ADS SS2300 Speaker System Review

Although ADS was one of the first to market a truly hi-fi miniature speaker system, it is better known for its more conventional, larger systems. The company obviously had the technological base to produce a “three-piece” speaker system (two small satellite speakers and a bass module) some time ago, but it was reluctant to rush to market with a product whose performance might be seriously compromised by incorrect installation or setup adjustments.

ADS has now overcome those possible objections to its own satisfaction, and the result is the new SS2300 “SubSat” system. It is based on the ADS L400, a “mini” speaker of excellent quality that is capable of being used as a full-range speaker system. The L400 is a 4-ohm, two-way acoustic-suspension system with a 6-inch woofer that crosses over at 1,500 Hz to a 1-inch dome tweeter. It is housed in a fine-finish wooden cabinet (available in either oak or walnut veneer) with a black metal grille. The speaker measures 11-1/2 inches high, 7-1/2 inches wide, and 6-3/4 inches deep.

The rated frequency response of the L400 satellites is a very impressive 60 to 20,000 Hz ± 3 dB. Its low-frequency performance allows a crossover to a common-bass system at a frequency sufficiently low to prevent the bass response from appearing as a "disembodied sound” and the bass module itself from being identified as a separate sound source. Although the size and appearance of the L400 permit it to be installed almost anywhere, a recommended placement is on the optional F400 floor stand. This unobtrusive black metal stand supports the speaker 29 inches off the floor and tilted slightly backward for optimum coverage of the listening area.

The bass range of the SS2300 system is handled by a self-powered module, the PB1500. It contains a pair of 10-inch acoustic-suspension woofers in acoustically isolated compartments and a pair of 100-watt amplifiers. The amplifier rating is based on the 4-ohm impedance of the bass drivers. The PB1500 is large and heavy, measuring 22-1/2 inches wide, 23-1/2 inches deep, and 16 inches high. It weighs about 90 pounds and is available in wood veneers to match those of the L400s. A black grille cloth covers the speakers, and a similar (nonremovable) grille is on the opposite side of the box for decorative purposes. The amplifier heat-sink fins are on the same surface as the driver openings.

The SS2300 would not be able to meet its designers’ goals of independence from the vagaries of room interaction and other unpredictable factors without the help of the C1500 control center furnished with the PB1500. This is a sophisticated electronic-crossover network—and much more. A knob on its front panel selects crossover frequencies of 72, 90, 115, and 145 Hz with 12-dB-per-octave slopes. A bass level control adjusts the acoustic output of the PB1500 to match that of the L400 speakers (which are driven from the regular system amplifier). Normally the C1500 is connected between the preamplifier and power amplifier of the main system. Alternatively, it can be placed in a tape-monitor loop whose switching function is duplicated by a tape monitor switch on the C1500. It has a master volume control which, in the preferred mode of connection, can be set for a suitable listening level with any desired setting of the system volume control and need not be used thereafter.

Two other knob controls modify the specific shape of the crossover curves, although each has a center detented setting which will be suitable in most cases. The hi-pass Q control is intended to compensate for the bass-rolloff characteristics of the satellite speakers (particularly if they are not ADS L400s). It boosts or cuts the output slightly in the crossover range to correct for either an overdamped or underdamped bass resonance in the satellite’s “woofer.” With the L400s, this control can be left centered.

The bass contour control is a shelving-type tone control designed to complement the characteristics of the PB1500 and L400 speakers. In some rooms it may be desirable to modify the bass response of the SS2300 system, and this is often best done with the contour control rather than the usual amplifier tone controls (although both have essentially similar functions).

The other C1500 controls are pushbuttons. There is a power switch with an adjacent pilot light and a tape monitor button. The defeat switch takes the C1500 and PB1500 subwoofer out of the circuit entirely. When it is pressed, the satellites receive the full program bandwidth and the PB1500 is silenced. This is a convenient way to evaluate the contribution of the subwoofer to the overall sound without disturbing any of the other system adjustments. The dynamic bass extender is controlled by two buttons. One activates the circuit, which boosts the lowest frequencies with a curve complementary to the natural bass rolloff of the PB1500 woofers. This provides several decibels of additional output in the frequency range from about 80 to 20 Hz (centered at about 30 Hz) together with a sharp infrasonic cut to eliminate rumble or other noises that could either cause overload damage or simply sound objectionable. When the 22/37-Hz button is pressed, the maximum acoustic boost occurs at about 50 Hz and the low-frequency cutoff is more rapid. This is most likely to be useful with popular or rock music, while the 22-Hz position is best with most classical music.

The nomenclature of the dynamic bass extender derives from its being controlled by the level of the bass signal. As the level increases toward the point of overdrive of either the bass amplifier or the speakers, the boost is progressively reduced until at high volume levels it it is effectively gone. Thus, it can be left in operation at all times without risking damage to the speakers or any audible unpleasantness. The final control is a phase button, which reverses the phase of the signals fed to the PB1500. In certain rooms or with certain speaker placements, better bass performance may be obtained with a particular setting of this switch; in many cases it makes no audible difference.

The ADS C1500 control center is finished in black. It is 17 inches wide, 10 inches deep, and 2 inches high. It can be powered from a convenience outlet on the main amplifier and switched by it if desired. Because of the remote placement of the PB1500 subwoofer, it is supplied with a 30-foot dual shielded cable fitted with phono plugs at both ends. The C1500 control center will normally be located near the amplifier, and the cable allows the bass module to be placed as desired in the room. It can be powered from any convenient a.c. socket and is turned on automatically when the control center is powered. The L400 satellites are connected to the main amplifier in the usual manner. The suggested crossover frequency between the woofer and the satellites is 90 Hz, which is well within the effective operation range of the L400 yet low enough to prevent audible localization of the woofer sound. Because of the attractive finish of the PB1500, it can be placed unobtrusively almost anywhere in the room or be used as a piece of furniture such as a lamp table or a coffee table.

On the front of the PB1500 subwoofer, visible though its black grille, are four warning lights. One is a green pilot that indicates it is powered. A red peak light flashes when the bass amplifier is clipping; this action will rarely be heard as distortion since the harmonics generated by overload usually fall outside the woofer’s operating bandwidth. The overload light warns of a possibly dangerous high temperature in the voice coils. It operates from a circuit that constantly monitors the power input to the speakers and disconnects them from the amplifiers (as well as lighting the warning light) if they are endangered. Normal operation is automatically restored when the voice coils have cooled to a safe temperature. There is an amplifier protection system with a signal light which disconnects the speakers in the event of a catastrophic internal failure or overload condition. In addition, a line fuse protects the entire PB1500 module.

The components of the ADS SS2300 are available separately or as a complete system. The L400 speakers are $189.95 each, and the optional F400 stands are $37.50 each. The PB1500 bass module, including the C1500 control center, is $1,349.95. The complete SS2300 “SubSat” system (not including stands) is $1,649.95, a saving of $80 over the total prices of the individual components.

Laboratory Measurements

Initially, we measured the L400 satellites as full-range speakers without the C1500 or PB1500. Except for a minor dip in the midrange (250 to 600 Hz) in the reverberant-field measurement, the output of the speaker at middle and high frequencies was very smooth and flat, varying only ±2 dB from 600 to 20,000 Hz.

With the C1500 control center set for a “90-Hz” crossover, the 110-Hz bass-resonance peak of the L400 was completely removed and the output fell off below 150 Hz. The close-miked response of the PB1500 peaked at 70 Hz, falling off fairly steeply below that frequency and with its high-frequency rolloff being a function of the selected crossover frequency. The bass contour control affected the entire bass output by a maximum of about ±5 dB. The hi-pass q control affected the response between 100 and 400 Hz, with a maximum range of about ±3 dB. The dynamic bass extender (22 Hz) increased the woofer output by 2 to 5 dB from 20 to 70 Hz; its 37-Hz position produced a total boost of 3 to 5 dB between 40 and 70 Hz and a much steeper low-frequency cutoff.

Splicing the bass-response curve to the L400 room-response curve was both easier and more difficult than with conventional single-unit speakers. There is no definable “system response,” since that depends on the relative placements of two sets of speakers and the various adjustments on the C1500. On the other hand, those controls make it possible to match the bass output to the middle- and high-frequency output almost as closely as one’s hearing permits, so we felt justified in splicing the curves for the most uniform overall response.

That response was within ±3.5 dB from 32 to 20,000 Hz. With the dynamic bass extender (22 Hz) in use, the lows were extended appreciably without changing the overall output variation—a 27- to 20,000-Hz response within ±5 dB. Of course, the added low-frequency output in any given installation will be largely a function of the room proportions, the location of the bass module, and the C1500 control settings. Our figures can do no more than suggest the added output from the bass extender, based on separate measurements of the system components. A quasi-anechoic frequency-response measurement of the L400, made at 1 meter using our INDAC FFT computer analyzer, confirmed the essential smoothness of the satellite speakers' response—a ± 3-dB variation in output from 500 to 18,000 Hz.

The system impedance of the L400 is about 3.5 ohms from 25 to 40 Hz and around 200 Hz, with maxima of 10 ohms at 90 Hz and 1 2 ohms at 1,400 Hz. The sensitivity, with a 2.83-volt input of pink noise in an octave band centered at 1,000 Hz, was 91 dB SPL at 1 meter, an exceptionally high value for a small acoustic-suspension speaker. The PB1500, having a 50,000-ohm input impedance and being driven from the 600-ohm output of the C1500, presents no loading problems to the main amplifier. The bass distortion of the woofer in the L400 satellite was about 0.5 per cent over its operating range as part of the SS2300 system.

The distortion of the PB1500 could not be measured in the usual manner, since we had no access to the drivers. We drove it through the C1500 (90-Hz crossover) with 2 volts at 100 Hz for the C1500 input. This corresponds roughly to a 1-watt drive to the L400s and was therefore used as an equivalent reference for the bass unit. The distortion was an excellent 0.5 per cent or so from 100 to 50 Hz, rising to 4 per cent at 30 Hz. A 10-dB level increase produced a room-shaking bass output and distortion measuring 1.5 to 2.5 per cent down to 60 Hz and 10 per cent at 37 Hz.

Comment

We listened to the ADS SS2300 system with the F400 stands about 3 feet from the facing wall of the room and 4 feet from the sides. The PB1500 was located at one side about 5 feet in front of the right speaker and 12 feet from the left speaker. The system was driven by a 200-watt-per-channel amplifier, with the C1500 control between the preamplifier output and power-amplifier input.

The balance, smoothness, and transparency of the sound from the SS2300 system was superb, to say the least, and easily comparable to what we have heard in the same room from some of the finest conventional speaker systems. The small size of the L400 satellites gives them a real “imaging" advantage over some larger systems, since cabinet interference with the polar response of the speaker is minimized. This could be appreciated when we used image enhancers such as the Carver “Sonic Hologram,” which functions best with speakers having a uniform phase response and symmetrical polar response in the horizontal plane. The ADS system worked excellently with the several such signal processors that we tried.

We have had very good results with several other “three-piece" speaker systems that use passive crossovers between the satellites and the bass module. However, most of these systems cross over at about 150 Hz, and under some conditions the position of the bass module can be identified by ear or the homogeneity of the sound can be disturbed by "disembodied bass." This is rare, in our experience, but it does happen. The 90-Hz crossover of the SS2300 appears to eliminate that problem. Switching off the satellites leaves only a deep bass originating from the PB1500, which is never heard as a distinct sound source while the complete system is operating. The bass level can be set to the listener’s taste over a very wide range from disco to symphonic balance. We adjusted the various bass controls until the music’s low-bass foundation could just be heard (or felt), but without imparting any heaviness to male voices. Of course, more bass was readily available, to the point of rattling every loose object in the room. We also noted that with the defeat button engaged (the L400s operating as full-range speakers) the sound was still excellent, often (in the absence of low-bass energy in the program) indistinguishable from the sound of the full system.

The installation and operating instructions of the SS2300 are quite complete and well illustrated. The confirmed “knob twiddler” can devote as much of his time as he wishes to adjusting the system response, but we found the center setting of most of the controls to be completely satisfactory. And our experience also suggests that the subwoofer placement is extremely noncritical, particularly remarkable considering the amount of trimming of bass response that the C1500 control unit makes possible.

As three-piece systems go, the ADS SS2300 definitely ranks among the best, and possibly at the very top. It is far from cheap, but the visual appearance and acoustic performance of the system are certainly commensurate with its price. For installations where the room decor cannot accommodate large and visible speakers but where no compromise with sound quality can be tolerated either, the ADS SS2300 may well be the ideal speaker system.

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