Infinity IRS Epsilon loudspeaker Page 2

Needless to say, the gains of the left and right upper-range amplifiers must be closely matched; the same is true for the woofer amps (footnote 2). But it's also important that the gains of the woofer and upper-range amplifiers be within 6dB of each other, or adjustable to within that range. Controls on the SCU can compensate for up to 6dB of gain difference between these amps, but no more. In addition, the voltage gain of the woofer amplifiers must also be within the 21–39dB range for proper setup—which includes almost all available power amps.

I encountered four problems in my efforts to get all of this right. First, the manual states that you can use any combination of balanced and unbalanced cables. Specifically, it should be possible to run balanced cables from the preamp to the SCU and unbalanced cables from the SCU to the amplifiers (or vice versa). Not so. When I first set up the Epsilons, I used exactly that configuration, and the bass was oppressively dominant. What was probably happening was that the internally bypassed connection for the top-end amplifiers was linking only one leg of the SCU's balanced input to its unbalanced output, negating any balanced-link gain advantage there. At the same time, the SCU's low-pass, active woofer circuitry was making full use of the potential 6dB–greater gain available with a balanced input. I cured the problem by using an all-balanced setup.

I originally intended to use two KSA-300Ses to drive the Epsilons, but the second problem resulted from my attempt to use a Krell KSA-300S to drive the woofers. In the Krell, the output stage's bias current is adjusted to progressively higher plateaus, depending on the demands of the program material. Circuitry within the amplifier "anticipates," almost instantaneously, the need to raise the bias. The woofer servo feedback loop, however, was immediately forcing the bias level on the Krell bass amp up to its maximum level, accompanied by alarming excursions of the woofer cones. It's possible that the action of the servo circuitry was hyperactively triggering the sensing circuits in the Krell that adjust its bias upward. I understand that Infinity is working with Krell to fix this incompatibility.

For most of my listening, therefore, I used a pair of Classé M-700 monoblocks to drive the Epsilons' woofers—and here encountered the third problem. After setting up the SCU for the appropriate gain using the rear-panel control, as described in the owner's manual, I fired up the system, only to be greeted by a crescendoing squeal from the woofers. I killed the power to the amps before any damage was done. The problem was cured by backing off the SCU's rear-panel control by several decibels below the recommended value.

A fourth problem—the source of which I hadn't yet determined at the time of writing—involved externally triggered transient spikes in the woofer circuitry, which I discovered when I turned on the fluorescent lights in the kitchen and heard a pop from the Epsilons' woofers in the listening room—15' away, and on a different electrical circuit. I dashed into the listening room and found the woofers pumping back and forth in large (but fortunately progressively damped) excursions. I noted the same phenomenon when I turned on the overhead fan or plugged in a lamp in the listening room itself; and, to a lesser degree, when I touched the equipment rack and dissipated a small static charge. In the year that I've been using this listening room I've never encountered any such power or static-related problems.

All of this means that you should be prepared to lean a bit more heavily than usual on your dealer in choosing appropriate associated components for use with the Epsilons, and in setting the whole thing up. In fact, my most serious reservations about the speakers are about this very complexity of setup. None of these "problems" would likely exist had the system been designed and furnished with a dedicated bass amplifier.

This would, of course, result in an increase in price, and the amplifiers would have to be designed to handle high sound levels in a large room. While Infinity's decision to allow the user to provide the bass amplifiers is defendable, there's no denying that it puts significant demands on users and dealers if the system is to perform as designed.

The hardest loudspeaker to review is the one that's difficult to criticize. The Epsilon is, for the most part, hard to review.

Compared with the Energy Veritas v2.8, the Infinity sounded less airy, open, and spacious. The Energy sounds more majestic, with greater "bloom"—certainly due at least in part to its more-than-generous bottom end—and every bit as dynamic as the Epsilon; perhaps even more so. The NHT 3.3 has, subjectively, the deepest, most potent, extreme bass of the speakers that have spent time in my listening room. The Epsilon does have some dynamic limitations at the very bottom end on the most demanding program material, a point upon which I will shortly expand.

Yet it's the Epsilons to which I would turn, without question, if I wanted to know what's going on in a recording—and if I wanted the most accurate, uncolored bass and midrange, and the cleanest, most pristine, least "electronic"-sounding treble. Thanks to its wide range of available adjustments (particularly for the bass), the Epsilon is the most likely of the three speakers to sound its best in a variety of rooms.

I haven't always been a fan of Infinity using planar midranges and tweeters in their loudspeakers. I've always liked the generally open, exciting, punchy sound, but hadn't particularly cared for the usually too-crisp, etched quality. The latter is not a quality of the Epsilons. In fact, when I heard the prototypes at last year's Winter CES, I was underwhelmed. If anything, they were too closed-in and lacking in openness. I'm happy to report that this is also not evident in the production version.

From the upper bass to the top treble, the Epsilon's balance was just about spot-on. Instrumental textures and timbres flowed naturally and easily. For example, the dynamics on David Buechner's superb recording of Gershwin solo piano works (Connoisseur Society CD 4191) were first-rate, the balance had just the right degree of warmth, and the whole was wrapped in the natural acoustic of the recording. The top-end balance was close to perfect, with a realistic but not overdone sparkle. From the natural woodwinds and brass on Stravinsky's Ebony Concerto (Reference RR-55CD) and the metallic, crisp percussion and more gutsy brass of the Eastman Wind Ensemble on the Mercury Living Presence Hands Across the Sea album to the clean, thrilling buzz and snap of guitar strings on David Wilcox's Home Again (A&M 75021 5357 2), the Epsilons presented a wealth of natural, unhyped detail.

Voice was also extremely well-served by the Epsilon's natural, uncolored midrange. From Mary Black to Cyndee Peters, Gordon Lightfoot to the King's Singers, the presentation was realistic and convincing. Not that all such recordings are beyond criticism over the Infinitys. The Epsilons didn't exaggerate excessive sibilance, but neither did they hide it. For example, for all its well-deserved audiophile popularity, I find that Holly Cole's voice on Don't Smoke in Bed (Manhattan B21Z-81198) hews too closely to the well-worn "eat the microphone" syndrome; though far from the worst I've heard, the sibilants are just too hot. The Epsilons brought this out, but without adding any apparent editorial comment of their own. Nor were all male vocals free of chestiness. Again, on the best recordings, where the miking has been done with some intelligence, the balance of the Epsilons was excellent.

The Epsilons' soundstage was wide and reasonably deep. I've heard more precise soundstaging from small, narrow-baffled boxes, but the spatial perspective of the Epsilons, if not absolutely pinpoint, was nevertheless realistic. When I began my listening, I aimed the Epsilons almost straight ahead, with only a small toe-in. The soundstage was wide enough, but lacked the sort of specificity I prefer. I ended up toeing them in considerably, despite Infinity's claim that the Epsilons are less likely than other loudspeakers to need this. As usual, this toe-in increased the center-stage focus at some sacrifice to soundstage size—a tradeoff that I don't mind. In this context, however, image width and depth were fine—especially on recordings recorded with an ear toward a believably layered, dimensional sound (eg, the Connoisseur Gershwin disc, and the Sneakers soundtrack, Columbia CK 53146).

Footnote 2: While the woofer amplifiers will likely be different from the upper-range amplifiers, I can't imagine anyone paying $14,000 for these loudspeakers and then using different amplifiers on the left and right channels.
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