Klipsch RB-81 Speaker System

Return of the bodacious woofer.

When I ran across the Klipsch RB-81—in the newly renovated Reference Series—I couldn't resist ordering a set. It's been years since I've reviewed a two-way design with a great big 8-inch woofer. The very concept brought on one of my increasingly frequent bouts of nostalgia.

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The store where hi-fi (as it was known then) first seduced me was blocks from my college dorm. One of the salespeople there was a fellow student, and, 30 years later, we are still the best of friends. The store cleverly aggregated American-made speakers, Japanese-made receivers, and European turntables in packages at a half-dozen price points. These were not today's HTIB packages. Usually, the manufacturers had nothing to do with one another. There were various microtrends that seem quaint now, like the year when dark-colored backlit FM-tuning rulers gave way to bright monochrome embossed ones. Back then, salepeople encouraged you to kick back and listen before you bought anything—what a radical innovation that seems today.

Woofers were big in those days. None of the packages included a subwoofer. Two speakers did all the work. If you bought speakers with anything less than 8-inch woofers, you just weren't serious about rock 'n' roll. I was a very serious kid—my first speakers, KLH 17s, had 10-inch woofers.

Whatever happened to the big woofer? It's become hard to find one in a two-way speaker. Today's big-woofer speakers are usually three-way designs that add a midrange driver—and an extra crossover. Meanwhile, two-way designs have shrunk. They typically have woofers of 6 inches or less and hand off bass duties to a powered sub. That's progress.

There are good reasons to avoid harnessing a woofer of more than 6 inches in a two-way design. For one thing, it's tricky to cross over from a big woofer directly to a tweeter. If you cross the woofer over too high, its dispersion will be too narrow to match that of the tweeter, producing sonic character that is often called the cupped-hands effect. If you cross the tweeter over too low, it may distort (or melt), because it can't handle all that power. Klipsch chooses to cross over the tweeter at an unconventionally low frequency, but, because the tweeter has above-average power handling, it doesn't break up (or just plain break) under normal conditions.

Chunky Monkey
The RB-81 is a chunky stand-mount speaker. At 19 inches tall, it's not what you'd call a bookshelf speaker (and a bookshelf isn't what I'd call a good place for a speaker, anyway). At 9.25 inches wide, it's not fashionably slim, and, at 30 pounds, it's no lightweight. The look is strictly utilitarian—at least until you pull the magnetically attached grille off that big box.

Beneath it, you'll find the distinctive, brightly colored Klipsch woofer. Although it's copper colored, it's made of anodized aluminum with a ceramic-like coating on both sides. This stiffens the driver so that its motion is more like a piston. Another benefit is better damping and less ringing, which provides a better-focused sound with less overhang.

The tweeter is a pure-titanium dome in a 4-inch-deep recess. That's the famous Klipsch Tractrix horn. To me, it looks like a horn within a horn. Klipsch calls it a compound-curvature horn. Furthermore, "the throat geometry is rounded off near the tweeter diaphragm. This lofted throat design serves two different functions—90-by-60-degree coverage for high frequencies and lower-frequency dispersion from the horn that matches the woofer." While the tweeters are identically matched throughout the system, the woofers vary. The RB-81's woofer is 8 inches, the RC-62 center channel's woofers are 6.5 inches, and the RS-52 surround's woofers are 5.25 inches.

Klipsch offers a noteworthy refinement in the center-channel speaker. Only one woofer operates all the way up the midrange to the tweeter crossover. The other one operates solely at low frequencies. This makes the center more of a 2.5-way design than a two-way. More importantly, it defeats the cancellation effect that occurs in dual-woofer designs where both woofers operate through the same frequency range. I wish more manufacturers would follow suit—conventional horizontal center-speaker design is the key weakness of most of the products I review.

The surround doubles both the woofers and tweeters in a modified bipole design that Klipsch says provides the right trade-off between immersion and localization. Both the main and center speakers have an eyebrow-shaped port that, according to Klipsch, reduces turbulence and provides the maximum port surface area for correct tuning. The RB-81 has threaded inserts for mounting (in spite of its bulk and weight), while the RS-52 has keyhole mounts.

Horn speakers are favorable in movie theaters for their efficiency and controlled coverage or pattern control. The RB-81 has a sensitivity rating of 96 decibels, and the RC-62 center and RS-52 surround are even more efficient at a claimed 98 dB. That's way beyond average in a market where sub/sat sets typically rate in the low 90s (or less) and where most sensitivity ratings are inflated. A 3-dB increase in true sensitivity cuts a speaker's power demand by half to produce the same volume level. As a result, even an average receiver should be able to power these speakers to high volumes. At the same time, these speakers can also handle plenty of power if you've got some. The RB-81 is rated for 150 continuous watts and 600 peak watts; the center and surround are rated for 100 continuous watts and 400 peak watts.

Pinker Than Ever
Lately, I've fallen in love with David Gilmour in Concert, a 2002 concert DVD recorded in Dolby Digital 5.1. The surrounds are used strictly for ambience, even in the spooky opening track performed on acoustic guitar with faint synthesized echoes activated by a pedal. Although he's grayer and heavier than he used to be, Gilmour could still hit the high notes with his otherworldly choirboy voice, and he augmented himself with nine backing singers. In fact, the singers on the stage outnumbered the instrumentalists, and, on surprise tracks like Bizet's "Je Crois Entendre Encore," the ethereal beauty associated with classic Pink Floyd floated to new heights. With such a vocally dominated recording, it was a relief that the Tractrix horns allowed me to move from side to side without major changes in vocal coloration—a drastic shift would have broken my concentration and destroyed the magic. It's pretty neat how the horns minimize room reflections as they spread relevant information throughout the listening area.

Unfortunately, this was one of the many multichannel recordings with an underused center channel. However, the distribution of Gilmour's voice and guitars into the left and right speakers did little harm. The material was heavily drawn from Pink Floyd's The Division Bell and Wish You Were Here, with various added treats. There were two versions of "Comfortably Numb" from The Wall, with guest vocals by Robert Wyatt and Bob Geldof, but the two Syd Barrett covers far outshone them, including an unplugged, shuffling, downright jaunty version of "Dominoes" that had all of the band members grinning. Oh, please, let this beautiful disc become standard demo material at trade shows.

The 8-inch woofers deserved a taxing solo performance—without a subwoofer—and got one with the DTS soundtrack of AVP: Alien Vs. Predator. Anyone who's used to a subwoofer would immediately notice the less-than-rock-solid bottom end. Still, enough bass came out of the speakers to tell the story, giant shifting stone walls and all. And, even with the speakers running full-range and loudly, the receiver's master volume was about 20 percent below where I normally have it.

Loud swells of violent effects were blessedly painless. These speakers do have a personality, but it is an amiable one. They are more gently voiced than any Klipsches I've heard in the past, with a civilized midrange and unhyped highs, although they give up nothing in vocal intelligibility. The vocal cupped-hands flaw audible in less refined horn designs was minimal, with just the faintest sensation of roundedness. It's the sort of thing you'd hear if you cupped your hand behind your outer ear and opened your fingers. Surround effects, which were sudden and plentiful in the movie, kept pushing my fight-or-flight button at the right moments.

The two-CD set called Richter Rediscovered is a 1960 New York recital and one of the best-recorded legacies of the amazing Russian pianist Sviatoslav Richter. With a sub, I would probably have gotten more impact from his mighty left hand, but I hardly noticed with everything else that was going on. The speakers adeptly juggled his radical dynamic shifts, muscular rhythm, and masterful nuance, which the instrument's innate sparkle and Carnegie Hall's reference-standard acoustics enhance. The knife-edged drama of his performance of Prokofiev's Sonata No. 6 had me goggling.

Late in the game, I finally added a sub to the system. The RSW-10d digitally controlled subwoofer is Klipsch's smallest sub—not necessarily a bad thing—and their smartest, which is definitely a good thing. Top-panel controls—complete with a blue-backlit liquid-crystal display—adjust volume, phase, EQ modes, user-adjustable presets, and crossover (in 5-hertz increments from 40 to 120, plus bypass). That leaves little on the back panel, apart from inputs and the power switch. EQ modes include Flat (no adjustment), Punch (60-Hz emphasis), and Depth (30-Hz emphasis). The latter made this little sub sound more powerful than its size suggested. Richter's left hand and AVP's thunderous effects became all the more stirring and intimidating.

What initially seemed a mere novelty, a curious artifact of the past, turned out to be a great-sounding speaker system. If your video display is a DLP or an LCD and you don't mind bulky speakers, the Klipsch RB-81, RC-62, and RS-52 should be on your short list of moderately priced options—especially if you like it loud and aren't ready to spring for a megabucks receiver or for separates. I enjoyed every second I spent with these fascinating speakers.

* Audio editor Mark Fleischmann is also the author of the annually updated book Practical Home Theater (www.quietriverpress.com).

Highlights
• Got some big fat woofers here
• These high-efficiency speakers can run off of virtually any receiver
• A kinder, gentler Klipsch

COMPANY INFO
Klipsch Audio Technologies
(800) KLIPSCH
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