Bose 901 brochure 3

Page 1

ngfi'fléLés

The technoloqu
~ DEhIlIU
THE SE 9

JUEE

DIRECT/35H [CT/NGESPEA/(Efl SYSTEMS

Page 2

This article is one of a series explaining the
features and benefits of the Base 901 - the most
highly reviewed speaker regardless of size or

price.

Whats behind the BOSE 901

DIRECT/ REFLECTING®

Speaker System?

If you have heard the BOSE
901 DIRECT/REFLECTING®
speaker system, or it you have
read the unprecedented series
of rave reviews, you already
know that the 901 is the long-
est step forward in speaker de-
sign in perhaps two decades.
Since the performance of the
901, covered by US. and for-
eign patents issued and pend-
ing, derives from an interre-
lated group of advances, each
depending on the others for
its full potential, we hope you
will be interested in a fuller
explanation than is possible in
a single issue.

In this issue, wed like to tell you
what our research revealed about
the roles of direct and reflected

sound in the reproduction of music.
The direct sound is what you would

hear if the walls and roof of the
concert hall were removed. If you
have ever listened to an orchestra
outside, without a reflecting shell,

you know that it is very soft and dull'

compared to what you experience
in the hall. The difference is the
reflected sound.

The reflected sound comes to your

ears from the walls of the concert

hall in almost equal quantities from

all directions whereas the direct
sound comes to you from the
direction of the instruments. The

direct sound is responsible for your

sense of localization while the
reflected sound contributes to the

fullness, presence and warmth of the

concert hall performance. As the
research indicates, this spatial

property of the sound incident upon
a listener is a parameter ranking in

importance with the frequency

spectrum of the incident energy for

the subjective apprecation of
music."

HOW THE 901 INCORPORATES
THESE FINDINGS

The 901 has eight speakers on the

back panels and one on the front.

This accomplishes two objectives.
First, it radiates the desired ratio of
about 39% reflected sound to 11%
direct sound. Secondly, by proper

choice of the angles of the rear
panels (see fig.) the 901 projects

the image of a musical performance

spread across a stage that is located
about two feet behind the speaker.

This image is established to the

extent that it is possible to hear the
full stereo spread from a wide range

of listening positions including

directly in front of one speaker - a

feat that is not possible with
conventional speakers.

This concept of direct and reflected

sound would result in an improved

speaker by itself but it would fall far
short of providing the realism offered

by the 901. There are three other
essential advances that must be

used in combination with the direct
and reflected sound to obtain the lull

benefits offered by the 901. These

will be the subjects of other issues.

SUREMENT AND EVALUATION OF
LOUDSPEAKERS, Dr. A. G. Bose,
a paper presented at the 1968 con-
vention of the Audio Engineering
Society. Copies of the complete
paper are available from the Bose
Corp. for fifty cents.

Frorn 'ON THE DESIGN, MEA-

JUSE "1

Framingham, Massachusetts 01701

A