PRICE D15-Chimera $1,799, D15-SC $499, MFL-6 $279 (shipping not included)
AT A GLANCE
Plus
Chimera by itself is very capable
Chimera & SC combo have an incredible price/performance ratio
Rated at 92dB sensitivity, the MFL-6 speakers are very efficient
MFL-6 can play loud without audible distortion
Minus
Chimera goes in and out of standby mode with an audible pop
Chimera & SC combo is pretty sizable
MFL-6 speakers require aiming discipline
Down-firing port on the MFL-6 could impact placement options
THE VERDICT
Perhaps the best price/performance ratio subwoofer on the market today, the Hsu D15-Chimera and D15-SC represent an incredible amount of product for the asking price. The two piece system isn’t small, but what it’s capable of makes the size seem reasonable. In the immortal words of Nigel Tufnel from the movie Spinal Tap, “these go to eleven”.
The MFL-6 speakers are too small to sound this big, what your eyes see and what your ears hear seem out of sorts. They are incredibly smooth and precise, effortlessly playing any content you care to throw at them. You have to be cognizant of their placement, but accommodate what they need and you’ll be rewarded with incredible sound.
Introduction
Hsu Research is not a company that releases products very often, they tend to perfect a design and then offer it virtually unchanged for years. That means when these folks launch 3 new products at the same time it’s newsworthy, especially when one of them is unlike anything else available. And what is that unique item? Say hello to the D15-Chimera, a sealed subwoofer with dual-opposed 15″ drivers. That’s not terribly uncommon, but what makes the Chimera stand out is the orientation; rather than a horizontal cabinet, it’s vertical. When used by itself anyway, but add their D15-SC (Super Charger) and things start to get interesting. When you do that it means we go back to horizontal. Confused yet? It will make more sense in a minute, but suffice to say the combination is surely distinctive.
Then there’s the MFL-6 speakers (MFL standing for Multi-Functional Loudspeaker). Featuring a down-firing port, 6.5″ midrange and an Hsu favorite; a horn tweeter. This particular one was designed in collaboration with the horn guru himself, none other than Don Keele.
As you’ve probably surmised by this point, there is nothing conventional about this Hsu Research 5.1 system. So where do you start in a situation like this? Explaining exactly what I have in front of me is the best place I can think of.
Impressions
When you see the D15-Chimera in person it comes across as a plus-sized subwoofer, but is that an optical illusion? Rather than a horizontal orientation, the Chimera is vertical; it goes up, instead of out into your room. Although unconventional, there are some advantages to this approach. For one, it doesn’t take up anywhere near as much floor space as a traditional subwoofer would. Another is physics. To produce deep bass, especially at volume, you need a sizable enclosure. Do that with a horizontal cabinet and your sub could noticeably intrude into the room. Small subwoofers with large drivers do exist of course, but generally speaking they achieve their output and extension using DSP (digital signal processing). That’s one way to attain the goal, but utilizing physics instead is often a better approach. That’s what Hsu has done. Then there’s the D15-SC, which is in a league of its own.
In their earliest days, Hsu Research sold subwoofers based upon a similar philosophy. They would start with something very capable, then extend that courtesy of extra porting provided via an external enclosure or adapter. Back then Hsu referred to them as Turbo Chargers, now they use Super Charger instead. Since a turbo utilizes air pressure to derive its benefits, whereas a super charger is mechanically driven, the Turbo Charger name seems more accurate. After all, D15-SC does use additional air movement to achieve its results. But hey, Hsu can call it anything they like.
A little less than a year ago I reviewed Hsu’s then new VTF-TN1. The TN1 utilizes a single front-facing 15″ driver with a pair of down-firing ports. The D15-Chimera uses the same cabinet as the TN1, but in this configuration it’s sealed and there are dual 15″ drivers firing from the sides. That’s roughly the cone area of a 21″ driver, yet the enclosure didn’t grow. The amplifier did however, from the TN1’s 600 watts to 1200 for the Chimera. Double the driver cone area and twice the amp power? Now we’re talking. Essentially the D15-Chimera is like having 2 of Hsu’s ULS-15 Mk2 subwoofers stacked vertically.
Do you wonder why Hsu Research calls the D15 “chimera”? I’m speculating, but here’s my guess… The chimera was a mythical creature that was reputed to have a lion’s head, goat’s body and serpent’s tail. The mythology was of a fire-breathing monster that terrorized all that came in contact with it. In the world of science and medicine however, a human chimera is a person whose body contains two different sets of DNA. Human chimera are extremely rare, but they do indeed exist.
Hsu covers the science aspect by virtue of the fact the D15-Chimera and D15-SC are essentially a single entity, yet with shared characteristics. With regards to the mythology angle, this thing is a 4 port subwoofer with dual 15″ drivers. Sounds like the making of a fire-breathing monster to me. Do you know of any other company offering a sub like this, or one that comes in modules you can couple together? Neither do I, which means it’s uncommon just like a human chimera. If everything I’ve surmised is correct, Hsu’s choice of the chimera moniker is simply brilliant.
And then there’s the MFL-6 speakers which, like the Chimera/SC combo, are a little different than what you’re typically going to encounter. The speakers height, width and depth are not out of line with the average bookshelf speaker you might come across, but that canted front panel at a 45° angle certainly is unique. So is a horn tweeter, and a down-firing port. Depending upon your situation that slanted face could become a factor though, as you’ll find out a little later. So too might the port, you may have to account for that as well.
Like all current Hsu offerings the Chimera, SC and MFL-6 come dressed in black satin paint. And just like all Hsu products I’ve come in contact with, it was applied perfectly.
Setup
The D15-Chimera’s amplifier offers the following…
Volume
Phase, 0° or 180°
Q Control (bass “tightness”)
Variable crossover frequency
Switchable operating mode (sealed, 4/3/2 ports open)
Crossover defeat switch
Power switch (On, Off, Auto)
XLR, low-level (RCA), high-level (speaker wire) inputs
Voltage selector (120V, 240V)
For documentation Hsu includes an owner’s manual and quick start guide, the latter of which does a good job with the basics. But do yourself a favor and take some time to go over their manual, in it they cover a surprising amount in just a few pages. They touch on placement, all the controls, tuning (with and without the SC module), modes, troubleshooting, specifications, pretty much anything you could want to know. A few minutes spent here will ensure you get the best out of this system.
Placement for the Chimera – with or without the Super Charger – is pretty straightforward, essentially the same thing you would do for any other subwoofer. The MFL-6 speakers require a bit more forethought however. Ideal aiming would have them pointing directly at the listener, if you can move your speaker stands far enough apart your front left and right shouldn’t present much of a challenge. With my setup I wasn’t quite able to do that so I had to angle the stands a bit. My surrounds are also on stands, positioned such that they point directly at my ears. There isn’t a lot of empty space behind me to move them further back to accommodate the novel front panel. Ultimately I chose to leave the stands in the same spot as they were, I just rotated them slightly to ensure the speaker drivers were directed at me. It looks a little unusual, but certainly doable. The center presented a slight hitch.
My TV and center sit on a cabinet that is only as tall as my kneecaps (I’m 6′ 1″), the MLP is about 14 feet away from it. When setting up speakers in general I use a laser level with crosshatch pattern to confirm they’re aimed correctly, with the MFL-6 that proved to be an invaluable tool. When I used it to see where the center channel was aimed – in relation to the MLP – it turned out to be about 3 feet above my head while seated. That was a little too far off-axis though, when I stood up the imaging was better than when I was sitting. I used a small wedge under the backside of the center, the type you might find holding a door open, and that pretty much solved the issue. The laser showed the center was still pointed above my head, but I was now within the sweet spot and was able to get better detail. For backs and heights you also need to do some planning. Backs will probably require similar considerations to surrounds, maybe with just a bit less discipline. Heights are where the angled front panel is really ideal, in that scenario you can flush mount them to the ceiling and let the configuration of the cabinet naturally aim them at you.
Perhaps sensing there might be some assistance required for mounting and aiming the MFL-6, Hsu thoughtfully includes a cardboard template with precise measurements you can use when drilling mounting screws. The template accounts for horizontal orientation, along with two vertical options; tweeter on top, or tweeter on the bottom.
I understand why Hsu Research opted for an angled front panel on the MFL-6, it does have some definite advantages, but perhaps they should consider offering a model with a more conventional flat front panel as well. That way their customers could choose which version worked best in the various locations they would be installed.
Adding the beast
Hsu lovingly refers to the Chimera and SC combination as “the beast”. Seen in person it does somewhat have that characteristic; sitting beneath the Chimera, the SC has quite the presence with its quad 4″ ports aimed directly at you. It creates a menacing appearance, and I mean that in a good way. Port plugs are included for all of them, the configuration options available are 2, 3 or 4 open, or totally sealed. Specifications when ported are as follows…
2 open : 14Hz, –3dB
3 open : 15Hz, –3dB
4 open : 17Hz, –3dB
To give you an indication of what’s involved converting a vertical Chimera to a horizontal one sitting atop the SC module I timed myself putting it together. For about 3 weeks I used nothing but the Chimera, after I had a really good feel for what it could do all by its lonesome I added the Beast. To make this a fair assessment I didn’t read the instructions prior to beginning, nor did I watch Dr. Hsu’s tutorial beforehand. I laid out everything in my living room – including tools – and then dove in. Because of how many screws are holding the amplifier in place I used a cordless drill with a #2 Phillips bit, but only for removal and partial re-insertion. I used a regular phillips screwdriver to snug everything back down. The screws are only anchored into MDF, I didn’t want to strip them out by using a cordless to fully tighten everything.
All in it took me 32 minutes for the conversion, which includes about 5 minutes of setup and testing before I screwed down the amp fully (the last thing I want to do is find out something isn’t working and I have to remove the amplifier a second time). It’s a straightforward process to go from Chimera to Beast, pretty much anyone should be able to accomplish it. I did note a few things worth mentioning that I wanted to pass along…
Pay attention to the instructions when they say put the amplifier back on the Chimera before coupling it to the Super Charger. The driver leads are fairly short, trying to balance an untethered amp while reaching inside via the amplifiers hole to plug them back in would be a struggle. With the pass-through for the Super Charger still open it’s much easier to get at the connectors.
There is foam tape around the connector plugs on both the amplifier and driver side, it’s there to prevent the plastic plug from rattling on the cabinet cross brace. That foam can hide the press tab on the connector though. If you don’t push down firmly on that tab, the two pieces won’t separate. That isn’t mentioned in the instructions.
The pins on the SC cabinet are mostly to align the Chimera enclosure when the two are coupled, they aren’t really an attachment method. The Chimera weighs about 100 pounds, so gravity will hold it in place, but the two cabinets are not locked together. To make it a bit more solid the pins could probably be a little longer, there’s barely any part of them going inside the Chimera’s rubber grommets.
The two enclosures do not sit flush, the SC has a foam-wrapped lip extending upwards that the Chimera rests on. That results in what appears to be a slight gap between the cabinets, but it’s not. The seal is air-tight, which is the most important part, so this is more of an observation than anything. They are attached, it just might not look that way.
On Hsu’s website the images of the SC show the opening between the cabinets to be completely clear. In real life it isn’t, the entire cavity is filled with a foam sheet. That serves a purpose, do not remove it. It’s glued in place for a reason.
After completing the entire install I then watched Hsu’s tutorial video, in it they say this is a 2 person job. I tend to agree, for most it should be. The Chimera is roughly 100 pounds, which isn’t necessarily a lot of weight, but the size of the enclosure – and the fact it has a smooth painted finish – could make it a struggle for one person to do. I did it by myself, so it’s certainly doable, but why chance damaging the new subwoofer or your back? Obviously once the cabinets are joined it will be cumbersome to move around, I would suggest you put it together very near where it will reside in your theater.
Fully assembled, the Beast takes on the appearance of an MLRS-like pod. If someone at home doesn’t find that appealing you can simply spin it around and face the ports toward the wall. Now it looks to be a D15-Chimera in a horizontal configuration, sitting on its own pedestal. But who are we kidding, those ports are going to be faced at the listeners. Why would you not?
Listening/In Use
This article was originally just going to be the Chimera and SC, I was not intending to evaluate the MFL-6 speakers. That was a deliberate decision on my part because I don’t really like horn tweeters. I don’t recall ever hearing one that didn’t sound irritating to my ears. There aren’t many company’s making speakers with horn tweeters, so my experience is limited to just a few different models, but all the ones I’ve heard had either a shrill sound or the dreaded “cupped hands” phenomenon. I have never really liked the hollow, enervated sound horns can produce. Played at volume, they often grate on my ears. No thanks.
About 2 weeks after getting the Chimera and SC I contacted Dr. Hsu about something unrelated, and for some reason – a moment of weakness perhaps? – I asked if he would send me five of the MFL-6 speakers so I could evaluate a full 5.1 system consisting of all the new Hsu products. Given my contempt for horn tweeters I’m not even sure why I said that to him, but being the gentleman he is Dr. Hsu was more than willing to provide whatever I wanted. Did I just set myself up for failure?
Thankfully not. These speakers turned out to be amazing, despite my trepidations there was absolutely none of the dreaded cupped hands sound horns are famous (infamous?) for. They were not harsh, thin or piercing in any sense of the word. The MFL-6 proved to be relaxed and smooth, very detailed, accurate, and just plain easy to listen to. No fatigue, no drama, nothing but pure unadulterated sound. Whether movies or music it didn’t matter, they handled both with aplomb. In hindsight I probably should have anticipated that, given Don Keele was involved in their design. Oh yea, and there’s an added bonus; they can absolutely keep up with the Beast. The MFL-6 speakers do not play second fiddle to Hsu’s 150 pound, 4 port subwoofer. Crank the volume and they happily come along for the ride.
As previously mentioned, I conducted this review in two parts; the first being just the D15-Chimera and MFL-6 speakers, the second was with the D15-SC module added (in 4 port mode). I did it this way so I could get a feel for how each configuration performed. Despite the logic behind the vertical orientation of the Chimera, it doesn’t go unnoticed in a room. When you add the Super Charger, and change to the horizontal position, it becomes even more evident. In order to test both setups, I did the movie and music portion in two stages.
Movies
If I said “8 seconds of fury”, how many of you would think PBR? No, not Pabst Blue Ribbon. I mean Professional Bull Riding. Play the opening from Edge of Tomorrow with the D15-Chimera cranked and you get a definite kick. Obviously not like a real bull, but it hit with enough authority to grab my attention. It wasn’t just the power though, it’s also the poise. The Chimera played this scene with flair, and I don’t mean that in a condescending manner; it combined output, depth, and composure in equal doses. The only thing I wished for was a bit more oomph from the 5th level of the pulsing effect this scene is renown for. It’s the deepest and most challenging for a subwoofer, by the time the Chimera got to that part you could tell a limiter had kicked in and killed the buzz to some extent. Introduce the D15-SC into the mix and things become decidedly different. There was no tapering off this time, no lost sense of impact. Think jackhammer, it pounded away. You want to really feel this effect? Unleash the Beast and you most certainly will.
With Black Hawk Down I suppose all I have to say is “Irene” and you know what I’m talking about. I’ve been to a number of air shows in my life, and for those who also have you know all about the physical sensations when a whirlybird takes flight. By itself the Chimera nailed the sound and most of the perception, but it wasn’t assertive enough to produce the requisite sense of impending doom. Similar to Edge of Tomorrow, it didn’t quite have the last bit necessary to make it totally convincing. Add the SC and all that changes, now you get drawn right in. Naturally it can’t quite replicate the fury of a real chopper, but in my HT it certainly made for a very engaging experience. While the bass was pounding away, the subtle undertones were handled effortlessly by the MFL-6 speakers. Depth and imaging remained intact, even with all the other noises being layered in. Of particular note were voices, in a scene like this they could easily be drowned out. Not so here, they were intelligible.
Frequently with Avatar I use the Assault on Home Tree scene as a test, so why change now. As the “sky people” approach in their gunships there was a strong pulsing from the Chimera, when the enemy aircraft hover and take up position it was still very convincing. Their opening salvo are gas rounds, each hit the ground and exploded with a crisp pop. That doesn’t scare off the Na’vi, in response the assailants launch incendiaries at them. Those detonated with a solid thump, causing the tribe to flee. As they were retreating the human insurgents decide to topple Home Tree, a sacred place for the Na’vi. Using missiles aimed at its gigantic above-ground root system, they bombard it with a relentless assault. The explosions created a cacophony of sounds, each having their own signature. Run that same scene in Beast mode and everything ratchets up a notch or three. All of the above now has a certain presence that wasn’t achievable with just the Chimera itself. It’s certainly no slouch, but if you want to feel like you’re part of the movie adding the Super Charger is the way to go. Despite all the chaos the MFL-6 remained calm, pumping out sound that was every bit the equal to what the Beast was doing. They effortlessly played all of it, no matter how loud I cared to go.
Rounding out the movie section is perhaps one of the most exaggerated soundtracks I have in my collection, TRON: Legacy. If you want to evaluate a subwoofer for both depth and precision, this flick certainly warrants your consideration. In particular, the Lightcycle battle. It basically has everything I’m looking for when pushing a subwoofer. I also have the MFL-6 speakers to consider, good thing there’s plenty for them to do in the same scene.
Fireworks herald the battle itself, they burst in the sky with vigor and weight. The undertone from the soundtrack was smooth and powerful, yet despite that the Beast didn’t overwhelm the speakers. They held their owned, intertwining brilliantly with the over-the-top bass. During the Lightcycle battle there are several different types of explosions and crashes, all of which were palpable. Where most subwoofers fall apart are the pulsing sensations you get during this scene – they can often sound muddy and indistinct – but not so with the Chimera/SC combination. This part of the scene wasn’t the least bit obnoxious or unpleasant, it was notably assertive. What tends to get lost amongst the mayhem is how much nuance is buried in the soundtrack, something the MFL-6 speakers latched on to. Delicate sounds did not get squashed by the potent low frequencies, these speakers were resolute and steadfast throughout.
Despite a very aggressive night of movie tests, the Chimera’s amplifier wasn’t stressed. No matter how hard I pushed this subwoofer it never got more than warm.
Music
“Pyrokinesis”. There aren’t many people who know about Tony MacAlpine, largely because nothing he does is mainstream or radio friendly. His brand of music leans firmly toward the aggressive and high energy side of the spectrum, filled with rhythms that are very difficult for mere mortals to play. That’s not surprising when you consider Tony favors guitars beyond the normal 6 string variety, he plays ones that have 7 and even 8 strings. As if that’s not enough, he is equally adapted with the keyboards and bass guitar. Must be nice.
To say “Pyrokinesis” is fast paced would be an understatement, but that’s partially why I chose it. Marco Minnemann’s kick drum was absolutely frenetic, with an almost machine gun-like quality to it. Each hit was clear and unmistakable. His snare had a sharp snap to it. Tony’s guitar was powerful and meaty, with pinpoint accuracy.
To keep the lively tempo going I went right to a band I saw open for Metallica close to a decade ago, Volbeat. The song “Seal the Deal” was perhaps the only one from their catalog that was ever in heavy rotation on FM and XM radio. That means unlike “Pyrokinesis”, you may have actually heard this one before. It’s the title track from their 6th studio album, which was released in 2016. Similar to most of this bands songs the vocals and guitars are recorded on the hot side, which the MFL-6 just ate up. Changes were crisp and fast, with tremendous poise. Underpinning the high-speed rhythm was a constant pounding from the drums, skillfully laying the foundation for this song. This all-Hsu system merged everything into a cohesive whole.
I love the opening of Hans Zimmer Live in Prague performance, which features a medley of “Driving/Discombobulate/Zooters Breakout”. Both the video and orchestra playing it nailed this perfectly. Hans is quite possibly the most prolific composer of soundtracks there has ever been. He has done the musical score for such acclaimed titles as Rain Man, Gladiator, Driving Miss Daisy, Inception, Crimson Tide, Interstellar, Madagascar, Pirates of the Caribbean, The Lion King, DaVinci Code, the list goes on. This sequence will surely test every facet of your system. From quiet interludes to expansive orchestral pieces, you will be given a clear indication of what your speakers and subwoofer are capable of. At one point there are ~70 pieces playing at full tilt. That’s a lot to manage.
In my mind, this has to be the type of scenario Hsu envisioned when designing the Chimera, SC and MFL-6 speakers. This medley is a tough ask for a system, especially at volume, yet they nailed it perfectly. Despite some pretty complicated material, it never sounded congested. From the interplay of the stings and woodwinds, to the pounding from drums and tympani’s, it was all there. Of the test material used, this piece was perhaps the most anticipated. When you’re looking forward to something there can be a letdown, mostly because you’ve built it up in your head to an unreasonable level. Not this time, Hsu treated me to a stirring rendition of this performance.
For years Hsu has included a demo CD with their subwoofers. I’ve actually used selections from it when evaluating other manufacturers subs, I would be remiss if I didn’t include at least one track from their very own disc. This CD contains various music passages, along with pink noise and test tones to use when configuring and evaluating your new Hsu sub. The song to use this time was an easy choice, “Saint-Saëns Organ Symphony”. I also chose that when evaluating the Hsu VTF-TN1, so why not again?
There’s an insert with the CD that details what each selection is, for the “Saint-Saëns Organ Symphony” the description says “WARNING: When playing this track for the first time lower the volume as your woofers may be at risk. The bottom octave of this recording may damage vented loudspeakers”. It goes on to say “this recording has the strongest and cleanest 16Hz of any recording I have come across”. For me that’s not a warning, it’s an invitation. The recording is only about 03:45 minutes long, but for quite a bit of it there is the aforementioned 16Hz tone. And it pulses rapidly, going off so quickly that the driver ends up pumping like a piston. Unless you’re sitting on a concrete slab you will feel it in your chair, something I certainly did that night. There was no evidence of distortion or stress, the Beast simply shrugged it off. I sat in my recliner and got a nice little massage, thank you Hsu.
Conclusion
Hsu Research is widely regarded as the value leader in the ID (internet direct) market. It’s not just low cost that is notable here, it’s what you get for your money. They eschew some of the more advanced features, like phone apps, but in exchange you get incredible bang-for-the-buck performance. The D15-Chimera with the D15-SC are a potent combination that should satisfy even the most demanding and discerning basshead. I don’t know of any other subwoofer on the market today that can touch this pairing for the price.
Based upon their specifications the MFL-6 seem to be little more than garden variety bookshelf speakers, but that’s deceiving. The detail and precision they’re capable of producing belies their less than traditional looks. These speakers are the textbook example of form follows function. As I said before, I’m not a fan of horn speakers. Well, at least I wasn’t until I heard the MFL-6. Now I might have to eat those words.
Specs
D15-Chimera
Driver: Dual 15″
Alignment: Sealed
Extension: 25Hz, -3dB
Power: 1200 watts RMS, 4000 watts peak
Inputs: XLR, line level (RCA)
Q Control: 0.3–0.7
Phase: 0°/ 180°
Dimensions: 30.5″x20″x18″ (HWD, vertical orientation)
Weight: 101 pounds
Warranty: 7 years woofer, 5 years amplifier
Price: $1799
D15-SC
Alignment: ported (2, 3, or 4 open)
Extension, 2 ports open: 14Hz, -3dB
Extension, 3 ports open: 15Hz, -3dB
Extension, 4 ports open: 17Hz, -3dB
Dimensions: 19″x18″x29.5″ (HWD, horizontal orientation)
Weight: 50 pounds
Price: $499
MFL-6
Tweeter: 1″ aluminum diaphragm (Don Keele designed constant directivity horn)
Midrange: 6.5″ paper cone, cloth surround
Frequency Response: 60Hz – 20kHz +/- 2 dB
Amplifier Power: 10-250W RMS
Impedance: 8 ohms
Sensitivity: 92dB
Enclosure: 3⁄4″ MDF, ported or sealed (port plug not included)
Dimensions: 15.4″ H x 8″ W x 5.8″-10.1″D (angled front panel)
Weight: 13 lbs
Warranty: 7 years
Price: $279
Test Bench
Measurements were taken using an OmniMic. The subwoofer was positioned in the center of my listening room. As per Hsu’s recommendation, the D15-Chimera was on the bottom with the D15-SC on top (opposite of how it would be used during normal listening). The microphone was on the ground 1 foot from the front/port side of the enclosure.
Legend
Sealed – Black
2 ports open – Red
3 ports open – Blue
4 ports open – Green
This graph represents frequency response only, it does not provide an indication of total output capability.
