Bose 901 Series IV Owner's guide - Page 14

V.

Living

with

your

BOSE

901

Loudspeakers

I

14

The

effect

of

listening

room

acoustics

is

to

radically

modify

the

tonal

balance

of

any

loudspeaker.

This

effect

can

be

greater

than

the

difference

between

two

loudspeakers

of

substantially

different

cost.

As

part

of

its

ongoing

research

in

sound

reproduction,

BOSE

Corporation

has

carried

out

an

extensive

program

examining

the

acoustic

properties

of

a

wide

range

of

listening

rooms.

The

development

of

the

901

Series

IV

loudspeaker

is

an

important

result

of

this

research

and

development.

The

901

Series

IV

loudspeaker

system

solves

the

problem

of

the

effect

of

the

room

on

speaker

performance

with

a

new

equalizer

design

that

provides

controls

specifically

designed

to

compen-

sate

for

the

effects

of

room

characteristics,

musical

sources,

and

speaker

placement.

A

contribution

in

achieving

this

new

performance

is

the

new

driver

used

with

the

901

Series

IV.

This

new

driver

assembly

has

an

improved

efficiency

in

the

range

of

10-15

kHz.

Improvements

in

components,

adhesives,

and

manufacturing

techniques

have

also

made

possible

further

improvements

in

the

high

-power

handling

capability

of

the

driver.

The

power

handling

capability

of

the

speaker

system

has

been

improved

to

the

point

that

there

are

no

restrictions

on

the

size

of

the

amplifier

used

with

the

901

Series

IV

in

non-commercial

ap-

plications,

providing

the

fusing

recommendations

in

this

owner's

manual

are

followed.

The

combination

of

new

equalizer

controls,

improvements

in

high

-frequency

efficiency,

and

high

-power

handling

capabili-

ties

make

the

901

Series

IV

speaker

system

unusually

flexible

with

respect

to

location

in

the

listening

room,

room

acoustics,

and

choice

of

power

amplifier.

A.

SOURCE

AND

ROOM

COMPENSATION

CONTROLS

The

901

Series

IV

Active

Equalizer

Controls

have

been

design-

ed

from

a

radically

different

vantage

point.

Currently

available

tone

controls

found

on

amplifiers

and

receivers

feature

bass

and

treble

controls

that

are

primarily

designed

around

estab-

lished

circuits.

These

circuits

were

designed

without

any

specific

compensation

requirement

and

therefore

cannot

compensate

for

the

specific

effects

of

room

acoustics.

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For

example,

most

current

bass

controls

not

only

adjust

the

mid

-bass

normally

affected

by

room

acoustics,

but

also

the

deep

bass

and

lower

midrange.

Also,

adjusting

the

treble

con-

trol,

will

adjust

the

extreme

highs

out

of

proportion

to

the

upper

treble

and

midrange.

The

new

901

Series

IV

equalizer

addresses

this

dilemma

with

two

new

controls

called

Source

and

Room

Compensation

Controls.

Certain

portions

of

the

midbass

of

any

speaker

system

will

tend

to

vary

dramatically

as

a

function

of

listening

room

acoustics.

BOSE

has

addressed

this

problem

with

the

LOW

FREQUENCY

CONTROL

that

provides

up

to

16

dB

of

change

in

the

100

to

400

Hz

range.

This

frequency

contouring

circuit

is

designed

to

provide

the

compensation

required

to

match

the

acoustics

of

your

listening

room.

The

HIGH

FREQUENCY

CONTROL

is

a

shelving

function

that

begins

affecting

the

sound

at

1

kHz

and

can

significantly

ad-

just

the

speaker's

presence

and

sonic

detail

over

the

midrange

and

high

-frequency

range

without

sacrificing

perfor-

mance

at

the

extreme

high

frequencies.

Regardless

of

the

acoustics

of

your

listening

room,

this

control

allows

the

speaker

system

to

achieve

the

correct

spectral

balance.

Bose 901 Series IV Owner's guide - Page 14

Living, Loudspeakers

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