SV Sound PB13-Ultra powered subwoofer

With the popularity of home-theater systems, subwoofers have proliferated. Because multichannel AV receivers are designed to provide a properly filtered, line-level subwoofer, or low-frequency effects (LFE) signal, many subs no longer come with built-in high- and low-pass filters for insertion into two-channel audio systems. However, the PB13-Ultra subwoofer from SV Sound does include these, which is what piqued my interest in it. After Ed Mullen, SV Sound's director of sales, assured me that the PB13-Ultra was capable of reproducing solid 20Hz organ-pedal notes in my listening room, I asked for one to review.

Description
The SV Sound PB13-Ultra ($1599) is the largest, heaviest subwoofer I've reviewed since the 205 lb REL Studio III (Stereophile, October 2004, Vol.27 No.10). Even so, it's 6" narrower, 4" shorter, 5" deeper, and 50 lbs lighter than the Studio III. Its single front-firing, 13.5" woofer—with 3" voice-coil and 2" peak–peak excursion—and three ports, are all mounted on the front panel. The cabinet is built of marine-grade laminated plywood; the ports are formed by tubes of polymer-wrapped compressed wood pulp.

The PB13-Ultra's 750W RMS amplifier is a Bridged Amplifier Switch Hybrid (BASH) design mounted on the inner surface of the metal service panel on the rear. It combines a fast-responding power converter with a low-distortion, class-AB amplifier claimed to be as efficient as a class-D design. The PB13-Ultra's Autostart function allows it to switch itself on only when a signal appears at its input terminals.

The PB13-Ultra is one of the most versatile subwoofers I've reviewed. Three foam plugs can be inserted into the ports to physically modify the frequency response, while the rear panel is crowded with controls for electrically tuning the frequency response. I had to slide the sub pretty far out from the wall in order to read the microscopic white lettering that identifies the various controls and jacks. Moving from left to right along the top row are: RCA input and output jacks for single-ended interconnect cables; an Auto On power switch; Phase (0–180°), Gain; low-pass filter; and RCA Hi Pass (for the RCA input only). Below this row are: the Room Comp and Subsonic filters and the Parametric EQ, with Freq, Level, and Q rotary controls. Below these are XLR jacks for the Balanced Inputs and Balanced Outputs (with an XLR Hi Pass On/Off toggle); and at the bottom of the panel are the Power On switch and an IEC jack for the detachable power cord.

A small cardboard tag attached to the Gain control warned that the plug and Subsonic Filter options must be set together: when all ports are open, the filter must be set to 20Hz; when one port is plugged, the filter must be set to 15Hz; with two ports plugged, the filter is set to 10Hz; and with all three ports plugged, the filter is set to its Sealed position.

Via a rotary control, the low-pass filter's corner frequency is continuously adjustable from 40 to 120Hz. A high-pass filter for attenuating the main speakers' bass response rolls off at 12dB/octave below 80Hz. The Room Comp control's four positions—Sml, Med, Lrg, Off—progressively roll off the PB13-Ultra's extremely deep bass response below 20Hz. The built-in parametric equalizer is used to trim the sub's output to counteract the room's largest natural bass peak. Similar parametric EQs are built into JL Audio's Fathom f113 and Revel's SUB30 (discontinued) subwoofers.

My review sample was finished in sturdy, utilitarian Fine Textured Black—optimal for me, who had to lug the 155-lb sub up a flight of stairs, unpack it, then repack it. Despite the PB13-Ultra's relatively low price, its hardware and its fit'n'finish are rugged.

Setup
I slid the 155-lb PB13-Ultra into the corner behind and to the right of my right-channel Quad ESL-989 full-range electrostatic speaker. The Quads were 5' from the front wall, 3.5' from the sidewalls, 5' apart, slightly toed-in, and 8' from my listening chair.

The PB13-Ultra's 23-page manual recommends using the Avia II: Guide to Home Theater test DVD (Ovation B19485, $44) to generate multiple test tones from 20 to 200Hz, but does not include it in the purchase price. Avia II is available from SV Sound's website, however, together with a RadioShack 33-2050 Analog sound-level meter, for a total of $80. Because Avia II requires a digital A/V receiver and a video display, I decided to instead use my Velodyne DD-18 subwoofer's built-in signal generator, microphone, and virtual spectrum analyzer (see review in June 2004, Vol.27 No.6). It sure was helpful.

I perched the Velodyne's calibration microphone on the back of my listening chair, 37" from the floor—my seated ear level—and turned the DD-18's volume control fully off so that it would not output any audio signal of its own. I then keyed the Velodyne's remote control to display the DD-18's System Response screen on my TV. This automatically triggered the DD-18's signal generator to emit an audible 20–200Hz sweep tone that it repeated every three seconds, and fed into my stereo system through a line-level input of my Mark Levinson ML-7 preamplifier.

I drove the ESL-989s alone without the PB13-Ultra and watched the spectrum analyzer display. The Quads' in-room low-frequency response (fig.1) showed a dip at 60Hz and peaks at 70 and 40Hz, the response falling off 10dB by 35Hz.

Fig.1 In-room response of Quad ESL-989s, no subwoofer (25dB vertical range, 20–200Hz horizontal range).

Next, I electrically inserted the PB13-Ultra into my system by running a pair of single-ended RCA interconnects from the ML-7 preamplifier's main outputs to the PB13-Ultra's right and left RCA inputs, and then running balanced interconnects from the PB13-Ultra's right and left XLR outputs to the XLR inputs of my Mark Levinson No.334 power amp. I tested the SVS sub only in its default 20Hz mode, with no foam plugs inserted.

Next was phase optimization. Playing "Cosmos, Old Friend," from James Horner's music for the film Sneakers (CD, Columbia CK 53146), I rotated the PB13-Ultra's Phase control to 0°, then 90°, then 180°. From my listening seat, I could easily hear that the 0° setting produced the loudest, best-defined drum beat.

I then matched the PB13-Ultra's output level to that of the Quads by watching the readout of the Velodyne sweep signal on my TV. This required setting the sub's Gain control almost to its Min position. The resulting sweep curve (fig.2) was remarkable: almost flat from 100 down to 20Hz. Then, using the Stereophile Test CD (Stereophile STPH002-2), I checked to see that the channel and phase of each hookup arrangement was correct.

Fig.2 In-room response of Quad ESL-989s with SV Sound PB13-Ultra (25dB vertical range, 20–200Hz horizontal range).

Company Info
SV Sound
6420 Belmont Avenue
Girard, OH 44420
(703) 845-1472
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