There are many definable aspects of what makes for good playback fidelity but none more important than dynamic realism. In order for music and noise to sound real through recording and playback, the electronics, recording medium, environment and loudspeaker must be capable of recreating the natural dynamic range and contrast of the event.

Druid Mk4 is a complete rework of our ground-breaking Druid loudspeaker and features our newly designed super-tweeter CNC machined from billet aluminum. The Druid mk4 has increased resolution, bass extension, improved amplitude linearity with reduced noise—the musical terms translation is better detail, improved soundstage depth and texture, more instrument color and a playback presence that is as good as it gets.

High sensitivity, easy load for amplifier, ultra wide dynamic range and high power handling—natural dynamic reproduction is the foundation on which the Druid range is engineered. Matching the natural dynamic range of an event with that of playback results in a dramatic increase in playback realism. In addition Druid tackles bandwidth, amplitude and group delay issues without breaking a sweat. Druid performance is largely due to our full-range driver. It features very high efficiency, ultra wide bandwidth, minimum group delay, linear dynamic contrast and uniform spectral amplitude—attributes that allow the elimination of crossover and other network components. The amazing dynamic range of the Druid is the result of a very powerful motor and unique acoustic coupling of the cone. The balance of cone weight, material, shape and mechanical suspension also enabled the Zu260FR driver to reach new benchmarks in bandwidth, dispersion and amplitude uniformity. (Standard hi-fi drivers are not capable of playing much over three octaves without having problems in dispersion, imaging, timbre, timing.) Complimenting our new driver is our original Griewe driver loading model. Why a new "box"? Because all popular models have some major problem—transmission lines and ported designs of all types control cone motion but at the expense of group delay and other forms of distortion; sealed enclosures perform with much less group delay distortions but cause cone motion to be excessive; horns damp cone motion well but distort amplitude and phase. Druid driver loading and low frequency goals are met through our proprietary Griewe driver loading design. This is the first loudspeaker to implement Ron Griewe's* alternating velocity theories.



Industrial Design

Small footprint, confident, exceptional fit and finish, timeless lines and materials. With one glance the observer will know the Druid loudspeaker is capable, well engineered and solidly constructed. The Druid's purpose and attention to detail command respect. Did we mention they leap tall buildings in a single bound?

Connection

Pure unplated copper Cardas binding posts accommodate spades (standard and oversized), bananas, pins or bare wire.

Amplification

Bipolar or F.E.T., class A or switching, O.T.L. or transformer isolated, one bottle single ended triodes or 500 Watt "who needs central heating" pentodes; Druid loudspeakers will work well with all audio amplification designs.

Multi-Channel

There is nothing that will match the level of fidelity that a set of Druid's will give in a large multi-channel playback system.

Stereo

Zu intimately sampled many of the best loudspeakers in the world. To be competitive you must know your competition. The only comparative shortcoming the Druid has in stereo playback is in the lowest octave. Fidelity in the extreme low frequency is excellent but lacks in amplitude and while a sub may be welcomed, it is not a requirement.

Druid Basic Technical Points

  • Zu-260FR-G2 full range driver. 8.5 octave bandwidth (-3 dB), 260 mm (10.3") diameter, very high Bl, linear motor function, 25 gram moving mass, natural fiber cone assembly, cast frame, precision machined motor and pole assembly, 12 Ohm nominal impedance, 101 dB nominal sensitivity (1 Watt).
  • Proprietary Griewe driver loading. Our evolutionary loudspeaker enclosure causes maximum wideband cone damping (minimizes cone motion), proper control and coupling of rear acoustic energy and reduces low frequency time delay.
  • Amplifier intimacy. Elimination of not just the crossover but also any other network element were part of the Druid concept. FET, bipolar, digital, vacuum tube, all amplification types benefit from the increased intimacy the Druid provides.
  • Druid loudspeakers accept 6mm (1/4") spades, 8mm (5/16") spades, bare wire, bananas and pins via Cardas™ pure unplated copper binding posts.
  • New Zu-T1 CNC machined billet aluminum super tweeter.
  • Zu, split highpass network, 12 kHz / 15 kHz on super tweeter.
  • Spikes are AISI 1062 steel, core hardened to Rc55.
  • 60-day satisfaction guarantee.
  • 5-year limited warranty on materials and workmanship.
  • Made in USA.

Is the Druid a bass reflex (ported) design?

The Druid is not a bass reflex design and does not correlate to Helmholtz resonators. While the reactance and impedance plot may look similar to those of a ported design, such measures cannot be specifically correlated to enclosure acoustics.

Without divulging the proprietary math and correlations, let me outline a few principles expressed in the Druid and contrast them with bass reflex (ported) designs. A bass reflex loudspeaker uses a simple Helmoltz resonator to augment lower frequencies and control cone motion. A Helmoltz resonator consists of a rigid-walled cavity (the volume) with a neck (“port”) with an area and length. The fluid (air) moves as a unit to provide the mass element and if the quarter wavelength is much greater than volume, the acoustic pressure within the loudspeaker box provides the stiffness element; the resistive element is provided by the opening that radiates the simple source sound. All Helmoltz resonators contain these basic elements.

The Druid enclosure is expressed, on a fundamental level, like that of a waveguide with uniform cross section and terminated and driven at one end. Propagation within the Druid is mostly planer and standing waves are not stimulated. Power radiation from the open end is expressed similarly to that of a standard open-ended pipe, driven and terminated from the opposing end. Though similar, the Druid cannot be fully defined by waveguide, loudspeaker transmission line or driven pipe models. Development of an acoustical model accounting for driver introduced dynamic variables and resulting model changes revealed areas of non planer propagation. The resulting turbulence is wavelength relational and proportional to amplitude.

Applied to loudspeaker design, the new Griewe model shows resulting noise distortions, in varying degrees, throughout the entire audible range. Modifications within and to an audio waveguide that improve loudspeaker are proprietary, the basic idea being to minimize or eliminate non-planer oscillatory propagation.

The enclosure acoustic design principles used in the Druid are based on Ron Griewe’s research and resulting patents. Ron has granted Sean Casey permission to use his research and collaborated on the fundamental application to loudspeakers. Ron Griewe was the editor and chief of Cycle World magazine for fourteen years and has worked as an engineer for several motorcycle manufacturing companies.