The Paradigm Signature SUB 25 is the biggest, baddest subwoofer in Paradigm's extensive product line-up. I recently reviewed Paradigm's Studio speakers with their Studio SUB 15 subwoofer. The Signature SUB 25 is outwardly similar to the Studio SUB 15, but at $3,999, it retails for $1,200 more. Needless to say, I was very curious to see if the SUB 25's $1,200 premium over the already impressive Studio SUB 15 would be worth it. For this review, I used the Paradigm's optional Perfect Bass Kit, priced at $299, which provides equalization for the subwoofer.

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The Signature SUB 25 utilizes a sealed box with a single 15-inch driver. The construction quality is first-rate and the glossy piano-black finish on my review sample was free from any blemishes or waviness. Finish quality was furniture-grade and I would suspect that the other finish options, cherry and natural maple, are equally well-executed.

The Signature SUB 25 is a large subwoofer, measuring 20 inches high by 18 inches wide by 21 inches deep and weighs a hefty 114 pounds. Despite its large size, the Signature SUB 25 is not as visually imposing as its dimensions may imply. The side panels gently curve as your eye travels towards the back of the SUB 25, giving the whole sub a very chic, almost triangular shape. The entire unit rests on outrigger feet with adjustable spikes. For placements on hard floor surfaces, spike covers are installed. The black cloth grille is non-removable, "due to the incredibly high power and tremendous output," according to the Paradigm website. I would surmise the real reason is to prevent buzzes and rattles. Underneath the non-removable grille is a 15-inch RCR mineral-filled co-polymer polypropylene cone. The driver features a three-inch, eight-layer voice coil, surrounded by large aluminum shorting rings and a massive 30-pound ceramic/ferrite magnet assembly to minimize distortion and increase linear power application. The subwoofer is powered by an internal 3,000-watt RMS, 7,500-watt peak, Ultra-Class-D amplifier. I found these numbers to be a bit high for believability, even if you use the supplied 15-amp power cord on a dedicated circuit. According to Paradigm, the amplifier uses their Power Factor Correction circuitry to obtain this amount of power from the AC available from the outlet. I am still a bit skeptical about the actual power ratings, but the subwoofer never seemed to run short on power.

The SUB 25's back panel is a piece of this beveled aluminum with a satin finish. The fit and finish is what I expect to find on the front of an expensive piece of stereo equipment, not hidden on the back of a speaker. The panel has three knobs across the top for phase, level and crossover frequency. Below the well-finished heat sink fins are a standard IEC power port, USB port, 12-volt trigger input, a toggle switch to choose between powering the subwoofer on via the 12-volt signal or auto-signal sensing, a single XLR input and a pair of single-ended inputs. The USB port can be used for firmware updates, as well as with Paradigm's Perfect Bass Kit room correction system.

The Hookup
I hooked up the Paradigm Signature SUB 25 to both my current reference theater system, which I recently used with my review of the new Paradigm Studio line, and to my two-channel system. The speakers I used with the Signature SUB 25 included full-range speakers, including MartinLogan Summits and Acoustic Zen Adagios. I also used Dynaudio's Contour 1.4s, which are bookshelf-sized speakers with limited lower-end extension.

I experimented with the positioning of the subwoofer, as even slight changes in position can make a huge difference. Placement was determined by the tried and true method of placing the subwoofer in the listening position and crawling around the room to find the best bass response. I ended up with the subwoofer about six inches out from the front wall, just to the right of the center channel speaker stand. While most of my listening was done with just the one SUB 25, I still had the Studio 15 in the house and did some listening with both subwoofers.

Paradigm's Perfect Bass Kit is sold separately for $299 and is derived from Anthem's room correction system, which is included with the newest version of their highly regarded D2v processor. The Perfect Bass Kit comes with a microphone, heavy-duty stand, software and two USB cables. The software comes with a file that is programmed for your specific subwoofer's response and runs on your Windows-based computer. In order to use the kit with any other compatible subwoofer, you simply need a USB input. The subwoofer and microphone are hooked up to your computer, which then generates and measures a series of test tones. The subwoofer's output is measured in five locations. The average measured response curve is displayed on the computer screen, as well as the target and theoretical corrected response curves. The appropriate equalization is then applied to the subwoofer.

Performance
Most buyers of this subwoofer are likely to install it in a multi-channel theater system. Accordingly, most of my listening was done with the Signature SUB 25 in my theater system.

As I watched Transporter 3 (Lionsgate Home Entertainment, Blu-ray), the SUB 25 had plenty of opportunity to flex its muscle. The movie is filled with lots of high-energy action and LFE channel activity. The SUB 25 had no problems coupling with and energizing my 12-by-17-foot room. Bass extension was deep and powerful, providing tactile as well as aural sensations. As I had not previously seen this movie, I did not have a reference point for the quality of the bass, but it sounded pretty good, as it was well-controlled, without any boominess. I'll note that I configured the subwoofer to turn on upon sensing a signal and that it worked quickly and quietly, without any thumps or other unpleasant noises.

I then loaded up a movie I have listened to over a few systems, Iron Man (Paramount Home Entertainment, Blu-ray). This soundtrack has lots of deep bass in connection with a variety of explosions and special effects. The continuity of the bass was extremely good between my full-sized main speakers and the SUB 25. I expected a very noticeable change in the character of the bass between both my electrostatic and small Dynaudio speakers and the SUB 25. Surprisingly, despite the large 15-inch cone, the continuity of bass was nearly as good as with the best 10-inch driver subwoofers. I ran the SUB 25 up as high as 70 Hz without any thickening or slowing. Despite the relatively high crossover point for a 15-inch driver, it kept up nicely with the Dynaudio's seven-inch woofer.

I then watched Pearl Harbor (Buena Vista Home Entertainment, Blu-ray), another action movie with lots of low-frequency energy. The attack scene is filled with numerous explosions and gunshots that gave the SUB 25 a real workout. The explosions as reproduced by the SUB 25 reached low, shaking my theater chairs and causing buzzes and rattles in my theater room that I had not previously heard. The firing of the heavy machine guns produced bass that was not as deep as the explosions but much sharper and more defined in character. The SUB 25 was fast on the attack producing a sharp, detailed and powerful staccato burst. The individual bursts were like sharp quick slaps, as opposed to the sensation of being picked up and moved with the larger explosions. Throughout all of my multi-channel listening, the SUB 25 was able to easily anchor the soundstage with a very solid and deep foundation.

After watching a few movies, I knew that Paradigm's Signature SUB 25 was extremely powerful and capable of reaching down to the lowest octaves with significant power. I wanted to see if the SUB 25 could do so with enough finesse to fit into a first-class music system. I eased into music with an album I recently used in my evaluation of the Paradigm Studio system, the Eagles' Hell Freezes Over (DTS, DVD). I felt that the SUB 25 bested the Studio 15 being slightly tighter and deeper on the drums on "Hotel California." The impact of the drums had more snap with the SUB 25. The drums on this album are well-recorded, with solid impacts and a detailed decay note. The biggest difference was that, on the decay notes, the Studio 15 did okay, but the SUB 25 was much more natural and lifelike, with a longer decay. They both started out the same, but the SUB 25 was able to resolve more detail. This was also noticeable with the bass notes on "Life in the Fast Lane." The SUB 25 revealed more of the texture of the strings than had any other 12- or 15-inch driver subwoofer I can recall.

I then moved the subwoofer to my two-channel system. The SUB 25 does not have a high-pass output, so if your speakers bottom out on lower frequencies, adding the SUB 25 will not increase dynamic range, as your speakers will still bottom out unless you have some sort of bass control options in your preamplifier. However, if your speakers simply run out of steam on the low end, the SUB 25 will help. I did my two-channel listening with the Acoustic Zen Adagios. They don't reach down as low as the Summits do with their powered subwoofers, but I have never had them bottom out with low frequencies either. Adding the SUB 25 to these speakers filled out the bottom octave, which they could not do on their own. Those of you who are familiar with the Adagios know that they are quick and revealing speakers. Keeping this in mind, along with their strong bass performance except at the very bottom end, I crossed the SUB 25 over right around 45 Hz, which provided a good blend between the Adagios and the SUB 25.

Holly Cole's "Train Song" from her album It Happened One Night (Blue Note) is well known among audiophiles for its acoustic bass. The SUB 25 fleshed out the bass lines nicely, enhancing the Adagios' low-end extension without slowing them down. When I added the SUB 25 to the system, the bass notes became deeper and more powerful, but did not lose any of the track's famed texture and detail.

Read more about the SUB 25's performance on Page 2.