

Leadership: For the love of hearing it all
20 years of advancing the art and science of loudspeaker design.
Our technologies
Time-Coherent Soundfields
To hear the original waveform, which contains all the musicality and entertainment,
the sounds from the woofer and tweeter must recombine at your ear as if there
was only one driver emitting the sound.
For this, they must move synchronously, as one unit. This can only be accomplished
when the drivers are well-behaved naturally, requiring only the simplest ‘first-order’
crossover circuit -- the only circuit design that allows the low and high signals
to pass through with no distortion in the time domain.
You will discover some additional benefits: You will stop reaching for the bass
and treble controls and also stop worrying about the quality of an album or
soundtrack before you buy it. You will want to hear everything you own -- and
watch hundreds of movies -- for the first time...again.
Adjustable Soundfield Convergence™
Since you may sit or stand anywhere, our speakers are adjustable to focus the
time-coherent sound axis to your position regardless of speaker location. In
our two-way models, the tweeter adjusts from front to rear. In the Eos, (left),
the tweeter is adjusted via an easy-to-use thumb-nut. In our three-way speakers,
the midrange and tweeter adjust independently and together as one unit. The
Pico Executive and Calypso feature channels that are easily secured with screws,
as seen in the Pico Executive's tweeter, (bottom left).
Frequency-Selective Dispersion™
The sound you hear from a speaker is a mix of its direct sound with reflections
from its surface, the floor, the wall behind, and the sidewalls. All of our
speakers are designed to deliver a dispersion pattern that smoothly narrows
with increasing frequency and decreases abruptly to the sides and rear. Far
less sound is sent to nearby surfaces so you hear everything more clearly even
when the speakers cannot be optimally placed -- and even when you are in another
room.
Freefield Tweeter Operation
You hear less ‘speaker’ when the tweeter itself is capable of producing a uniform
tone balance across the treble with no help from reflections off the cabinet
surface or its own surface. We take it to the next level by mounting that tweeter
outside of the woofer enclosure, so that its sounds freely expand into the room.
It is always a strange sensation at first to see the speakers but hear that
the sound has nothing to do with them.
Balanced-Phase™ Crossover Circuits
When the quality of the drivers allows the simplest crossover circuit to be
used, then only a single inductor keeps highs out of the woofer and a single
capacitor keeps lows from the tweeter. Those two components can then have ‘mirror
image’ values that offset the inductor’s rising impedance-with-frequency with
the capacitor’s falling resistance-with- frequency. Your amplifier does not
‘see’ either the inductor or capacitor, because the ‘Balanced-Phase™’ of those
two opposite electrical components cancels out their differences and leaves
only what seems to be a perfect Y-adaptor for the signal.
Golden-Ratio Baffles™
When any speaker enclosure has an internal dimension exceeding about 18", no
acoustic lining will absorb the tones with wavelengths longer than 4x18", or
72". This is because the air molecules at these tones from that low-voice range
and on down are not moving back and forth very fast. Thus, they have little
velocity to be ‘scrubbed off’ by acoustic-absorption materials and they begin
to echo inside, forming resonances and cancellations at different frequencies.
The simplest way to counter their formation is to introduce a baffle across
that longer cabinet dimension having carefully-calculated openings to break
up those waves. The mathematics behind our baffles were based on the Golden
Ratio, so that no whole-number multiple of a wavelength (1/2, 1/3, ¼, ...) is
allowed free passage from one end of the enclosure to another. The result is
a far less ‘boxy’ sound, with much more clarity and greater pitch definition,
especially on complex music and soundtracks.
Q-Stone™ Cast Marble
Q-Stone™ was developed over a 10-year period before being introduced in the
Europa in 2001. It is a blend of marble dust and resins that are then cast in
specially-designed molds. Here, Q-Stone™
is being poured into an Eos mold. Q-Stone™ produces enclosures
that are extremely rigid and non-resonant in shapes that provide the best possible
dispersion of sound, without reflection. ‘Q’ is the symbol for the tendency
of something to ‘ring.’ A low ‘Q’ has the least resonance.
Optimum Curvature Diffusion™
Because reflections from the face of a cabinet are harmful to the sound, especially
in the voice and treble, they can be absorbed and diffused. They also can be
avoided altogether. The multi-dimensional curves to all our Q-Stone™ enclosures,
as seen in the wood master of the Eos faceplate, left, were calculated to let
the enclosure ‘get out of the way’ as soon as possible, for the least reflection
at any listening angle. The speakers disappear even more and you enjoy a much
wider range of music and soundtracks.
Texture-Kote™ Paint
This is our adaptation of a tough industrial paint, shot through a specialized
spray gun that produces a fine pin grain, black-leather texture. It does not
fade.
Inverse Anechoic Horn
First seen in our Continuum 0.5 Center Channel/Shelf speaker, and later the
Aperture, this is a region of angled wool-felt and acoustic foam baffles surrounding
the tweeter that absorb all sounds headed into its labyrinth, so that all you
hear is the direct sound coming straight from the tweeter. It was necessary
to allow the Aperture to be placed completely into a bookshelf, so that no upper-range
tones could be sent to all the nearby surfaces. The sound is much cleaner and
multiple voices on soundtracks are far easier to follow.
Anechoic Transmission Line™
Ideally, all but the very lowest bass tones should be directed away from the
rear of the woofer to never return. When a long transmission-line tunnel is
placed behind a woofer, the idea is to absorb all the middle-bass and high-bass
tones as they travel along -- by an acoustic stuffing usually of wool -- so
they cannot come back to resonate with the woofer. However, all conventional
transmission lines have reflections that cannot be absorbed -- most notably,
the one tone with a wavelength three times shorter than the main length -- which
happens to be right in the middle bass. The ATL design connects a shorter transmission
line to a longer one, and the resulting path-length difference completely cancels
this resonance.
Bi-Port™ Bass Ports
First used in the Eos (left), this allows twin bass port openings to be placed
in the front of the enclosure where they do the least harm to the air-pressure
support that the remaining solid front of that enclosure must give to a smaller
woofer. That frontal surface area is needed so that the woofer can maintain
proper tone balance in the low-voice and highbass ranges, regardless of the
speaker’s position in the room. Yet, on the inside of the cabinet, there is
only one prime location for the intake of those two ports, so the Bi-Port™ design
merges their two intakes into one large, aerodynamically-shaped opening positioned
at just the right spot to take in the pressure changes coming back to it from
all parts of the enclosure’s interior.
Resistive Loading for Midrange Drivers
Any midrange driver has its own low-frequency resonance because it has a moving
mass (the cone) bouncing off a spring (its suspension and/or the air in its
sealed chamber). Even when this natural resonance occurs far lower than the
midrange driver’s lower crossover frequency, it still affects the action of
the crossover circuits’ filtering, and makes life a little less pleasant for
the amplifier. While it is possible to damp this resonance by adding more parts
to the crossover circuit, that solution is never good for sound quality.
Instead, we were the first to successfully adapt a resistive vent to a midrange
enclosure that optimally damped this resonance mechanically, before it begins.
Think of it as an ‘air brake’ to the motion of the cone, allowing the midrange
driver to operate in a resonance-free environment. The amplifier also sees far
less energy returned to it, because none is being regenerated. This vent is
used in all of our three-way speakers.
Multi-layer Wood Cabinets with Epoxy-Marble Foundations
We could cast a large woofer cabinet out of Q-Stone™, but who would or could
lift it? When wood must be used, we glue different types and thicknesses of
MDF wood together with non-resonant adhesives and combine that with Baltic-Birch,
multi-ply hardwood plywoods. To prevent torsional and shear vibrations of the
cabinet, all corner joints are painstakingly inlaid and overlaid, then overlaid
again with another layer of MDF. The base of the enclosure has an interior reinforcing
lining of epoxy/marble compound for the utmost rigidity and stability. Remember
that nothing should move but the woofer’s cone -- so it is a little disconcerting
to hear and feel everything in the house shaking while your hand remains still
when placed on the cabinet.
©
Green Mountain Audio Inc.