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PARAMETERS DEFINING OMNIDIRECTIVITY
EVOLUTION OF DESIGN OBJECTIVES
SPHERICAL SOUND SOURCE REALIZATION
EXPERIMENTAL MEASUREMENTS
DODECAHEDRON POLAR PATTERNS
OMNIVOX VERSUS SPHEROVOX COMPARISONS
SUMMARY AND CONCLUSIONS
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Omni is a Latin prefix
meaning "all" or "every“
DIRECTIONS – BUT
HOW MANY - 4, 5, 6,
12, 20, 120 or MORE –inf
ISO-3382 – AS OMNI
DIRECTIONAL AS
POSSIBLE
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MONOHEDRON
DIHEDRON
TRIHEDRON
TETRAHEDRON
HEXAHEDRON – CUBE
OCTAHEDRON
DODECAHEDRON
ICOSAHEDRON
LETS OPEN THE FACE (HEDRA) – AND
THINK OF IT AS BEENG MOUTH OF A
HORN WITH ITS DRIVER INTO THE
CENTER OF THE POLYHEDRON
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ICOSA-HORN
DODECA-HORN
OCTA-HORN
HEXA-HORN (6 HORNS ON
6 SURFACES OF A CUBE)
PENTA-HORN
TETRA-HORN
TRI-HORN
DI-HORN
MONO-HORN
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BY REDUCING THE HORN
NUMBER, INTERFERENCE
ZONES ARE REDUCED
THE LOWER THE NUMBER,
THE LESS IS INTERFERENCE
BY MATCHING -6dB POLAR
PATTERN HORN ANGLE
WITH SOLID SPHERICAL
POLI-ANGLE,
INTERFERENCES COULD BE
MINIMIZED
THE LONG WAY FROM PENTAHORN-THRU
TRIHORN TO MONOHORN
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Three 100x100 deg Horns 120
deg apart, forming the
cylindrical surface
Two Conical Horns at the end
of a Cylinder
5 Compression Drivers – 3
Horizontally radiated and 2
vertically (up/down)
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Two 15” Coaxial Loudspeaker
at the end of a Cylinder
Three 100x100 deg JBL 2344A
Horns 120 deg apart, forming
the cylindrical surface
Two Bass reflex openings
WEAKNESSES
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ON-AXIS (ROOM) INTERFERENCES
HARDLY POSSIBLE FOR 2344A TO GO BELOW 630 Hz
LACK OF FULL ROTATIONAL SYMMETRY (3-fold Symmetry Only Available)
FROM PENTA-HORN TO MONO-HORN / SPHEROVOX
MAIN FITURES
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3 PAIRS OF DIPOLES IN
MONOPOLE CONFIGURATIONS
EVERY LOUDSPEAKER
COMPONENT HAS ROTATIONAL
SYMETRY
ALL LOUDSPEAKER
COMPONENTS SHARE THE SAME
(VERTICAL) AXIS
THE TWO LOUDSPEAKERS IN
EACH PAIR ARE AS CLOSELLY
MOUNTED ONE TO THE OTHER
AS POSSIBLE
VIRTUAL POINT SOUND SOURCE
To HF Co-AXIALS
2–10 kHz
INPUT
DELAY-H
HIGH/250W
AXIS of ROT. SYMMETRY
X-OVER DSP/EQ
500Hz–10kHz
H L
MID-HIGH/250W
50–500 Hz
DELAY- L LOW/1200W
To LF Co-AXIALS
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MEASURING SIGNAL –
FREQUENCY MODULATED
SINEWAVE WITHIN 1/3oct DR. BENJAMIN BERNFELD CD UNDER PIERRE VERANY
LABEL -1984
400Hz,500Hz,630Hz 1/3 Oct
FM-PN
500Hz 1/1 Oct FM-PN –
MIXING 400,500,630Hz 1/3
MEASURING ROOM – SEMI
ANEQOICK CHAMBER
150m3
PINK NOISE VS FM-SINE
WAVE EQUIVALENT
SIGNAL
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ADVANTAGES
FAST MEASUREMENT TIME
EXITE ALL ROOM MODES
WITHIN THE BAND
DON’T NEED HUGE POWER
AMP TO CARY PEEKS
HIGHER DYNAMICS OF
MEASUREMENTS
VERY PRECISE FOR TURN
TABLE MEASUREMENT AT
LOW FREQUENCY
ADVISABLE FOR ANY
ACOUSTIC MEASUREMENT AS
PINK NOISE ALTERNATIVE
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125 Hz (OUTERMOST)
250 Hz
500 Hz
1kHz (INNERMOST)
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2kHz oct (outermost)–1.6k/2k/2.5k, 1/3oct-RGB
HF Co-Axial Drivers Switched off
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VERTICAL
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HORIZONTAL
ALL HORIZONTAL POLAR
PATTERNS ARE IDEAL
CIRCLES FOR ALL
FREQUENCY, AT ANY
FREQUENCY BAND – 1/1oct,
1/3oct, PURE SINE WAVE
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4kHz oct (outermost)–3.2k/4k/5k, 1/3oct-RGB
HF Co-Axial Drivers Switched off
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There are an infinite
number of different polar
pattern planes of
measurement across the
dodecahedron center
Four axes, however,
determine particular
dodecahedron symmetry
These two planes of
measurement don’t coincide
with any loudspeaker axis
There are 10 such 3-fold symmetry axis
There are 6 such 5-fold symmetry axis
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This first “vertical” plane of
measurement crosses 4 LS
acoustic centers
This second “eccentric” axis
uses plane of measurement
trough 2 LS acoustic centers
These two planes of
measurement share common
mic axes equally distant to 2
pairs of LS at a time, and
another ones equally distant
to 5 LS centers
There are 15 such 2-fold symmetry axis
There are 30 such axis
LOW FREQUENCY
LOUDSPEAKERS–RED CURVES
HIGH FREQUENCY
COMPRESSION DRIVERS –
BLUE CURVES
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2kHz oct (outermost)–1.6k/2k/2.5k 1/3oct-RGB
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4kHz oct (outermost)–3.2k/4k/5k 1/3oct-RGB
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MEASURING IN A PLANE, IN WHICH NO
LOUDSPEAKER AXIS LIE – SO CALLED “HORIZONTAL
PLAIN”
GIVEN IS SOUND POWER LEVEL FREQUENCY
RESPONSE INSTEAD OF POLAR PATERN
SMOOTHING ANGULAR RESOLUTION, AS DONE IN
ISO3382 PAPER STANDARD BY “GLIDING” CONCEPT –
PRESENTING SO CALLED “DEVIATION FROM
OMNIDIRECTIVITY”
GIVING MISLEADINGLY GENUINE SPHERICAL SHAPE
– EVEN WITH SPHERICAL PROTECTING GRILS
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SPHEROVOX - 2kHz
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OMNIVOX – 2kHz
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SPHEROVOX - 4kHz
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OMNIVOX – 4kHz
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SPHEROVOX - 4kHz
Coaxial Drivers Switched off
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OMNIVOX – 4kHz
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SPHEROVOX - 4kHz
Coaxial Drivers Switched off
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OMNIVOX – 4kHz
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Free Field Directional
SPL Differences - dB
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SPL Frequency Response at 3 random, 15deg apart,
off-Axis Steps – 2m Mic Distance
Spherovox – Verical 15deg Steps
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Omnivox – Horizontal Plane 15deg Steps
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Two 15” Coaxial
Loudspeaker
Double Dual Diaphragm
Large Format CD MonoHorn
US Patent 5,878,148 – 1997
Inventor – D.Dimitrov
ADVANTAGES
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REDUSED HORN CUT-OFF FREQUENCY WITH THE
SAME EXTENTION RATE
CROSSOVER FREQUENCY DOWN TO - 250 Hz
THD PERFORMANCE АТ 125dB/1m <-40dB (2nd),<-50(3th)
– 50Hz-10kHz
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It is impractical to have HR
dodecahedron 3-D polar pattern
measured .
Maximum directional SPL deviation
in any band however could easily be
evaluated by a single polar pattern
in a plane, determined by at least
two loudspeaker axes.
30 dB L/R 1/3 octave band
maximum SPL variation values, and
about 20 dB octave ones for 2kHz to
4kHz bands could be expected in
rooms with dodecahedron
measurements in horizontal plane.
Spherovox will give 2-3dB
maximum L/R variations under the
same conditions, which is 10 times
better.
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Spherovox has about 10 dB higher
SPL sensitivity and about 10db
higher Power handling capabilities
than marketed Dodecahedrons –
meaning about 20 dB higher SWL
Capabilities.
Spherovox exhibit perfectly circled
horizontal polar patterns for all
frequency 50Hz-10kHz, and for all
frequency bans including pure sine
wave, and “3 or 5 equally rotational
steps” during measurements are
misconception.
Some spatial parameters measured
with dodecahedrons are hardly
usable after “3 or 5 equally
rotational steps” averages.
Both Omnivox and Spherovox are
fully ISO3382 compliant , which is
deeply erroneous.
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[1] Hak, Wenmaekers, Hak, van Luxemburg - The Source Directivity
of a Dodecahedron Sound Source determined by Stepwise Rotation,
FORUM ACUSTICUM 2011/27. June - 1. July, Aalborg, Denmark.
[2] ISO 3382-1 International Standard ISO/DIS 3382-1: Acoustics
Measurement of room acoustic parameters–Part1:Performance
rooms. International Organization for Standardization, 2009.
[3] Angelo Farina, Advancements in impulse response measurements
by sine sweeps, Presented at the 122nd AES Convention 2007 May 5–
8 Vienna, Austria.
[4] Leo L.Beranek, Acoustics pp103,104.
[5] T. W. Leishman, S. Rollins, and H. M. Smith, “An experimental
evaluation of regular polyhedron loudspeakers as omnidirectional
sources of sound,” J. Acoust. Soc. Am. 120, 1411–1422 (2006).
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Plamen Valtchev – plamen@spherovox.com
Dimitar Dimitrov – dimo@spherovox.com
Rumen Artarski – rumen@spherovox.com
www.spherovox.com