Fig. 1
MANUFACTURER'S SPECIFICATIONS:
Input Impedance: 8 ohms. Recommended Power Input (for average-size room): 20 watts minimum. Speaker Complement: 10" acoustic suspension woofer; 1 1/2" mid-range hemispherical dome; 3/4" high frequency hemispherical dome.
Controls: Independent mid-range and high-frequency-driver level controls.
Dimensions: 13 1/2" W x 24" H x 11 1/2" D.
Weight: 39 lbs.
Available Finishes: Glossy walnut, oiled walnut, cherry, oiled teak, mahogany, birch or unfinished pine.
Price: From $156.00 (unfinished) to $175.00.
On first listening to Acoustic Research's new AR-5 systems, we were immediately impressed by the similarity between the excellent sound they produced and that of the now famous AR-3a's, AR's top-of-the-line system selling for about $75.00 more than the AR-5. Further investigation disclosed that the mid-range and high frequency drivers of these new systems are identical to those used in the more expensive model. Only the woofer, a 10-in. soft-suspension element that embodies a new molded cone, is different. Cone suspension is re-designed, too, and involves the use of a urethane polymer which, the manufacturer claims, helps to reduce low-frequency distortion.
If, as the manufacturer states, the use of the smaller-diameter woofer (10-in.) in this model cuts bass response by 1/3 of an octave (as compared with the larger AR-3a), this very negligible sacrifice is more than offset by an amazing lack of distortion in the bass region. Our 'scope measurements disclosed complete absence of "doubling" to below 40 Hz! In addition to listening tests, frequency response measurements taken in free air disclose exceedingly smooth response, with no significant "peaks" or valleys greater than 3 dB in amplitude at any point in the audio spectrum. AR does not specify frequency response in its published specifications, contending that useful response is dictated by room acoustics as well as a great many other factors. While we heartily concur with this point of view, we nevertheless would rate the response as being useful from about 35 Hz to 18,000 Hz. Crossover frequencies for this system have been set at 625 Hz and 5000 Hz. The lower of these frequencies, between woofer and mid-range, is a bit higher than the frequency used in the AR-3a.
Since two controls are available (mid-range and high-frequency level), we found it necessary to take several response curves. In the course of these experiments we concluded that the controls actually afford a bit too much control. As an example, it was possible to alter the output at 500 Hz by about 8 dB, while response at 10 kHz, using the "tweeter" level control, was variable over a range of nearly 12 dB. The task of adjusting two such controls for optimum response is not easy-there are just too many combinations and permutations of settings. As it turned out in our case, optimally flat response under our listening conditions (fairly "live," medium-sized listening room) was achieved with the mid-range control set about half way up, and the tweeter control set slightly above the half way mark. In all probability, other listening situations would call for settings not too dissimilar from ours and, after all, amplifiers do have tone controls.
Fig. 2--Impedance characteristics of AR-5.
Input impedance characteristics of the AR-5 are plotted in Fig. 2, and although the impedance "trend" seems to fall a bit below the nominally stated "8-ohm" figure, at no point does the input impedance fall below the "danger line" (for some solid-state amplifiers) of 4-ohms. Interestingly, the impedance at the very high end was significantly affected by settings of the tweeter level control, the higher curve corresponding to full clockwise setting of that control. This curve also confirms the fact that woofer resonance is at 55 Hz when measured in its enclosure. Acoustically, the region around woofer resonance had no significant peaks, a fact which further aids to produce an "uncolored" bass sound.
Performance
For all the warnings regarding "adequate power" given by AR and other manufacturers who produce acoustic suspension designs, we found the AR-5 to be remarkably efficient in its class. An amplifier having really low distortion, particularly in the bass region, need have little more than 15 watts of power-handling capacity to drive these systems to reasonable dynamic levels. Of course, more power will afford just that much more reserve and we can safely state that feeding power peaks as high as 40 and even 45 watts rms to the AR-5s resulted in absolutely no bottoming of the woofer cone or any other noticeable distortion. Sonic balance was maintained at all dynamic levels and transient response was as good as anything we have heard. Mid-range dispersion was particularly good and most effective when we played selections in stereo having a hit more deliberate separation than usual.
Our microphone tests disclosed only about a 3-dB attenuation of 10,000 Hz at a 60-deg. angle off-axis, which speaks very well for the hemispherical dome-tweeter and mid-range designs which have been carried over into the AR-5 from previous designs.
Unless you have a lot of music containing frequencies below 35 or 40 Hz that you just have to hear (or "feel"), can satisfy the bookshelf-size needs of many audio buffs who have systems in the medium to moderately high price range. And one need not have a 50 watts rms/channel amplifier, since a very good 15 watts rms/channel or just plain clean 20 watts rms/channel amplifier would do just fine.
(Audio magazine, Jan. 1970)
Also see:
Acoustic Research (AR) Model AR90 Loudspeaker System (Nov. 1979)
Acoustic Research AR-6 Loudspeaker System (Equip. Profile, Jan. 1972)
AR-7 loudspeaker (Equip. Profile, Feb. 1973)
AR (Acoustic Research) AR-7 loudspeaker (ad, Feb. 1973)
AR M1 Speaker (Equip. Profile, Jan. 1992)
Acoustic Research AR98LS Speaker (Jan. 1985)
AR (Acoustic Research) MGC-1 loudspeaker (ad, Nov. 1986)
Acoustic Research LST Speaker System (Dec. 1972)
Jensen TF25 High Fidelity Bookshelf Speaker System (Feb. 1970)
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