrayer of technical norms. Even the low-sensitivity measurement of the Diamante does not depict its "real-world" performance, as it is always difficult to show how well the sound continues to carry outward into a room. The Diamante is audibly more sensitive than, say, the B&W Silver Signature (rated at 88dB for 1W at 1m), not only because of its dynamic response and good phase behavior, but also because of the first-order crossover. Its woofer, mid, and tweeter broadly overlap, creating a modified line source which then lets drivers "reach" farther into the room: waves decay less rapidly over distance.
Finally, your comments on the artistic merits of the cast marble enclosure did not go unnoticed. Cast marble can be used to create beautiful structures, good for acoustics as well as aesthetics.
Our thanks to Steve and John for a thorough evaluation that unquestionably revealed the most important aspects of a very different approach to loudspeaker design. I appreciate that this was not an easy task. Keep up the good work.—Roy Johnson, President/Product Designer, Green Mountain Audio