Duntech Ambassador Speaker System Review
Duntech loudspeakers have earned an enviable reputation among critical audio enthusiasts. Designed and manufactured in Australia, they have generally been notable for their size, weight, sound quality, and price, all of which have combined to set them apart from most other speaker systems.
The company, which recently set up a sales office in Illinois, now offers a considerably expanded line of speakers to the American market. Still manufactured in Australia, they have retained their high-end character and range in price from $2,000 to $30,000 a pair. The Ambassador, which we tested, is one of the lower-priced models, although it shares the basic characteristics of the others.
Like other Duntech Classic Series speakers, the Ambassador features what the company calls a "pulse coherent" design, with two vertically arrayed 6-1/2-inch woofers with coated-fiber cones flanking a single 1-inch soft-dome tweeter with magnetic-fluid cooling. This arrangement (sometimes known as the D'Appolito configuration) is becoming increasingly common in column-type speaker systems because it enables the tweeter radiation to be acoustically coincident with the output of the woofers in addition to minimizing the width of the cabinet. Duntech says that as used in the Ambassador speakers the design causes the full frequency spectrum to arrive simultaneously (in phase) at a point 12 feet in front of the pair of speakers. A major audible benefit of such phase coherence is claimed to be the creation of an accurate soundstage at the listening position.
The Duntech Ambassador is a narrow-profile columnar speaker. The front is covered by a removable woodframed black cloth grille. The speaker's drivers occupy slightly more than half of the front panel height, with the tweeter about 34 inches from the floor. The portion of the panel occupied by the speakers is covered with 3/8-inch felt to minimize diffraction, which could affect the focus of the sound. The tweeter is recessed, presumably to place its dome in the acoustic plane of the voice coils of the cone drivers, and the region around it is treated with several layers of felt.
The fully sealed enclosure is made of 1-inch-thick medium-density fiber-board (MDF), with three internal shelf braces for maximum rigidity. Its base is equipped to use spikes (supplied with the speakers) for tightest contact with the floor. Near the bottom of the rear panel are two pairs of recessed input connectors (which accept single or dual banana plugs, wires, or lugs), normally joined by gold-plated straps. Removing the straps enables the system to be used in a biwired or biamplified configuration.
The internal crossover network is a first-order design (6-dB-per-octave slopes), which Duntech credits with a vital role in the system's stereo imaging and overall spatial quality. No inductors are used in its low-frequency section, eliminating one of the potentially nonlinear elements of conventional speaker designs.
We set up the Duntech Ambassador speakers about 7 feet apart, well away from side walls and the wall behind them, and angled slightly inward. The owner's manual supplied with the speakers was considerably more informative than most with respect to the placement of the speakers relative to each other, the room boundaries, and the listeners. Although we were unable to locate the speakers optimally in our room, our measurements confirmed the validity of the manufacturer's installation instructions.
The averaged room response of the left and right speakers, measured using a sweeping tone with a one-third-octave warble, was impressively flat and free from major irregularities. The close-miked woofer response reached its maximum at 100 Hz, falling at 12 dB per octave below 70 Hz and much more gradually above 100 Hz.
The bass response spliced easily to the room response, with an overlap of more than two octaves, yielding a composite frequency response of 63 Hz to 20 kHz ±2.5 dB. The manufacturer's rated response for the system is 55 Hz to 20 kHz +2, -3 dB, which was essentially confirmed by our measurements, made under completely different conditions.
Quasi-anechoic MLS frequency-response measurements confirmed that the Ambassador speakers should be about 12 feet from the listener for a fully coherent signal to be heard. Our initial measurement, at 1 meter, showed a pronounced "hole" (about 15 dB) at about 5 kHz. A second measurement at 2 meters reduced the hole to about 7 dB at 11 kHz, and a third at 3 meters (about 10 feet) was still smoother, with a +5-dB variation from 300 Hz to 20 kHz. The system's directivity was typical of 1-inch tweeters, with a slight output reduction (less than 5 dB) at 45 degrees off-axis up to 10 kHz, increasing to approximately 12 dB at 20 kHz.
The system's rated impedance is 4 ohms. Our measurement showed a minimum of just over 4 ohms at 10 kHz, a maximum of about 17 ohms at 75 Hz, and a typical reading of about 7 ohms over most of the audio range.
System sensitivity was variously rated at 90 or 91 dB in different parts of the data supplied to us by Duntech. Our measurement was 90 dB. At that level (with an input of 2.83 volts) the woofer distortion was very low, measuring between 0.4 and 0.7 percent from 2 kHz down to 80 Hz and rising to 1.5 percent at 55 Hz and 5 percent at 20 Hz (where the output was down considerably).
The Ambassador had no problems handling single-cycle pulses at 1 kHz and above (our amplifier clipped at 600 to 1,200 watts before the speaker was in trouble), but the small woofers emitted rasping sounds with a 100-Hz input of about 35 watts into their 9-ohm impedance. The system is recommended for use with amplifiers rated at 30 watts or more, and we used amplifiers rated in excess of 100 watts with no problems, even at rather high output levels.
Our listening experience with the Duntech Ambassador speakers was uniformly enjoyable. Even at less than the recommended 12-foot distance, the soundstage they created was extraordinarily sharp in its spatial definition. They have a strikingly uncolored sound, including a top end that managed to be crisp without ever sounding shrill. Probably the biggest surprise was the bass performance, which never sounded in any way deficient or thin. In fact, the only time we were made aware of the speaker's low-frequency limitations was when we switched on a subwoofer while playing one of our favorite deep-bass demo CD's.