Orban 674A Stereo Equalizer Brochure

STEAM POWERED RADIO.COM

PERFORMANCE

HIGHLIGHTS

D Eight bands per channel, each

with

TUNING

AND

BANDWIDTH

controls

D Each

band

tunes

over

3:

I fre-

quency

range

D

"O"

typically

variable

between

0.3

and

20 (center TUNING)

D ± I 6dB equalization range

D EO controls are

long-throw

dust-

shielded slidepots

for

good

resolution

D TUNING

and

BANDWIDTH

controls

marked

with

"tics"

indicating

typical settings

D

Narrowband

notching

capability

ideal

for

sound reinforcement

D Bands

totally

non-interacting

D A dedicated stereo device

with

con-

trols arranged

for

optimum

ease

of

maintaining

stereo balance

HP/LP Filter Sections

D Each section

continuously

tunable

over

I 00: I range in 2 decades

D Each section

independently

switch-

able

D I 2 dB/octave slopes

D Filters

follow

graphic section.

Separate main/lowpass

and

high-

pass

outputs

allow

use

as

filters

or

as

full

electronic crossover

General

D

Very

low

noise

and

distortion

D

High

slew

rate

for

minimum

TIM

(SID)

D Front-panel

GAIN

controls; I 2dB

gain available

D "Peak-stretching" overload lamps

warn

of

clipping

anywhere

in

equalizer

D

Active

balanced inputs; unbalanced

outputs. Transformer-balanced out-

puts

optional

D

RF

suppression

on

inputs, outputs,

and

power

leads

D I I 5/230V, 50-60Hz

transformer

is

standard

D Industrial-grade parts

and

construc-

tion

including

socketed IC's

D

Highly

cost-effective

A

MONO

VERSION

OF

THIS

PRODUCT

IS

ALSO

AVAILABLE

AS

MODEL

672A

Introducing

the

674A

Stereo Equalizer

The

Orban

674A

is

a cost-effective,

pro-

fessional, quasi-parametric equalizer

with

the

convenience

of

graphic-type

EO

controls

.

Wide-range

high-

and

low-

pass filters

with

I 2d8/octave

Butter

-

worth

slopes

follow

the

EO section

for

added

versatility. The

674A

has

two

outputs

per

channel,

arranged

so

that

these filters can also be used

as

a

fully

tunable

electronic crossover.

The space-saving

674A

offers

the

facilities

of

two

complete

mono

672A's

in a single chassis. Ganged, concentric

controls

make

one-hand

stereo opera-

tion

of

bandwidth

and

tuning

a snap.

Graphic-style EO

controls

are split

parallel

for

each

of

the

eight

bands.

Separate

high-and

low-pass filters

on

each

channel

offer

stereo

two-way

elec-

tronic

crossover capability.

While

it

is

possible

to

operate

the

unit

with

two

unrelated

mono

program

sources,

under

some circumstances

high-

frequency

crosstalk

may

be experienced.

Therefore, crosstalk requirements

should

be

evaluated

in

such applications.

(See

Specifications)

The

674A

is

a professional

product

designed

to

provide

a large measure

of

versatility, convenience,

and

quality

at

a

very

attractive

price.

While

it

meets

the

requirements

of

the

demanding

profes-

sional,

it

is

also designed

and

priced

to

make

it

understandable

and

available

to

the

advanced

audiophile.

To make

the

674A

easy

to

use

in

situa-

tions

where

its

full

versatility

isn't

need-

ed,

"tic"

marks

have

been

included

on

the

dial calibrations

of

the

TUNING

and

BANDWIDTH

controls

.

When

these con-

trols

are set

to

the

tics,

the

674A

behaves like a standard octave-band

graphic

equalizer

with

the

eight

bands

on

ISO

frequencies

from

63

to

8000Hz

.

Each feature

of

the

674A

has been

thoughtfully

chosen

and

cleverly

im-

plemented

to

make

the

equalizer a par-

ticularly

powerful

tool

in

nearly

all areas

of

audio:

sound

reinforcement,

public

address, recording studio, broadcasting,

motion

picture sound, disco,

theater

...

Why

"Quasi-

Parametric

"?

There are

two

basic types

of

parametric

equalizer: full-

and

quasi-parametric.

Orban

manufactures

both

types.

Both

offer

far

more

effective

control

than

other

kinds

of

equalizers, like graphics.

Our

popular

dual-channel

6228

is

a full

parametric. This means

that

you

have

totally

non-Interacting

control

over

the

three

fundamental

parameters

of

equali-

zation:

the

amount

of

peak

boost

o.

(in dB),

the

tuning

(the

frequency

m

affected

by

the

equalization),

and

the

"O"

(wh1ch relates

to

the

sharpness

of

the

EO

curve-the

degree

to

which

fre-

quencies

on

either

side

of

the

peak fre-

quency

are affected

by

the

equalization).

As opposed

to

our

6228

Equalizer,

the

674A

is

quasi-parametric. This means

that

the

"O"

changes

when

you

adjust

the

TUNING

and/or

EO controls.

Other

control

adjustments are

completely

non-

interacting

: TUNING

and

EO

do

not

af-

fect each other.

The

other

important

performance

dif-

ference

between

the

full-parametric

6228

and

the

new

674A

is

that

the

622B's EO curves are

"constant-0";

the

674A's

curves are

"reciprocal".

"Con-

stant

O"

curves are

valuable

in

that

they

permit

infinite-depth

notches

to

be

created; reciprocal curves

limit

the

max-

imum

cut

to

the

same

number

of

dB

as

the

maximum

boost. In

the

case

of

the

674A,

I

6d8

of

cut

is

available. This

is

fine

for

tuning

out

ring-modes

in

sound

reinforcement

systems,

but

might

not

be

adequate in all circumstances

to

remove

hum

or

other

fixed-frequency

inter-

ference

from

a signal.

On

the

other

hand,

some

people

prefer

reciprocal.

curves because

the

boost

and

cut

ar

mirror

images

of

each

other,

thus

per-

mitting

to

be

readily

"undone"

later. Careful design

of

the

circuitry

gives

the

674A

In

boost

mode

a characteristic similar

to

the

622B's desirable

"constant-O"

curve

family.

Why

did

we

choose

the

quasi-para-

metric

technique

for

the

674A7

Because

it

offers a

way

to

produce

a

very

high

quality,

stable equalizer

at

low

cost

without

compromising

distortion,

noise,

accuracy,

or

reliability.

Applications

Sound

Reinforcement

and

•

Monitor

Tuning

There are

many

ways

to

use

the

674A

in

sound reinforcement

and

monitor

tuning:

I)

In

an

economy

biamped

installation,

replace

both

the

third-octave

equalizer

and

the

electronic crossover

with

the

674A

. The

674A

's

narrowband,

tunable

notches can deal

with

ring-modes

more

effectively

than

the

third-octave

unit

could. Use

three

or

four

of

the

674A

bands

for

narrowband

notching;

leave

the

rest

for

wideband

EO.

2)

In a

higher

budget

biamped

instal-

lation,

use

the

674A

as

an electronic

crossover plus a

narrowband,

tunable

notch

filter

for

ring-mode

suppression;

incorporate

a separate

third-octave

equalizer

to

correct

the

house curve.

3)

Use variations

of

(I)

and

(2)

above

with

an electronic crossover;

the

674A's

highpass

and

lowpass

filters can

then

be

used

to

roll

off

the

frequency

response

of

the

system

in

a

controlled

manner

.

4)

In a

non-biamped

system (like a stage

monitor),

use

the

674A

to

equalize

the

monitor,

and

use its filters

to

restrict

response

in

the

extreme

high

and

low

frequencies.

5)

Use

the

674A

as

a

partial

electronic

crossover plus equalizer/filter

bj

devoting

one

channel

of

674A

equaliza-

•

ion

to

each

driver;

one

filter

is

required

o

perform

the

crossover

function;

the

other

can be used

for

its

normal

high-

pass (or lowpass)

function

.

6)

For super

power

in

mono

reinforce-

ment

applications,

connect

both

chan-

nels

in

series.

You'll

then

get

sixteen

EO/notch

filter

bands,

an

electronic

crossover,

and

an

extra set

of

filters

to

limit

system

bandwidth.

In

all

cases,

the

BANDWIDTH

control

can be adjusted

to

make

the

totally

non-

interacting (series-connected) bands

"combine"

-a

most

desirable charac-

teristic

in

sound

reinforcement

.

Any

way

you

cut

it,

the

674A's

economy

and

extraordinary

versatility

make

it

one

of

the

sound

reinforcement

practitioners'

most

useful tools.

Recording Studios

Every

recording

studio

needs a

few

channels

of

674A

equalization

to

handle

the

tough

chores

that

the

internal

con-

sole equalizers

can't

deal

with.

Patch

that

problem

track

through

a

674A:

its

fine-tuning

ability

lets

you

clean

up

the

track

far

more

effectively

than

you

could

with

a

graphic

or

"three

knob"

console equali?er. Use

the

tunable

filters

to

help

eliminate rumble, cymbal splash,

kick

drum

leakage-you

name it!

If

you

need

to

correct

the

equalization

of

a track because

of

second

thoughts

during

or

after

the

mix,

the

674A

can

create

the

finishing

touches

as

no

or

-

dinary

equalizer can. It's

better

than

a

third-octave

graphic, because

the

674A

can generate

broad,

non-ringing

boosts,

whereas

the

graphic

is

much

more

col-

ored

and

ringy.

The

674A

is

also

an

ideal

adjunct

to

an

electronic music

synthesizer-you

can

create

high

"O"

formats

and

shape

the

spectrum so

that

the

sound

comes alive.

Motion

Picture

Sound

The

674A

is

an

ideal replacement

for

the

graphic

equalizers

ordinarily

used

for

dialogue

equalization

in

motion

picture

sound.

Set

the

TUNING

and

BAND-

WIDTH

controls

to

the

"tics"

on

the

panel,

and

you

get

the

equivalent

of

a

familiar easy-to-operate graphic.

But

when

you

need

the

extra

control

and

flexibility-such

as

notching

out

the

ex-

traneous

sounds

that

always

seem

to

plague

location

recordings-that

power

is

there

instantly,

without

patching

or

the

use

of

external

dip

filters. The

high-

and

lowpass filters are

invaluable

for

cleaning

up

noise

and

rumble

without

affecting

dialogue-and

without

using

up

EO channels

to

try

to

achieve filter-

ing. In

addition,

many

"effects" (such

as

telephone,

pocket

radio,

or

"old

time"

recordings) can be easily created

with

the

674A

alone.

In

addition,

the

674A

can be used

to

equalize

the

"8-chain"

in

the

re-record-

ing

theater

to

the

acoustic response

specifications

of

the

studio. The

lowpass

filter

can

effectively

simulate

the

"Academy

Rolloff"

or

its

current

modifications.

Stereo Broadcasting

Use

the

674A

in

the

production

studio

to

enhance

the

announce

mike,

"sweeten"

stereo music,

and

to

create

special

production

effects

that

make

your

station stand

out

among

its com-

petitors.

Meanwhile,

another

674A

can

be

quietly

and

efficiently

equalizing

the

stereo

program

line

for

maximum

punch

and

brightness

on

the

air. Use

the

674A

to

equalize

phone

or

remote lines

for

flat

response-it's

much

more

versatile

than

the

standard

phone

company

equalizers.

In

the

main studio, use

it

on

the

announce

mike channel

to

equalize

for

maximum

presence,

and

also

to

notch

out

sounds like mechanical

hum

from

cart machine

motors

or

air condi-

tioning

noise.

Whatever

your

applica-

tion,

the

674A's

RF

suppression

and

op-

tional

output

transformer

mean

prob-

lem-free

installation

in high-RF en-

vironments.

Dance

Bars

The 674-A

is

an

.excellent dance

bar

stereo equalizer. The

sound

contractor

installing

the

system can

offer

the

management exactly the sound

desired-

including

solid,

punchy

bass free

from

muddiness

and

boom-and

an

aggres-

sive, sizzling

top

free

from

ringing

and

coloration

typical

of

a full-octave

graphic

equalizer. The

eight

bands per-

mit

substantial

work

to

be

done

in flat-

tening

out

undesired response devia-

tions in

the

upper

bass

and

midrange

.

Narrowband

notches can

even

deal

with

the

difficult

resonances sometimes

encountered

in

high-efficiency

horn-type

loudspeakers. In biamped installations,

use

the

separate

lowpass

and

highpass

filter

outputs

as

a complete electronic

crossover.

No

other

crossover

is

necessary.

The

674A

costs a

bit

more

than

an

octave-type graphic. But,

unlike

a

graphic,

it

really solves

the

problem

.

o,ban

Orban

Associates Inc.

645

Bryant

Street

San

Francisco, California 94107

(415) 957-1067

Telex: 17-1480

Cable:

ORBANAUDIO

STEAM POWERED RADIO.COM

Technical Description

The

674A Equalizer consists

of

a balanc-

ed

input

buffer

amplifier, eight

main·

equalization amplifiers connected in

series,

and tunable lowpass and

high

-

pass

positive feedback I 2d8/octave But-

terworth

filters. The

output

of

the high-

pass

filter

is

buffered

to

drive 600 ohms,

and

is

available separately. By suitable

switch settings, the main

output

can be

made

to

carry a lowpassed signal. Thus

the 674A c~n be used

as

an equalizer

cascaded

with

a full electronic crossover,

or

as

an

equalizer cascaded

with

low-

pass

and

highpass filters.

Each

amplifier in the equalizer section

provides equalization

for

one band

only,

assuring

no

interaction

between

bands.

The total equalization

is

simply the sum

(in

dB)

of

the equalizations

provided

by

each

of

the sections.

Peak

boost

is

accomplished

by

adding

the

output

of

a

two-pole

bandpass

resonator

to

the main signal; reciprocal

dip

occurs

when

this resonator

is

sym-

metrically connected

as

a feedback ele-

ment in the main equalizer amplifier.

Specifications:

All

specifications

apply

when

driving

600 ohms

or

higher impedances. Noise

measured

on

an average-reading meter

through

a 20-20,000Hz bandpass filter

with

I SdB/octave

Butterworth

skirts.

ELECTRICAL

Input:

Impedance,

Load(each

leg):

IOOK

in

parallel

with

I

OOOpF,

electronically

balanced

Impedance, Driving: Ideally 600 ohms

or

less,

balanced

or

unbalanced

Nominal

Input

Level: Between - I 0

and

+4dBm

Absolute Overload Point: + 26d8m

Output:

Impedance, Source: 47 ohms in parallel

with

IOOOpF,

unbalanced (Optional

transformer balanced 600

ohm

outputs)

Impedance, Load: Should

be

600 ohms

or

greater-will

not

ring

into

any

capacitive load

Nominal

Output

Level: + 4d8m

Max.

Output

Level Before Clipping:

greater

than

+ I 9d8m, 20-20,000Hz

Frequency Response:

± 0.25dB; 20-20,000Hz:

EQ

controls set

at

zero detents

Avallable Gain:

+ I 2dB; adjustable

to

-infinity

by

means

of

front-panel

GAIN

control

Slew Rate:

Varies between 6 and I 3V/us depend-

ing

upon

setting

of

GAIN controls; slew-

ing

is

symmetrical. Internal bandlimiting

assures

that

slew rate limiting

will

not

occur even

with

the most severe

equalization and program material.

Square

Wave

Response:

Square

wave

exhibits

no

spurious ring-

ing

at

any

output

level. The

only

ringing

8000 I 6-000-02

2/81

The

EQ

IN/OUT

switch

bypasses the last

seven main amplifiers and defeats

equalization in the first amplifier. Gain

and signal

polarity

are equal in the IN

and

OUT modes. As the BANDWIDTH

control

is

operated, the skirts

of

the

equalization curve move in and out,

but

the peak gain and peak frequency re-

main constant. As the EQUALIZATION

controls are operated, the frequencies

of

peak gain remain constant.

However,

as

the TUNING control

or

EQUALIZATION

control (in dip mode) are operated, the

bandwidth

("O'')

will

chr,ge,

because

of

the simplifications in the "quasi-para-

metric" bandpass resonator. Careful

design has enabled

us

to

produce curves

(in boost mode only) essentially identical

to

the desirable

"constant-Q"

curves

provided

by

our

6228

true

parametric

equalizer in its boost mode.

The EQUALIZATION controls all produce

peaking curves;

if

shelving curves are

desired,

they

can be approximated

by

tuning

the

lowest

band

to

20Hz and the

highest band

to

20kHz. The breakpoint

of

the shelving characteristic

is

then

ad-

justed

with

the BANDWIDTH control.

observable

is

that

theoretically

associated

with

any

given equalization

curve.

Total Harmonic Distortion:

Less

than

0.

08%

, 20-20,000Hz

(+

18dBm)

SMPTE Intermodulation Distortion:

Less

than

0.

05%

( + I SdBm: 60/700Hz,

4:

1)

Noise

at

Output:

Less

than

-78dBm

(EQ

in, filters out,

controls centered)

Overload/Noise Ratio:

Better

than

I I 3dB

for

any

single band-

pass filter,

for

any

settings

of

TUNING

or

BANDWIDTH controls.

Equalization Ranges:

± I

6d8

peaking EQ, Reciprocal

Tuning Ranges:

20-60Hz;

40-1

50Hz;

110-31

0Hz;

230-750Hz; 480-l 900Hz; I . I

-4

.5Hz;

2.8-9.0kHz; 5.

9-21

kHz. Dials calibrated

at

ISO

preferred frequencies.

Crosstalk:

Typically better

than

-55dB@ 20kHz;

improves

at

6dB/octave

below

that

fre-

quency.

"O " Range:

Greater

than

0.5

to

IO

for

any

setting

of

the TUNING control.

Low

Pass

FIiter Section:

Tunable in 2 ranges: 200-2000Hz

or

2.0-20kHz, I 2dB/octave, (2nd-order But-

terworth)

High

Pass

FIiter Section:

Tunable in 2 ranges: 20-200Hz

or

200-2000Hz, I 2dB/octave, (2nd-

order

Butterworth)

Overload

Indicator:

Lamp lights

for

200ms

if

the instan-

taneous peak

output

of

any

amplifier

rises

to

within

I

dB

of

its clipping point.

Summary

Many

people are

now

aware

of

the

power

of

parametric equalization: the

almost sensual satisfaction

of

getting the

sound really right.

These

same

people

are also demanding professionals, in-

sisting

on

inaudible noise and distortion, •

human engineering,

quality

"feel",

and

uncompromising reliability.

Orban

is

well-known

for

its line

of

fine

parametric equalizers, like the 6228.

Now

with

the 674A,

it

brings equaliza-

tion

of

the

same

rigorous

quality

to

ap-

plications

where

it

could never before

be afforded. The 674A

is

inexpensive

enough

to

qualify

it

for

serious con-

sideration in applications

which

would

otherwise

be given

by

default

to

a much

less

able graphic equalizer.

The

674A

rounds

out

the line

of

Orban

"Professionals' Parametrics." Between

the 6228

true

parametric and the 674A

quasi-parametric, there

is

an equalizer

for

virtually

every need and budget. The

Orban

"Professionals' Parametrics" are

available

at

your

authorized

Orban

dealer.

Active

RC

realized

with

FET-input

opamps. Line driver employs discrete

transistor current booster.

Operating

Temperature:

o-50°

c

Power

Requirements:

I I 5/230VAC ± I

0%

; 50/60Hz;

12

watts

PHYSICAL

Operating Controls (each channel):

EQUALIZATION, TUNING, and BAND-

WIDTH

for

each

of

eight bands. TUN-

ING, RANGE

(XI

; X

10),

and

FILTER

IN/OUT

for

each filter. EQUALIZATION

IN/OUT, POWER ON/OFF, and GAIN

for

entire equalizer.

Panel:

19

" x 5

1

/i''

(48.3 x 13.3cm): 3 units

Chassis

Depth

Behind Panel:

51

/4

"

(13.3cm)

Weight:

Net

: I I

lbs.

(5

kg); Shipping:

13

1

/i

lbs.

(6.1

kg)

AC

Cord:

3-wire

U-ground

to

USA Standard

Connectors:

140 type barrier strip

(5#

screw); holes

punched

for

XLR-type connectors

(Switchcraft D3F and

D3M

or

equal)

Circuit Ground:

Available

on

barrier strip;

normally

jumpered

to

chassis.

Options:

I)

Plexiglass security cover

for

EQ

and

filter sections

2)

Balanced transformers in

two

or

four

outputs

3)

XLR-type connectors

on

input

and

two

or

four

outputs

4)

Phone jacks

on

input

and

two

or

four

outputs

Spec1f1cat1ons

su

bject

to

change without

noti

ce

STEAM POWERED RADIO.COM

J_

•

~DINCLAB

REPORT

NORMAN

EISENBERG

AND

LEN

FELDMAN

ORBAN 674A

STEREO -EQUALIZER

"

...

an

engineering tour-de-force

which,

as

far

as

I

know,

is

unmatched

by

any

Other

single

device!'

Comment

by

Norman Eisenberg

"

...

making

this

the

most

powerful equalizing

tool

for

pro

audio work

that

I

have

yet

to

come

across!'

Comment

by

Len Feldman

Reprinted by permission of MODERN RECORDING AND MUSIC

October

1981

STEAM POWERED RADIO.COM

•

Orban 674A Stereo Equalizer

General Description:

The

Orban

674A is a stereo

version of

the

Orban 672A

(MR&M,

November 1979).

Each

channel is divided into

eight

frequency bands,

each

band

with

its

own slider for graphic equalization.

As in

the

former model,

parametric

operation is provid-

ed

by

continuously variable controls for

adjusting

center frequency

and

bandwidth

of each frequency seg-

ment.

In

addition, each

EQ

section

is

followed

by

wide·

range low-pass

and

high-pass filters

(12

dB

/octave).

The

filters also

may

be

used

as

an electronic crossover

in bi-amped

systems.

Each

of

the

sixteen

EQ

sliders

has

a nominal

boost/cut range of

±16

dB, marked in

gradations

of 2

dB

and

with center

detents

for

O

dB. Above each pair of

sliders is a dual-concentric knob control for left-

and

right-channel

tuning

of

the

center frequency.

Each

knob has six frequencies marked,

with

a

box

around

the

ISO frequency for

that

particular

range. Below

each pair of sliders are additional dual-concentric

knobs for

varying

the

bandwidth

("Q") separately on

each channel. These knobs are labeled from

O

to

10,

representing a

range

from a

very

steep

Q

to

a very

broad

Q.

The average Q of 7 is denoted

by

the

box

marking.

Each

filter section has individual controls for left

and

right

channels.

The

HP

filter controls include

in/out

and

selectable

range

buttons

plus continuously

variable frequency selector knobs.

The

markings

for

the

knobs indicate frequencies of 20, 25, 32, 40, 50, 80,

125, 160

and

200 Hz.

Pushing

ir.

the

range

button,

of

course, multiplies

these

frequencies by 10.

Similarly,

the

LP

filter section

has

its

own

input

and

range

buttons

and

tuning

knobs.

Here

the

knobs

are

marked 2

K,

2.5 K, 3.2

K,

5 K, 8

K,

12.5

K,

16 K, 18 K

and

20

K.

Pushing

in

the

range

button

here multiplies

these

frequencies

by

0.

1-that

is,

it

reduces

the

range

to

a

span

of 200

Hz

to

2 kHz. Thus, when

the

HP

range

switch is

set

for

"X

0.1 "

and

the

LP

range

switch is

set

for

"X

10"

both

filters cover

the

same range of 200

Hz

to

2 kHz which facilitates

the

device's use

as

an elec-

tronic crossover for

any

frequencies within

that

range.

Below

the

filter controls are

the

unit's

power off/on

switch

and

indicator;

separate

EQ

in/out

buttons

for

each channel;

separate

gain controls

with

overload in·

dicators for each channel. The panel is colored light blue

with white markings, and is rack mountable .

Signal

input

and

output

connections are made via

screws on a barrier strip.

As

supplied,

the

unit

is ready

for use

with

two-conductor shielded cable. However,

it

also may be

used

with optional

XLR

connectors which

may

be installed

and

wired behind a removable plate on

the

rear of

the

chassis.

In

addition,

the

owner's manual

includes

instructions

for

using

single-conductor shield-

ed

cable

and

¼-inch phone-plugs.

Each

channel's

input

is balanced.

The

output

is unbalanced, although

it

can

be changed

to

balanced with

an

optional transformer.

A block

diagram

showing signal

paths

is

printed

on

the

rear, which also contains

the

unit

's fuse-holder

and

the

AC power cord fitted with a three-prong plug.

The

Orban 674A

may

be used

as

a stereo graphic/

parametric

equalizer with stereo high·

and

low-pass

filters,

or

as

a stereo equalizer followed

by

stereo elec·

tronic crossover for two bi-amplified speaker systems.

Among

its

suggested

applications, covered in

the

owner's manual, are stereo matching; sound reinforce-

ment, including "house

tuning

"

and

notch filtering;

full

and

partial

electronic crossover (the

latter

involves

equalizing individual drivers in a given speaker

system); special uses in dance bars, recording studios,

motion picture sound,

broadcasting

and

electronic

music.

Test

Results: Neither

the

temporary operating

manual which arrived

with

our

test

sample, nor

the

full

manual

that

came a

bit

later, contained a formal list of

performance specs for the model 67 4A.' There were

some references

to

a few

items

such

as

the

±16

dB

EQ

range

and

so on,

and

a

statement

of

"very

low noise

and

distortion

."

Without

formal specs,

but

mindful of

the

fact

that

the

674A is essentially a stereo version of

the

672A which

had

been

tested

some time ago,

we

were

not

"in

the

dark

" with

this

service,

and

between

bench

tests

(see

"Vital

Statistics")

and

'scope analyses

we did

run

a comprehensive series on

the

new Orban

and

came up with very favorable results

that

confirm

the

model 674A

as

a

most

versatile, clean-performing,

equalizer of impressive capabilities.

Figs. 1

and

2 show

our

plots of

the

high-pass

(low

cut)

and

low-pass (high-cut) filter sections. The slopes

are

12 dB

per

octave (as claimed),

and

the

overlap (from

about

100 Hz to 2 kHz) does allow these filters

to

be

used

as

adjustable

electronic crossovers,

with

frequen·

cies of your own choosing.

Fig

. 3 shows

the

wide range of

adjustment

of center

frequency possible for one

of

the

device's eight bands

(the one chosen for this

test

was nominally centered

at

Manufacturer's Notes

1 Specifications have been included

in

the Operating Manual

in

response to this appreciated criticism.

STEAM POWERED RADIO.COM

72

Fig.

1:

Orban

67

4A:

Extreme and intermediate fre-

quency settings

of

high-pass (low-cut) filter yields

these curves. Slopes are 12

dB

per octave.

1 kHz). Again,

the

results confirm

the

manufacturer

's

claim of a

3:1

range in

actual

frequency for

the

band

.

The

variable

bandwidth

or

"Q" characteristic was

examined

as

shown in Fig.

4.

For

the

multiple response

curves shown here

we

allowed

the

center frequency

to

remain fixed

at

around 800 Hz,

and

we

varied

the

"Q"

control for

that

band

from

its

narrowest (about 0.5

Q)

to

its

widest (about

10)

.

For

use

as

a simple graphic equalizer,

we

ran

the

test

whose results are shown in Fig.

5.

In

this

instance we

set

all of

the

frequency controls

at

their indicated

marks on

the

front panel, which

puts

the

centers

ap

·

proximately

an

octave

apart.

We

then

adjusted

the

Q-controls

to

their front-panel indicated marks. Then,

by

varying each

band

's slider control (as

we

normally

do for

plotting

the

response of

any

graphic equalizer),

we

obtained

the

multiple response curves shown in Fig.

5. We did note

that

by

using

the

suggested

settings

Fig.

2:

Orban 674A: Extreme and intermediate

fre

-

quency settings of low-pass (high-cut) filter yields

curves shown. Slopes

of

this filter are also 12

dB

per

octave.

Fig. 3: Orban 674A: Each band

of

this quasi-

parametric/graphic equalizer can

be

tuned

over

a

range

of

approximately

3:1

in

frequency. Boost and

cut response curves shown are for two

of

the

ex-

treme settings and a mid-frequency setting

of

the

nominal 1 kHz band control.

shown on

the

front panel

we

did

not

end

up

with equal

values of Q (bandwidth) for each of

the

band

filters.

However, with a

bit

of experience,

we

could

have

read·

justed

the

Q

settings

to

make all of them more nearly

equal.

The

point

here was merely

to

show how

the

674A could be

used

as

a simple graphic equalizer.

As a final

test

of

the

tremendous flexibility of this

combination graphic/parametric equalizer/filter

set

/

crossover network,

we

decided

to

create

the

kind of

complex response curve

that

many

acoustic en·

vironments

might

make you wish you could do with a

less "powerful" equalizer. This is shown in Fig.

6.

Those experienced in room equalization

might

ap·

preciate

what

can be accomplished with this one instru-

ment:

For

instance, a narrow

bass

peak

that

needs

Fig.

4:

Orban 674A: The "Q"

or

bandwidth of each

of

the 8 bands of the unit

is

variable between 0.5

(nar-

rowest display) and

10

(broadest looking curve

cover-

ing the entire audio spectrum).

MODERN RECORDING & MUSIC

•

STEAM POWERED RADIO.COM

•

"sucking

out"

(without losing a good deal of

the

music);

the

desirability of a more

gradual

bass

boost

below

that

frequency

to

get

another

fraction of an

oc-

tave

from

the

speaker system; a

smooth

dip in

the

up-

per midrange to

take

care of midrange drivers

that

may

sound a

bit

"squawky;"

and

finally, a gradually rising

response

to

perk

up

the

top of

the

tweeter's range.

General Info: Dimensions are 19 inches wide; 5 ¼ in-

ches high; 5¼ inches deep (behind panel). Weight is

13.5 lbs. Price: $1179.

Individual Comment

by

L.F.: I

can't

help think-

ing

that

manufacturers of semi-pro

and

pro

audio con-

sider

it

a sacred obligation

to

send

out

first production

units

of

any

new

product

with

"temporary"

operating

manuals

and

the

usual

letter

of apology telling us

that

if

we

will

but

be patient,

the

final fancily

printed

(and

more complete) owner's manual will be along in due

time.

Perhaps

I've

become so accustomed to

these

omissions because

most

manufacturers

want

us

to

get

a chance to evaluate new

equipment

as

quickly

as

possible. Still,

it

is

rather

a

pity

that

this Orban

equalizer did

not

come

with

its

final booklet d

uring

our

tests, because there is so much more

about

this

magnificent

and

flexible equalizer

that

I'd

like

to

know.

Since no central listing of basic specifications were

supplied with

the

unit, we measured

the

usual

things

such

as

distortion

at

several frequencies, signal-to-

noise

and

frequency response. These measurements,

though, do

not

tell you

anything

about

the

true

worth

of

this

unit

. As far

as

I'm

concerned,

the

debate

over

whether parametric or graphic equalizers are more

useful in

pro

audio work can

stop

right

now.

With

the

Orban 674A you have

the

best

of

both

EQ

approaches,

plus lots more, such

as

continuously

adjustable

elec-

tronic crossovers.

Most

parametric equalizers

we

have

tested

previous-

ly had three, four

or-at

most

-five control bands.

Here is a

unit

that

has

eight

bands, all of

them

totally

controllable in

terms

of boost

and

cut, center frequency

and

bandwidth

or

"Q."

And

the

range of

the

control for

each of these

parameters

is awesome,

making

this

the

most

powerful equalizing tool for pro audio work

that

I

have

yet

come across. Especially revealing is

the

curve

shown in

Fig.

6-1

can't

think of

any

equalizer I have

ever checked

out

that

could

create

such a response

curve. I think, in a way,

that

curve tells

it

all.

By

the

time

this

appears

in print,

the

Orban 674A will come

with

its

"permanent

" owner's manual, which should

increase

my

enthusiasm

for this

device-if

that

's

possible.

Individual Comment by N.E.: As I commented

earlier on

the

Orban 672A (the mono forerunner of

the

674A),

the

parametric options for

eight

bands

were

most

impressive

and

"ear

opening"

and

handling the

device really gives you a feel for

its

utter

flexibility

and

professionalism, covering a whole

span

of possible

tonal variations from

subtle

to

major. Offering all this

for stereo is something of

an

engineering tour-de-force

OCTOBER 1981

Fi

g.

5: Orban 674A:

By

following the suggested "Tic"

marks

on

tuning and bandwidth controls for each

band of the equalizer, we obtained the eight boost

and cut curves shown above. Note that "0 " seems to

be broader at high-frequency of the display.

which,

as

far

as

I know, is

unmatched

by any

other

single device.

As

with

any

"combination" unit,

the

old question

comes

up

of

its

merit in

any

of

its

numerous functions

vis-a-vis

other

devices

that

specialize in only one or two

of those functions.

In

other

words,

as

a pure

parametric equalizer, how does

the

Orban

stack

up

against

others

that

are basically parametric? How does

it

compare

to

others

that

are purely graphic equalizers?

How does a stereo

unit

of

this

type

compare with two

otherwise equally

competent

mono units?

The

last

question is somewhat answered

by

Orban in the

owner's manual-

and

it

strikes

me

as

an honest state-

ment of

its

"limitations

."

Since

the

corresponding"

A"

Fig. 6: Orban 674A: Neither a simple 8-band graphic

equalizer

no

r the typical three

or

four band

parametric equalizer could have produced the com-

plex and prec

is

ion overall response curve obtainable

with this Orban

EQ

, which attests to i

ts

extreme flex-

ibility of contro

l.

73

STEAM POWERED RADIO.COM

and

"B"

controls

had

to

be placed physically close

to

each other, "there

is

slight

crosstalk between

the

chan-

nels

at

very high frequencies (typically

better

than

-55

dB

at

20

kHz, falling

at

6 dB/octave

at

lower fre-

quencies). A small

amount

of leakage from one channel

to

the

other

may

be heard if

you

attempt

to

use each

674A channel

to

equalize entirely indep

endent

pro-

gram

material,

and

we recommend

that

the

674A be

used only with stereophonic

program

material.

If

you

require absolute isolation between

the

two channels,

we

recommend use of a

pair

of 672A equalizers

instead."

Orban

says

this

right

up front,

to

its

credit.

As

to

parametric options,

the

674A is clearly in a class of

its

own,

what

with

eight

frequency

bands

rather

than

the

customary

three

or

four. Are

eight

bands of parametric

"too much?" I don't know. There are

many

audio

pro

s

who feel

that

really good low-pass

and

high-pass filters

combined

with

three

or

four

bands

of parametric are all

that

they

need.

And

yet,

there

is

that

"weird" response

curve

we

were able

to

get

(Fig.

6)

with this device

that

documents a complexity

and

precision

that

seem un-

precedented for a single-unit equalizer. As a straight-

forward graphic equalizer,

the

eight

bands

of the Or-

ban

are, of course, two less

than

the

usual ten octaves

found on pro-grade units. How

important

those

extra

two

segments

are,

as

against

all

the

other

versatility of

this model (including

its

electronic crossover options),

is something you'

ll

have to decide for yourself. Whatever,

the Orban 674A merits very serious consideration.

ORBAN 674A STEREO EQUALIZER: Vital Statistics

PERFORMANCE CHARACTERISTIC MANUFACTURER'S SPEC

Frequency response ( - 3

dB)

NA

Harmonic distortion

1 kHz NA

20

Hz

NA

20

kH

z NA

IM distortion (SMPTE) NA

Signal-to-noise ("A" wtd) NA

All

stated operating parameters

CIR

CL

E 20 ON READER SE

RV

ICE CARD

LAB

MEASUREMENT

10

Hz to

70

kH

z

0.12% (1 V Input)

0

.1

0%

(1

V input)

0.

13

%

(1

V input)

0.13%

(1

V input)

85

dB

(1 V input)

Confir

med

Orban pro

fe

ss

ional audio products are sold

wo

rldwide through authorized d

ea

lers.

o,ban

Orban Associates Inc

.,

645 Bryant St

re

et, San Francis

co

, CA 94

10

7

(4

1

5)

957-1067

806008-000-01

2/

82

•

STEAM POWERED RADIO.COM

Revision 15;

Effective

1 February 1986

Changes:

Add

275A,

275A/RC

No

price

changes

Change

Security

Cover

fran

"GY"

to

"WH"

ltxlel

Description

lllB/1

Spring Reverberation

(2

channels)

245F

Stereo

Synthesizer

275A

Autanatic

Stereo

Synthesizer

275A/RC

Remote

Control

for

275A

412A

414A

418A

422A

424A

536A

622A

622B

672A

674A

canpressor/Limiter

(1

channel)

Canpressor/Limiter

(2

channels)

Stereo

Canpressor/Limiter

Gated

canpressor/Limiter/De-Esser

(1

channel)

Gated

canpressor/Limiter/De-Esser

(2

channels)

Dynamic

Sibilance

Controller

(2

channels)

Parametric

F,qualizer

(l

channel)

Parametric

F,qualizer

(2

channels)

M:>no

Graphic

Parametric

F,qualizer

Stereo

Graphic

Parametric

F.qualizer

Professional

Audio

Products

Suggested

List

$899.00

$399.00

$1,895.00

$295.00

$425.00

$799.00

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$629.00

$989.00

$539.00

$569.00

$879.00

$689.00

$1,299.00

Prices

are

domestic u.s.

only;

F.O.B. San

Francisco.

Prices

based on

Buyer's

acceptance

of

Orban Standard

Terms

& Conditions

of

Sale

are

subject

to

change without

notice.

All

units

are

supplied

for

115V,

50/60

Hz

operation

unless

otherwise

specified.

See

reverse

side

for

accessories.

ORBAN

ASSOCIATES

INC.

645

BRYANT

STREET,

BAN

FRANCIBCD,CA

94107

(415>

957-1067

TELEX

17-1480

803001-000-15 1/86

Orban 674A Stereo Equalizer Brochure

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