HAUT-PARLEUR A SOURCE DE LIGNE COAXIALE

COAXIAL LINE SOURCE LOUDSPEAKER

Abrégé anglais

A coaxial line array loudspeaker including a plurality of midbass acoustical
drivers with
an elongated thin film diaphragm high frequency acoustical driver centred in
front of the
midbass driver array.

Revendications

Claims:
1. A loudspeaker system comprising a linear array of at least 2 midbass
acoustic drivers
in an acoustic enclosure and an elongated monopole high frequency thin film
diaphragm
acoustic driver aligned along the centre and directly in front of the midbass
line array.
2. The loudspeaker system of claim 1 with the high frequency acoustic driver
mounting
system which allows both vertical height adjustment to cover the full height
of the
midbass enclosure and rotational adjustment to allow a directional orientation
of up to 60
degrees from straight ahead.
3. The loudspeaker of claim 1 where the midbass line array consists of a long
narrow
film diaphragm acoustical driver.
4. The loudspeaker of claim 1 consisting of a plurality of midbass enclosures
each with
at least 1 midbass acoustic driver stacked vertically to achieve the line
source array
configuration.
5. The loudspeaker of claim 1 with the rear of the high frequency driver
formed to
minimize reflections and interference with the sound wave produced by the
midbass
acoustic drivers.

Description

CA 02617105 2010-09-07
The rear of the high frequency element can be formed (23) to minimize
reflections from
the wave produced by the low frequency element and to allow the inset (24) of
the
support tube (25) It can be swivelled and raised and lowered to offer the
maximum
flexibility in positioning for producing the ideal response in a variety of
rooms and to suit
individual listener tastes
A coaxial line source loudspeaker (15) with a monopolar thin film elongated
diaphragm
(16) (ribbon or electrostatic transducer), placed directly in front of the low
frequency
transducer line array, has the following advantages
it is phase coherent horizontally and vertically
it has extremely even horizontal dispersion
it has very limited vertical dispersion
it minimizes baffle bounce since the high trequency driver is located ahead of
the
baffle of the midbass drivers (17) and any high frequency sound reaching the
midbass
baffle will have very low energy.
- diffraction will be minimized by the small size relative to the wavelengths
being
produced and contoured shape of the high frequency drivers baffle (front
plate).
- it offers greater fidelity in a larger area of listening space than any
other loudspeaker
configuration
The sole acoustic drawback of this innovation is depth displacement (time
alignment
shift) (18) of the higher frequencies caused by placing the High Frequency
driver ahead
of the midbass driver. This kind of timing distortion is of small audible
significance and
can be corrected 100% in the electronic domain by means of a delay placed on
the
midbass drivers (19). This will yield a loudspeaker which will be 100% phase
coherent
over most of the listening space
A large Ribbon driver (19) with a long narrow film diaphragm (26) eliminates
the
multitude of nodes and cancellations inherent in a line array of small high
frequency
drivers for example 1" dome tweeters (20) with widely separated small
diaphragms
The monopole (sealed back) Ribbon (19) is a necessity to avoid excitation and
distortion
of the high frequency diaphragm by strong low frequency waves created by the
midbass
drivers directly behind it.
The height (21) and rotation (22) adjustment capability of the high frequency
Ribbon
structure allows exceptionally easy fine tuning of the sound radiating pattern
of the
speaker to ideally balance direct and reflected sound to suit the room
environment and
the listeners' taste.

CA 02617105 2010-09-07
A line source array produces a pattern of dispersion that effectively extends
the "near
field" response ie the response of the loudspeaker before it is affected by
interaction
with the room further into the listening area. The distance the near field
effect is
projected depends on the length of the effective diaphragm and the frequency
it is
reproducing.
Linear or line source arrays have much more controlled vertical dispersion (7)
and
therefore excite fewer detrimental room interactions but as implemented have
introduced several other deficiencies of their own. These deficiencies stem
from the
alignment on the same plane of the drivers in 2 or more vertical parallel
lines each other
(8). By placing radiating surfaces beside each other, the waves (9) created by
them will
arrive at different horizontal points in the room at slightly different times
causing many
amplitude and phase anomalies which degrade the perceived accuracy of the
music.
Only in one very narrow area are these anomalies minimized giving rise to the
term
"head-in-a-vice sweet spot". (Fig 4) Slight movement of the head produces
distinctly
different audible performance.
The horizontal area where these effects are minimal is quite small ('10) and
small
movement of the listener's body or even just the head will produce audible
degradation
of the musical experience. This also precludes more than one listener from
enjoying
ideal response. Conventional wide dispersion speakers have a wider (11) sweet
spot
and the coaxial line source configuration offers an exceptionally large sweet
spot (12).
For conventional or parallel line source loudspeakers, phase anomalies due to
the
physical offset of the drivers cannot be corrected over a large listening area
by electrical
means. A coaxial line source holds much higher potential for delivering phase
and
frequency response accuracy over a large area in any listening space.
Besides phase differentials, other causes of these anomalies include baffle
bounce (13)
and diffraction (14). Baffle bounce occurs when a wave from a driver
(typically high
frequency) radiates to the side of the driver and "bounces" off of the baffle
or the
diaphragms of other adjacent drivers. Diffraction occurs when the sound wave
encounters a radical change in the baffle surface along which it is radiating -
either a
corner of a loudspeaker enclosure or the edge of a panel speaker.
Description
A loudspeaker is constructed with multiple vertical arrays of drivers. The low
frequency
element is a linear array of similar transducers aligned vertically or large,
narrow
rectangular film driver. The high frequency element is a monopole transducer
placed
directly in front of the low frequency element yielding a horizontally and
vertically phase
coherent loudspeaker. This line source array configuration yields superior
performance
in minimizing the degrading effects of listening space acoustics. The coaxial
alignment
eliminates the horizontal nodes and cancellations commonly referred to as comb
filters,
which are inherent in conventional line source (multiple transducers in a
linear array or
single long, narrow transducer) designs where the high frequency and low
frequency
elements are placed side by side.

CA 02617105 2010-09-07
Initial Description
A loudspeaker is constructed with multiple vertical arrays of drivers. The_
low frequency
element is a linear array of transducers aligned vertically or large,
rectangular film
driver. The high frequency element is a monopole ribbon transducer placed
directly in
front of the low frequency element yielding a horizontally and vertically
phase coherent
loudspeaker. This line source array configuration yields superior performance
in
minimizing the degrading effects of listening space acoustics. The coaxial
alignment
eliminates the horizontal nodes (comb filters) which are inherent in
conventional line
source (multiple transducers in a linear array or single long, narrow
transducer) designs
where the high frequency and low frequency elements are placed side by side.
The high frequency element is formed to minimize reflections from the wave
produced
by the low frequency element and it can be swivelled and raised and lowered to
offer
the maximum flexibility in positioning for producing the ideal response in a
variety of
rooms and to suit individual listener tastes.

CA 02617105 2010-09-07
Background of the Invention
Music reproduction whether in the home or in larger public venues is degraded
by the
acoustic effects of the physical space (room; Reflections and standing waves
distort
the accuracy for the listeners of the sound produced initially at the
diaphragm by the
loudspeakers
Control and minimization of room effects is one of the critical frontiers of
music
reproduction. Delivering the soundwave faithfully to the listener's ears in a
typical
listening environment is the objective of this development
The ideal loudspeaker would deliver consistent, accurate, high quality sound
to any
point in the listening space. This invention delivers consistent, high quality
sound to a
larger portion of the listening space than has been possible before.
The innovation described here is inherently free from the flaws of
conventional and past
designs and incorporates features which allow a large area, where very
superior
reproduction can be enjoyed, to be quickly established in many different rooms
for
many different listeners
This innovation removes previous drawbacks and makes it possible for a much
higher
level of fidelity to be achieved in a vide variety and sizes of listening
spaces. This
configuration can be scaled up or down to properly match a space or dynamic
requirement with no ill effects
The traditional loudspeaker consists of a larger cone diaphragm bass
transducer (1
possibly a cone or dome midrange (2) and a cone or dome (3) high frequency
tweeter
This configuration has a number of significant acoustic drawbacks in its
ability to deliver
the soundwave that the separate drivers create faithfully through the acoustic
space to
the listeners ear. The overlapping hemispherical dispersion patterns (4) of
conventional
loudspeakers using small round diaphragms assure that large numbers of room
resonances are excited and that reflected sound arrives at the listeners ear
from many
different sources at different times to degrade the integrity of the original
wave created
at the diaphragm
Line source loudspeakers (5) have either an elongated rectangular thin film
diaphragm
or a plurality of identical transducers (6) reproducing the same frequency
range Hence
the resultant dispersion pattern (7) duplicates that of a single diaphragm of
a height ano
width equal to the overall dimensions of the array

CA 02617105 2010-09-07
List of Diagrams
Figure 1 : coaxial line source , height and rotational adjustability
Figure 2 :radiation patterns of conventional speakers, parallel line source
speakers
and single line source speakers
Figure 3 :height and rotational adjustability pictures and shapes of high
frequency
Ribbon drivers
Figure 4 sweet spot areas
Figure 5 electronic phase correction. baffle bounce, diffraction, dome line
source
radiatior