Brent has been a professional audio journalist since 1989, and has reviewed thousands of audio products over the years. He has served as editor-in-chief of Home Theater and Home Entertainment magazines, contributing technical editor for Sound & Vision magazine, senior editor of Video magazine, and reviews editor of Windows Sources magazine, and he also worked as marketing director for Dolby Laboratories. He's now on staff at Wirecutter.
Home theater enthusiasts get fussy about subwoofers. They sweat over a couple of Hz difference in frequency response, a couple of dB difference in maximum output, whether or not the sub is down-firing or front-firing, etc. Much of this has little real-world impact, especially considering that moving your listening chair two feet in any direction is likely to change the sound more. Sometimes, though, the little things do make a difference, as Outlaw Audio's new Ultra-X12 reminded me once again.
The $639 Ultra-X12 is the first new Outlaw subwoofer in more than half a decade. As company president Peter Tribeman told me, "Our existing subs are really good, but we've had them in our line for six or seven years. Technology has changed, and we wanted to create something new. We wanted to build a sub that was roughly the size of our LFM-1 Plus, which was popular because it's not too big, but we wanted to more or less match the performance of the big LFM-1 EX."
Technically, the biggest difference between the old designs and the Ultra-X12 is in the amplifier. The old amp was a 350-watt BASH amplifier. The new one is a 350-watt Class HD amplifier from Audera, a company founded by engineers who worked on the BASH amp. Both are high-efficiency topologies, designed to consume less power at idle than a traditional Class AB amplifier does. I've seen varying descriptions of the BASH technology, but it appears to have been a Class G or H device, with a power supply that tracks the incoming audio signal and adjusts its output to reduce the power delivered to the amp whenever possible. Audera's Class HD is a combination of Classés H and D -- the power supply tracks the incoming signal as in a Class H amp, but the amplifier itself is a high-efficiency Class D (also referred to as a switching or digital amp) design. I can't say if one is better than the other; my assumption is Class HD is more efficient than BASH but would emit more radio-frequency (RF) energy.
According to Tribeman, the most audible difference is due to a new design for the internal bracing that stiffens the enclosure. He told me that, when the company's engineers re-evaluated the original designs, they found a slight bump in the response around 60 to 65 Hz, which resulted in a sound they considered a little too fat. They traced the problem to inadequate internal bracing, which was allowing the side panels to resonate around those frequencies. The original Outlaw LFM-1 models had internal braces running in only one direction. The new Ultra-X12 has braces in a "window pane" pattern, running in both directions, a change Tribeman says flattened the mid-bass response considerably.
The basic design of the 66-pound Ultra-X12 is simple, straightforward, and muscular. The driver is a beefy, down-firing 12-incher. The ports are also down-firing. Two sound modes are offered: Max Extension and Max Output. The former lets the Ultra-X12 play a little deeper, while the latter lets it play a little louder.
The Ultra-X12 is, like most powerful subs, rather bulky. However, it's not as huge and decor-unfriendly as monster subs like the Hsu Research VTF-15H or the SVS PB13-Ultra. It fit easily into my listening room's "subwoofer sweet spot" against the wall under my projection screen between my center and front right speakers, which I've found works best with most subwoofers in my room. (Your room's subwoofer sweet spot is probably different.)
I used the Ultra-X12 with two preamp/processors: an Outlaw Model 975 and a Denon AVR-2809Ci receiver connected for line-level output. Both fed an AudioControl Savoy multichannel amp. I tried it with three of my tiny but mighty Sunfire CRM-2 speakers in front, with two CRM-2BIP surround speakers. I also used a pair of MartinLogan Motion 60XT tower speakers (review coming soon). With the former, the crossover point was set to 100 Hz; with the latter, to 80 Hz.
The pre/pros fed the Ultra-X12 through a line-level connection to its LFE input. There's also an LFE output that allows daisy-chaining a second subwoofer. Stereo RCA line-level inputs are included, as are speaker-level inputs and outputs, so it should be reasonably easy to interface the Ultra-X12 with almost any kind of system. The internal crossover is adjustable from 60 to 120 Hz, and there's a zero-/180-degree phase switch.
There's only one thing I disliked about setting up the Ultra-X12: the Max Extension mode requires stuffing the included foam plug into one of the ports, but it doesn't say this on the back of the sub, near the mode switch, as it does on, say, the Hsu VTF-15H. If you can't remember which mode requires one of the ports to be plugged, you'll have to go deep into the manual, on page 13, to find out. This is an especially problematic oversight because using the sub in Max Extension mode with both ports unplugged can damage the driver. Do as I did: write "PLUG 1 PORT" on a piece of painter's tape, and stick the tape below the Max Extension label underneath the switch. [Editor's note: Brent's review was completed before the subwoofer began shipping, and Outlaw has informed us that they have addressed this issue by printing the needed warning/instructions on a separate sheet that will be inserted in the manual.]
I'll start by stating that the Ultra-X12 should definitely be considered a high-performance subwoofer. Live Die Repeat: Edge of Tomorrow, the latest Tom Cruise post-apocalyptic action pic, opens with fragmentary snippets of sound, then introduces very loud bass tones starting at 100 Hz and reaching down to 29, 24, and 19 Hz. It's sort of like a reverse dog whistle, something than will be heard only by home theater enthusiasts who have really good subwoofers; people who use soundbars will likely never hear those lowest tones.
Not expecting such intense tones to appear in the first few seconds of the movie, I thought the subwoofer or something else in the system was malfunctioning. I played the VUDU HD stream of the movie again to make sure. (And again and again and again.) Yep, those tones were in the soundtrack, and the Ultra-X12 reproduced them cleanly and very loudly.
The Ultra-X12 was similarly unfazed by the deep sounds of submarine engines in the scene from U-571 where the sub dives under a German destroyer. It's here where I got the inspiration for my first paragraph, where I talked about little things in a subwoofer sometimes making a big difference. I didn't think I'd develop much preference for either the Max Extension or Max Output modes, but for movie soundtracks, the Max Output mode did a substantially better job. The depth charge explosions in U-571 had much more impact in Max Output mode. In Max Extension mode, the sub's punch decreased, its distortion increased a little, and the improvement in ultra-low-bass response seemed negligible. Thus, I left the Ultra-X12 in Max Output mode for almost all of my Blu-ray viewing and Internet video streaming through VUDU and Amazon.
For most of my listening, I kept the subwoofer properly balanced with the main speakers, but I also listened to Star Trek Into Darkness with the subwoofer's level raised +3 dB to see if I could push it past its limits. I was never able to push it into gross distortion, but in Max Extension mode, the notes started to lose their definition at extreme levels. In Max Output mode, the output seems adequate for anything but the biggest home theaters (say 4,000 cubic feet and larger).
However, for music listening, I preferred the Max Extension mode, which seemed to have a flatter response that blended better with the MartinLogan Motion 60XT tower speakers. For example, the bass line on Steely Dan's "Aja" sang along more smoothly in Max Extension mode, with a melodic groove that never called attention to itself with excessive punch or resonance. The notes in the bass line also seemed to stop faster instead of ringing subtly as they did in Max Output mode. Of course, your preference for these modes will vary with your room acoustics, whether or not you're using room correction such as Audyssey or Dirac Live, your listening material, and your personal taste. I'd suggest experimenting to see what you like; but, if doing audio comparisons isn't to your liking, just use Max Output if you listen mainly to movies and Max Extension if you listen mainly to music.
Click over to Page Two for more Performance, Measurements, The Downside, Comparison & Competition, and Conclusion...
The super-deep yet somewhat melodic synth bass line in Olive's "Falling" confirmed my choice. It sounds good in Max Output mode, but I always got the feeling I was listening to a subwoofer. In Max Extension mode, the system sounded more like an ideally set up pair of very large tower speakers. In this mode, the system simply rendered every bass note cleanly and evenly without distortion, instead of adding extra punch and unnatural dynamics -- something subwoofers often do, which is one reason many audiophiles shy away from them.
Of course, no subwoofer evaluation would be complete without an audition of the Saint-Säens "Organ Symphony" -- the famous recording from the Boston Audio Society Test CD, with pipe organ notes that drop down to 16 Hz. The Ultra-X12 had no problem reproducing the deep notes in either mode, but the response seemed smoother and more consistent from note to note in the Max Extension model. I found that, in either mode, the Ultra-X12 could easily shake my projector image during the lowest notes.
Here are the measurements for the Outlaw Ultra-X12 subwoofer. Click on the photo to view the chart in a larger window.
Max Extension: ±3.0 dB from 19 to 179 Hz
Max Output: ±3.0 dB from 21 to 173 Hz
Crossover low-pass roll-off
Maximum output (Max Output mode)
(1M peak) (2M RMS)
40-63 Hz avg 120.7 dB 111.7 dB
63 Hz 122.3 dB L 113.3 dB L
50 Hz 121.4 dB L 112.4 dB L
40 Hz 117.8 dB L 108.8 dB L
20-31.5 Hz avg 113.7 dB 104.7 dB
31.5 Hz 116.1 dB L 107.1 dB L
25 Hz 115.0 dB L 106.0 dB L
20 Hz 108.3 dB 99.3 dB
Maximum output (Max Extension mode)
(1M peak) (2M RMS)
40-63 Hz avg 119.2 dB 111.2 dB
63 Hz 120.8 dB L 111.8 dB L
50 Hz 120.2 dB L 111.2 dB L
40 Hz 115.8 dB L 106.8 dB L
20-31.5 Hz avg 111.4 dB 102.4 dB
31.5 Hz 112.9 dB 103.9 dB
25 Hz 111.5 dB 102.5 dB
20 Hz 109.3 dB 100.3 dB
The chart here shows the frequency response of the Ultra-X12 in Max Extension (blue trace) and Max Output (green trace) modes. The response is for the most part flat, with a broad but very mild rise between 60 and 130 Hz.
The CEA-2010A results for the Ultra-X12 are fairly similar to those of the closest competitor I've measured, the SVS PB-2000. In the low bass (40-63 Hz) region, the Ultra-X12 in Max Output mode has a +1dB edge, delivering 120.7 dB average output vs. 119.7 for the PB-2000. In the ultra low bass (20-31.5 Hz) range, the Ultra-X12 puts out -2.6 dB less than the PB-2000, achieving 113.7 dB average output vs. 116.3 dB for the PB-2000.
Here's how I did the measurements. I measured frequency response using an Audiomatica Clio FW 10 audio analyzer with the MIC-01 measurement microphone. I close-miked the woofer and ports; summed and scaled the port responses; then summed the combined port responses with the woofer response. Results were smoothed to 1/12th octave.
I did CEA-2010A measurements using an Earthworks M30 measurement microphone, an M-Audio Mobile Pre USB interface, and the CEA-2010 measurement software running on the Wavemetric Igor Pro scientific software package. I took these measurements at two meters peak output, then scaled them up to one-meter equivalent per CEA-2010A reporting requirements. The two sets of measurements I have presented here (CEA-2010A and traditional method) are functionally identical, but the traditional measurement employed by most audio websites and many manufacturers reports results at two-meter RMS equivalent, which is -9 dB lower than CEA-2010A. An L next to the result indicates that the output was dictated by the subwoofer's internal circuitry (i.e., limiter) and not by exceeding the CEA-2010A distortion thresholds. Averages are calculated in pascals.
I can't conjure a complaint worth noting about the Ultra-X12's sound, especially considering its affordable price. It'd be nice if there were some way you could switch between Max Output and Max Extension modes remotely -- especially if you're planning to install the Ultra-X12 in a cabinet or behind a fabric wall -- but I can't imagine how that might work, considering you have to physically insert or remove a foam plug to change modes.
Although the Ultra-X12 can shake the floor, it doesn't have the raw air-moving power of larger 15-inch models, or 12- or 13-inchers with more powerful amps and bigger enclosures. But all of those subs, to my knowledge, are larger and more expensive.
Comparison and Competition
To get a better handle on the Ultra-X12's performance, I compared it with my reference sub, an Hsu Research VTF-15H that costs $879 (plus $139 shipping, and soon to be replaced by the VTF-15H MK2). I used the Hsu in EQ2 mode with one port plugged, which gave me a sound roughly similar to that of the Ultra-X12 in Max Output mode.
The 15-inch driver and the much larger enclosure of the Hsu enabled it to shake my listening chair almost as if the driver were physically connected to it; it delivered a visceral experience that the smaller Ultra-X12 couldn't match, even though the Ultra-X12's maximum output measurements (see below) come pretty close to the Hsu's. I liked the way the Ultra-X12 really dug into electric bass lines, though, and the Ultra-X12 seemed to blend better with the MartinLogan Motion 60XTs, especially with the sub in Max Extension mode.
In terms of competition, the closest model in the SVS line is the 12-inch, $799 PB-2000. It's a great sub, with a few dB more output than the Ultra-X12 in the ultra low bass (20 - 31.5 Hz) range, but it doesn't offer different sound modes like the Ultra-X12 does. The closest model in the Hsu line is the $639 VTF-3 MK4, a 12-inch model with sound modes similar to the Ultra-X12's. Unfortunately, I haven't tested it, so I can't say anything about it. Axiom's EP175 v4 is a bit more expensive at $685 and has a smaller, 10-inch driver.
There are many outstanding, affordable subwoofers available today. Many of them perform very similarly and look practically indistinguishable. It seems to me that it's not a matter of choosing the best subwoofer, it's a matter of choosing the best for your budget, tastes, and application. So where does the Ultra-12X fit in? It's for two types of enthusiasts: 1) those who want true high-performance subwoofing but want to keep their investment to a minimum; and 2) those who want smooth bass response across several listening positions (i.e., for multiple listeners) and who thus plan to use two smaller subs instead of one larger one.
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