Bose 601 review 1982

Page 1

AUDIO

New Equipment Reports

Preparation supervised by Michael Riggs, Robert long, and Edward 1. Foster.
Laboratory data (unless odierwise noted) supplied by Diversified Science Laboratories.

A Bose for
All Systems

Sou 001 Sort" II lloor-atlndlng loudspeaker synem.
Dimlnlll: 14 by 29% Inchol (from), 13 lncllal
«opt Prloo: saw par p-lr. errlnty: full, rm yum
pun mu mm. Il-nullcjuror: am. Com, too Th-
Moumlln Hold. Filminghlm, III, 01701.

ROOM RESPONSE CHARACTERISTICS
DB
+5
0
,5
> 0
H220 50100 200 500 m 2K
boundarydependent region
on-axis response
----- arr-axis (30°) response

5K 10K 20K

SENSITIVITV (at 1 meter; 2.5-volt pink noise,
250 Hz to 8 kHz) 87 dB SFL

AVERAGE IMPEDANCE (250 Hz to 6 kHz)
17.9 ohms

12

FOUNDED IN THE mid-Sixties by its name-
sake, Dr. Amar Bose (then, as now, a pro-
fessor of engineering at the Massachusetts
Institute of Technology), the Bose Corpora~
tion has gone on to become one of the
worlds largest manufacturers of high fidel-
ity loudspeakers. Dr, Bose started his
research in acoustics and loudspeaker
design largely out of a sense of frustration:
As a music lover and amateur musician, he
felt that even the most highly rated loud-
speakers failed to convey a realistic impres-
sion of live music. His investigations led
him to the conclusion that most of the sound
should reach a listener indirectly, via reflec-
tions off the Walls and ceiling of the room,
to simulate the conditions of a concert per-
formance. And that finding prompted a rad-
ical departure from conventional design
tenets, which was embodied in the compa-
nys first important consumer product: the
Bose 901 Direct/Reflecting loudspeakerr
Instead of a tweeter to reproduce the
high frequencies and a woofer to handle the
lows, the 901 used a multitude of identical
full»range drivers electronically equalized
for flat frequency response. Eight of these
were distributed over two angled panels that
formed the rear of the enclosure, while a

ninth was placed on a flat front baffle. The
rear drivers faced the wall and generated a
large amount of reflected sound; the func-
tion of the single front-firing driver was to
provide enoughdirect sound radiation to
establish stereo localization.

That is the way the top»ofAthe-line
Model 901 (now up to Series IV) is con-
structed to this day, The four other models
in the Bose line are also Direct/Reflecting
loudspeakers, although some compromises
have been made for the sake of economy.
(For example, they use separate woofers
and tweeters, rather than equalized full-
range drivers.) One step below the 901 is
the speaker under consideration here, the
Bose 601 Series II. The 601 is a low, floor-
standing tower designed for placement two
to five feet from the nearest side wall and
within a foot of the rear wall. The body of
the 601 is a ported enclosure for two 8-inch
woofers. One of the woofers faces forward,
while the other is mounted on top of the
enclosure, tilted back about 60 degrees,
forming part of what Bose calls a Free
Space Array. The array is completed by
four 3-inch tweeters carefully aimed to
establish an essentially omnidirectional ra-
diation pattern.

HIGH FIDELITY

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AUDIO New Equipment Reports

A carefully balanced mix of direct and
reflected round is the goal of Borer Free
Space Array, which includes four tweeters
aimed in diflerent directions and a woofer
tilted back approximately 60 degrees.

14

To make the transition from the woof-
ers to the tweeters, Bose uses what it calls a
Dual-Frequency crossover network, which
enables both sets of drivers to operate
together (at slightly reduced levels) over
almost an octave. This is said to improve
the smoothness and spaciousness of the
601 s midrange reproduction. The tweeters
begin operating at about 1.5 kHz, and the
woofers start rolling off at about 25 kHz.
In addition, each woofer is loaded by its
bwn subenclosure, which is molded into the
main enclosure. These subeuclosures are
ported into the interior of the loudspeaker
and function to smooth the woofers
response through the midbass, to prevent
boominess. Bose 601 Series II loudspeak-
ers come in mirror-image pairs with walnut~
grain vinyl side panels. Amplifier connec-
tions are made via thumbscrew terminals on
the rear of the enclosure.

Diversified Science Laboratories took
its measurements with a 601 Series [1
speaker placed about three inches out from
the rear wall. The 601s power-handling
ability proved excellent: It accepted without
distress the full 58-volt peak output of
DSL's amplifierequivalent to 26% dBW
(420 watts) into 8 ohms-in the 300-112
pulse test and the 28.3-volt (rms) maximum
levelA-equivalent to 20 dBW (100 watts)
into 8 ohms-of the 300-Hz continuous-
signal test. Consequently, we were not sur-
prised to find that the speaker produced
very low distortion. At a moderately high
sound pressure level of 85 dB, total har-
monic distortion (THD) remained less than
1%% over DSLs entire 30 Hz to 10 kHz
test range and averaged only about 1/2%.
Even at 95 dB SPL. THD never rose to
more than 3%% and averaged less than
1'/2%. It wasnt until DSL jacked the output
up to a thunderous 100 dB SPI. that signif-
icant distortion began to appear. These are
excellent results.
The 601 Series Ils sensitivity is fairly

high, as is its average impedance. Ranging
from a minimum of 7 ohms at 33 Hz to a
maximum of 31 ohms at 60 Hz, the imped-
ance dips below 8 ohms only twice, at 33
and 140 Hz; by the standard rating method,
the 601s nominal impedance would be
7.5 ohms. These figures indicate that the
601 Series II should be an easy load for any
decent amplifier, and we would have no
qualms about running two pairs in parallel
from the same amp.

Both the on- and off-axis frequency
response curves lie within a range of
approximately til/2 dB from 35 Hz to 16
kHz. Moreover, the two curves are quite
similar, even at very high frequencies,
where conventional speakers become in~
creasingly directional. Response is espe-
cially smooth through the bass and mid-
range, varying only 121/2 dB from 40 Hz to
1 kHz on axis and barely more than that off
axis. '

After some experimentation, we
placed the 6015 several feet from the side
walls and about a foot out from the rear wall
for our listening tests. The overall sound of
the 601 Series II is rich, warm, and spa-
cious-a hallmark of Bose loudspeakers.
Bass response, particularly, is full and very
extended. Reproduction of instruments
with considerable treble energy-especial-
ly plucked strings-is sometimes less clear
and detailed than we are accustomed to. On
the other hand, there is none of the shrill-
ness or harshness that is sometimes appar-
ent in loudspeakers with more prominent
treble response. .

Taken as a whole, the 601 Series II is a
fine loudspeaker and a worthy next~in-line
to the more elaborate and expensive 901.
Moreover, its physical, electrical, and
acoustical characteristics make it easily
adaptable to most home stereo systems and
listening environments-a highly desirable
feature. If the price is within your budget,
you owe it to yourself to take a listen.

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