Orban 674A Stereo Equalizer Brochure
User Manual: Orban 674A Stereo Equalizer Brochure
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PERFORMANCE
HIGHLIGHTS
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Eight bands per channel, each with
TUNING AND BANDWIDTH
controls
Each band tunes over 3: I frequency range
"O" typically variable between 0.3
and 20 (center TUNING)
± I 6dB equalization range
EO controls are long-throw dustshielded slidepots for good
resolution
TUNING and BANDWIDTH controls
marked with "tics" indicating
typical settings
Narrowband notching capability
ideal for sound reinforcement
Bands totally non-interacting
A dedicated stereo device with controls 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 switchable
D I 2 dB/octave slopes
D Filters follow graphic section.
Separate main/lowpass and highpass 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 outputs 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 construction including socketed IC's
D Highly cost-effective
A MONO VERSION OF THIS
PRODUCT IS ALSO AVAILABLE AS
MODEL 672A
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Introducing the 674A Stereo Equalizer
Applications
The Orban 674A is a cost-effective, professional, quasi-parametric equalizer
with the convenience of graphic-type
EO controls. Wide-range high- and lowpass filters with I 2d8/octave Butterworth 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.
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 installation, 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 equalizaion to each driver; one filter is required
o perform the crossover function; the
other can be used for its normal highpass (or lowpass) function .
6) For super power in mono reinforcement applications, connect both channels in series. You'll then get sixteen
EO/notch filter bands, an electronic
crossover, and an extra set of filters to
limit system bandwidth.
The space-saving 674A offers the
facilities of two complete mono 672A's
in a single chassis . Ganged, concentric
controls make one-hand stereo operation 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 electronic crossover capability.
While it is possible to operate the unit
with two unrelated mono program
sources, under some circumstances highfrequency 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 professional, it is also designed and priced to
make it understandable and available to
the advanced audiophile.
To make the 674A easy to use in situations where its full versatility isn't needed, "tic" marks have been included on
the dial calibrations of the TUNING and
BANDWIDTH controls. When these controls 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 implemented to make the equalizer a particularly 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 equalization: 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 frequencies on either side of the peak frequency 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 noninteracting: TUNING and EO do not affect each other.
The other important performance difference 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". "Constant O" curves are valuable in that
they permit infinite-depth notches to be
created; reciprocal curves limit the maximum 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 interference from a signal. On the other
hand, some people prefer reciprocal.
curves because the boost and cut ar
mirror images of each other, thus permitting previous equalization 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-parametric 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.
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In all cases, the BANDWIDTH control
can be adjusted to make the totally noninteracting (series-connected) bands
"combine" -a most desirable characteristic 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.
ing. In addition, many " effects" (such as
telephone, pocket radio, or "old time"
recordings) can be easily created with
the 674A alone.
Recording Studios
Every recording studio needs a few
channels of 674A equalization to handle
the tough chores that the internal console 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!
In addition, the 674A can be used to
equalize the "8-chain" in the re-recording theater to the acoustic response
specifications of the studio. The lowpass
filter can effectively simulate the
"Academy Rolloff" or its current
modifications.
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 ordinary 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 colored 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 BANDWIDTH 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 extraneous sounds that always seem to
plague location recordings-that power
is there instantly, without patching or
the use of external dip filters. The highand lowpass filters are invaluable for
cleaning up noise and rumble without
affecting dialogue-and without using
up EO channels to try to achieve filter-
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 competitors. 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 conditioning noise. Whatever your application, the 674A's RF suppression and optional output transformer mean problem-free installation in high-RF environments.
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 desiredincluding solid, punchy bass free from
muddiness and boom-and an aggressive, sizzling top free from ringing and
coloration typical of a full-octave
graphic equalizer. The eight bands permit substantial work to be done in flattening out undesired response deviations 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
Technical Description
The 674A Equalizer consists of a balanced input buffer amplifier, eight main·
equalization amplifiers connected in
series, and tunable lowpass and highpass positive feedback I 2d8/octave Butterworth filters. The output of the highpass 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 lowpass 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 symmetrically connected as a feedback element 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 depending upon setting of GAIN controls; slewing 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 ringing at any output level. The only ringing
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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 remain 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-parametric" 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 adjusted 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 bandpass 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 frequency.
"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 Butterworth)
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 instantaneous 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, insisting 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 equalization of the same rigorous quality to applications where it could never before
be afforded. The 674A is inexpensive
enough to qualify it for serious consideration 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 BANDWIDTH for each of eight bands. TUNING, 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:
5 1/4 " (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 subject to cha nge without notice
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~DINCLAB
REPORT
NORMAN EISENBERG AND LEN FELDMAN
ORBAN 674A
STEREO -E QUALIZER
•
"...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
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STEAM POWERED RADIO.COM
Reprinted by permission of MODERN RECORDING AND MUSIC
October 1981 © Cowan Publishing Corp.
Orban 674A Stereo Equalizer
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General D escription: 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 provided by continuously variable controls for adjusting
center frequency and bandwidth of each frequency segment. 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 electronic 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
1
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 shielded 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 reinforcement, 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
Specifications have been included in the Operating Manual in response to this appreciated criticism.
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•
Fig. 1: Orban 67 4A: Extreme and intermediate frequency 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 intermed iate frequency settings of low-pass (high-cut) filter yields
curves shown. Slopes of this filter are also 12 dB per
octave.
72
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Fig. 3: Orban 674A: Each band of this quasiparametric/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 extreme 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 instrument: 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 (narrowest display) and 10 (broadest looking curve covering the entire audio spectrum).
MODERN RECORDING & MUSIC
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"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 octave from the speaker system; a smooth dip in the upper 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 inches high; 5¼ inches deep (behind panel). Weight is
13.5 lbs. Price: $1179.
Individual Comment by L.F.: I can't help thinking that manufacturers of semi-pro and pro audio consider 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 during 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-tonoise 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 electronic crossovers.
Most parametric equalizers we have tested previously 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.
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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
STEAM POWERED RADIO.COM
Fig. 5: Orban 674A: By following the suggested "Tic"
marks on tuning and bandwidth controls for each
band of the equalizer, we obta ined 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 statement of its "limitations." Since the corresponding" A"
Fig. 6: Orban 674A: Neither a simple 8-band graphic
equalizer nor the typical three or four band
parametric equalizer could have produced the complex and precision overall response curve obtainable
with this Orban EQ, which attests to its extreme flexibility of control.
73
and "B" controls had to be placed physically close to
each other, " there is slight crosstalk between the channels at very high frequencies (typically better than
-55 dB at 20 kHz, falling at 6 dB/octave at lower frequencies). 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 independent program 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 pros
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 unprecedented for a single-unit equalizer. As a straightforward graphic equalizer, the eight bands of the Orban 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
LAB MEASUREMENT
Frequency response ( - 3 dB)
Ha rmonic distortion
1 kHz
20 Hz
20 kH z
IM distortion (SMPTE)
Signal-to-noise (" A" wtd)
All stated operating parameters
NA
10 Hz to 70 kH z
NA
NA
NA
NA
NA
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)
Confirmed
CIRCL E 20 ON READER SE RVIC E CARD
•
Orban professional audio prod ucts are sold worldwide through authorized dealers.
o,ban
Orban Associates Inc., 645 Bryant Street, San Francisco, CA 94107 (4 15) 957-1067
806008-000-01
STEAM POWERED RADIO.COM
2/82
Revision 15; Effective 1 February 1986
Changes: Add 275A, 275A/RC
No price changes
Change Security Cover fran "GY" to "WH"
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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
803001-000-15 1/86
(415> 957-1067 TELEX 17-1480
STEAM POWERED RADIO.COM
Source Exif Data:
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