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SVS SB12-Plus Active Subwoofer: The Mouse That Roars

“This is an SVS subwoofer?” That was my reaction when Fed Ex delivered the little box to my doorstep. Sonnie Parker was in town for a visit and he was equally surprised, owning a couple of SVS’ more substantial subwoofers himself.

Breaking open the box revealed a diminutive subwoofer barely a cubic foot in size, with a breath-taking piano black finish. We were both anxious to see how it would perform as we evaluated it over the next few days.

Since its inception, SVSound has earned a reputation for building high-performance ported subwoofers. With the introduction of the now-legendary PB10-ISD a few years ago, SVS stated their goal was to “create a new deep-bass standard for the crowded $400 price range.” Most would agree they accomplished that objective. SVS has now set its sights on the difficult high-performance, mini-sub class. The SB12-Plus also breaks new ground for SVS in another way, being the company’s first sealed box design.


Published Specs/Features/Description
The diminutive SB12-Plus weighs in at a mere 43 lbs. and measures 13.5” x 13.5” x 14.5”, half-an-inch less all around than SVS’ published figures. The company’s web site specifies frequency response as 22-150 Hz +/- 3 dB from a 425 watt BASH amplifier. The amplifier includes a boost in low-frequency output below 35 Hz, which presumably is required to compensate for the extension penalty that typically results with a large driver/tiny box combination such as this.

The heart of this little subwoofer is SVSound’s own Plus 12.3 driver, the same driver used in their larger ported subs that also carry the “Plus” designation. It’s the first driver the company has both designed and manufactured in-house, at their Ohio factory. SVS confirms the Plus 12.3 was developed for both sealed and ported roles right from the start.

As the picture below shows, the SB12’s rear panel is really busy, with more controls, knobs and connections than you’ll find on most subwoofers. For high-level connections, there are gold plated binding posts for speaker input and outputs. RCA inputs are included for low-level signals, and there are RCA outputs as well, for systems that don’t have a built-in electronic crossover. Lastly, a rare connection option: Balanced XLR inputs and outputs. A nice feature, considering that subs can often be a considerable distance from the rest of the system. A balanced signal maintains excellent noise rejection properties with long cable runs, provided you have a processor with balanced outputs.

The rear panel also includes the standard controls you’re likely to find on most subwoofers, such as a level (i.e. gain) knob and auto-on switch. The built-in crossover offers user-selectable settings ranging from 40-120 Hz. A defeat switch provides the option to disable the crossover. SVS tells me the crossover slope is 12 dB/octave; you will probably want to bypass it for the steeper (and preferable) 24-dB/octave slopes most receivers and pre-pros have these days.

There are additional controls for features that are not as commonly seen on a powered subwoofer. Instead of the typical 0- or 180-degree phase switch, there is a continuously variable control. This essentially functions like an analog delay adjustment that helps time-align the subwoofer with the main speakers, better assuring smooth response through the crossover region. Needed phase compensation can vary with your receiver’s crossover slope, and the sub’s placement in relation to the main speakers, so in certain installations a variable phase control can be highly useful.

Another unique feature is a single-band parametric equalizer, with frequency, gain, and bandwidth controls. The equalizer is a cut-only design, intended to diminish a room-induced peak in response up to 12 dB.

A new SVS innovation making its debut on this subwoofer is a three-way, selectable Room Compensation function that can be set for “Small,” Medium” or “Large” rooms. The feature addresses a phenomenon known as “room gain” (a.k.a “cabin gain”), where measured and perceived response at the lowest frequencies increases the smaller a room gets. While other SVS subs offer variable port tuning to adjust ultra-low output to a particular room, the SB12’s Room Compensation addresses the effects of room gain electronically, by introducing a high-pass filter that attenuates response below 32 Hz at a pre-set value. In the “Small” position, response is reduced –9 dB/octave. The “Medium” and “Large” positions reduce at -6 dB and –3 dB/octave respectively. A “Bypass” position restores the BASH amplifier’s normal response with upward-tilting low end, for use in the largest rooms. So, practically speaking, the Room Compensation curbs the low-end boost in varying degrees.

Julian Hirsch Pose w-text.jpg

Of course, improved dynamics can be realized in large rooms by setting the Room Compensation to “Small,” but at a loss of extension. (Personally I’d rather have the extension.) Maximizing both extension and dynamics will require the SB12 be primarily used in smaller rooms, and indeed SVS recommends it for use in rooms 2400 cu. ft. or less.

The SB12-Plus comes with a three-year warranty against defects and workmanship; prices range from $699 to $799, depending on the finish option you choose. Our piano-black version is the most expensive.

SVSound web site
SB12-Plus web page

We’ve come to expect quality construction from SVS, and the SB12-Plus does not disappoint. Close inspection reveals an impeccable attention to finish and detail, with practical and thoughtful embellishments throughout, starting right up front with the grille.

Remove the grille and you will notice there appears to be no visible means of attachment. That’s right - no embedded rubber grommets for the standard snap-on grille frame. SVS has employed a unique invisible mounting technique that hides small but powerful neo magnets under the surface of both the frame and the enclosure. Fitting the grille to the front panel gets a soft “thunk” as the magnets engage. The frame is constructed more like a baffle board than a traditional grille frame - in other words, it has 12” hole in the center. The driver is not fully recessed into the cabinet, but raised about 1/4” or so above the surface. This allows the 12” hole in the grille to fit snugly around it, centered and true, since there are no stationary pins and grommets to do that.

All in all, it’s an innovate and elegant design. A nifty benefit is an unblemished front panel that looks great with the grille off, as the pictures show. The SB12-Plus’ upgraded finishes include the magnetic grille mounting system, while the basic black vinyl finish uses standard chrome steel retainers.

Opening up the SB12 reveals the cabinet’s sturdy construction, featuring a 1” baffle and 3/4” side and rear panels, which – considering that the cabinet is barely a foot cubed - makes for an extremely rigid build. A thick layer of insulation covers all four side panels. I expect most manufacturers would have felt they could get by with 1/2” or 5/8” construction with a sub this small; it’s nice to see that SVS didn’t compromise.

No SVS subwoofer would be complete without an impressive-looking driver. The Plus 12.3 driver is a heavy-duty monster with a cast aluminum frame that weighs a stout 21 lbs., accounting for fully one-half of the subwoofer’s total weight.

The heavy driver is secured with machined 8-32 square recess screws into threaded inserts. Like the grille magnets, the inserts are embedded into the cabinet. This would appear to be a better system than the T-nuts SVS has used in the past, which can easily be dislodged and ruined if too much torque is applied to the screw.

The woofer includes a rubber trim ring that fits over its mounting flange, a novel approach which serves at least three purposes: It functions to seal the driver to the cabinet, serves as a dress ring to make the front panel more attractive, and insulates between the driver and the close-fitting grille, insuring the latter will remain quiet and resonant-free during operation.

The Plus 12.3 driver connects to the BASH amplifier via 16-ga. wire. The electronics panel also shows SVS’ attention to detail, as evidenced by the liberal use of a hot-melt sealant at all places where there could potentially be an air leak. Other hot melt appears to be added in the interest of increased durability – around the capacitors, for instance. SVS tells me much of this sealant is added at their own factory, above and beyond what their vendor provides for the assembly.


Unfortunately, the prototype I was sent didn’t have a manual, so I was flying in the dark on how to operate some of the SB12's features. As of this writing there is still no on-line manual for it, but presumably SVS is shipping them with a published one. I bring this up because some of its features, such as the Room Compensation and the on-board parametric equalizer, are less then intuitive.

The equalizer in particular isn’t terribly user friendly, despite its straightforward appearance. Normally I don’t have a problem figuring out how to operate an analog equalizer, but nothing I did with this one seemed to work right. For instance, the labeling for the Level knob: I assumed that “Min” was cutting gain, and “Max” was boosting, which is perfectly logical to anyone who’s ever used a parametric equalizer. Yet, it appeared the equalizer was working backwards, attenuating the selected frequency at the full “Max” setting.

Electronics 1-a w-text.jpg

It wasn’t until after I returned the sub that I found out that the PEQ is actually a cut only design. I will say that SVS principals Ron Stimpson Tom Vodhanel were prompt and courteous at answering all my inquiries, so I’ll put the blame on myself for not taking the time to get in touch with them until after I had shipped the SB12 back.

Nevertheless, I encourage anyone who buys a SB12 to review the manual before attempting to use the parametric equalizer. Presumably this is the same equalizer found in a few other SVS subwoofers, like the PB12-Plus model. You can download its manual here: PB12-Plus manual

That said, I have some issues with the actual function of the parametric equalizer as well as the labelings:

  • I’d prefer to see the Q control labeled as “Wide” and ”Narrow” (or perhaps use emblems indicating the same) instead of “Hi” and “Low,” since Q is not readily known or understood by audio novices.
  • The labeling of the “Level” control as “Min” to “Max” is a rather disingenuous approach for a cut only equalizer. I’d prefer to see a more correct “0 dB” to “-12 dB” labeling. Furthermore, turning the knob clockwise to cut is counter-intuitive. Of course, anyone who reads the manual won’t be confused, but as we all know, real men don’t read manuals. :D
  • The “Level” control is exceedingly non-linear, getting virtually all its action in the last fifty-percent of knob travel – i.e., between straight up and “Max.”

SB12 parametric EQ.jpg

I had a difficult time determining how functional the SB12’s equalizer really is. If it’s identical to the PB12-Plus EQ, its bandwidth settings are extremely wide. The “Low” setting (given as a Q value of .9 in the PB12-Plus manual) is a full 1-1/2-octave, and the “High” setting (Q value of .1) is a shocking 6-2/3-octaves! (This manual is mistaken in its description of high and low Q, by the way. High Q is [logically] numerically high, low Q is numerically low - not the reverse.)

I was informed by SVS that the SB12’s equalizer’s Q values span from 2.0 to 0.2, which is 2/3 octave to 4-3/4 octaves. Better, but still pretty wide, even at the narrow setting. Too wide to be of any practical use. It would have been far more functional to have the Q adjustable between say, 14.4 and 2.9 (1/10 and 1/2 octave).

However, an Audioholics review of the SB12-Plus preceding this one includes a response plot of the parametric’s action at narrow, medium and wide settings, which shows Q ranging from about 8.7 to 1.4 (1/6 octave to 1 octave). Assuming the graph is accurate (and I have no reason to believe it isn’t), it appears the parametric EQ would be useful at its narrow (“High”) position. However, it’s probably best not to stray too far from there, because the graph also shows that medium and wide bandwidth adjustments are virtually identical. In other words, the “Q” knob appears to be plagued by the same non-linearity as the “Level” knob, getting all its action in only fifty-percent of its travel.

Electronics 2a w-text.jpg

In their defense, SVS says they are aware of many of these shortcoming and tells me they have been complaining to their vendor for a couple of years about the “‘less than medical grade accuracy of their knob tolerances,” as Tom Vodhanel puts it.

In light of all this, it’s hard to get excited about the SB12’s equalizer, which is a real shame because it has the potential to be a really useful feature. If you do try to use it, be sure and check the results with a response-plotting program like John Mulcahy’s excellent Room Equalizer Wizard, since you really can’t rely on the accuracy of the control settings.

(By the way folks, if you feel somehow lacking or intimidated because you don’t understand all this Q stuff, don’t sweat it. I’m only able to keep it all straight because I have a Q to octaves conversion table. :) )

Without the benefit of a manual, I also was in the dark on how to use the Room Compensation feature. Being familiar with the fact that small rooms naturally boost bass and big rooms lose bass, I assumed that the “Large Room” setting was going to boost the lows that are normally deficient. At the time I didn’t know the SB12 already had a built-in boost for the lows “programmed in,” and an additional boost would have only – well, it would not have been good. So naturally I was finding the Compensation wasn’t working like I expected it would. Fortunately, anyone with the benefit of a manual won’t have that problem. The main downside from not fully understanding how the Room Comp feature worked is that I was unable to evaluate its effectiveness.

Aside from these things, which were basically the result of me flying blind with a one-off prototype, the only other thing I had trouble with was the auto-on feature. Sometimes it wouldn’t kick in with TV shows, which often feature low levels of bass.


Since in-room output and extension are the main things I look for in measurable subwoofer performance, I kept the measurements simple. For those who feel they need a more thorough analysis, see Ilkka Rissanen’s SB12 test.

In-room frequency response measurements were taken using the Room Equalizer Wizard program. I also had an AudioControl R-130 1/3-octave real time analyzer on hand to monitor various aspects of the sub’s output and performance. Response measurements were taken both unprocessed and with equalization from a Behringer DSP-1124 digital parametric equalizer. All measurements were taken with the SB12’s Room Compensation and Parametric EQ functions turned off.

The primary measuring location was our large family room, which is open to other areas like the dining room, kitchen and upstairs landing. The total volume is a cavernous 9200 cu. ft., but the listening position is about 13-14 ft. from the sub. In addition, I took some measurements in our 2450 cu. ft. master bedroom.

I also had on hand a PB12-NSD that SVS was kind enough to provide for comparison purposes.

Raw combined graph top.jpg
Raw combined graph bottom.jpg

Data Analysis
REW readings showed the PB12-NSD had robust output down to 18 Hz, even with no equalization employed. The huge room takes a toll on the little SB12, with response falling rapidly below 30 Hz. However, with equalization the SB12’s extension improves significantly, maintaining flat response down to about 24 Hz.

Maximum SPL readings were taken using broadband pink noise as a signal source, with the Behringer 1124 equalizer engaged. Sure, that exacted a penalty in output, but I felt the figure should be a “real world” measurement – in other words, the same way most of us will use it. Despite this encumbrance, the SB12 managed to hit 98 dB - not a bad figure considering voluminous size of the room. Keep in mind also that pink noise is a more demanding program source than any movie will be. All things considered, most users should have no problem hitting over 100 dB with bassy action movie scenes.

Filtered combined graph top.jpg
Filtered combined graph bottom.jpg

In the master bedroom with no equalization and the Room Compensation disengaged (i.e., the BASH amplifier’s low frequency boost intact), the little SB12 cranked out an impressive 106 dB. Once again, output probably would have been even higher with movie programming and if I had utilized the “Small Room” Compensation to reduce the lowest frequencies.

Running 1/12-octave sine waves from 18 Hz up, there wasn’t much action until 22-23 Hz, which confirms our room response and SVS’s published specs rating the SB12 down to 22 Hz.


Reference System
Rather than go into details on the gear used for this evaluation, readers can refer to my equipment list at this link (yes I know, some updates are in order :) ). Subjective listening tests were conducted in our 9200 cu. ft. family room, which presents a challenge for a single-diver subwoofer.

Cabinet Internal w-text.jpg

My reference subwoofers are a quasi-DIY rig using a pair of 12-inch Shivas in undersized 2.4 cu. ft. sealed cabinets. I say “quasi” because I didn’t build them myself; I gutted some 1970’s vintage tower speakers I had laying around and pressed them into duty. I’m referring to them as “reference subs” only because they’re what I’m used to listening too, not because they’re anything special. :) The Shivas are each driven with 325 watts from an Adcom GFA-555II amplifier, and equalized with a Behringer DSP-1124 parametric equalizer.

All listening evaluations were performed with both the SB12 and PB12 equalized for best frequency response.

Movie References
War of the Worlds
While I had both of these subwoofers at my disposal, I though it would be fun to host a meet with some of our local home theater buffs, as it would be a rare opportunity for them to audition a pair of SVS subs. One attendee asked to demo the War of the Worlds DVD he had brought. I was a little worried about that, because I had heard about the extreme bass in this movie toasting people’s subwoofers. I don’t remember which chapter they had me cue up – presumably it was a demanding one. Not only did the SB12 not evaporate in a cloud of smoke, but everyone was pleased with its performance of the selected scene. “Everything was there,” was the comment from the person who had brought the disc.

Lord of the Rings: The Fellowship of the Ring, Chapter 1, “Prologue”
This chapter is a serious subwoofer torture test, featuring at least a couple of dynamic bursts of ultra-low frequency energy. One of them is when Sauron’s ring finger is cut off and it falls to the ground at 3:59. There a burst of low frequency energy at 25 Hz and below that makes my amplifier clip and extends my Shivas to their limits. Moments later there is a reverse low frequency sweep that starts above 100 Hz and descends to nearly 50 Hz. After a momentary pause, it picks back up again at extremely low frequencies – 20 Hz or lower - ending at 4:19, when Sauron’s helmet hits the ground. This is a great extension test!

SVS SB12 driver w-text.jpg

The limiters in both subs prevented them from conveying the burst of energy well, as could be expected with both the huge room and equalization sucking up headroom. However, a tad more impact was noticeable with the larger PB12-NSD. Both subs remained well behaved during this demanding passage, emitting no audible sounds of distress. SVS has done a good job matching limiters to drivers – no easy task, I imagine – to get the most performance from their subwoofers.

Both subs showed off their excellent extension with the reverse sweep, but it was here that the PB12 demonstrated a clear advantage over the little SB12. Just before the sweep comes to a stop at 4:18, the lows are so low that they’re felt more than heard. When I switched from the SB12 to the PB12, everyone attending our meet indicated they could tell the difference: The PB12 made it all the way to the bottom, while the SB12 couldn’t quite get there.

Flange Detail w-text revised.jpg

Music References
Basia, The Sweetest Illusion
Track 1, “Drunk on Love,” is my favorite music track for revealing low frequency detail. The bass guitar has a very prominent “texture” or “growl.” Since there is a lot of mid-bass energy in the recording, it will come through on both the mains and subs. The test of a musical subwoofer, naturally, is how well it conveys the “growl.” Ideally, it should be able to render the detail and texture as distinctly as what you hear in the mains. If not, you only get the texture from the mains, while it “runs together” at the supporting lowest frequencies. A good way to tell if the sub is “up to speed” is to listen to it without the mains. The SB12 and PB12 both did an admirable job with this track.

Basia, London Warsaw New York
On track 1, “Cruising for Bruising,” the bass instrument has “texture” like “Drunk on Love” from the other disc, but here it’s very subtle and can be even more of a challenge to resolve. It was all there, with both the subs.

Track 5, “Ordinary People,” which features a bass line that runs two full octaves, is my “gold standard” demo track for determining if a system has linear bass response from the lowest notes to the highest. The upper notes should be clearly heard, the lowest notes felt as well as heard, with notes in between a smooth blend between the two. Naturally, being fully equalized, both subs did a stellar job with this track.

Manhattan Transfer, The Offbeat of Avenues
This under-appreciated Grammy-nominated album includes some great tracks for bass detail. Track 2, “Sassy,” features a series of quick staccato triplets in the bass line at 0:23, during the intro before the vocals begin. At 0:58 and other places in the song, the bass line does a syncopated pattern on a single note, with only a few milliseconds of “dead space” occurring as each new note is struck. If a sub isn’t fast and precise, the pattern will “bleed” together and sound more like a single long note than several shorter ones. Both subs did a good job with this track, although not quite as well as I’m used to hearing.


In my mind there are three characteristics that qualify a sub as “high performance”: Excellent tightness (often labeled speed) and detail, dynamics (i.e. headroom), and extension.

Both the SB12-Plus and the PB12-NSD did a surprisingly good job in our 9200 cu. ft. family room - better than I expected. Neither subwoofer could be expected to deliver outstanding dynamics in a room as large as this, but they left little to be desired in the way of extension. If I had to give up one, I’d prefer to have the extension.

With music, where dynamics and extension take a back seat to detail, it’s not as cut-and-dried. After a half or hour or so switching between the two, I honestly couldn’t tell a difference between the SB12 and PB12. Neither seemed to be as tight as the PB10-ISD I auditioned two years ago, but we’ve moved since then and our new place is a bit more “live”, which may account for that. However, both the SB12 and PB12 are more detailed than my throw-down reference subs, as was the PB10. (I’m thinking I need some better “reference” subs!)

The local enthusiasts attending our meet were generally impressed with how well the SB12-Plus performed, especially given its size. However, most indicated that performance was the bottom line and preferred the PB12-NSD because it was able to reproduce the lowest passages (hey, they’re enthusiasts, after all!). I would be remiss not to point out, however, that even these enthusiasts were duly impressed with the SB12 until I switched over to the PB12 and re-played that passage from Lord of the Rings...

SB12 Oak Front.jpg


All things considered, the SB12-Plus’ performance is simply amazing. If you have a small room and /or require a small subwoofer, the SB12-Plus won’t leave you feeling short-changed.

And it packs some great features to boot. Although I was unable to fully evaluate it, the Room Compensation should prove useful to real-world users (i.e., people not attempting to use the SB12 in cavernous rooms like mine). I‘m confident some users will also find the balanced connections useful. Sure, the parametric EQ is iffy, but most of us are going to use a more sophisticated outboard equalizer anyway. Hopefully it doesn’t add much to the bottom line.

I’ve never used a high-output mini sub before, so I can’t say how the SB12-Plus fares against its competition. But considering how well it held up to the PB12-NSD, I’d have to say SVS has set the bar for this category pretty high. You would quite reasonably expect a sub three times larger to blow it away, but with movies the SB12 gave up only a slight margin in dynamics and extension to its bigger brother, and only then with the most demanding movies. Put them both in a room under 2400 cu. ft. (which is the largest SVS recommends for the SB12), it wouldn’t surprise me if the SB12 could keep up with its big brother in at least the dynamics department, narrowing the gap between them even further. In our master bedroom, it was amazing how remarkably unobtrusive the SB12-Plus was: just a little box sitting in the corner. It shouldn’t be a problem for anyone to find a place for it, even in the smallest room. I’m confident the WAF will be very high for this subwoofer.

But more than that, there’s almost something magical about the SB12-Plus. Simply put, it’s just too cool for words. You can’t help but love this sub. It’s so beautiful and so small, and it roars like a big sub – what’s not to love? I’m not kidding, I found myself getting emotionally attached to it! It was hard – hard I tell you - to part with it! (Ron Stimpson has noted that piano black finish seems to be the “sentimental favorite” of the available finishes - I have to agree.) I asked my wife, “You think it’s possible for a guy in Colorado to file grand larceny charges against us?”

Wayne A. Pflughaupt
February 2007

Thanks to:
Donna Pflughaupt, for help with the graphs and pictures.
John Mulcahy, for the excellent Room Equalizer Wizard program.
Sonnie Parker, for taking the REW measurements and pictures at our HT meet.
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