Speaker device

Details Speaker device Speaker device

1999-08-23

2003-12-16

Harvey, Minsun Oh (Department: 2644)

Electrical audio signal processing systems and devices

Having non-electrical feature

And loudspeaker

C381S345000, C381S354000

Reexamination Certificate

active

06665412

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a speaker device capable of stably providing a desired directivity provided by a combination of omnidirectionality and bidirectionality, down to ultra low frequencies and capable of enlarging a listening range providing excellent stereophonic feeling by a comparatively small-sized system constitution and wherein excellence is capable of enlarging a listening range providing surround effect.
BACKGROUND OF THE INVENTION
Conventionally, there is known a speaker device of a closed type or an open back type. In this case, the directional characteristic at low frequencies constitutes omnidirectionality in a closed type speaker device and bidirectionality in an open-back type speaker device. Further, at middle and high frequencies where a speaker cannot be regarded as an ideal point sound source, radiated sound wave per se of the speaker is provided with directivity. That is, according to the conventional speaker device, as the directional characteristic at a low frequency region, only the omnidirectionality or the bidirectionality can be provided.
Further,
FIG. 28
shows a state in which a conventional stereophonic speaker device is arranged in a test listening room
100
. The speaker device is constituted by a left channel speaker device
1
L having a sound signal reproducing speaker for reproducing a left channel sound signal and a right channel speaker device
1
R having a sound signal reproducing speaker for reproducing a right channel sound signal.
According to such a speaker device, basically, at a listening position on a center line M of the speaker devices
1
L and
1
R, for example, at point a, correct sound image localization is provided between the speaker devices
1
L and
1
R by which inherent sound stage of a 2-channel stereophonic system is reproduced. However, at a listening position deviated from the center line M, for example, point b, there is constituted sound image localization deviated to a direction of the speaker device
1
R owing to sound attenuation in distance of sound wave or the like and then inherent sound stage as the 2-channel stereophonic system is not reproduced.
That is, in
FIG. 28
, when sound signal reproducing speakers of the speaker devices
1
L and
1
R are driven by the same signal, sound image at a listening position on the center line M of the speaker devices
1
L and
1
R, for example, at point a, is localized in a center front direction as shown by an arrow mark. Accordingly, when ordinary stereophonic signals are reproduced, continuous sound stage is reproduced between the speaker devices
1
L and
1
R (illustrated by dot-dash-line La).
In this case, in respect of sound image localization of 2-channel stereophonic sound, in view of auditory sensation, the following property is known. When there is a difference in levels of sound pressures of sound waves from the speaker devices
1
L and
1
R, the sound image at a listening position on the center line M of the speaker devices
1
L and
1
R, for example, at point a, is moved in a direction of a speaker device having a higher sound pressure level. Further, when a delay time period of 1 through 30 ms is provided to either of signals for driving sound signal reproducing speakers of the speaker devices
1
L and
1
R, the sound image at a listening position on the center line M of the speaker devices
1
L and
1
R, for example, at point a, is moved in a direction of a speaker from which sound wave arrives earlier in time. This phenomenon is referred to as precedence effect, which is well known.
In view of such a property in auditory sensation, consider sound image localization at a listening position, for example, point b, deviated from the center line M of the speaker devices
1
L and
1
R. At point b, distances between a sound receiving point and the speaker devices
1
L and
1
R differ from each other and therefore, in the case where the directivities of the speaker devices
1
L and
1
R are omnidirectional, there causes a difference between arrival times of sound wave from the speaker devices
1
L and
1
R and there causes a difference in levels of sound pressures. That is, the arrival time is earlier in the case of sound wave from the speaker device
1
R and the sound pressure level is higher in the case of sound wave from the speaker device
1
R.
Accordingly, sound image at a listening position, for example, at point b, deviated from the center line M of the speaker devices
1
L and
1
R is localized to significantly deviate in a direction of the speaker device
1
R as shown by an arrow mark in
FIG. 28
owing to the above-described difference in sound pressure levels in addition to the precedence effect caused by time difference. Accordingly, sound stage in the case of reproducing ordinary stereophonic signals is deviated to a side of the speaker device
1
R (illustrated by two-dot-dash-line Lb).
There has been proposed a method of utilizing the directivity of a conventional speaker with regard to a method of reproducing 2-channel stereophonic sound, which intends to improve the problem of deviation of the sound stage, mentioned above, that is, to enlarge the listening position providing excellent stereophonic feeling. In
FIG. 29
, sound signal reproducing speakers
2
L and
2
R of the speaker devices
1
L and
1
R are attached to closed type cabinets
3
L and
3
R such that respective principal axes (reference axes) are directed inwardly by about 45° in view from a central listening position, which is a method of utilizing directivities provided to speakers per se at middle and high frequencies based on the fact that diaphragms of the speakers
2
L and
2
R are provided with limited areas. Further, in
FIG. 30
, as sound signal reproducing speakers
4
L and
4
R of the speaker devices
1
L and
1
R in charge of middle and high frequencies, there are used bidirectional (directivity in 8-like shape) speakers and the speakers
4
L and
4
R are attached to baffle plates
6
L and
6
R in cabinets
5
L and
5
R front faces of which are opened such that respective principal axes thereof are directed inwardly by about 450° in view from a central listening position. Further, solid lines a
L
and a
R
respectively designate the directivities of the speakers
4
L and
4
R.
According to the examples shown by FIG.
29
and
FIG. 30
, by providing directivities to the sound waves radiated from the speaker devices
1
L and
1
R, the sound pressure level of sound wave from the speaker device
1
R is reduced and the sound pressure level of left channel sound wave from the speaker device
1
L is more or less increased at a listening position, for example, at point b, deviated from the center line M (refer to
FIG. 28
) so that the devices are operated to correct a difference between sound pressure levels based on a difference in sound attenuation in distances from the two left and right channels, whereby a listening position providing excellent stereophonic feeling is enlarged.
However, according to the example shown by
FIG. 29
, when the directivity is intended to provide from lower frequencies, the speakers
2
L and
2
R having larger apertures need to use and the system constitution becomes large-sized. Further, according to the example shown by
FIG. 30
, when the low frequency limit of the reproduction band is intended to widen, the baffle plates
6
L and
6
R attached to the speakers
4
L and
4
R need to enlarge. Similar to the example shown by
FIG. 29
, the system constitution becomes large-sized.
Further,
FIG. 31
shows a state in which conventional front surround speaker devices are arranged in the test listening room
100
. The speaker device is constituted by a left channel speaker device
11
L and a right channel speaker device
11
R. For example, the speaker device
11
L is provided with a sound signal reproducing speaker for reproducing a left sound signal as well as a surround signal reproducing speaker for reproducing a surround signal, and the speaker device
11
R is provided with a sound signal reproducing speaker for reproducing

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