Design Acoustics PS-103 Floor standing speakers
With the exception of one outdoor model, all loudspeakers from Design Acoustics are designated PS, for Point Source. The goal behind each is to produce a "clear, defined signal with no trace of loudspeaker sound"-in other words, as if that signal were emanating from a single, infinitesimally small location (an ideal point source). Such a design seeks to eliminate front-baffle diffraction effects as well as the phase cancellation and relative delay that can occur among the multiple drivers in a typical loudspeaker. More simply put, Design Acoustics aims to eliminate boxy sound.
The PS-103 is the top model in a line of six PS systems. Its outward appearance is subdued, with handsome solid-oak endcaps and trim and a full-length, wraparound black grille cloth. Each cabinet can be wheeled about on four casters. Beneath the PS-103's conventional exterior, though, lies an unconventional configuration designed to minimize the baffle area of all three drivers.
A subenclosure in the lower two thirds of the cabinet houses a 10-inch woofer, which fires downward from the base. The casters should not be removed, as they raise the cabinet (and therefore the woofer) a calculated distance off the floor for optimum bass performance. Two horizontal sections within the subenclosure form asymmetrical ports to minimize standing-wave resonance. A second, trapezoidal enclosure in the upper portion of the cabinet contains a 6-inch midrange driver and, centered above it, a 3/4-inch dome tweeter. The trapezoidal shape minimizes the baffle area surrounding each driver. Although visible from the back, the upper enclosure is hidden in front by a nonremovable stretch grille.
As a further measure against phase and time-delay problems that might affect stereo imaging, Design Acoustics has chosen nominal crossover points-at 100 Hz and 3 kHz-that fall outside much of the range in which the ear is most sensitive to phase. The company says the woofer actually begins rolling off at 80 Hz (confirmed by Diversified Science Laboratories' measurements) and therefore classifies it as a subwoofer and the midrange driver as a midwoofer.
Inset toward the bottom of the back panel are well-constructed color-coded binding posts that accept four varieties of speaker connections: bared wire, banana plugs, terminal pins, or spade lugs. There are three pairs of terminals, each linked by a jumper. For normal, full-range operation, the jumpers are left in place, as they were throughout our testing. If you wish to biamp the system- that is, drive the woofers with a dedicated amp-simply remove the jumpers and make the connections as instructed (when you do so, the woofer's crossover is completely bypassed). Biamping requires the use of an electronic crossover, which divides the output of your preamp for feeding two power amps-one just for the woofers, the other for the mid-range drivers and tweeters. The electronic crossover should be set the same as the one it replaces, at 100 Hz with a slope of 12 dB per octave. Last on the back panel is a tweeter-level switch that can attenuate high-frequency output by approximately 3 or 6 dB.
Design Acoustics suggests you experiment with the placement of the PS-103s in your listening room. DSL made two sets of response measurements-one with the speakers three inches out from the back wall, the other at about three feet away. Our graph, which represents the near position, shows that both the on-axis and off-axis curves remain within +4 dB from just below 50 Hz straight out to 20 kHz, except in the range between 125 and 250 Hz (where the woofer is crossing over to the midrange driver). There, response drops down nearly 7 dB on both curves. The only other noteworthy features in the otherwise smooth curves appear in the on-axis trace: a hump between 600 Hz and 1 kHz and a hiccup at 16 kHz. Both are within + 4 dB and of little significance in comparison to the dip in the upper bass.
DSL made distortion measurements at its four standard test levels: 85, 90, 95, and 100 dB SPL. At 90 dB, the average distortion-discounting the very deep bass-is only 3/4 percent. While the 1-kHz test frequency yielded figures significantly above the average at all four levels, there were nevertheless no signs of distortion in normal listening. In the 300-Hz pulse power-handling test, the PS-103s swallowed the full output of the lab's test amplifier (equivalent to 27.9 dBW, or 613 watts, into 8 ohms), which translates to a healthy dynamic range of 117-1/2 dB. Sensitivity measured 89-1/2 dB, about average for a speaker this size.
Impedance averages close to 10 ohms from 20 Hz to 20 kHz. It hits a low of 4.7 ohms at 300 Hz, beyond which it gradually swells to a peak of more than 20 ohms at 2 kHz. Most amplifiers should be able to safely drive the PS-103s in parallel with another pair of 8-ohm-rated speakers. Incidentally, the setting of the tweeter-level switch has only a minor effect on the impedance above 3 kHz.
Listening tests are more important for a loudspeaker than any amount of technical data, which is why we don't look at data until we have completed our listening ritual. But the data can help explain what you've heard. First, the good news. The PS-103s deliver more than adequate (if somewhat loose) bass, even below 50 Hz; clean and extended high frequencies, with no unseemly forwardness; and rock-solid stereo imaging with a fairly wide and deep soundstage. And they easily handle the dynamic demands of the best CDs. I kept the tweeter switch in the flat position, but the two cut positions would be very effective for attenuating high frequencies in a live room. As with any speaker, the PS-103s deliver more bass when moved into a corner, which in effect enables you to tune your setup; their overall tonal quality is not compromised by such repositioning.
However, the PS-103s do not entirely succeed in their mission to escape boxy sound. While the soundstage is broad, vocals-usually prominent at the center of a stereo mix-take on a nasal quality. This effect correlates with our response curves, which show a significant depression in the upper bass that affects the lower registers of voices. Other instruments are sometimes also affected, but to a far less noticeable degree.
That last point is important, since listening to the PS-103s is otherwise pleasant-whether your tastes tend toward Top 40 or Beethoven's Ninth. I was quite satisfied with their low lows and high highs, their good stereo imaging, and their ability to play loud without turning the music to mush.
