Theta Digital Enterprise monoblock power amplifier Page 2

The upper mids were a bit prominent for what I consider to be tonal neutrality, but not to the point of being hard, harsh, or glaring. Instead, the slight prominence helped impart a snap and excitement to high-frequency transients that only enhanced the overall clarity and subjective purity of the attack. The Enterprise's high-frequency performance walked the fine line between analytically pure and slightly hot, but never became hard, harsh, brittle, or mechanical—a charge leveled against the big Krell amps, though I can't speak from firsthand experience.

I was using the Musical Fidelity kWP preamp and Wilson WATT/Puppy 7 speakers: some people like the Focal tweeter Wilson uses, but its many detractors feel it sounds hard and mechanical on top. A Focal enthusiast might blame the Theta Enterprise's somewhat hot high-frequency balance for bringing out the worst in the tweeter, while an Enterprise partisan might say that the amp's honest extension highlights the tweeter's flaws. Who's correct? Who knows?

But you don't get music unless you weave all these elements together. Playing my usual reviewing favorites, especially the CDs and LPs I used for the amplifier reviews preceding this one, the Enterprise's sound was impressively transparent and clear, with cleanly rendered transients and a pleasing effervescence overall. That was the case with Beck's Sea Changes SACD, but to my ears, the Theta's HF spotlighting was a bit much. On the stupendous-sounding LP reissue of Ian and Sylvia's Northern Journey (Vanguard/Cisco), Sylvia's voice was more vocal cord than head and body, and the acoustic bass didn't drive and grip the music as effectively as I might have hoped for—but these were subtle shadings, not gross sonic deformities.

On the title track of Davy Spillane's Atlantic Bridge, a benchmark recording for me, Christy Moore plays a bodhran—a small, high-pitched drum with a wood frame and a goatskin head, played with a wooden stick. The Enterprise's taut, slightly forward presentation made it sound as if Moore was hitting a countertop instead of goatskin. Béla Fleck's banjo was all wire strings and no stretched skin. While the recording's subterranean bass was not delivered quite as forcefully as I would have liked, the Enterprise's supple, texturally nuanced low end was more than satisfying, if not physically overwhelming.

It didn't take long to realize that MF's single-ended kWP preamp was not the ideal mate for the Enterprise, so I shut things down and replaced it with the lusher, warmer-sounding, 12AX7-driven VTL TL-7.5, which is also fully balanced. The overall presentation took a sharp turn for the better, the VTL's subtle midband warmth neatly filling in the Theta's perceived recess in that part of the spectrum, and the preamp's smoother, more subtle top end taming the amp's somewhat aggressive thrust. The price paid for the improvement was a slightly weaker bottom end, as the VTL's bottom-end punch, while extended, is somewhat broader than it is tight and deep—the latter being a quality that would be more complementary to the Enterprise's bottom end.

With the VTL 7.5 in the chain, the system's overall balance was much improved, though the lack of low-end punch was somewhat more pronounced. No doubt designer David Reich went for detail, definition, and articulation in voicing the Enterprise, because that's what the amp delivered from top to bottom, sacrificing some bottom-end clout, some midband lushness, and some high-frequency airiness in order to create a seamless, orderly sound.

The Enterprise was no more a match made in heaven for the WATT/Puppy 7 than was the big Halcro dm68. Speaker design is still as much art as science, and Dave Wilson's latest WATT/Puppy is a canny combination of both—but with its high-Q bass tuning, slight midbass bump, not particularly extended bottom end, and that Focal tweeter, the 7 is not well-suited to an amplifier with a slightly forward upper-octave thrust, a less than lush midband, and a less-than-iron-fisted bottom end. I'm not criticizing either product—after all, I emptied my pockets to buy my WATT/Puppy 7s. The 7 is not a "textbook" design, but as this series of amplifier auditions tells me, it's very revealing, and clearly a suitable reviewing tool. And I love listening to it, which helps.

So my month with the Theta Enterprise was no honeymoon, even though a few months with the Citadels driving Aerial's L/R 5s and CC5 center-channel was a torrid affair. That combo had slam, drive, power, detail, richness, and everything else one might want from a music or film system. For some reason, the Enterprise driving the Wilsons couldn't deliver that kind of excitement; I never warmed up to the amplifier, though I did develop respect for its overall balance and superb resolution.

The Enterprise is rated at 500W into 4 ohms, which is the WATT/Puppy 7's nominal impedance. The Theta never delivered the kind of macrodynamic wallop that that much power would seem to indicate, though it did drive the efficient Wilsons to high SPLs without strain or edginess. Instead, it excelled in microdynamic subtlety. The Enterprise is a high-powered amp with the speed and agility usually associated with much smaller designs. Experience tells me, however, that power and agility need not be mutually exclusive.

Enter the Aerial 20Ts
Toward the end of my time with the Theta Enterprise, Aerial's Michael Kelly delivered a pair of opulent-looking 20T loudspeakers for review. He told me that the 20T, with two 9" woofers in a massively braced, 170-lb bass cabinet, was designed to be flat to below 30Hz with a smooth rolloff thereafter. The 20T also uses a true ribbon tweeter (not a sheet of etched Mylar) said to be extremely revealing and essentially flat to 30kHz, and extending out to 40kHz.

The Aerials installed, we sat down for a listen. One thing was soon abundantly clear: the Theta Enterprise's high-frequency performance was ultra-clean, fast, and detailed. It was, as I'd thought, completely free of grain and etch, and slightly elevated, as I'd heard through the Wilsons. But driving the smoother-sounding Aerial ribbon, that elevation seemed less congested, less spotlit. However, the Theta made it very clear that the tweeter was a ribbon, and I worried that I'd spend the next reviewing cycle trying to not hear a ribbon tweeter not quite integrating with a cone midrange and cone woofers.

Then I played Davy Spillane's "Atlantic Bridge." I knew that the Wilson has that slight midbass bump, and that my room has a 3-4dB suckout at 67Hz (though it's otherwise commendably flat). But the absence of this track's bass foundation was shocking.

I put on Sundazed's stupendous mono vinyl reissue of Bob Dylan's John Wesley Harding (Columbia/Sundazed), which delivers Charlie McCoy's granite bass lines with unsurpassed detail, impact, and extension. The results were positively wimpy, though the transient attack was outstanding. The superb two-channel SACD of this album fared no better. Perhaps I'd gotten used to the Wilsons' midbass bump (we'd played the mono disc via the Wilsons before moving them out of the room). However, I still felt there was a lack of extension and impact on the bottom, a slight leanness in the middle, and a subtle emphasis on top that called attention to the ribbon tweeter (though at the time I didn't know if it was the speaker that I needed to adjust to, or whether I was hearing the Enterprise).

I shut down the Enterprises and hooked up the Music Reference RM-200, a 100Wpc amp that I'd bought as a tubed reference, and put on the Sundazed John Wesley Harding, then Acoustic Sounds' absolutely stunning 45rpm reissue of Count Basie's 88 Basie Street (AJAZ 2310-901). The lean midbass fattened up and the foundation kicked in—especially Kenny Buttrey's bass drum on the Dylan disc. Warmth returned to the midrange, and the top end stopped screaming "Ribbon tweeter!"

After Kelly had left, I put the Enterprises back in and listened for a few more days before finishing this review. Two very different speaker systems, two different results, but both pointed to the same conclusions regarding the Enterprise's sonic character: detail, definition, articulation, and some high-frequency airiness but some sacrifices in bottom-end clout and midband lushness.

I've concentrated on the Theta's tonal balance because that's what easily stood out. In terms of spatial presentation, the Enterprises were first-rate, delivering an airy soundstage that was appropriately deep, wide, and tall, with pinpoint three-dimensional imaging and mesmerizing overall transparency. The Enterprise's high-frequency transient performance was equally noteworthy.

With all of these positive attributes, I can only conclude that—as with the big Halcro dm68s, which I didn't review but was lucky enough to hear—the Enterprise's whole was less than the sum of its parts. In both cases, I was left respecting the Enterprise's musical presentation without ever warming up to it.

It's always more fun to write a raving, rapturous review. I couldn't in this case, even though Theta's big Citadel, which is said to be very similar to the Enterprise, was one of the most impressive amps I've heard. And don't make assumptions about the fact that I listened to the Citadels during a Stereophile Guide to Home Theater project—I used them to listen to dozens of SACD and DVD-Audio discs for a surround-sound roundup.

Like the Halcro dm68, the sleekly packaged Enterprise is an amp I could respect but not love. I had the same reaction a few years ago to the one Mark Levinson amp I've heard in my system. I was less put off by the Theta's slightly forward presentation than I was by its somewhat disappointing bass impact and lack of midbass weight, which for me robbed the music of richness, warmth, and rhythmic comfort.

When I listen to a component, I don't immediately say, "Oh, the bass is somewhat lacking in impact" or "The top end is somewhat prominent" or "The midrange is somewhat recessed." Instead, while everything might sound fine, for some reason I'm not responding to the music. I'm not moved. Only then do I work to find out why.

With the Theta Enterprise, I had to work because the amp didn't do anything overtly incorrect. It was fast, detailed, and somewhat forward on top, but there was no hint of grain, etch, or false "edge enhancement." If you're not used to this high a level of resolution, such an amp can be absolutely mesmerizing, as musical and spatial details you've never heard before emerge from your favorite recordings. If you have an overly warm link in your sonic chain—especially your speakers—the Enterprise just might be the wake-up call your system needs.

I worked hard to extract genuine musical pleasure from the $9000/pair Thetas, but in my system—even with multiple component substitutions and with the Richard Gray's Power Company stuff in and out (much better in, but more about that another time)—they just didn't deliver. Perhaps when you build a no-holds-barred amp like the Citadel, you can't just take a slice off the top and make a smaller version that performs equally well.

Theta Digital
5330 Derry Ave., Suite R
Agoura Hills, CA 91301
(818) 597-9195