THE MODEL 16
The model 16 loudspeaker system by deep is the culmination of an intense development program aimed at creating a system possessing certain specific characteristics. After evaluating many high-end loudspeaker systems, it was our feeling that most of them, no matter how exotic, often lacked a subjective feeling of body and visceral presence. We decided to explore this, and in the process develop a loudspeaker system capable of extreme palpability and analogue-esque solidity. Utilization of extreme transducers and an approach of obsessive experimentation, intense subjective critique, deep contemplation, and iterative prototyping resulted in the model 16…a loudspeaker connoisseur’s dream.
Motivated by a desire to find an alternative sound-texture to the current
trends in high-end audio, the development program’s primary aim was
to create a loudspeaker device with a subjectively deeper groove…one
that would blend analysis with enjoyment…find a convergence point
between intellectualism and boogie…somehow fuse the extreme
high-end with street-level-phat.
It was not conceived as a laboratory system where every last vestige of energy
storage or distortion would be hunted down and eliminated. Rather, it was
conceived and carefully voiced to enhance and “analogify” the
texture of Small Ensemble Jazz, Funk, and Acid Jazz music genres.
MODERN vs. VINTAGE
Amongst loudspeaker aficionados, there exists a range of sub-cultures. One interesting group encompasses those who seem committed to classic vintage designs by Altec and JBL. For this group, the magic formula is a 2-way system based around a 15” woofer and a high-frequency compression driver, usually driven by vacuum tube amplification. On what basis does this group remain faithful to this seemingly archaic approach? Well, the feeling is that many modern high-end loudspeaker designs, in a quest to lower colouration and maximise detail and linearity at all costs, have been unable to achieve these objective virtues without leaving many treasured recordings sounding subjectively thin and stripped of body. It is this perceived weakness that the vintage approach specifically addresses. On the other hand, there is an open admission that these vintage systems accept moderate levels of colouration and shortcomings in measurable accuracy in exchange for their claimed virtues. [Interestingly, this trade-off exists at all levels in the audio chain, an example being the choice by a recording engineer to employ a vintage tube-microphone in preference to a modern alternative to enhance a solo vocalist].
The model 16 loudspeaker system represents both an acceptance of the
vintage formula, and an extreme development of it. Using the
classic 15” woofer
and compression-driver recipe as a starting point, it is an exploration of
radical design decisions and subtle tweaks that push certain sonic characteristics
to the limit, the target being a loudspeaker that captures the body and soul
of the best vintage designs, but also achieves fidelity characteristics totally
unapproached by them, allowing a balance of usually mutually exclusive virtues
to co-exist on a higher continuum than any known modern or vintage loudspeaker
device.
THE CHOSEN TRANSDUCERS
In order to achieve our goals, we knew we would need to utilize ultimate transducers. We were looking for a very special large-format 15” woofer and compression-driver combination. After exhaustive evaluations of drive-units from all over the world, two units were identified that offered a totally unique blend of technical attributes: the TAD 1601A woofer and TAD TD4001 compression driver.
TAD (Technical Audio Devices) was founded in the late seventies by a
team of audio-engineers from California and Japan. Funded by Pioneer
Corporation,
the sole aim was to design a range of drive-units that would exceed the
performance of all previously known transducers of the type typically
employed at the
time in large-format studio monitor and mastering systems. The TAD
1601A 15” woofer and TAD TD4001 compression driver were the first devices
to emerge from these efforts. These units formed the basis of custom studio-monitor
designs by Shozo Kinoshita, Tom Hidley, and George
Augsperger. They were
also quickly recognized and sought out by fanatical Japanese audiophiles
and vacuum tube devotees. [More recently, TAD transducers may also be found
in cost-no-object surround monitoring systems such as at George
Lucas’s
Skywalker Ranch]. However, rarely were they implemented in high-end hi-fi
loudspeaker designs in the West, very likely due to the massively large enclosures
and horns usually associated with them, and not insignificantly, their extreme
cost. However, after auditioning these drivers for the first time, we knew
immediately that these were the units we should develop around, and accepted
the challenge of implementing them into a smaller (smaller being relative!)
and more contemporary design.
THE TAD 1601A
The TAD 1601A is a beautifully made 15” paper-cone pleated-fabric surround low frequency driver. This membrane represents the pinnacle of paper cone artistry (TAD being the only loudspeaker manufacturer in the world to maintain its own plantation so as to ensure a source of its special paper pulp!). It was our feeling after listening to this unit for the first time that none of the alternative modern cone material drivers we were experimenting with (Kevlar, carbon-fibre, plastic/polypropylene, aluminium alloy, magnesium alloy, proprietary sandwich technologies etc) could approach the TAD paper cone for warmth and naturalness of tone.
One feature that distinguishes this driver from other units is the aluminium
nickel cobalt (Alnico) motor system. The use of Alnico magnetic materials
in loudspeakers was generally abandoned in the early seventies due to its
rising cost and the availability of the cheaper ceramic-ferrite alternatives.
However, there were those at the time who felt that this was not a change
for the better. Today, only a very few die-hard specialist loudspeaker
manufacturers continue to insist on using Alnico, and the Alnico
motor systems developed
by TAD, and utilized to such devastating effect in the TAD 1601A
and TAD TD4001, are widely regarded as the finest in the world. Our listening tests
indicated that Alnico seemed to have certain characteristics associated
with it that didn’t manifest in drivers based around ferrite or neodymium
motor systems.
Although a large-format woofer at 400mm frame diameter, the TAD 1601A was not optimised for subwoofer applications. Rather, it was designed
to have
a balance of virtues that would allow it to be used far into the midrange
in 2-way applications. In fact, its rich midrange reproduction is possibly
the beguiling aspect of this unit. Nevertheless, a sensitivity of 97dB/W,
in combination with a peak-to-peak linear excursion of 16mm, motivated
by 11,800 Gauss of magnetic flux sweeping 881mm2 of cone area, ensures
sufficient
low frequency punch is available when required…
THE TAD TD4001
The TAD TD4001 high frequency driver is possibly even more impressive than its partner from a technical standpoint. It is based around an exotic dome formed from pure beryllium. Beryllium has the highest stiffness to weight ratio of any known metal. It usually only finds applications in aerospace, satellite, and space shuttle components where it’s high cost can be offset against it’s low mass and resulting cost-of-launch calculations. This exotic 100mm diameter dome weighs less than 1 gram, but is driven by an Alnico magnetic circuit achieving a flux density of 19,000 Gauss. Its usable frequency range covers an astonishing 600 Hz to 20 kHz at a sensitivity of 110dB/W, over which it speaks with unmatched expressiveness. It differentiates high frequency textures in a way that eludes even the best dome tweeters, and has a solidity and body behind its delivery that is unavailable from ribbon transducers. It is the only high frequency driver we have come across that portrays the dark earthy qualities of vintage hand-hammered K Zildjian cymbals correctly. A careful examination of other high frequency drive-units will reveal that TAD is the only manufacturer to offer the combination of a beryllium diaphragm and an Alnico motor system.
THE ENCLOSURE
The enclosure for these drivers was developed to support and maintain as much as possible the inherent virtues and characteristics of the TAD drivers. This was no easy task. It required both advanced materials and an in depth exploration of enclosure types in order to achieve the special results we were looking for [See FAQ section for an in depth look at enclosure parameters]. The development of a proprietary composite panel material, consisting of outer and inner aluminium skins laminated to an MDF core pressed together under a pressure of 30 tonnes / m2, was necessary in order to achieve specific mass and stiffness targets within a thin wall structure.
One instantly obvious feature of the design is the cut-to-the bone geometry
of its front baffle, leaving the TAD 1601A bass driver exposed and unloaded
by planar surfaces to the sides and above, resulting in the narrowest possible
baffle for a system based around a large-format 400mm drive-unit. This
is in stark contrast to other designs that implement drivers of this
size and
genre.
Even more challenging, but also intrinsically related in philosophy, is
the choice to use the TAD TD4001 compression driver sans any kind of horn
device,
mounted out in the open, external to the main enclosure. This is a key
feature of the system; the application of minimalist principles yielding
sonic virtues
of openness and holography impossible to achieve in designs that utilize
horns. Significantly, it also allows perfect physical alignment of high-driver/low-driver
wave-launch origins, an issue that is always compromised in horn designs.
It is no coincidence that much of our subjective drive-unit evaluation
testing was done with drivers suspended by cables in free air, and
having become
accustomed to the spatial portrayal of this zero-baffle arrangement, we
wanted to maintain these qualities (as much as is possible within
the limitations
of a box loudspeaker) in the final design. Many prototypes where empirically
evaluated, searching for that special synergy between drive-units and loading
that is beyond simple Thiele-Small calculations and computer predictions.
The final floor standing device is pure in its intent…to
deliver as much pure musical energy as possible from as small a radiating
area as possible
at the correct listening height with maximum impact focused upon a self
indulgent near-to-midfield sweet-spot.
THE CROSSOVER
It is often the case that simple designs are the best, and in the case of passive crossover networks for loudspeakers, this principle has particular relevance. Some designers of high-end loudspeakers have attempted to correct all deviations from perfect flatness of amplitude vs. frequency by employing complex networks with multitudes of resistive, inductive and capacitive elements. Sometimes photos of elaborate networks are paraded in advertising media almost to suggest that these complex circuits contain merit in and of themselves. On the other hand, we feel that for every increase in circuit complexity and component count aimed at better evenness of frequency response, there is always the trade-off of an insidious small loss of dynamic life and presence from the original signal. This is something judged only by the human ear on music program, and is not possible to discern by analysing frequency sweep data. We realized that in order to extract the most music possible from the amazing TAD drive units, we would need to remain conscious of this, and develop filters with minimal componentry both in series with and in parallel to the signal path, carefully balancing the desire for even frequency response against these insidious losses. This design attitude was in fact far more difficult to adhere to than an approach where one just “throws more parts at the problem”. It required a willingness to iteratively fine-tune a simple circuit to an almost ZEN like balance, searching for a synergistic combination of circuit topology, component values and component type which would combine to give a greater than sum of its parts result. A purist’s solution of 4 circuit elements was finally realized. This simplicity, in combination with point to point wiring techniques, Teflon insulated silver-plated compression-extruded ultra-high purity copper internal wiring, and high-silver content quad-eutectic solder, achieves maximum directness and musical energy.
THE AESTHETIC
Many devices permeating the high-end audio world appear to have been heavily contrived to look expensive, high-tech and flashy. At best, some of these are good examples of industrial art, but more often than not many seem garish and overdone. With the model 16 we wanted to avoid any such contrivance by adhering to principles of ruthless minimalism and form-follows-function. The result is a clean design, devoid of unnecessary adornments or add-on audio jewellery; the final form conveying a strong sense of purpose and intent. In the context of extreme audio devices for extreme music lovers, the model 16 makes perfect sense. Viewed away from this context, it is as irrelevant as a Formula 1 race car.
