December 2016


German Physiks Unlimited MK II Loudspeaker
An ingeniously designed omni-directional speaker system.
Review By Tom Lyle

  German Physiks' Unlimited MK II is a very modern looking speaker. I suppose some might describe it as looking like futuristic furniture. Or perhaps as a three-and-a-half-foot tall robot to maybe even a modern light fixture. Of course, this all stems from the fact that the Unlimited MK II speaker does not look like a typical high-end speaker. It is not only a modern looking speaker, but a speaker with a unique modern design, as it is an omni-directional speaker that uses a uniquely designed omni-directional driver.

Although I described it as looking modern, omni-directional speakers aren't all that new, as there have been a few different models on the market for some time, in fact, there are currently a few very successful models from a few different manufacturers being sold today. But what sets German Physiks apart from these other manufacturers is their DDD (Dick's Dipole Driver), named after Peter Dick, who in the 1970s took up where the Walsh di-pole speaker left off, refining this speaker until finally Holger Mueller founded German Physiks, and thus putting the DDD driver to work.

As one can see in the photo of the Unlimited MK II, the DDD driver sits atop the speaker's cabinet. Its inverted cone has its driver element at the top of this cone. The main difference between this cone and a conventional piston driver (besides looking completely different) is that when a piston driver moves, the entire cone moves with it (at least it should). Therefore, the majority of these driver manufacturers use the stiffest materials they can, because when the voice coil of a piston driver moves, the entire cone movers with it, again, at least it should. The sound waves of the driver move in the same direction as the movement of the cone. That's why one usually aims a piston cone driver at the listener.

The DDD driver of the German Physiks speaker might look to some as a simple device. It isn't. It has four modes of operation. Rather than bore you with a technical treatise on these four modes, I'll just state that as the voice coil of the DDD driver moves, the whole cone does not move together with it as a piston driver does. Instead, in the DDD driver the voice coil causes a wave that travels from the small end of the cone down to its open end. And rather than using a material for the driver that is stiff as possible, the DDD driver material is made of a super-flexible and light foil that is 0.025mm thick titanium or a 0.15mm thick carbon fiber. The cone is easily excitable, and moves when even the slightest signal is applied to it. Things get more complicated when discussing how the soundwaves are generated sideways, as the angle of radiation with respect to the cone wall becomes progressively more acute with increasing frequency due to dispersion of the bending waves.

Additionally, the driver's operating mode changes with frequency. A detailed description of the mechanisms involved is beyond the scope of this review, partly because I don't have the space, but also because I would simply be copying and pasting this technical information from German Physik's website, which one could easily reference. But one should note that on this website German Physik's says that their DDD driver is 'revolutionary." Why? They say this is because they have eliminated the limitations of a conventional driver. The combination of high displacement, low mass, and high acceleration allows the DDD driver to operate linearly over a very wide frequency range -- the range of human hearing -- at the same time it has an excellent impulse response, low distortion and a flat phase response. German Physiks says that their DDD driver 'can offer an improvement in sound reproduction that we feel quite justified in describing as revolutionary." The DDD covers the entire frequency range from approximately 200Hz to 23kHz. As such, it is essentially a point source for all but the lowest octaves. That of course is what is responsible for the incredible coherence, which is simply not obtainable with a multi-driver dynamic speaker, in which each driver has its own distortions and dispersion characteristics, and in which the crossover, no matter how well designed, invariably introduces its own artifacts. The German Physiks speakers avoid this entirely.

Modest
The Unlimited MK II is German Physiks' most modest model. Yet $14,500 isn't cheap, so one can correctly assume that the technology and mechanical craftsmanship (not to mention the research and development) that have gone into even their least expensive speaker are not insignificant. Conversely, German Physiks makes some mind-blowing models that take the technology that they have developed to its fullest expression. One can correctly assume that these models demand a large listening room and the associated equipment to bring these speakers to life, and have them exhibit the characterization that their designers intended. The Unlimited MK II that is reviewed here, on the other hand, also demands competent ancillaries, but can work in a much smaller room with ancillaries that of course should be competent, but also should be accessible to a real-world audiophile.

Quality
The Unlimited MK II uses their DDD driver that sits atop a 32.5' rectangular MDF (Medium Density Fiberboard) cabinet covered in a 'high quality acoustic vinyl" that is available in white, grey, black and dark brown. The review sample is covered in black vinyl, and has a very nice 'satin textured" finish. The finish has two layers. The layer closest to the cabinet is said to provide a 'significant amount" of vibration dampening, while the outer layer is cosmetic, providing texture and color. German Physiks uses a damping material called Hawaphone on the interior of the speaker's cabinet. They claim that this material "achieves a broadband attenuation of structure-borne sound of more than 50dB." In combination with the finish that sits closest to the cabinet, they say that cabinet vibration is significantly reduced. At the bottom of the cabinet is a downward firing 8" woofer. With the spikes that are included with the speakers installed, there is about 2" of space between the bottom of the cabinet and the floor.

As the Unlimited MK II speakers are an omni-directional speaker, the manual states that one should shoot for a minimum distance of about 20" from the front and side walls of one's listening room, and the distance of one's listening position should be about 1 to 1.5 times the distance from the plane of the front of both speakers. I set them up in my listening room as far away from both the side and the front walls as I could, and ended up with each speaker about four feet away from any surface. Through experimentation I also found that the speakers sounded best by having my listening position equal to the distance between the two speakers, forming an equilateral triangle. When using this type of speaker, I suggest you do as I did and experiment. These speakers behave unlike any speakers I've ever had in my listening room, and unless you've had the pleasure of having omni-directional speaker in your room in the past, I suggest you do the same.

Upstream
The Unlimited MK II's are quite sensitive to upstream components, especially one's chosen power amplifier. For most of the review I ended up using a pair of Merrill Audio Veritas monoblocks that I had on loan that put out 400 Watts each into 8 Ohms. One certainly doesn't need this much power to drive the Unlimited MK II, but it was nice to not worry about clipping or other anomalies from using a power amp that didn't have enough juice. I also had on hand my resident Pass Laboratories X350.5 power amp that has 350 Wpc at 8 Ohms. It was a toss-up as to which amp sounded 'better," but as I ended up using the Veritas more often than the Pass Labs I might have answered that question, at least to myself. I still had in-house a rather opulent 12 foot run of Westlake speaker cables, so I ran those between the speakers and the amplifiers. Preamplifiers were either the Mark Levinson No. 523 that I reviewed in November's issue, the Luxman C-700u that I reviewed in October's issue, or my resident tubed Balanced Audio Technology VK-33. Most of the time a computer-based music server with a Furutech USB cable connected to an AURALiC VEGA DAC was the digital front-end, but there's also an Oppo BDP-83 Special Edition universal player for playing physical digital media, such as SACDs.

Of course, my large CD collection on the shelves of my listening room are for referencing the booklets, and the discs themselves as back-ups, as all their data has been transferred to hard-drives that feed the music server. The analog front-end thankfully remains a Basis Debut V turntable with a Tri-Planar 6 tonearm. Phono cartridges mounted on the tonearm include a Kesiki Purple Heart or a Gold Note Tuscany, or the soon to be reviewed Van den Hul Stradivarius. The turntable's AC synchronous motor's power cord is connected to a power supply that provides the ‘table with a pure AC sine wave with the appropriate frequency for its chosen speed, 60Hz for 33.33rpm, or 81Hz for 45rpm. The phono preamplifier is the Pass Labs XP-15, the bulk of the components are connected to each other via MIT Shotgun S3.3 balanced interconnects, and the heavy equipment rack is an Arcici Suspense. Occasionally I augmented the sound of the speakers with my Velodyne subwoofer, which has a 15" driver and a 2500 Class E onboard amplifier

Serious
The pair of German Physiks Unlimited MK II I was sent for review were already broken in, so I could immediately get down to some serious listening once they were properly set up. I quickly learned that I was going to have to become accustomed to a totally different approach to enjoying sound reproduction with these speakers. My reference electrostatics certainly have a different approach to reproducing music from speakers using dynamic drivers, but the omni-directional nature of the German Physiks Unlimited MK II was a very different experience. Entirely! It took more than a little getting used to, but after a while I came to realize how many audiophiles could thoroughly enjoy this experience. And after a little while longer, I came to realize how it could not only be a different way of enjoying the reproduction of music in one's home, but the way to enjoy the reproduction of music.

When I purchased Led Zeppelin's catalog as they were reissued on meticulously pressed 200-gram vinyl in the early 2000s I didn't do so because these records would eventually become very valuable. I acquired them because I was a fan of the music, and wanted to hear these albums in the best possible sonic light possible. There are diehard fans that still debate with one another as to which is the best pressing of each album, but there is no question that these Classic Records pressings are at the top of every list. I suppose that's just one of the reasons why these pressings fetch so much on the used market. I tried to ignore all that nonsense when I put on Led Zeppelin II.

The recording quality varies on this release from track to track since they recorded it in different studios while touring. But the first track, "Whole Lotta Love," is a fantastic multi-track recording. Through the Unlimited MK IIs the band was not only spread across the front of my listening room, but fully enveloped me. Each instrument and Robert Plant's voice were separated from one another in space. But as when listening to a band in a live situation, one can hear where the instrument is located, but it isn't as if there is a boundary drawn in the air were this sound stops. These speakers also sound clearly different from a multi-driver dynamic speaker in that there is no bass-mids-treble delineation; there was just the sound of the instruments in space. Yes, if one were to nit-pick the bass was somewhat separated from the rest of the sound due to the downward firing woofer, but the omni-directional nature of bass frequencies makes this mostly a non-issue.

The freak-out middle section of 'Whole Lotta Love" was a trip, no pun intended. John Bonham uses the crown of the ride cymbal to keep time, and this cymbal sounds über-realistic through the Unlimited MK II. The myriad of sounds coming forth from both the musicians and the studio console filled the air of my listening room and swaddled me in sounds, as Jimmy Page's Theremin sounded as if it was being emitted from a source nowhere near the location of the speakers, but from within the air itself. One small complaint I had was that the highest treble was a bit indistinct through these speakers, at least when compared to the best dynamic and even my reference electrostats, yet this hardly ruined the sound of the speakers, as the treble was still quite extended and added to the speaker's ability to create an enveloping sound. Getting lost in this music was never so easy.

The bass of the Unlimited MK IIs reached much lower than I would have expected from a single eight-inch woofer. My listening room has several acoustic treatment panels along its front, back and side walls, which in the past have helped bring out the best in many different types of speakers. The specifications published with the Unlimited MK II claim that the speakers can go down to 32 Hz (although it doesn't specify the accuracy of this number), and I don't doubt that. That is an awfully respectful specification for an 8" woofer. Because of the loading scheme of the woofer German Physiks has enabled this woofer to perform admirably, that's for sure. I was quite surprised at how low the bass went, as were visitors to my listening room. It was more than just how low, but the quality of these lows that impressed during long listening sessions. German Physiks sure knows how to load a woofer!

Shortly after spending an afternoon and part of the night going through a good portion of Led Zeppelin's catalog, but still staying with Classic Records' 200-gram LP reissues, I put on the RCA Living Stereo version of Prokofiev's Lieutenant Kije, which has on its B-side Stravinsky's Song Of The Nightingale. Audiophiles can carry on all they want about how their systems mimic the sound of a symphony orchestra, but in truth, we can come only so close to this holy grail. In our homes through a pair of stereo speakers a large orchestra spread across a stage with a proscenium the size of Kingsway Hall isn't going to happen. Yet there are certain clues to this reality that can be reproduced, often with stunning results. Each type of speaker, whether it be dynamic, planar, or electrostatic has its strong points when it comes to reproducing real instruments playing on the stage of a concert hall.

The strong points of the German Physiks Unlimited MK II are many, one of which is its huge soundstage. But it also has the uncanny ability to elicit an emotional response when it reproduces the sound of an orchestra. The omni-directional sound places each instrument and group of instruments within this huge soundstage, and this soundstage is occupied by extremely realistic sounding instruments to create the illusion that one is hearing a facsimile of an orchestra in miniature. It does this by creating a three-dimensional sound of the instruments and groups of instruments that occupy this soundstage. On a good recording, I could not only hear the sound in front of, but to the sides and behind the instrument, plus the air around each of the instruments.

Of course, the sound I described above will depend greatly on the quality of the equipment in the rest of one's system. The German Physiks Unlimited MK II are very sensitive to upstream gear, especially the amplifiers feeding it, as well as the source that is feeding the amplification. In this review, I've so far used LPs when describing the sound of these speakers, but I spent many hours also using digital sources to enjoy what the Unlimited MK IIs offered. I could hear the stark difference between plain vanilla Red Book "CD-quality" sound and files with 24-bit/96kHz resolution. When listening to DSD files or SACD discs the sound got much better still. One certainly doesn't need super-fine gear to hear the difference between these formats, but the German Physiks speakers made the differences greater than I've ever heard before. Interconnects, power supplies, and tweaks all made a huge difference when listening to the Unlimited MK II speakers.

When I switched out the Unlimited MK II's rubber feet for the supplied spikes in my carpeted listening room, the speaker's bass became tighter by the nth power. I could even hear differences creep up into the sound of the lower mids when putting in the spikes, as the midrange of the Unlimited MK II is luxurious sounding. Female vocals were rendered with a super-realistic, seductive sound. When I played the DSD file of the EMI recording of Elgar's Sea Pictures with Janet Baker singing, it was if I could picture her standing in front of the orchestra at Abbey Road Studios singing into the microphone. But it was more than that, often it sounded as if there were no speakers in my listening room, the sound of the orchestra and her voice were just there.

Ingenious
The German Physiks Unlimited MK II are unique speakers that use an ingeniously designed omni-directional driver. Yet these speakers attempt to reach the same goal as any other type of high-end speaker – to bring us closer to the music – the musicians who make this music and the producers and engineers that record this music, and ultimately the sources we use to feed our speakers. But the Unlimited MK II makes many speakers that don't use omni-direction drivers seem primitive when it comes to many of the cues that make recorded music correspond to what happened on the other side of the microphone or recording console. The German Physiks Unlimited MK II loudspeakers' approach to reproducing music might not be for everyone, as the omni-direction driver isn't perfect. But neither is any other type of speaker that humankind has developed. Every audiophile owes it to him or herself to hear what Unlimited MK II speakers have to offer, especially those which are a relatively affordable gateway into German Physiks' omni-directional sound. After an audition one may never consider another type of speaker again.

Specifications
Type: Two-way loudspeaker system with special DDD driver
Frequency response: 32Hz to 24kHz
Impedance: 4 Ohms
Power Handling: 110 Watts nominal and 170 Watts short term
Recommended Amplification: Minimum 90 Watts @ 4 Ohms
Crossover Frequency: 200Hz
Crossover Slopes: 
DDD section: 6dB/octave electronic & 18dB/octave acoustic
Woofer section: 18dB/octave electronic & 18dB/octave acoustic

Sensitivity: 88dB/W/m
Operating Principle: Two-way loudspeaker with 360° surround radiation using the German Physiks DDD driver
Input Connectors: One set of binding posts
Drivers: One carbon fiber DDD driver and one 8" woofer

Finish: 
Unlimited Mk II: Acoustic vinyl in satin finish white, black, light grey or dark brown
Unlimited Mk II Ultimate: High polish polyester black or white
Unlimited Carbon: Carbon fiber

Dimensions: 9.5" x 41.3" x 9.5" (WxHxD)
Weight: 63.7 lbs.
Warranty: Five years
Price: $14,500

Company Information
United States of America Distributor
Distinctive Stereo LLC
808 Loretta Drive 
River Vale, NJ 07675

Voice: (201) 391-00279
Email: sales@distinctivestereo.com
Website: www.DistinctiveStereo.com