Aiwa XR-M70 - Manual (Page 19)

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Aiwa’s Front 180’ Speaker System provides excellent sound
balance for true stereo reproduction from any listening angle.
In stereo sound reproductions systems up to now, the listening
area where the optimal stereo effect is obtained has been
extremely narrow. This is due to the following reasons.
As shown in Figure 2, a conventional stereo system has speakers
on the front panel of the speaker system, pointing forward. It is
designed for listening in a location directly in front of the front
speaker panel.
In this case, as shown in Figure 2, a listener at point located
on the center line between the right and left speakers, hears the
voice of a singer coming from the center front. Instrumental
sounds are distributed evenly between both speakers for an
optimal stereo effect.
At point ®, however, located off fhe center line between the
speakers, the distance from the left speaker to the listener is
greater than the distance from the right speaker. Sound from
the left speaker appears to be faint, and sound from the right
speaker appears to be loud. Sound is perceived as coming from
the speaker with the greater volume, so that the singer’s voice
appears to shift toward the right speaker. The normally balanced
instrumental sounds also appear to come primarily from the right
speaker.
Moreover, since the directivity of speakers increases with higher
frequencies, high-frequency sounds from the left speaker
become even harder to hear, increasing the impression of
imbalance. For these reasons, the listening area which provides
even sound balance and the optimal stereo effect is limited to
the narrow area shown in Figure 2-@.
To solve this problem, Aiwa has developed unidirectional
speakers for this new speaker system featuring cardioid directivity
for frequencies of 1 kFIz or less. These speakers are pointed
inward at angles of 45° (see Figure 1). Driven by left and right
stereo sound signals, these speakers act to increase the width
of the optimum listening area (see Figure 3). Because of their
cardioid directivity and the 45° angle of their main speaker axis,
they provide enhanced sound reproduction at point ® in Figure
3. The left speaker is pointed toward the listener, and the right
speaker is pointed away from the listener, so that the directivity
of the speakers compensates for the differences in perceived
volume caused by the differences in disfance to the listener.
Therefore, the sound of a singer’s voice is perceived as coming
from a point midway between the speakers, and instrumental
sounds are distributed evenly.
Figure 1 Front 180° speaker system
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Figure 2 Stereo effect with a conventional speaker
system
Main unit
Left
speaker
■ Right
speaker
@ Center listening point: Balanced sound heard from left
and right speakers
® Off-center listening point: Right speaker sounds louder than
left speaker
Sound pressure level
|: Stereo listening area
Figure 3 Stereo effect with Aiwa Front 180°
speaker system
True stereo sound can be heard at point ® as well as point @.
Main unit
Left
speaker
Right
speaker
Sound pressure level
: Stereo listening area of new speakers
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