Infinity IRS Epsilon loudspeaker Page 3

The Epsilons driven by the Pass Aleph 0 single-ended, solid-state monoblocks continued to sound remarkable. While my auditioning with the Alephs was too brief for me to state definitively whether I preferred them to the Krell KSA-300S in this application—the Krell certainly left little to be desired—the former did appear to be incredibly fine amplifiers. They do run very hot, however—one shut down twice after several hours of use—but were easily reset by merely being turned off, then on again. Perhaps setting them up side-by-side resulted in a bit too much heat buildup, though they otherwise had plenty of ventilation.

The overall performance of the Epsilons, from the upper bass to the top of the treble, was nothing less than superb. If I could criticize anything, it might be that slight lack of spaciousness at the very top of the treble range. But the Energy Veritas v2.8s produce enough space to let the Starship Enterprise reach warp speed; had I not been listening to them extensively just prior to the Epsilons, it's unlikely that I'd have thought this quality worthy of comment.

The bass, the bass
At its best, the bass performance of the Epsilon was absolutely stunning. With the best material, it combined tightness with extension in an extremely rare manner. I found no better example of this than the Patriot Games soundtrack (RCA 66051-2), on which the Epsilons sounded wondrous—I don't know any other word to describe them. As before, the top end was clean and detailed without any artificiality not present in the recording, and the midrange was open, transparent, and uncolored.

I've heard this recording numerous times—occasionally with more deep-bass extension to below, say, 30Hz—but never have I heard it with this much tightness and sheer punch. The first drum whacks in "Attack on Ryan's House" set me back in my chair. The Epsilon simply excelled at this sort of percussive impact. Bass drum on the best recordings had an all-too-rare clarity that was a delight to hear.

The Epsilon's very clean-sounding bottom region may appeal to listeners who have avoided large loudspeakers in the past because of their perceived "big," exaggerated bass. Properly set up, the Epsilon didn't suffer from this. It did have a touch of warmth on much material, but just enough to keep the sound from becoming lean and antiseptic.

Though the Epsilon's bass extension was plenty deep, it wasn't quite the equal of the NHT 3.3's, which is otherwise unable to match the Epsilon's low-frequency definition. Though the NHTs were no longer available to me for direct comparison, I do recall their bottom end being somewhat more potent in Jean Guillou's organ adaptation of Mussorgsky's Pictures at an Exhibition (Dorian DOR-90117). The Epsilon had plenty of power from 30Hz up, but that guttural growl I recall from the NHT—at least on organ—was slightly subdued. Nevertheless, the Epsilon's bass was undoubtedly extended: my chair—sitting on a slab floor—was vibrating. On the stunningly recorded Rutter Requiem (Reference RR-57CD), the bottom organ pedals, while subtle, nevertheless made a more potent, dramatic statement through the Epsilons than through the Energy v2.8s.

The bass controls on the Servo Control Unit contributed significantly to the effectiveness of the Epsilon's bass. Used in concert, they helped establish a proper system balance. I tweaked them over a wide range of material, then pretty much left them alone. I turned back the midbass contour a few decibels, and the low-bass contour control up by about the same amount. This gave me the best combination of tight mid- and upper bass and low-end extension.

In another room, or at a different position within the same room, I would expect the optimum settings to be different. The same goes for the overall bass level, which for me worked best at 0dB (despite a difference in gain between the Krell and Classé amplifiers). Proper setting of overall bass balance is critical to one's total perception of a system's sound; it's difficult with most loudspeakers to adequately control this. (While changing the placement helps, it's rarely enough.) Such controls as those on the Infinity—Okay, it's equalization. So what?—helped tremendously in getting things right.

There was a drawback to the Epsilon's bass: It needed all of the power I could feed it. Remember, the servo network functions, for all intents and purposes, as a bass equalizer. According to a figure in Infinity's own White Paper on the Epsilon project, this results in a bass boost of 8dB at 30Hz, and 17dB at 20Hz. In the latter case, all else being equal, a 200W demand in an unequalized system would translate to 10,000W in a system with this much bass boost! Fortunately, there's little program material with flat response to 20Hz. At a more reasonable 30Hz, the Epsilon's required 8dB boost still translated to nearly 1300W to satisfy the equivalent of a normal system's 200W demand.

Before settling on the Classé M-700 amplifiers, but after the bass episode with the Krell, I tried driving the bottom end of the Epsilons with an NAD 208, which puts out a specified short-term power of 750Wpc into 4 ohms. It worked fine until serious demands were made of it, after which it gave up, turning the opening drum strokes on the Jurassic Park soundtrack (MCA MCAD-10859), for example, into a flatulent T-Rex. And while the Classé sailed through this passage with nary a problem, it still ran out of steam on some material—even with its rated 1400W capability (into 4 ohms). In the climax to Weinberger's Polka and Fugue from Schwanda the Bagpiper, on Pomp & Pipes (Reference RR-58CD), the bass in the left channel abruptly fell apart on the most challenging passage. To be fair, the Energy Veritas v2.8 had also had difficulty traversing this track, but the breakup there had been a little less obvious.

For those looking to use the Epsilons in an audio/video system, the sustained bass thud from the falling boulder in Aladdin's "Cave of Wonders" scene (if you've seen it, you know what I'm referring to) caused a breakup that made me lunge for the volume control—again, in the left channel. Though the Epsilons survived to fight another day, I can't say the same for my nerves. This exceptionally difficult test was traversed without incident at the same or higher level (in a larger space) by the B&W THX subwoofers. The B&Ws (evaluated in a different room, it must be emphasized) can't match the tightness or punch of the Epsilons' woofers (though they're nonetheless commendable in these qualities), but do appear to be less susceptible to dynamic-range limitations on killer video sound-effects and very challenging music passages.

Remember how a servo system operates? As the driver/enclosure system tries to give up producing sound below the system resonance (in the case of the Epsilon's sealed-cabinet system, dropping off at a rate of 12dB/octave), the servo says don't stop! and increases the drive level to the woofer to compensate—thus the heavy low-frequency boost typical of a servo design in a normal-size enclosure. Clearly, if nothing is done and the program material continues to demand high levels of low frequencies, a servo system will either run out of available amplifier power, or the driver will destroy itself trying to respond to the servo's demands.

Obviously, a servo system must incorporate low-frequency limits to keep this from happening; below a certain frequency, it simply ceases asking for more. If not carefully chosen, these limits can get you into trouble. I once heard even the IRS—an early version—overload on the cannon shots from Telarc's version of the Overture 1812 at an admittedly high level in a large CES demo room. And that design has how many low-frequency drive-units...?

The Epsilon has a high-pass filter in the SCU's bass channel to provide the necessary limiting, but the above observations tell me that the limits chosen may be insufficient. An outboard subwoofer would solve the problem, and, again, the Epsilon will handle with ease 99% of the material fed into it. But we expect that last 1% from $14,000/pair speakers—especially when less expensive systems will deliver it.

The Epsilons did have excellent bass qualities, but when they ran out of headroom, they did so abruptly and jarringly. All of this reinforces the case for using a dedicated amplifier with a bass servo system. With a careful balancing act, the designer can then trade off bass extension, (known) amplifier power, cone excursion, system sensitivity, and limiting to obtain the desired results within the capabilities of the chosen system design. Requiring the user to provide the bass amplifier puts an important aspect of the design beyond the designer's control.

Nevertheless, used within its still generous limits, the quality of the Epsilon's bass was outstanding.

The Epsilons were difficult to criticize. Certainly, I would stack them up against any of the other Class A contenders, though, because of the deep-bass limits on their bass dynamic-range capabilities, they'd have to go in the "Restricted-LF" category. Whether or not that limitation is due to available amplifier power or system limits becomes a moot point when 1400W doesn't seem to be quite enough power.

Nevertheless, the Epsilon can't be ignored—it definitely belongs in Class A. And for those unable to afford them, less expensive siblings using much of the same technology will certainly follow. In the meantime, Disneyland may no longer have E-ticket rides, but Infinity sure does: the Epsilon.

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