Polk Audio RT5 loudspeaker Page 2
No such cynicism is apparent in the RT5's design. It's built out of ¾" MDF, with a 1" front baffle. Rapping the cabinet produced a solid if somewhat resonant thunkI've heard deader, but it's very solidly constructed. The rear panel sports a wall-mounting bracket and an input plate supporting a pair of plastic nutted binding posts on the exterior and the crossover on the inside.
That crossover is simple, consisting of a first-order low-pass filter for the wooferessentially just a series ferrite-core coil. The tweeter's high-pass filter is second-order, using a electrolytic cap bypassed by a Mylar cap. DiComo explained that Polk designed the drivers to require as little crossover compensation as possible. Speakers that use overly complex crossovers, he said, frequently lack excitement.
Polk manufactures both drivers employed in the RT5. The company's vertical integration, DiComo pointed out, is a crucial component in offering valueespecially at the most affordable levels. "We can certainly build a far, far better driver at a given price than we could buy."
The woofer's 6.5" cone is a composite materialpolymer with mineral filling added for stiffening. The cone is injection-molded, not vacuum-formed, which allows it to have a cross-section that's not uniform: it's thicker at the outside than it is toward the voice-coil. The surround is also injection-molded for the same reason; it, too, is thicker at the edges than in the middle. "This makes the surround absorb energy traveling through the cone better," claimed DiComo. "It becomes a shock absorber, if you will." The surround extends over the edge of the basket and is cemented to it. "Otherwise," DiComo said, "it would ring like a bell. But if you tap the basket with the surround in place, you just get a nice dull dunk."
The tweeter's a fairly straightforward 1" polymer dome, but even so, Polk has designed in a few nice touches. The voice-coil former has been bent up to meet the dome, which gives "ten times more contact area between the two. We've found that to be very effective in reducing modal resonances in the tweeter," explained DiComo. The tweeter's faceplate has a gentle roll that, DiComo claims, controls dispersion.
There are two flared front-firing ports of different lengths. One is specifically intended to counteract the main internal cabinet resonance by reproducing that frequency in inverted phase. Polk calls this their "Acoustic Resonance Control" system.
A most auspicious beginning
When the RT5s arrived, I simply substituted them for the $8000 B&W Silver Signatures I'd been listening to in my reference system. The Polks were by far the least expensive component in the systemand that includes the speaker stands they perched upon. They sounded huge, beefy, and very, very musical. To say I was stunned would be an understatement.
"Musical"? What does that mean? Simply that, rather than hooking them up and leaving them playing to break in, I wound up playing several of my favorite songs from the pile of discs growing on top of my CD player, which made me late for workagain.
Later in the afternoon, first Larry Archibald and then John Atkinson "dropped by" to check out the Polk. Both of these sessions began with hoots of laughter at the sight of $330 speakers attached to $15,000 Kimber Black Pearl speaker cables. They ended with all of us shaking our heads and saying, "These cost only $330?" A most auspicious beginning.
Over the course of my audition, I swapped the Polks in and out of a variety of systems. I did listen to them in the context of my reference system quite a bitthat's what reference systems are for, after all. But I also recognized how ridiculous it was to do so exclusively, so I used several "real world" integrated amplifiers, such as Krell's 150Wpc KAV-300i and Myryad's 60Wpc MI-120. The RT5 was about as undemanding of an amplifier as any speaker I've usedit did not change its essential character no matter which amplifier I connected it to.