Bookshelf Speaker Reviews

First-generation audio critics had an arguably more-exciting job than their descendants. When audio was a lanky and boisterous youth, the differences between seemingly similar products could be dramatic. In those days, doing an A/B comparison of loudspeakers was like crossing the border from Austria into Italy. Each one had its own unique sonic culture.

There are still plenty of discernible differences between speakers, as well as European cultures, but anechoic chambers and the European Union have narrowed the respective differences. A company the size of Harman International has enough resources to all but eliminate chance from loudspeaker design. So, if the Infinity Beta Series sounds different from the discontinued Alpha Series—and it does—that is purely a matter of choice.

Pressure and Flow
One choice Infinity has made is to recess the tweeter into—oh dear, is this really what they're calling it?—a Constant Acoustic Impedance waveguide. The simplest definition of "acoustic impedance" I've run across is on the Website of the University of New South Wales in Australia: It is "a ratio of pressure to flow." According to the helpful Australians, "The acoustic impedance of musical wind instruments varies spectacularly with frequency because these instruments are designed to produce one or several frequencies only in a particular configuration."

Loudspeakers, however, are not musical instruments. A speaker whose acoustic impedance "varies spectacularly with frequency" would bend music spectacularly out of shape. In a speaker, it's more desirable for acoustic impedance to be as constant as possible. Now you know why Infinity considers Constant Acoustic Impedance to be worth bragging about.

Infinity sculpted the Constant Acoustic Impedance waveguide using computer-aided design to create a series of graduated curves that flare from the inside to the outside of the waveguide. This contributes to better dispersion and increased sensitivity. The waveguide shapes the transition between on- and off-axis response more smoothly than most horned speakers. As you walk from the center of the soundfield to the side, there's no sudden falloff in high-frequency response. You have to sit almost outside the soundfield before any vocal coloration becomes apparent. Within the soundfield, the waveguide reduces reflections off of the ceiling and sidewalls.

Size and Sensitivity
Monitor-size speakers are among the most underrated, so I opted to review a pair of Beta 10s, plus the Beta C250 center speaker, with its similar tweeter and woofer. I used the Beta ES250 surrounds in bipole mode to overcome my room's diffusive clutter with energy from both sets of drivers. You can also run the ES250 as a dipole (with one face's phase reversed), as a monopole (using only one set of drivers), or with a single cabinet delivering two separate surround channels (mounted in the middle of the back wall).

The center speaker has the highest claimed sensitivity rating—not a surprise nowadays—at 90 decibels. The Beta 10 is rated at 88 dB, and the ES250 at 87 dB. These numbers are slightly on the low side by today's surround-driven standards, which required me to crank my receiver a bit higher than usual. I also set higher-than-usual sub levels both on the sub's back panel and within the receiver.

All of the Beta drivers are made of Infinity's patented CMMD, or Ceramic Metal Matrix Diaphragm, which consists of a ceramic compound deep-anodized onto an aluminum core. Using it for every driver gives the set a certain pleasing organic unity, regardless of technical merit. CMMD also stands up well to the thermal and physical rigors of high-volume beatings.

The curved metal grilles make the Beta speakers and associated subs look more upscale than the Alphas. The grilles are backed with a light, synthetic fabric. I'm not sure if it was the metal or the fabric, but the grilles had a slight dulling effect; after a few weeks, I pulled them off. I hated doing it—they looked nice and hid the waveguide, purging the obsession with Constant Acoustic Impedance from my troubled mind—but I vastly preferred the extra zing and transparency I heard with the grilles removed.

Infinity offers a choice of complementary subwoofers: the 10-inch CSW-10 ($999) and the 12-inch SW-12 ($799), both of which have parametric EQ to notch out room-related bass anomalies. The 10-inch sub has a heavier enclosure (52 versus 45 pounds) and a more-powerful amp (650 versus 500 watts), and it comes with a room-correction kit that enables you to measure your room's impact on the sub and arrive at the best EQ settings.

My reference gear included the Rotel RSX-1065 receiver, the Integra DPS-8.3 universal disc player, Monster MS1.2 speaker cables, and BetterCables.com audio interconnects (along with an LG LCD projector and Tributaries video interconnects). Demo time.

Drums and Thunder
Monitor-size speakers can produce a decent drum sound. I gave the Beta Series speakers a chance to blast "Read About Love" from the DVD-Audio release of Richard Thompson's Rumor & Sigh. Even without the sub, they painted the drums and bass guitar in bold strokes, with a more-schematic depiction of the bass drum. Switching in the sub, using an 80-hertz crossover, produced an awesome rhythm section.

Navigating DTS soundtracks, the sub hardly broke a sweat during the rap-club scenes in Eminem's 8 Mile and Led Zeppelin's rich self-titled DVD concert. The CMMD tweeters excelled with the distinctively trebly black-and-white Danelectro electric guitar that Jimmy Page plays on "White Summer" and "In My Time of Dying."

Once Upon a Time in Mexico (in Dolby Digital 5.1) sent gunshots whizzing throughout the soundfield. I enjoyed what my notes refer to as "the low-frequency swoosh of doom," a wind-like effect that always seemed to foreshadow subsequent bloodshed, accompanied by the kind of drum rolls that evoke an approaching thunderstorm.

That put me in the mood for real thunder: "Thunderstorm" from Echoes of Nature, a five-CD set. In lieu of the low-frequency riot I'd hoped for, Dolby Pro Logic II's music mode manipulated the midrange component of clashing air masses, causing them to arc from the front speakers to the bipolar surrounds. I enjoyed it so much that I let the disc run on to the "Frog Chorus," with hundreds of warty Pavarottis singing their souls out in nature's concert hall. When will someone start making these outdoor recordings in discrete 5.1 surround?

The Beta midrange is upfront, not laid-back, so I leaned to the reticent side of my classical library. One beneficiary was the German Requiem by Brahms, as played by Herbert von Karajan and the Vienna Philharmonic. The Dolby Digital DVD-Video release is a quad recording, with a silent center channel, but the Beta 10s delivered enough detail to hold the front soundstage together. A CD of Dvorák's Cello Concerto also fared well, although the cello timbre didn't focus perfectly until I removed the grilles.

A Formidable Performer
Any set of speakers that can navigate a minefield of pounding rap and heavy metal, rarefied electric guitars, gunfire, low-frequency swooshes of doom, drum rolls, thunderstorms, and frogs is clearly formidable. Minus grilles, the Infinity Beta Series speakers achieve greater transparency than the Alpha Series while maintaining their ability to play loud and cost little. Thanks to national distribution, you shouldn't have to drive too far to find them.

* Mark Fleischmann is the author of Practical Home Theater, available through www.quietriverpress.com.

Highlights
• Constant Acoustic Impedance waveguide shapes tweeter dispersion and confuses the infidel
• The sub uses parametric EQ to offset room-acoustic flaws