System of sound transducers with controllable directional properties

• US 20040028238A1
• Filed: 08/06/2003
• Published: 02/12/2004
• Est. Priority Date: 09/13/2000
• Status: Active Grant

• Current Assignee: PCI Limited (Chuan HUP Holdings Limited)
• Original Assignee: PCI Limited (Chuan HUP Holdings Limited)
• Inventors: Van Der Weff, Johan
• Granted Patent: US 7,343,018 B2
• Time in Patent Office: Days
• US Class Current: 381/82
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407

Abstract

The invention relates to loudspeaker systems or loudspeaker columns as used in public address systems and at (pop) concerts. Such systems heretofore possess a frequency-dependent coverage angle and strong second and third order side lobes. The invention describes formulae of the voltage to be applied to the separate loudspeakers of the loudspeaker column, which makes it possible to realize the constant coverage angle over the entire frequency range and to suppress the side lobes to a far-reaching extent.

Claims

1. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a voltage V_n, according to:

2. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a voltage V_n, according to:

V=a−

b.cos(m)+c.cos(2.m) 

 

(2)

wherein;

a, b and c are the constants which determine the window,

m;

is m^th fraction of unit circle (in radials) according to;

$m=\frac{0,1,2<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(n-1\right)}{\left(n<br><br>\text{\hspace{1em}<br><br>}<br><br>l<br><br>\text{\hspace{1em}<br><br>}<br><br>s-1\right)}·<br><br>2<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}$

 

wherein;

nls;

operative number of loudspeakers in the array, depending on coverage angle and frequency according to the relation below;

$\mathrm{nls}=\frac{k}{\mathrm{\varphi <br><br>}·<br><br>f·<br><br>c·<br><br>d}$

 

wherein;

φ

;

desired coverage angle in degrees

f;

frequency in Hz

c;

sound velocity (ca. 340 m/sec in air)

d;

center-to-center distance between the transducers in meters

k;

constant to some extent-depending on window type;

3. A system according to claim 2, wherein a=0.5, b=0.5 and c=0.

4. A system according to claim 2, wherein a=0.54, b=0.46 and c=0.

5. A system according to claim 2, wherein a=0.42, b=0.5 and c=0.08.

6. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for delaying in time the signal that is applied to a loudspeaker n in the column, according to the formula

7. A system according to claim 6, wherein a=33.

8. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a power P_f,φ

according to;

9. A system according to claim 8, characterized in that the value of k is between 18 and 25.

10. A system according to claim 9, characterized in that k=18.