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July 2009
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Rythmik Audio F12SE Subwoofer
These guys are indeed on to something.
Review By Clarke Robinson
Click here to e-mail reviewer


Rythmik Audio F12SE Subwoofer  I have all the bass I need in my system. The speakers I've owned since first reviewing them nearly two years ago, the Ascend Acoustics' Sierra-1, play down to 40 Hz with confidence (lower still with boundary reinforcement). This is far enough to cover the vast majority of music listened to. Of course, that doesn't mean I have all the bass wanted in my system. I still hear a tiny devil on my shoulder from time to time saying, "don't you wish you had that bottom octave?" Of course I would. Thing is, it is not enough just to have 20 to 40 Hz as producing an accurate and musically satisfying experience is just as paramount as the rest of the range. Add to that, it can't be in a box the size of a refrigerator plus be affordable. A tall order? Sure. But an order that Brian Ding of Rythmik Audio claims to fill.

Brian has a combination of qualities that are all-too-rare in the audio industry: he is both a passionate music lover and a Ph.D. in electrical engineering. He has been running Rythmik Audio with his wife since around 2002, selling drivers and plate amplifiers (using his patented "Direct Servo" technology...more on that in a moment) to the DIY crowd. He has long promised that one day Rythmik Audio would offer completed subwoofers to those without the tools/talent to build their own boxes (like myself), and that day has now arrived. Rythmik's offerings come in two flavors: 12" and 15". The F12SE under review here is identical to their regular 12-incher, the F12, but finished in piano black. The pair I received (yes, a pair... more on that in a moment as well) is apparently B-stock, although I haven't found a single blemish on them that would qualify them as such.


First Impressions
There are no "red flags" in the build quality of the F12SE. Construction is solid, and the finish is practically mirror-smooth. Grilles attach firmly, and the subs ship with a set of four solid metal cones for "feet". The F12SE is just under 16 inches tall and wide, and 18.5 inches deep with the grille on. Not exactly tiny, but small enough that it can be tucked away fairly unobtrusively in a corner or under an end table. Servo-based subwoofers have been available for years, and typically use an accelerometer attached to the driver cone to provide feedback to the amplifier, essentially to "tell" the amplifier what the driver is doing so that it can make adjustments. Direct Servo uses a sensing coil adjacent to the driver's voice coil that provides instantaneous feedback without adding mass to the driver. A detailed description is available at Rythmik's website, but in short, all of this is done in service to the common audiophile demand for "fast" bass.

Bass is perceived as "fast" when the woofer cone is able to start and (more importantly) stop very quickly. In engineer-speak, this means the driver should have a low Q value and low memory effects. Subjectively, this results in bass that has good articulation and pace...two of Brian's most important goals for Rythmik Audio subwoofers. In a world where success is often judged by SPL alone, these are refreshing goals indeed.


I firmly believe that the interaction between speakers and room is the most important "component" in an audio system. Nowhere is this more true than with bass, where the wavelengths easily exceed the dimensions of typical domestic living spaces: a 40 Hz tone produces (roughly, depending on temperature and altitude) a 28-foot long sound wave. A 20 Hz tone is twice that. How these interact with the walls, furniture, etc. in your room is impossible to predict... setting up a subwoofer is the process of best tuning it to your room to facilitate the presentation of these massive sound waves.

Over the course of the review period, I tried the F12SE in a number of different locations around my 25 x 13 foot listening (read: living) room. Some positions worked better than others, and I'm still not 100 percent convinced that I've found the absolute best placement/setup for my system (these things take time, but deadlines loom regardless). That said, I was able to get results that I could live with from any position I tried; thanks largely to the flexibility offered by the F12SE's broad array of setup options. In my case, "results I could live with" means a smooth transition between mains and subwoofer, bass that doesn't localize to the sub, with standing wave peaks minimized (or eliminated). Getting back to the Rythmik's setup options, there are too many to catalog them all, but here's a few that I found most interesting/useful:

Low Pass Filter: Unlike most subwoofers that have a single knob that selects the crossover point, Rythmik provides a switch that selects a general crossover point as well as a 2nd (12dB/octave) or 4th (24dB/octave) order slope. Meant to be used to determine if the subwoofer will be receiving a full-range or a bass-managed signal, it's also useful for mating with sealed or ported speakers, each of which roll-off at different rates. A crossover knob is also provided for fine tuning.

Delay/Phase: I'm not sure if this is any different from a typical subwoofer phase adjustment, but Brian has a completely different approach to how this should be used. Instead of simply setting it where the output is loudest, he provides a formula on his site for setting it based on the subwoofer's distance from the mains by adding delay. Of course, delay can only be added (subtracting delay would require time travel), so nothing can be done to correct situations where the subwoofer is farther away from the listening position than the mains.

Parametric EQ: Extremely useful, and by far my favorite feature. Parametric EQs are common in high-end subwoofers, and I never want to be without one again. Standing waves will forever be the enemy of smooth, well-integrated bass as long as you are listening indoors (and your audio system isn't in a barn). The EQ made quick work of taming the nastiest of these peaks in every placement the F12SE found itself in.

In lieu of a manual, Rythmik provides a single sheet outlining the controls on the plate amp, and detailed (if not particularly clearly written) setup instructions are available on their website. Fortunately, support is available from Ascend Acoustics, Rythmik's exclusive distributor in the United States.


The Rythmik F12SE played all the normal bass-nut subwoofer test tracks with ease: Bela Fleck & the Flecktones' "Flight of the Cosmic Hippo"? Check. Primus' "My Name is Mud"? Check. Mickey Hart's "Temple Caves"? Check. The F12SE presented these subterranean chestnuts with as much impact and authority as I've ever heard, if not more so. Pipe organ music was similarly impressive. The classic RCA Living Stereo recording of Charles Munch conducting the Boston Symphony Orchestra in Saint-Saëns Symphony #3 [RCA Living Stereo SACD 61387] shook the air to life when the deepest bass notes hit. Gillian Weir and the English Chamber Orchestra's performance of Poulenc's Concerto for Organ [Linn CKD 180, 2001] was different. One of the great strengths of this recording is the near-perfect blend between organ and orchestra. This balance was maintained with the F12SE in place, but the subwoofer added an ominous sense of awe when the 32' stops resounded.

Small-group jazz recordings showed that the F12SE doesn't only bring improvements to bass-heavy material. Adding the Rythmik to the mix brought a noticeable sense of solidity to Peter Brötzmann, Fred Hopkins and Rashied Ali's 1991 masterpiece Songlines [FMP CD 053, 1991]. This album already sounded great on my system, but the foundation provided by the F12SE brought a more dramatic sense of realism, in particular to Hopkins and Ali (one of the greatest rhythm sections ever recorded). I had a similar reaction to Bag It, the latest offering by Mats Gustafsson's Scandinavian super-group The Thing [Smalltown Superjazz STSJ155CD, 2009]. Despite their traditional instrumentation (bass, drums, tenor saxophone), calling The Thing a jazz trio misses the point somewhat. For Bag It, veteran indie rock producer Steve Albini (who apparently doesn't even like jazz) further erased stylistic boundaries by bringing the band's punk edge even closer to the surface. Actually, "closer to the surface" doesn't do it justice...it's more like he scoops it out and splatters it all over your walls. Impossible to ignore when played on my regular system, the F12SE turned listening to this album into a visceral experience.

Of course, bass and drums are obvious choices when showing off the low-frequency abilities of a subwoofer. A subtler, but in some ways even more stunning, demonstration came from a solo vocal performance by singer/songwriter Kenny Rankin. Rankin recorded Because of You [Chesky JD63] in 1991 at RCA Studio A in New York City (called BMG Studio A in the liners, but I'm pretty sure it's the same place). Large enough to record as many as 20 musicians at once, Studio A had a natural ambiance that David Chesky loved...his label recorded there almost exclusively until the studio's closure in 1993. The track "Always" features Rankin solo, accompanying himself with only snaps and hand claps. Playing this track on my regular system put Rankin in my living room...turning on the F12SE put me in Studio A. What was going on here? Even though he doesn't produce any bass content himself, low frequency energy is generated by sounds reflecting around the large space. The Rythmik made this low-frequency content audible, where it provides our brain with spatial cues that help suspend disbelief. The effect is subtle but unmistakable, and is only something I've heard with very, very good subwoofers.


Take Two
As I mentioned earlier, Rythmik sent me two F12SEs to experiment with. This I did in two ways:

1) in a stereo bass setup; and

2) in a Welti/Geddes-style "multi-sub" configuration.


Stereo Bass: Conventional wisdom states that, since bass frequencies an non-directional below 270Hz, a subwoofer can be placed anywhere with no impact on stereo localization. However, some audiophiles report that using two subwoofers in stereo (given adequate physical separation and distance from the listening position) will noticeably widen the soundstage and provide more lifelike and accurate imaging.

Conventional wisdom won out in my listening room. Having two subs was nice in that I got even more output with lower gain from each of the subwoofers' plate amps, but it did nothing to improve soundstage, imaging, or anything else (I do believe there is something to low-frequencies' impact on the soundstage, as I experienced with the Kenny Rankin recording mentioned above, but that was with a single subwoofer located in the corner). The fact that stereo subwoofers had no effect in my room have as much to do with my mains as anything else...playing flat to 40 Hz may provide all the benefit that stereo bass has to offer.

Welti/Geddes Configuration: In 2002, Todd Welti of Harman International submitted a paper to the AES entitled, "How Many Subwoofers Are Enough?" in which he found that multiple subwoofers could be used effectively to address standing waves in small rooms, thus smoothing bass response in typical domestic listening situations (a simplified version of the paper can be downloaded for free from Harman's website. Welti's study is theoretical, as it begins with a round of computer modeling, and finishes with measurements taken in a real room with real subwoofers, but nonetheless a room that bears little resemblance to any listening room I've ever seen.


Since then, acoustician and speaker designer Earl Geddes has taken Welti's conclusions much further into the practical realm, reportedly having set up audio systems in several of his clients' home theaters, successfully smoothing bass response with the use of three subwoofers (instructions for Geddes' technique are posted here.

These guys are indeed on to something. I started with an F12SE in the left corner of my listening room...an excellent location for a subwoofer actually, but it did produce an obvious lump in the response at around 40 Hz (during the solo subwoofer listening sessions above, I eliminated this node using the parametric EQ). I then placed the 2nd subwoofer at a point roughly midway down the wall on the opposite side of the room, adjacent to my listening position. The 40 Hz spike was gone! Well, not exactly gone. It did attenuate noticeably, but not as much as I was able to do with the EQ. The experience of having a bass lump go away when turning on a 2nd subwoofer was so shockingly surreal, the effect seemed a bit more pronounced at first then it ended up being under closer listening. Also, it was "replaced" to a degree by another peak around 70 Hz... not as obnoxious as the first, but certainly audible.

70ish Hz is a very common node in rooms with 8 foot ceilings, like mine, and presumably (according to Geddes) it could be reduced by the addition of a 3rd subwoofer located somewhere above the midpoint of my room. I didn't have a 3rd F12SE, and even if I did, I don't have any furniture large and sturdy enough to position one that high. Still, not a bad experiment, something I'm sure that could be useful to anyone who happens to have three subwoofers around.


Buying Advice
Taking on the lowest octave(s) is a challenge for the budget audiophile. Considering that a single F12SE runs about the same price as a pair of Sierra-1, they aren't a particularly good value...at least if value is expressed in a "dollar : frequency range" ratio. But that's the thing about reproducing bass...to do it right requires large drivers, large cabinets, and large amplifiers, and that isn't cheap. The vast majority of music lives in the midrange, and if that satisfies you (and you don't want to burn holes in your wallet), by all means go in the strength that you have.

What I found over the course of this review period, however, is that there is magic in the bass, at least when it's done properly. It can produce deeper levels of musical involvement, and not just with music that "goes there" per se. The question remains, then, does Rythmik do bass properly? The answer is an unequivocal yes! I'm hooked...line and sinker. The F12SE is in my system for good... Brian is not getting it back.

Would I recommend one or two (or three)? That depends mostly, of course, on how much you are willing to spend. A single F12SE is adequate for my listening room, and with the on-board EQ I can get the response as smooth as I need. Two would be nice, mostly so they can do their job without having to work so hard, but I don't know if that's worth another kilobuck (or nearly so) to me.

But that's my budget. For those in an entirely different audio tax bracket, there are several world-class subwoofers on the market that run $3000 each and higher (JL Audio, REL, and Velodyne all come to mind). I don't have any on hand to compare, but I'm confident that Rythmik can hang in that crowd without embarrassment... I'd take a pair of F12SEs over a single one of these megabuck behemoths any day of the week. If this is the price range in which you are shopping, I highly suggest you put a set of Rythmiks on your short list.


Associated Equipment
Ascend Sierra-1 stand-mounted loudspeakers
Parasound Model 2100 Preamplifier
Parasound Model 2125 Amplifier
Marantz SA8003
Listening room is approximately 13 feet wide and 25 feet long. Acoustic treatments include wall-wall carpet, curtains, and a large overstuffed sofa.



Sub-bass (10Hz - 60Hz)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear  
Soundscape Depth Behind Speakers

Soundscape Extension Into Room

Fit And Finish

Self Noise

Value For The Money


Type: Amplified subwoofer
Driver: 12-inch high excursion with custom sensing coil
Driver Materials: Black or silver anodized aluminum with rubber surround,
                        cast aluminum basket and copper flux modulation shorting rings
Amplifier: 370 watt RMS Class A/B patented servo controlled
Frequency Response: 14 to 100 Hz (-2 dB @ 14 Hz)
Crossover Slope: Selectable 12 or 24 dB / octave
Crossover Range (Low pass): 40 to 100 Hz
Rumble Filter (High pass ): 14 / 20 / 28 Hz 18 dB / octave
Phase Response: 90 degrees phase shift at 20 Hz
Phase Adjustment: 0 to 180 degrees continuously variable
Bass Damping Factor Settings: High (Q=0.5), med (Q=0.7), and low (Q=1.1)
Finishes: Piano Gloss
Dimensions: 15.75 x 15.75 x 17 (WxHxD in inches)
Shipping Weight: 80 lbs
Warranty 5 years warranty on driver and 2 years on electronics 30 day satisfaction guarantee 
Price: $899


Company Information
Rythmik Audio
11621 Woodland Hills Trail
Austin, TX 78732

Voice: (512) 565-3712 
Fax: (512) 266-2506 
Website: www.rythmikaudio.com


Exclusively Distributed Worldwide By
Ascend Acoustics, Inc.
934 Calle Negocio Suite D
San Clemente, CA 92673

Voice: (949) 366-1455
fax: (949) 366-1455
E-mail: sales@ascendacoustics.com
Website: www.ascendacoustics.com














































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