ADS S-700 Speaker System Review

The new ADS S-Class family of compact loudspeakers was designed, the company says, to provide exceptional sound quality at moderate prices. The ADS S-700, which we tested, is the largest of the three models currently in that line.

The S-700 is intended primarily for stand mounting, and ADS says that for best results it should be placed at the listener’s ear level, away from the room walls, and at least two feet from any corner. Its cabinet, made of 3/4-inch-thick medium-density fiberboard (MDF), has a deep charcoal-gray matte finish. A removable frameless perforated-metal grille, matching the color of the cabinet, is supported on stand-offs about 3/4 inch from the front baffle.

ADS designed and built the drivers as well as the crossover network. The S-700 is a two-way system with a 7-3/4-inch woofer operating in a sealed (acoustic-suspension) enclosure and crossing over at 3 kHz to a 1-inch dome tweeter. Both drivers are mounted flush with the baffle. The woofer cone and tweeter dome are made of a proprietary copolymer material, and the tweeter’s voice coil is protected against burnout by an automatically resetting solid-state device.

The four input terminals (separate pairs for the tweeter and woofer sections) are five-way binding posts recessed into the back of the cabinet.

Normally, the two sets of driver inputs are connected together in parallel by a small printed-circuit board, which can be removed for bi-wired or bi-amplified operation of the system.

The S-700’s nominal impedance is-4 ohms, and its rated sensitivity is 88 dB sound-pressure level (SPL) at 1 meter with 2.83 volts of pink-noise input (equivalent to 1 watt into 8 ohms). ADS recommends using the speaker with amplifiers rated from 20 to 200 watts per channel. The rated frequency response is 40 Hz to 20 kHz ±3 dB.

We placed the S-700’s on stands that located them well away from the room walls and with their tweeters at the recommended height. The averaged frequency response of the left and right speakers, derived from swept sine-wave room-response measurements above about 500 Hz, was spliced to a close-miked measurement of the woofer output below that frequency to form a composite frequency-response curve.

The room response was impressively flat, within +2 dB from 500 Hz to 20 kHz. The woofer response, which had a broad maximum at 150 Hz, spliced easily to the room curve with about an octave overlap. The resulting composite frequency response was approximately +4 dB from 55 Hz to 20 kHz. As with any audio installation, the actual frequency response will depend on the room’s geometry, its acoustic treatment, and the placement of the speakers.

Quasi-anechoic MLS frequency-response measurements at 2 meters showed an overall variation of only ±3 dB from 300 Hz to 20 kHz. The tweeter’s horizontal dispersion was typical of 1-inch domes, with the output 45 degrees off the forward axis dropping by less than 5 dB at 10 kHz and by 12 dB at 20 kHz compared with the on-axis readings.

Our frequency-response data correlated very well with test graphs ADS made on the same pair of speakers, which confirmed that the maximum output is in the octave between 100 and 200 Hz, with a 5-dB drop from 200 Hz to between 2 and 3 kHz and a strong top-octave response from 10 to 20 kHz. That degree of similarity between speaker measurements made under totally different conditions is extremely rare in our experience.

The system’s sensitivity was 88 dB, as rated. Its minimum impedance was 4.3 ohms at 148 Hz and 20 Hz, the maximum 21 ohms at 58 Hz and 1.3 kHz. Woofer distortion with an input of 3.5 volts (equivalent to a 90-dB SPL output in our sensitivity measurements) was typically about 0.5 percent from 70 Hz to 2 kHz, rising to 2.5 percent at 50 Hz and 10 percent at 20 Hz. The drivers were able to survive peak inputs well in excess of their ratings without damage. At 100 Hz, a single-cycle sine-wave input of 275 watts into the system's 5-ohm impedance at that frequency caused the woofer cone to bottom noisily, though with surprisingly little waveform distortion in its acoustic output. At higher frequencies the amplifier reached its clipping level (400 to 800 watts, depending on frequency) before the speaker exhibited any signs of distress.

We had listened to the speakers for some time before making any measurements, and hearing them left no doubt that they were very good speakers in every respect. Still, it was gratifying to find that our microphone and instruments rendered the same judgment. The ADS S-700 is a deceptively compact speaker whose sound quality gives few hints of its size (or price, for that matter). As unobtrusive visually as it is sonically, this affordably priced speaker should be ideal for stereo music systems or modest home theater installations.

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