ΚerrAcoustic K300 MK III Τιμή το ζεύγος χωρίς τις βάσεις.
The K300 is a 2-way stand-mount loudspeaker, which breaks new ground in compact loudspeaker performance.
The 6.5” sliced wood-fibre cone integrates seamlessly with a true ribbon tweeter, for unmatched speed and transparency. Featuring the Kerr Acoustic transmission line, the K300 produces a stunningly accurate and extended frequency response from 33Hz – 45kHz which remains linear and uncoloured at all playback levels.
Now in its third incarnation, the mk.3 update brings improvement in midrange clarity and stereo imaging. Following extensive re-development of our passive crossovers, we have managed to further refine our circuit topology making the K300’s response more linear and efficient.
Available in a range of real wood veneer finishes, including Oak, Walnut, Rosenut and Black Oak, as well as either satin or high-gloss lacquer in any RAL colour.
LF Driver 165mm Wood-fibre cone with extended linear suspension system and patented symmetrical drive motor design
HF Driver 60mm True Ribbon tweeter with 0.027g diaphragm mass
Response 33Hz – 45kHz
Sensitivity 89dB (2.83V/1m)
Impedance 6 Ohms (nominal)
Crossover 1.95kHz – 2nd order (12dB/ Octave)
Dimensions H:420 | W:195 | D:395 mm
Construction 18 / 24mm Baltic Birch plywood transmission-line
Weight 12 kg (per cabinet)
Connections One pair of 4mm copper 5-way binding posts
We feel that ribbon tweeters are an area often shrouded by misconception.
KERR ACOUSTIC TRANSMISSION LINE
Based on quarter-wave technology, the Kerr Acoustic transmission line represents a breakthrough in frequency response and extension. We have carefully refined every detail of our transmission lines, to ensure exceptionally well-controlled and extended bass, and clear uncoloured midrange. The resultant performance truly belies the physical size of our speakers, bringing remarkable sonic reproduction into your space.
CROSSOVER WITHOUT COMPROMISE
We firmly believe that a crossover network can make or break a loudspeaker design, which is why we consider the quality of these circuits to be of the utmost importance. Using bespoke hand-wound air-core inductors, and the highest quality pair-matched film capacitors and resistors, our crossovers are kept utterly neutral and transparent. Each crossover is hand-assembled on our custom PCB boards. and individually measured before being installed. We use pure OFC copper internal wiring in each loudspeaker, and feature high-quality 5-way copper binding posts.
TRUE RIBBON TWEETER
Whether you’re a professional mix engineer who requires surgical precision when creating music, or a discerning audiophile who wishes to hear every nuance when listening for pleasure, the true ribbon tweeter delivers unprecedented clarity and resolution. Once you become accustomed to listening with this level of precision and detail without fatigue, you’ll never switch back to a conventional tweeter.
BALTIC BIRCH PLYWOOD
The physical loudspeaker cabinet is arguably the most fundamental component in any speaker design, whilst simultaneously being one of the most overlooked. We place a great emphasis on the materials and construction quality of our cabinets, taking every possible measure to eliminate unwanted resonance. Each cabinet we produce is handcrafted from the highest grade responsibly-sourced Baltic birch plywood. The 90-degree alternating cross-grain makeup of our plywood allows us to create panels which are entirely self-damping and acoustically inert. As a result, our cabinets are extremely strong and rigid, and transfer minimal levels of mechanical energy into their surrounding environment. When compared with cabinets made from MDF and other less costly alternatives, the difference in performance is starkly clear.
STUNNING CUSTOM FINISHES
Our finishing options are of the very highest quality, and guarantee your loudspeakers to be a stunning addition to any space. It’s no secret that while sonic performance is the ultimate goal, aesthetics play a large role in the ultimate enjoyment of your loudspeakers, and that in many cases you may wish for your loudspeakers to fit into a pre-existing setting. Using the RAL colour system, we are able to match to over 200 different colours in automotive-grade polyester lacquer, in either satin or high gloss finishing options. We also offer a range of sumptuous real wood veneer finishes, with customisation available upon request.
For more detailed technical information about the technology used in our designs, please view our technical white paper at the link below. Or, to find out how our products translate into the real world, read the testimonials left by some of our happy customers.
Transmission Lines and Ribbon Tweeters: The Best Route to Loudspeaker Design for Accurate Musical Reproduction
General Introduction
The professional music and consumer electronic industry has strived for decades to optimise loudspeaker design for time response, frequency response, dynamic and timbral accuracy within the constraints set by cost, size, and positioning limitations. Bass response has historically presented inevitable trade-offs in terms of low frequency extension and control, as well as cabinet size and drive current requirements. Equally, advancements in electrostatic, planar magnetic and orthodynamic headphone technologies have highlighted the less-than-perfect nature of high frequency reproduction from most typical loudspeaker systems. Recent developments in ribbon tweeter technology, combined with a revised approach to bass-frequency reproduction through the refinement of transmission line technology, allow a designer to tackle some of the fundamental limitations of loudspeaker design and sound reproduction, resulting in a level of absolute sonic accuracy as well as a cost/performance ratio that has been previously unavailable.
INTRODUCTION TO TRANSMISSION LINE PRINCIPLE AND SONIC BENEFITS
An acoustic transmission line is essentially a tuned labyrinth (or ‘rear waveguide’) that begins directly behind the main low-frequency driver in a speaker system, and gradually tapers until it reaches its terminus – which typically has a surface area equal to the cone of the driver. Depending on the format of the enclosure, this labyrinth will consist of a number of internal folds to allow the desired line length to be achieved. In smaller designs, this line length can be decreased in conjunction with a reduction of the area of the terminus to achieve similar effects, with the compromise of losing some extension and overall output. In the truest sense, a transmission line would consist of an infinitely tapering chamber, which in practice is a physical impossibility. To this extent, the term is partially misused, and acoustic ‘transmission lines’ work on the basis of being tuned to 1/4 or 1/3 of the wavelength of the resonant frequency of the driver, and are heavily damped with absorptive material. The output from the terminus greatly reinforces content below 80Hz, with the unwanted higher frequencies from the rear of the driver being absorbed by the internal dampening.
The compromises associated with transmission-line designs include a cabinet size that is often larger than typical sealed or bass-reflex enclosures. Furthermore, transmission line speakers have historically been considered ‘low efficiency’ designs, which require more power to achieve the desired output level. In addition, the cabinets are highly complex to design effectively, and equally complex to manufacture. The advantages offered by transmission line designs include a dramatically improved extension in the low-frequency range when compared to sealed/reflex designs, and a far more gradual ‘roll-off’ in this region. In addition, the definition and accuracy of the bass is greatly improved, and midrange response is far purer and less coloured by distortion. This is as a result of unwanted energy being directed away from the cone, removing the non-linear distortion that often occurs in sealed or reflex enclosures. In such enclosures, this distortion typically occurs as a result of the unwanted, rearward directed energy resonating and reflecting inside the cabinet, and either exiting via a port (in the case of reflex enclosures) or reflecting back through the cone itself, introducing non-linear behavior and colouration.
Kerr Acoustic has devoted significant research and development time to harness the benefit of transmission lines, addressing their inherent drawbacks to create designs optimally tuned for maximum acoustic performance. This has allowed us to greatly increase efficiency, and to achieve clean and accurate low frequency response extending all the way down to 33Hz, in the case of our stand-mount K300 speakers. With the recent advances in this technology, the sonic benefits of transmission lines must be matched by improved performance in the definition and time response of other components in the loudspeaker system. This is particularly true of the tweeter, which handles the bulk of the critical information we perceive when listening to music. One important consideration is the Fourier transform limit – an important principle of physics that governs a variety of technologies (including optical communications) which dictates that the time response of a system is always limited by its frequency response. Hence, use of a large bandwidth tweeter would not only add additional high-harmonic content and spatial information clues to the sound of speaker, but it would also allow a much faster time response. This is an ideal way to preserve, enhance and complement the fast and accurate bass response of transmission line designs.
Further reading in relation to the history and physical principals of transmission line loudspeaker technology can be found at the following resources:
INTRODUCTION TO RIBBON TWEETERS – A NEW OPPORTUNITY FOR INNOVATIVE SPEAKER DESIGNERS
An effectively incorporated transmission line offers the most frequency-complete and time- accurate bass response. This calls for the use of true ribbon tweeters, with their extended frequency response and ultra-fast time response. Ribbon tweeters are another area shrouded by some misconception. While planar tweeters are not uncommon, true ribbon tweeters are rarely featured in ‘affordable’ products, and the term ‘ribbon’ is often misused to describe the majority of planar tweeter designs on the market. The most commonly seen planar tweeters consist of a folded plastic film or membrane, which has a conductor either weaved into the material, or bonded to the material’s surface. This assembly is suspended within a strong magnetic field, and is technically classed as an ‘air-motion transformer’ design. Typically the resultant response is faster and better extended than most dome tweeters, though arguably more ‘abrasive’, particularly when used over long periods of time. This effect is chiefly responsible for listener fatigue, and is the primary reason that they are considered a compromise – particularly in the professional field. In a true ribbon tweeter, the diaphragm is itself the electrical conductor, and is made from an ultra-thin strip of conductive material (typically aluminum). This guarantees that there is no excess mass whatsoever – the only moving mass being the conductor itself. However this solution comes with some additional complexity and cost. While most planar tweeters present similar impedance and sensitivity characteristics compared to dome designs, true ribbon tweeters must incorporate an impedance-converting transformer to match the amplifier and crossover impedance to that of the diaphragm. This impedance matching is essential to allow proper function of a ribbon tweeter, due to the nature of alternating current flowing directly through the large conductor.
Further reading in relation to the physical principals and different functional types of tweeter technology can be found at the following resource:
The sonic benefits of using true-ribbon tweeters are clear: they offer a time response and a level of high-frequency reproduction unmatched by other designs. One of the key factors here is the physical mass of the diaphragm/conductor, which is typically just 20-30 microns thick and can weigh as little as 20 milligrams (compared to a typical 170 milligram air- motion-transformer tweeter, and around 0.5 grams for a conventional dome). As an example, the ribbon tweeter diaphragm featured in our K300 model weighs 0.027 grams, and has an effective surface area of 720 square millimeters. For comparison, most conventional domes have a 700 square millimeter radiating surface area, but on average have a moving mass that is eighteen times greater.
This incredibly low mass allows for a uniquely fast response, which is crucial for accurate reproduction of the very highest frequencies. Ribbon tweeters are therefore purported to possess an extremely airy and transparent sound, owing to the absence of voice-coil inductance, linear magnetic field, and extremely low diaphragm mass. Again, the Fourier transform principal is highly relevant to the reason why the perceived sonic presentation from ribbon tweeters is so aurally preferable over alternate technologies.
Historically, these designs have been prohibitively expensive to implement into cost- effective, competitively priced products, and have included compromises including low power handling and reliability issues. Equally, their off-axis response has been historically regarded as inferior to dome designs, owing to the rectangular shape of the diaphragm. The performance and cost related issues have been addressed by a recent breakthrough in design and manufacturing processes, that has made the technology suitable for high-quality, non-prohibitively expensive ribbon tweeters. This is largely as a result of having improved manufacturing tolerances, and far greater access to a wider range of precision tooling for construction, assembly, and testing. Off-axis response has been greatly improved through a combination of ribbon surface corrugation, and incorporation of diffractive and reflective elements within the tweeter enclosure.
Despite this tremendous progress, the process of designing a loudspeaker that fully exploits the benefits of ribbon tweeters and accounts for their residual idiosyncrasies is not trivial, and requires acute balancing of the accompanying components, and very careful crossover management. Ultimately, if one can design a system that fully exploits the benefits of ribbon tweeters, whilst simultaneously managing their behavioral characteristics, they represent the very best in tweeter technology available today. When combined with transmission line technology, they have the potential to unleash unprecedented frequency extension and time response, leading to the most accurately defined reproduction of harmonic content, dynamics, spatial information and – most importantly – timbre, available.
Kerr Acoustic has capitalized on the previous absence of a loudspeaker system that fully exploits the combined benefits of transmission lines and ribbon tweeters, while mitigating all the sonic and practical drawbacks that have been associated with such technologies in the past. We have tackled this challenge according to the following design principals:
Efficient, transparent, low-loss crossover networks – for ease of drive and dynamic integrity.
Frequency and time response accuracy for absolute transparency and fidelity, in both studio and domestic applications.
Insensitivity to boundary conditions and linear off-axis response, for maximum flexibility with positioning.
Robust and acoustically inert cabinets for minimal colouration and maximum stability.
APPROACH TO LOUDSPEAKER DESIGN
During the intricate design process, a combination of precise acoustic measurement and tuning by ear is employed in an effort to produce loudspeakers with highly linear frequency and time responses. While acoustic measurement is considered an important factor, great emphasis is placed on constant, critical aural assessment throughout design and fine-tuning of the products. An extensive benchmark is offered by designer Jes Kerr’s personal ownership of and experience in listening to a vast number of loudspeakers, spanning every conceivable technology and design topology available. This is reinforced by extensive experience in the fields of musical performance and production, and regularly being in the presence of acoustic instruments and voices in their inception. In addition, Kerr Acoustic has extensive in-house knowledge of bespoke joinery, which allows for extremely cost-effective and time-efficient development and manufacture of new cabinet designs. Below we expand on the methodology behind our approach to design, and explain how each point of differentiation listed above is facilitated and addressed.
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