Technics SB-6000A--Lets You Dream You're Conducting
The Equipment: Technics SB-6000A floor-standing speaker system in wood case with black pebble-grain finish. Dimensions: 16 3/4 by 33 1/4 inches (front); 13 3/4 inches deep.
Price: $299.95. Warranty: "limited," five years parts and labor.
Manufacturer: Matsushita Electric, Japan; U.S. distributor: Panasonic Division of Matsushita Electric Corp. of America, 1 Panasonic Way, Secaucus, N.J. 07094.
Comment: If the general appearance of the Technics SB 6000A does not convince you that it is a most unusual loudspeaker, removal of the grille cap that conceals the rearward offset tweeter and binding post for amplifier leads almost certainly will. The position of the tweeter identifies the speaker as a member of the Linear Phase series. Even the binding posts, to which bare wires are connected by inserting each into a hole and tightening a nut, are of a design we do not recall seeing elsewhere.
The SB-6000A has other uncommon characteristics, of course. One is its unusually high sensitivity-86 dB aver age omnidirectional sound pressure level at 1 meter across the range from 250 to 6,000 Hz from a 0-dBW (1-watt) pink-noise input. Complementing the sensitivity is good power-handling capability, which enables the unit to pro duce a steady-state level approaching 110 dB (on axis) at 300 Hz from an input of 173/4 dBW (60 watts) before objectionable distortion becomes apparent. Driven with pulses, the speaker reaches peak levels of 120 dB from a power input of 281/4 dBW (654.5 watts)-all the test amp could manage-without excessive distortion. A dynamic range such as this will, in a normal room, come close to, if not exceed, the limits of the ear.
Nominal impedance is 5.5 ohms, which is close to the rated value of 6 ohms. Excluding the peak at the low-frequency resonance, the impedance curve is smooth and lies between 8 and 3.6 ohms through the audible band. In view of the fact that the curve reaches its minimum in the vicinity of 1 kHz, parallel connection of two of these speakers to a normal amplifier output is not recommended.
The tweeter level control (under the grille cap) varies the level of that driver from full off to full on, shelving the response above about 2.5 kHz by 4 to 6 dB downward when set to its center point. Interestingly, when the tweeter is full off the woofer response is almost precisely 3 dB down at the nominal crossover frequency (1.8 kHz). Precise control of crossover frequency seems to be an important factor for speakers meant to maintain "linear phase." (See Peter Mitchell's article elsewhere in this issue.) From about 150 Hz upward, the Technics controls harmonic distortion very well. At a 0-dBW input both the second and third harmonics remain below-usually well below -1%. At a power input equivalent to 100 dB SPL at 300 Hz, the third harmonic is barely higher than in the 0-dBW case for frequencies from 200 Hz up. The second harmonic, a more tolerable intruder, rises significantly above 1% only between 5 and 10 kHz (the upper limit of distortion testing) and below 100 to 200 Hz, where the increasing excursion demanded of the woofer raises distortion fairly markedly. The low-frequency behavior of the speaker is, nonetheless, quite reasonable, with distortion some what less than average.
Frequency response of the SB-6000A in the CBS anechoic chamber is relatively smooth from about 65 Hz to 10 kHz, rolling off with increasing frequency by about 7 1/2 dB across that range with only about ±2 dB of variation in this basic response pattern. Low-end response seems to hold up well to at least 50 Hz and below that falls off smoothly at about 12 dB per octave--as does response above 10 kHz. The curves indicate that above 700 Hz or so the radiated energy is concentrated toward the forward on-axis direction. This characteristic is entirely in keeping with the special nature of a "linear phase" speaker and is there, we are certain, by design. Pulses at 300 and 3,000 Hz are cleanly reproduced; the 3,000-Hz pulse response in particular implies excellent synchronization of the woofer and tweeter near crossover.
For listening, we positioned the speakers with their backs against the wall, several feet away from the corners.
(It is probably wise to avoid placing the speaker so that the distance from the woofer to the floor or the vent to the floor is equal to or a low sub-multiple of the distance from the woofer to the side wall or the vent to the side wall.) The sound of the Technics is crisp and clear, with a rather etched-out definition of the high end. The bass end is solid and tight-and capable of reproducing orchestral fundamentals with authority. While we found no style of music in which the SB-6000A seems notably weak, the symphony orchestra is its natural habitat. Strings, winds, and percussion are convincingly reproduced, and none is favored at the expense of others.
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And what of the "linear phase" (which is better called uniform time delay)? As we have found with other models designed for this characteristic, the principal subjective effect is an enhancement of the front image--including its apparent depth--at the expense of hall ambience, but we hear it more in the Technics than we have heard it else where. The sound is very pleasant, for our tastes especially so when the recording contains a large amount of reverberation. With a "drier" recording the sound becomes highly analytic, which should be very enjoyable for a listener seeking the perspective of the podium.
Like any loudspeaker, the SB-6000A has properties that must be evaluated by personal audition. One of these is its (relatively mild) coloration. Another, which is more striking, is its partiality to the front image. There is also the fact that the listening position is rather restricted-which is really a trace-off for the accurate time response. But if being close to the music is important to you, this is a speaker that certainly can put you there.
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In this issue, HIGH FIDELITY is introducing a new format for loudspeaker frequency response curves.
Readers familiar with the speaker graphs that formerly (until about a year ago) appeared in our re ports will notice several differences-all calculated, in our present format, to forestall the questionable assumptions that we found readers might make on the basis of the old graphs. The curves are identified as "anechoic," meaning that they reflect the behavior of the speaker in a totally nonreflective environment. The bass end of the curves stops at 63 Hz, which is about as far down as we can be reasonably confident of data taken in a chamber of the dimensions used at CBS. And response below 500 Hz in a real listening room will, as the graph suggests, vary from the anechoic response--perhaps drastically, depending on the size and shape of the room, its furnishings, and the position of the speaker. We will continue to discuss considerations such as these in the texts of our reports.
Also new is an improved measuring technique for distortion-which allows us to characterize it at all significant frequencies in the loudspeaker pass band-and a revised form of efficiency (sensitivity) data; see "In the Loudspeaker Testing Lab" in this issue.
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Preparation supervised by Robert Long, Harold A. Rodgers, and Edward J. Foster Laboratory data (unless otherwise noted) supplied by CBS Technology Center
REPORT POLICY:
Equipment reports are based on laboratory measurements and controlled listening tests. Unless otherwise noted. test data and measurements are obtained by CBS Technology Center, Stamford, Connecticut, a division of Columbia Broad casting System, Inc., one of the nation's leading research organizations. The choice of equipment to be tested rests with the editors of HIGH FIDELITY Manufacturers are not permitted to read reports In advance of publication, and no report, or portion thereof, may be reproduced for any purpose or in any form without written permission of the publisher. All reports should be construed as applying to the specific samples tested, neither HIGH FIDELITY nor CBS Technology Center assumes responsibility for product performance or quality.
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(High Fidelity, Oct. 1977)
Also see:
KLH Model 35 speaker (Equip. Profile, Oct. 1977)