Paradigm Export/BP Floor standing speakers
The Export/BP loudspeaker system, designed and manufactured in Canada by Paradigm Electronics, Inc., is a bipolar design with identical sets of drivers on its front and rear panels. The front drivers provide the signals normally heard from a conventional front-firing system, supplying program detail and image-localization information to the listeners. The rear drivers contribute spaciousness and in combination with the front drivers create a virtually omnidirectional sound field in the horizontal plane. The speakers are normally placed several feet in front of the wall behind them, so that the reflected output of the rear drivers is heard with a slight delay that contributes to the sense of ambience.
Each of the Export/BP's two sets of drivers comprises a two-way vented system consisting of a 6-1/2-inch woofer crossed over at 1.7 kHz to a 1-inch soft-dome tweeter. Both sets of drivers are located near the top of the columnar enclosure, about 3 feet from the floor. The woofers share a common internal volume and exit port, near the bottom of the cabinet's back panel.
The enclosure is made of 1-inch-thick MDF (medium-density fiber-board) panels, heavily braced internally and damped by fiberglass and other materials. Each speaker weighs 55 pounds. The all-black cabinet is enclosed in a snug-fitting black cloth sleeve, or sock. The top and base are covered by wood plates that snap into place and hold the sleeve firmly (the bottom plate also has fittings for optional spikes, which are provided with the system). The end plates are available in a choice of finishes, including four woodgrains and a black gloss. The Export/BP is fitted with two pairs of gold-plated binding posts that permit biwiring or biamplification. Recessed into the rear of the cabinet near its bottom, they are normally joined by gold-plated jumper strips.
The instructions furnished with the speakers are quite specific in the advice they offer on installation and placement. Paradigm also has a brochure ("The Elements of Better Speaker Design") that is refreshingly factual and free of hype - well worth reading whether you are in the market for its speakers or not.
We set up the Export/BP speakers as recommended, about 3 feet from the wall behind them and 3 to 4 feet from the side walls. The room response, averaged for the two speakers, was extraordinarily flat from 750 Hz to 20 kHz, with a +/-1.25-dB variation over that range (and within +/-2.5 dB down to 300 Hz). Almost unique in our experience, there was no trace of a response irregularity in the vicinity of the crossover frequency. This is the flattest response we have ever measured from a speaker over such a wide range that includes its crossover region.
The close-miked bass response reached a maximum at 170 Hz, falling by 6 dB at 65 and 750 Hz. Splicing it to the room curve was not as unambiguous as we would have liked, and the measured woofer output appeared to drop off faster than what we heard actually suggested. At the system's rated lower limit of 42 Hz, its output was clean and undistorted, and even at 32 Hz the room was filled with powerful, clean bass that gave no clue to the relatively small size of the speaker's woofers.
Horizontal dispersion was typical of good 1-inch dome tweeters. The output 45 degrees off-axis was down 4 dB at 10 kHz, relative to the on-axis response, and down 8 dB at 20 kHz.
Paradigm gives the Export/BP's sensitivity as 90 dB SPL (sound-pressure level) in a room and 86 dB in an anechoic environment; we measured it as 87 dB. The speaker's impedance is rated as 6 ohms nominal, and Paradigm specifies the minimum as 4 ohms, which we confirmed. The Export/BP clearly should be an easy speaker for any decent amplifier to drive.
With a 4-volt input, corresponding to a 90-dB-SPL output, the system's distortion was between 0.3 and 1 percent from 120 Hz to 2 kHz, climbing at lower frequencies to 3 percent at 40 Hz and 5 percent at 30 Hz - very impressive performance from a pair of 6-1/2-inch drivers. The small woofers were able to take single-cycle 100-Hz tone bursts of 325 watts into their 6-ohm impedance before the output became audibly raspy. At higher frequencies the system easily absorbed everything we could put into it with no sign of damage or distress, limited by the amplifier to between 500 and 1,500 watts in the range of 1 to 10 kHz.
The measurements essentially confirmed our impressions from the extended listening sessions that preceded them. Although the Export/BP's sound tended to be slightly "soft," there was no hint of boom or tubbiness. That can be credited to the system's combination of a remarkably clean and extended low bass together with the flattest middle- and high-range response we have seen from a speaker.
The system's basic imaging characteristics seemed to be determined entirely by its front radiation, as claimed. The vertical and lateral positioning tests of the Chesky JT-37 test CD produced stereo location effects as good as we have heard, apparently undiluted by the output from the rear drivers. But in addition to contributing to the system's overall low-bass performance, the rear drivers did contribute an unmistakable sense of air and space.
Although bipolar speakers are not new, Paradigm's execution of the concept is noteworthy. The considerable effort the company says it put into the Export/BP's drivers and construction has paid off handsomely in the speaker's superb performance.
