RTR Model PS/1 Pyramid "full-range satellite" loudspeaker system plus Model DAC/1 Rhombus floor-standing subwoofer, both in walnut-veneer enclosures. PS/1 dimensions: 12 1/4 (max.) by 22 inches (frond 8 inches deep. DAC/1 dimensions: 29 by 28 inches (top), 21 1/4 inches high.
Price: PS/1, $325; optional stands for PS/1, $29.95 per pair; DAC/1, $575.
Warranty: "limited," five years parts and labor.
Manufacturer:
RTR Industries, Inc., 8116 Deering Ave., Canoga Park, Ca. 91304.
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When we decided to place special emphasis on subwoofers for this issue, we looked for one system in which subwoofers and satellites, though sold separately, had been engineered for each other, to be used on a mix-or-match basis. There are several candidates, but none is more impressive in terms of total system flexibility-or of sheer size-than the RTR combination reviewed here. The Pyramid satellites are three-way full-range systems in that they will deliver reasonable bass all by themselves, but they include a defeatable high-pass crossover filter at 120 Hz for use when the range below is to be handled by a subwoofer. The matching Rhombus subwoofer, which RTR recommends be used in pairs (one per channel), includes a complementary low-pass crossover filter (also defeatable, a downward-firing 12-inch driver, and a pair of 15-inch mass-loaded passive radiators behind the grilles on opposite sides of the massive "coffee table" enclosure.
The first question raised by the design, therefore, is whether you will have enough room for it-even if you ignore RTR's advice and use a single subwoofer. In the larger-than-average room in which our listening was conducted, we felt distinctly cramped. Better planning to allow for the system doubtless would have helped, though the sizes and shapes still would have been at odds with the room's traditional decor. Big, open, modern spaces should accommodate the ensemble much more comfortably.
The second question involves system configuration. Assuming that you will be using both the satellites and the subwoofers, you can biamp them either via an electronic crossover (with the built-in filters defeated) or with their own passive crossover. Or you can parallel the two units in each channel (with filters on) from a single stereo amp. Or you can choose biamping with a stereo amp driving the satellites and a mono amp driving a single subwoofer (with either an electronic crossover or the built-in filters). You can buy the Pyramids first and use them as full-range systems until the bank account has recharged, and then buy either the Rhombus(es) or another sub-woofer; a different subwoofer may match the Pyramids' 120-Hz filter, or they may be better matched via an electronic crossover. If you already have small speakers in want of downward response extension, one or two Rhombuses (with or without electronic crossover) may be the answer. Obviously we could not try all of these permutations; while we investigated some, the major thrust of the testing (both at the lab and in listening) was on biamping a pair of Pyramids plus a pair of Rhombuses, using the built-in filters, and on the potential of the individual units.
Let's begin (as piecemeal buyers will) with the satellites. With their tweeter controls at the full-open ("flat") setting, they sound the way you might expect from the omnidirectional anechoic response curve: flat within a very few dB over most of the range-say, 100 Hz to 10 kHz-with just a hint of roughness in the lower treble (actually the province of the midrange driver and the upper end of the woofer, around the 1.5-kHz crossover between them). Reducing the tweeter controls produces a more "old-fashioned" high-end rolloff without going to extremes, even with the control all the way down. The sound seems clean, if somewhat etched-due, perhaps, to the fact that at listening levels the "nastier" third harmonic predominates over the second (which is generally below 1/2 %), as measured in the CBS distortion tests. Even the third harmonic is well controlled, however; it is below 1% at almost all points across the frequency range and increases only negligibly in the high-power test, where the second harmonic rises to about 2% throughout the midrange and at around 3-5 kHz in the treble. The 3-kHz pulse, as photographed on an oscilloscope, shows slightly more overhang and reflections than average. Depending on the program material, the bass is quite respectable, though it begins rolling off before about 80 Hz and should not be expected to deliver full deep-bass underpinnings in big-orchestra or organ music.
The Rhombus appears to deliver astonishingly flat response in this range in the CBS chamber, and it readily lets you know whether your recordings contain cleanly captured low fundamentals. (As with other subwoofers, it seems to do little with much program material simply because it is given little to do.) Actually, it is rated to 16 Hz, with a sharp cutoff below. The CBS chamber (which, of course, is not rated for quantitative analysis to anything like this extreme) shows response as holding up well to at least 25 Hz and confirms the steep cutoff to prevent reproduction of warp information. Second harmonic distortion is fairly well controlled-at both power levels in the CBS tests-around the crossover range (say, 60 to 1 50 Hz), though it does reach the neighborhood of 5% both above and below this. But the third harmonic content generally stays below 1% and is surprisingly low in the ultra-bass, particularly in the 0d8W (normal listening level) test.
The Rhombus does not confine its activity to its chosen range; with the built-in filter off, the greatest output is at around 400 Hz. The filter's gentle slope (6 dB per octave, according to RTR; the figure is difficult to assess from the measurements) shaves something between 6 and 9 dB off this peak and provides a good match to the Pyramids used with their filter. With other satellites, it might be necessary to go for an electronic crossover with sharper slopes to get a good match with the Rhombus.
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New Measurement Standards: In making comparisons between current reports and those published in the past, readers are cautioned to pay particular attention to the reference levels and similar test criteria cited. S/N ratios for electronics, in particular, are measured very differently now that we have adopted salient features of the new IHF amplifier-measurement standard. While we believe that the new technique (which also implies a saner approach to loading of all inputs and outputs) will result in measurements that more perfectly reflect audible, in-use effects, they cannot be compared directly to the numbers resulting from the former, more conventional lab measurements.
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RTR gives a 6-ohm impedance rating for both units. At the high end, the Rhombus appears to deliver a purely resistive load of about 5 ohms, but both it and the Pyramid drop to below 4 ohms at some frequencies. Since the Rhombus impedance curve is extremely flat and the Pyramid's bass-resonance impedance peak falls (at 70 Hz) well below the filter bandpass, a value of 4 ohms for the entire system might be more representative.
The sound of the ensemble, set up as RTR recommends, is truly impressive.
If you're paying this kind of money, we would advise that you spring for the extra cost of biamping as well and consider using an electronic crossover. (This last refinement will, in our opinion, net only subtle improvement over the built-in filters.) The Pyramids, taken alone, are not likely to impress buyers willing to spend more than S300 apiece; many other speakers in this price range will Co a better job without the subwoofers--though, of course, they may not integrate nearly as well with the Rhombuses, if that is the ultimate objective. The Rhombus itself-whether used singly or in pairs, and whether or not it is mated to the Pyramids-is a superb subwoofer in its deep response, reasonably high efficiency (for easy matching to non-RTR satellites), and sharp infrasonic cutoff. It's bulky, and it's not cheap, but who ever said a good subwoofer had to be otherwise?
(High Fidelity, Oct. 1979)
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