Revel Ultima Gem loudspeaker & Ultima Sub-15 subwoofer Page 2

The Gem is a graceful, narrow-aspect-ratio stand-mounted design, with twin mid/woofers vertically flanking a central 28mm tweeter (a high-performance soft-dome design from Danish manufacturer ScanSpeak). The 5.25" low-frequency drive-units are from Revel and use a one-piece titanium concave dome with a fluoroelastomer rubber surround, neodymium magnets, and a 2" edge-wound voice-coil with a Faraday ring to reduce magnetic distortion. The woofers are reflex-loaded with a 2"-diameter flared port some 6" deep; this vents on the rear panel. As with most of Kevin's Snell designs, a second tweeter on the rear of the cabinet equalizes the speaker's power response above 8kHz to compensate for the front tweeter's increased directivity above that frequency. All drive-units are magnetically shielded to optimize the design for home-theater use.

The crossover uses high-quality components, such as polypropylene-dielectric capacitors, and is hardwired using Kimber cable. It operates just above 2kHz, and the woofer and tweeter sections are physically separate, communicating with the outside world via separate sets of binding posts. Switches are provided for independent adjustment of the levels of the two tweeters.

The enclosure is constructed from MDF and is available in matte- or gloss-black finishes. Wooden or aluminum cheeks bolt on to the sides, with slight extensions at top and bottom to hold the vestigial grille frame. Laser interferometry was used extensively in designing both cabinet and woofers in order to minimize resonant modes and, in the case of the latter, ensure true pistonic behavior to at least an octave above the crossover frequency. The 28.5" stands match the Gem visually and come with the central pillar ready-filled with sand.

Kevin Voecks and his colleagues at Harman have been pioneers in developing both truly objective listening tests and measurement techniques that correlate well with what is heard. Such tests played an important role in the Gem's design. There is not the room to describe them in this review, but I encourage readers to visit the Revel web site and check these tests out for themselves.

The Ultima Sub-15/LE-1
The sealed-box Ultima Sub-15 visually matches the Gem, though the side cheeks are now top and bottom cheeks. A monstrous 15" driver with a stiff kapok- and Kevlar-impregnated pulp cone, a huge nitrile rubber surround, and a cast aluminum alloy frame provide the grunt. This drive-unit features a 4" edge-wound voice-coil that weighs almost six ounces and is said to be capable of 1.5" of peak-peak excursion!

The Sub-15 is intended to be used with Revel's Ultima LE-1 monophonic power amplifier, which incorporates the optimum crossover and response-shaping circuitry. Specified power is 725W into one Sub-15 or 1200W into two. A remote control is provided so that the user can adjust the blend between the satellites and subwoofer from the listening position—a red LED display on the front panel provides visual feedback. This amplifier can be used to drive one or two Sub-15s, and has both balanced and unbalanced inputs and outputs.

Gem sound
Setup proved rather time-consuming in that the Gem was very sensitive to small changes in position in my room, particularly regarding a thickness in the transition region between the upper bass and the lower midrange. I realized that, with its tall stands, the positions that had worked well for the Silver Signatures were resulting in two of the woofer-to-boundary distances for the Gems being almost the same. (The woofer-to-sidewall, woofer-to-floor, and woofer-to-front-wall distances should be as different as possible.) Eventually, I ended up with the drive-units about 49" from the wall behind them and 70" from the sidewalls. The subwoofer was placed close to one corner, in front of the ASC Tube Traps that live there, but was left turned off for all the preliminary auditioning, which involved the Gems on their own.

Playing a wide variety of program material, I settled on the rear tweeters being on and set to "0" and the front tweeter set to "-0.5dB." Without the rear tweeter, which basically covers the top audio octave only, the balance in my quite well-damped room lacked a little air. Setting the front-tweeter level proved interesting in that even the 0.5dB level steps on its control seemed too large at times. But when I thought about it, a level shift of 0.5dB covering the entire operating range of the tweeter represents a large "area under the curve"—ie, a lot in energy terms—so it should be quite audible.

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