Subwoofer Reviews

Subwoofer technology is moving fast, with automated room equalization and system integration now a reality. A wave of new products has appeared in the past five years, all using different approaches to solving the problems of optimizing subwoofer response in listening rooms.

Subwoofers—including the Digital Drive 18+'s predecessor, the DD-18, and the Revel Ultima SUB-30—first tackled the problem of room optimization by displaying the room response on a PC and having the user adjust virtual sliders. More recently, JL Audio's Fathom f113 and Fathom f212, removed the user from the setup process: JLA's automatically self-adjusting firmware routines used calibration microphones, internal signal generators, and processors to optimize these subs' frequency response for a single room node, with no graphic display or user input. A further step forward was provided by Bowers & Wilkins's DB1 subwoofer, which required the listener to take a series of eight measurements, after which the sub automatically calculated, equalized, and graphed the result.

Velodyne's DD-18+ now takes the technology a step further with the addition of automated room compensation. While the sub's internal circuitry can adjust automatically, it also offers manually adjusted, menu-driven equalization that graphs any room-response changes in the DD-18+'s output on a computer screen in real time. Offered the chance to review Velodyne's newest 18" subwoofer with these features, I jumped at the chance.

Description
While there's a strong family resemblance between the DD-18+ ($5799) and its predecessor, the DD-18 ($4799), which I reviewed in the June 2004 issue, the DD-18+ visually dominates when the two are placed side by side. This is because the DD-18+ is 6.5" deeper, 19 lbs heavier, and has 28% more internal volume. It also features strongly tapered sides, 1"-thick walls of MDF, a large internal window brace to which the single drive-unit's motor is affixed with large bolts, and ¾"-thick bracing panels to minimize vibrations. These improvements are said to permit the DD-18+ to play 4.5–6dB louder than the DD-18, with lower distortion.

The magnet alone of the DD-18+'s 18" drive-unit weighs 39.7 lbs. The driver features a 3" diameter, six-layer, custom-wound voice-coil and improved heat dissipation. The cone is made of a fiberglass-over-Rohacell foam composite that's stiffer, lighter, and stronger than the heavy paper of the DD-18's cone. The large surround helps the cone handle the long excursions needed to reproduce potent bass transients. The driver is capable of 1.3" excursion—greater than with previous Velodyne subs.

The sub's 1250W RMS, class-D amplifier, while rated at the same power as the DD-18's amplifier, is claimed to be more efficient owing to Velodyne's proprietary energy-recovery system. Not only does the DD18+'s DSP circuitry enable the automated equalization, it also controls drive-unit distortion, using a servo-loop accelerometer, which takes 3000 measurements per second—far more than the analog device in the DD-18, which measured only 16 times per second.

My review sample was finished in a stunning veneer of Black Gloss Ebony. Each DD-18+ is shipped with four metal spikes/glides that screw into the cabinet bottom and are secured with metal locking rings set off by felt washers, so as not to scratch the finish. The hardware and connections are sturdy, easily accessible, and should last a lifetime.

Controls
The DD-18+ has a seemingly endless number of connections and user options. It can be adjusted with its three front- and three rear-panel controls, with the 34 buttons on its remote control, and with a large number of virtual controls displayed on the two screens of its Windows setup program. These include a Frequency Response and Parameter Screen (7 parameter settings, 4 parametric filter settings, 3 EQ Optimization Selection and Initiation options), and a Preset Screen (10 settings for each of 5 presets). The Digital Drive Windows Setup Program User Interface is detailed in a separate 38-page booklet, the most comprehensive subwoofer manual I've seen; it provided excellent help.

The DD-18+'s remote manages many functions on its own, as listed in the main owner's manual, provided on CD-ROM. Once the power switch on the DD-18+'s rear panel has been turned on, the remote's Power button toggles the sub between active and standby modes. Other buttons are assigned to listening functions (Volume, Night mode, Presets), turning on and off the sub's front-panel LCD display (hidden behind the grille), and optimization controls for Auto EQ and for EQ setup using a TV screen. The last include six audio presets, each with a contour EQ frequency boost and default volume level (Theater, Rock, Jazz, Custom, Games, and None, which removes all equalization). Presets 1, 2, and 3 are set at the factory and can't be changed, while preset 4 can be adjusted by the user. The Night mode lowers the DD-18+'s volume to 30% of the default mode. The Light control toggles on and off the DD-18+'s LED display, which shows the volume and status of the Auto EQ process.

Hidden along with the display under the DD-18+'s grille are some important controls. From left to right are a USB jack for connecting to your computer to run the EQ software, a mini-XLR jack for the calibration microphone, an IR port for remote-control signals, knobs for volume and crossover frequency, and an Auto EQ button. The LCD display is visible through the grille.

On the rear panel are the on/off switch, and input connectors for mono RCA and XLR inputs for the low-frequency effects (LFE) channel from an A/V processor; stereo RCA and XLR inputs from a stereo preamplifier's auxiliary main outputs; a mini-jack for a trigger on/off signal; and an IEC inlet for the detachable power cord.

Turning on the DD-18+'s main power switch puts it in Standby until it detects an audio signal. The sub's amplifier is then turned on and its DSP processor booted up. In the 12V trigger mode, the DD-18+ won't respond to the remote's power-on button until the 12V trigger is activated. Additionally, the DD-18+ will respond to run-time commands via its serial port from control systems such as those made by Crestron.

My review sample had a minor glitch. Its rear panel offered six socket-type (input style) XLR chassis connections both for its two balanced inputs and its four balanced outputs. Unlike RCA single-ended interconnects, balanced XLR interconnects have different connectors at each end. Because chassis-mounted XLR jacks conventionally use pin-type jacks for output and sockets for input, balanced cables can be hooked up in only one direction. making it impossible for me to use the DD18+'s balanced inputs.

I notified Velodyne of this problem, and they immediately shipped me XLR adapters that converted the four XLR sockets labeled Output to the proper pin-type XLRs. They assured me that this problem was corrected for the DD-18+'s second production run.

Velodyne's Digital Drive Plus Software Program Automates Integration The DD-18+'s Digital Drive Plus equalization and room-optimization software is compatible with the Windows XP and 7 operating systems. It can be run in three different modes—Self EQ, Auto EQ, or Manual EQ—all selected via Windows Interface Setup Software on the owner's PC (see Sidebar "Velodyne's Windows Setup Program for the DD-18+"). One of the room-optimization routines is run during installation. Alternatively, the user can calibrate and fine-tune the DD-18+'s response by connecting it to a TV screen and using the Velodyne's remote pointed at the subwoofer. The sub's front-panel display will give further information.

Setup
The DD-18+ was shipped in a large, double carton strapped to a pallet, weighing 178 lbs in all. I pushed the box up a short flight of stairs, unpacked the DD-18+, then slid the sub into my room's right front corner until it was about 8" from the sidewall, behind my Quad ESL-989 main speakers, firing into the room. This placed the sub about 10' from my listening position. My experience of other subwoofers has led me to conclude that this is the best position in my room.