|Paradigm Reference Seismic 12 Subwoofer|
|Home Theater Loudspeakers Subwoofers|
|Written by Christopher Zell, Ph.D.|
|Thursday, 01 July 2004|
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Paradigm Electronics Inc. has established a well-deserved reputation in the subwoofer market, particularly with their impressive and affordable Reference Servo-1. I have spent considerable time integrating and listening to numerous Servo-15s in a variety of systems and rooms over the last few years, and can verify that the Paradigm woofers are a real player in the field. However, Paradigm did not offer an option for those space or décor-challenged customers who desired a diminutive but powerful bona fide subwoofer. After four years of intensive research and development, Paradigm has answered this demand with their recently released entries into the ultra-small powered subwoofer arena, the Reference Seismic 10 and Reference Seismic 12. It was with a considerable amount of anticipation and high expectations that I received Paradigm’s larger model, the Reference Seismic 12 subwoofer ($1,699) a few months ago.
Subwoofers are often the hardest things to justify to the significant other of a home theater buff. The large, usually ugly boxes generally are not well received in the typical home theater room that often serves a dual purpose as a family or living area. With the advent of minimally-sized yet potent subwoofers, such as the Paradigm Seismic Series, this has become an easier sell in many cases, improving placement flexibility and therefore often ultimate performance. Despite having considerable experience with mini-sized subs, I am always amazed at how small and downright cute they can be. Maybe cute is not the right word after you strain to lift this dense, 67-pound unit, but the 14.75 inches high by 14.25 inches wide by 14.25 inches deep Seismic 12 is no exception, its size disguising the power and impact it can produce. Paradigm designed and manufactured the downward-firing, 12-inch driver, featuring a low-mass, high-stiffness cone, with greater than two inches of peak-to-peak excursion. The rugged, mineral-filled co-polymer polypropylene driver includes a number of innovations, including dual spiders, one linear and the other progressive, resonance controlled ribs to minimize unwanted distortions and a computer optimized magnet structure. The powerful Ultra-Class-D internal amplifier is rated at 1200 watts RMS from 20 to 150 Hertz, and 4500 watts peak. Bass response is extended to a reported 17 Hertz with the aid of dual 10-inch high-velocity passive radiators located on opposing cabinet sides.
Cosmetically, the Seismic series subwoofers are more than just a standard black cube. A blue, lighted Paradigm logo on the black front cabinet face provides a touch of class. The rounded top edges make for a gentler profile, blending nicely into the gloss black, inlaid top surface. The gently sloped outrigger feet, similar to those on the Studio 100, raise the downward-facing active driver slightly above the floor. Of course, the two passive radiators visible on each side face let you know that this is a subwoofer and not a piece of furniture, but the overall look is attractive.
The rear of the cabinet contains all inputs and control facilities. An IEC power cord jack and amplifier power controls are located to the left. The Seismic 12 can be switched on and off manually, automatically turned on and off based on the presence of an input signal, or controlled by an external trigger. The upper middle section of the back panel contains two low-level, mono-only inputs, one RCA jack for standard single-ended inputs, and an XLR jack for balanced signals. Four continuously variable dials located on the right of the back panel control subwoofer level, cut-off frequency (35 to 150 Hertz), phase alignment (0 to 180 degrees), and bass contour boost (0 to +6dB at 60 Hertz). A very nice touch is the handy frequency response illustrations and accompanying text next to each dial, depicting and explaining the purpose of the particular control. This is very useful for those who may be a bit confused about exactly what each control does, and also allows easier dial identification when the sub is in its final, possibly inconvenient position. There are a couple of omissions concerning the functionality of the Seismic 12, including the absence of a switch defeating the low pass filter. If the bass management system of your processor or receiver is utilized, then ideally you do not want a low-pass filter at all in the subwoofer itself. As is unfortunately the case with many current subwoofers, the best you can do is to set the crossover frequency as high as possible. Even with the Seismic 12’s cut-off set to the maximum 150 Hertz, there still will be some interaction with the processor crossover, which is typically set at 80 Hertz per THX recommendations. Additionally, the Seismic 12 does not contain a high-pass filter for your main loudspeakers. If this is necessary, Paradigm recommends one of their X-series crossover controllers for integrating this subwoofer with your main loudspeakers. The X-series controllers also work well for summing the bass from a stereo preamplifier output into a mono subwoofer signal. This is not normally needed for home theater usage, since your processor or receiver’s bass management system normally provides preamp level, high-pass loudspeaker outputs, and also an appropriate mono subwoofer output signal.
An obvious consideration when you own a set of full-range main left and right loudspeakers in a home theater is whether or not a subwoofer is really necessary. In my mind, the answer is yes for several reasons. First, when optimizing the location of your left and right mains, qualities such as imaging, clarity and balance across the midrange and treble are paramount. A location that maximizes these properties is almost never the optimal location with respect to low bass response (less than 80 to 100 Hertz) and balance across seating locations. A separate subwoofer can be placed where it produces the flattest frequency response across the widest range of listening positions. What better way to achieve this than to have a small subwoofer, such as the Paradigm Seismic 12, that can be located in a multitude of relatively inconspicuous positions, yet still deliver low-end power and flat frequency response. Second, there are advantages to relieving the main loudspeakers and amplifiers of the lowest bass, alleviating the need for additional power and minimizing low-frequency driver excursion. Additionally, unless the main loudspeakers have a true subwoofer that is crossed over under 100 Hertz or so, removing large low-end bass driver excursions allows it to act more in its linear range and minimizes some Doppler distortion that may otherwise occur. I do not believe that this means full-range mains are undesirable for a high-end home theater. Having the option of turning the subwoofer off and running the mains as “large” for two-channel music is appealing for reasons of maximum integration and purity. Also, although the mains will most likely be cut off at 60 to 80 Hertz by the home theater processor’s bass management system, this does not mean that all frequencies below that are eliminated. On the contrary, it is important to remember that crossovers are generally not infinitely steep, and that a significant amount of signal energy is still present in the mains more than an octave below the cutoff frequency, albeit at reduced levels.
It is far easier to get a full and synergistic meld of a subwoofer and main loudspeakers when the bass response is devoid of large frequency peaks and nulls. Nulls, which are normally caused by cancellations, can make the bass sound non-integrated, non-continuous and sometimes anemic. Conversely, if there are large resonant peaks, they stick out like a sore thumb, giving you the illusion of one-note bass. Balancing the peak level with the rest of the system will come at the expense of reduced output for the majority of the bass range, thereby losing all of the power and visceral impact that you were craving before you got the sub. Despite the temptation that most of us must battle when we first get a sub, to rattle our windows and crack the foundation, what you ultimately want is integrated bass that does not sound like a separate source, but instead adds power and impact, yet remains musical.
As a prerequisite, you’ll want to adjust the subwoofer distance/delay setting in your preamp set-up before adjusting the Seismic 12’s controls. The output near the crossover frequency will be strongly affected by this delay setting, since both the subwoofer and the main loudspeakers contribute equally at that point. In my Revel Ultima Salon and Voice-based reference home theater system, I first placed the Seismic 12 in a proven subwoofer location, between the Salons, and behind the Voice center channel. While listening to 20 to 100 Hertz bass sweep signals, I moved the subwoofer around slightly until the response seemed the flattest. After my initial adjustments, I used my trusty Radio Shack SPL meter, calibrated to adjust for its inherent low frequency roll-off, to have a quick look at frequency extension and consistency. There was a noticeable but acceptable peak around 45 Hertz that is likely caused by a room-length resonance. In my environment, the Seismic 12 was solid until near 20 Hertz, with some useable output below that point.
As a final set-up note, I was impressed with the wealth of useful information contained in the short but concise owner’s manual, which walks you step-by-step through the set-up and calibration of your subwoofer. Paradigm’s manual provides some useful tips on placing and setting the Seismic subwoofer controls, as well as information regarding the use of two subwoofers in a single room.