The Unicorn Mk II is the loudspeaker that many claim they would take to a desert island if it was the only choice! An outstanding single-driver, horn-loaded, omnidirectional loudspeaker. A true UNICORN! Optimized for music with dynamics, mainly jazz, blues, ethnic, small ensembles and chamber music, it is unique in its performance and appearance. As with all German Physiks loudspeakers, it is phase coherent and provides a large soundstage and accurate reproduction of the recorded material. It can be coupled with high quality tube amplifiers that are able to drive 4-ohm loads, or small class A amplifiers. The Unicorn loves class A amplifiers.
Ultra Fast Low Distortion Bass
Considerable work went into designing the Unicorn’s horn system. The final design comprises a high gain horn coupled with a tuned bass trap. The bass trap keeps mid-frequency energy out of the horn. This would otherwise lead to smearing due to time differences between the DDD driver’s direct radiation and the horn, as well as cause a bump in the mid frequency response. To achieve a completely even frequency response in the transition region, a small amount of equalization is applied to the input signal by a network which is housed in a separate case. The excellent qualities the DDD driver shows in its normal mode of operation are exhibited in the bass produced by the horn. It is fast, agile and extremely clean. There is no hint of bloat or overhang and distortion is impressively low.
How was the Unicorn Born?
The Unicorn is the only German Physiks design that uses a single DDD driver to cover almost the entire audio range: 40Hz to 24kHz. It started life in 1998 as an experiment to produce a DDD driver based design with improved integration of the very low frequencies, hitherto handled by a conventional bass driver and the range normally handled by the DDD driver – approximately 200Hz to 24kHz. Whilst the integration of our designs offered was good by the standards of the time, it had not reached the levels that we now achieve after 25 years of experience.
The Challenge
This however, was not so simple. A horn could provide more than 10dB of lift and so compensate for the DDD driver’s falling bass response, but achieving perfect integration of the DDD driver and horn posed three major challenges:
- In the region where the DDD driver’s response was falling off, the horn would provide too much lift.
- When the DDD driver’s response had fallen by more than the horn’s acoustical gain, the system response would drop noticeably.
- The horn would also boost the mid-range, up to several hundred hertz and this would produce a time smear effect due to the path difference between the energy radiated by the horn and the direct radiation from the DDD driver.
The Solutions – Acoustic
The first part of the solution was to combine a high gain horn with a bass trap located in the throat of the horn. The bass trap itself consisted of two parts:
- A damped Helmholtz resonator similar to that used in the Borderland Mk IV and HRS-130 models.
- A pressure-release system like a Tube Trap.
The bass-trap keeps almost all of the mid-range out of the horn and also attenuates the region from 70Hz to 140Hz. At the point where the attenuation provided by the bass-trap is falling off and the DDD driver’s response has also dropped significantly, the horn is coming into effect, thereby lifting the response and providing a smooth transition from the direct radiation provided by the DDD driver and the output from the horn.Because the horn provides an extremely fast transient response, the bass is very fast and very precise and this provides an excellent match with the fast transient response offered by the DDD driver.
The Solutions – Electronic
An equalization network placed between the power amplifier output and the loudspeaker was used to protect the DDD driver from being damaged by large low frequency signals. This was especially important with the early version of the DDD driver that used a titanium foil diaphragm, as this was easily damaged when subject to large excursions. The current carbon fiber diaphragm DDD driver is very much more rugged in this respect. The network also provided adjustment of the low frequency roll-off and the high frequency level, similar to that now provided on many other German Physiks designs.
In the Unicorn Mk 2, the original passive equalizer has been replaced by a DSP based unit, which sits between the preamplifier and power amplifier. This allows the Unicorn to be connected directly to the power amplifier. The passive equalizer is still available to special order.
In 1999 prototypes of the design, now officially known as the Unicorn because of its single DDD driver, were given a number of private demonstrations. These produced enough orders to convince German Physiks to put the design into production. The Unicorn Mk I sold steadily, mostly in the Far East, where horn loudspeakers were very popular and the unconventional looks were not a barrier. In fact, compared to what some customers were using, the look could almost be considered conservative.
In 2005, the Unicorn Mk I was replaced by the Mk II version, which featured a modified horn design. This continues to sell today, still mostly in the Far East. While the limited very low bass rules the Unicorn out for devotees of extreme low frequencies, its exceptional coherence, clarity and speed enable it to provide a wonderfully involving and enjoyable musical experience with jazz, female vocal and small to medium scale classical music. Many Unicorn owners comment that the clarity and agility of the bass it provides is more than adequate compensation for its reduced very low bass response. If you want a demonstration of this, please look at this You Tube clip from High End Munich 2012, showing two visitors to our room seriously getting in to a pair of Unicorn Mk IIs doing a very good job with Pink Floyd’s iconic track Money.
Summary
The essence of the Unicorn has best been summed up by the late Wes Philips, who wrote in his CES 2009 report for Stereophile magazine:
“I initially listened to the Unicorns waaay over against the wall, but I still got a coherent, solid soundstage. When I sat in the sweet spot, I essentially heard what I’d heard over to the side—only a tad more of it.
The more I learn about hi-fi, the more I find I need to unlearn. I always thought I didn’t like 360° speaker designs, but it was specific designs I didn’t care for. The Unicorns were fast, focused, and convincing.” There you have it.
Stereophile Magazine, Wes Phillips, CES 2009 Report
Specifications
Impedance
4 ohms
Frequency Response
40 – 24,000Hz
Power Handling
Nominal 100W
Short term 140W
Amplification required
Minimum 60W/4 ohms
High frequency adjustment
-2dB, flat, +2dB and +4dB centred at 8,000Hz
Low frequency adjustment
Flat, +1.0dB, +2.0db and +3.5dB centred at 60Hz
Sensitivity
88.0 dB for 1W at 1m
Operating principle
Full range loudspeaker with 360° surround radiation
using the German Physiks DDD driver
Input connectors
1 set of WBT nextgen™ binding post
Drivers
1 x carbon fibre DDD drive
Recommended room size
8 – 46 square metres
84 – 486 square feet
Finish options
Satin or high polish veneer
High polish polyester black or white
Satin or high polish paint
Carbon fibre
Please see Finishes page for more information
Dimensions
Loudspeaker
550mm W x 1,241mm H x 460mm D
21.7″ W x 48.9″ H x 18.1″ D
Network housing
270mm W x 173mm H x 230mm D
10.6″ W x 6.8″ H x 9.1″ D
Weight
Loudspeaker 56.0kg / 123.2lbs
Network housing 4.4kg / 9.7lbs
Warranty
5 years
As part of our process of continually improving our products, we reserve the right to change specifications without notice.
Other Resources
“The low-frequency range of the Unicorn MkII is stunning too. Its character matches the unobtrusive, smooth nature of the midrange and treble reproduction. The DDD doesn’t produce an ascetic pseudo-bass, but a real, rich and powerful low-frequency range, that is even able to fulfill party and “level-orgy” needs. The only broadband loudspeaker without compromise and the best full-range design in the world? Yes, Mr. Mueller!” view/download
hifi vision, 2012
Publication: HiFi Statement Review, 2012 (in German), link/download
Publication: LP, 2012 (in German), link/download