Dentman
Well-Known Member
As a child I would stare at these speakers while audio shopping with my dad. I can remember just what a nig seal these things were when the came out in the late 70's. I always told my father that "one day I will own these speakers". I intend to hold that promise, I always check ebay for a steal on a pair. For one reason or another the timing is never right for me to buy, one day it will be.
I'm not saying these are the greatest, they are not, but it's an itch I must scratch before I'm planted. I bring this up because I stumbled across a review from the pages of Stereo Review. I want to post some clips from the review not so you could read about the speakers but to enjoy an informitive review that also teaches few things along the way. Agree or dissagree with the Authors findings you have to give credit for a great review. I wish you could find writing like this today.
Here's a few remarks from the writers review(1978):
"The low-frequency portion of the AR9 consists
of a pair of 12-inch acoustic-suspension
woofers mounted on opposite sides of the columnar
cabinet as close as possible to the floor
and rear wall surfaces. The speaker is meant
to be placed as close as possible to the rear
wall in order to prevent the cancellation of
mid-bass response that occurs when a conventional
front-facing woofer is used in a
floor-mounted speaker system. (This is
caused by out-of-phase reflected waves from
the floor or wall boundaries.) At 200 Hz there
is a crossover to a front-mounted 8-inch cone
driver placed 28 inches above the floor on the
center line of the panel. This is installed within
its own sub-enclosure inside the main cabinet,
and the reflections of its output from the
wall and floor occur below its normal operating
range.
Above the lower mid-range driver and on
the same vertical line are two dome-type radiators
at approximately ear height for a seated
listener. The upper-mid-range unit, which
takes over from the 8-inch driver at 1,200 Hz,
is a fully sealed 1½-inch-diameter dome driver.
Its diaphragm is surrounded by a metal
ring that AR calls a "semi-horn": they claim it
provides better coupling to the air in the upper
part of the driver's operating range (above
3,000 Hz). At 7,000 Hz there is another crossover,
to the -Y4-inch-diameter sealed dometype
tweeter. Both of the high-frequency
dome speakers employ high-temperature
magnetic fluid for heat conduction and mechanical
damping of their voice coils.
Below the 8-inch lower-mid-range driver
arje three small toggle switches that adjust, respectively.
the output levels from the tweeter.
upper-mid-range, and lower-mid-range speakers.
Each has three positions and is able to reduce
the output of its driver by either 3 or 6
dB from the maximum (0-dB) level, which is
the nominally "flat" condition."
"The frequency response of the AR9 was remarkably
smooth—within ±2 dB from 25 to
12.000 Hz—even measured by our unconventional
test method. It rose slightly at the high
end, to about +4 dB at 15.000 Hz (which is
the upper limit of our microphone calibration).
We are quite sure that this rise was
caused by an imperfect correction on our part
to the microphone and room response, and we
have no doubt that the true response of the
speaker would fall within the ±2-dB range
shown on the AR reverberant-room measurements
from 500 to 19,000 Hz (and, for that
matter, down into the lowest audible octave).
The low-frequency distortion, as might
have been expected from a pair of 12-inch
acoustic-suspension woofers in a correspondingly
large enclosure, was very low. At a constant
2.8-volt drive level (2 watts into the
nominal 4-ohm impedance), the distortion
was well under 0.5 per cent from 100 to 40 Hz,
reaching I .3 per cent at 25 Hz and 2.5 per cent
at 20 Hz. With a 10-dB power increase (to the
equivalent of 20 watts) the distortion was typically
about 0.5 per cent down to 50 Hz.
reaching 3 per cent at 30 Hz and 6.7 per cent
at 20 Hz.
The AR9 delivered its rated 87-dB SPL at a
1-meter distance when driven by I watt of
random noise in the octave centered at 1,000
Hz. The frequency-balance switches had
approximately the rated effects. The tweeter
switch controlled the output above 4.000 Hz,
the upper-mid-range switch operated between
1.000 and 10.000 Hz with most of its effect between
1.500 and 5,000 Hz, and the lower-midrange
switch affected the output between 100
and 1,200 Hz. The tone-burst response was
very good, especially considering that the
AR9 is a four-way system and therefore has
more than one driver operating over a considerable
part of the frequency range. which usually
causes acoustic-interference effects that
can complicate a tone-burst response.
The impedance curve of the speaker shows
evidence of the tailoring" action of the
crossover network. The maximum impedance
values of 8 and 10 ohms were reached at 27
and 750 Hz. respectively. Elsewhere the
measured impedance was between 3 and 5
ohms. the former value being the d.c. resistance
of the speaker system as seen at the
terminals. Incidentally, this points up the general
futility of using amplifiers with extra-high
damping factors to improve the sound of a
speaker system. With an amplifier damping
factor of infinity (and speaker cables having
zero resistance), the effective damping factor
of the AR9 speaker system would be approximately
one! The usual precautions against
paralleling two of these speakers apply (for
the protection of the amplifier), but, frankly.
we cannot imagine anyone's paralleling two
sets of AR9's! On the other side of that coin,
the low impedance of the AR9 will allow it to
draw the maximum possible power from any
amplifier."
"In view of the response we measured at our
normal listening position, it occurred to us
that we were probably hearing for the first
time what a truly flat frequency response
sounds like in our reasonably normal listening
room. If that is so (and it is admittedly conjectural).
we can report that "flat response"
doesn't provide any special effects (just as a
"flat" amplifier or phono cartridge has no
sound of its own). This may seem anticlimactic.
but it is really quite logical. This speaker
gives the listener an opportunity to hear just
what it particular record, radior broadcast, or
other program source sounds like with a minimum
of modification from the speaker or the
listening room. Judging from our limited experience
with the AR9, these program sources
vary in quality from excellent to terrible—but
we knew that before we started!"
Equipment Test Reports
By Hirsch-Houck Laboratories
I'm not saying these are the greatest, they are not, but it's an itch I must scratch before I'm planted. I bring this up because I stumbled across a review from the pages of Stereo Review. I want to post some clips from the review not so you could read about the speakers but to enjoy an informitive review that also teaches few things along the way. Agree or dissagree with the Authors findings you have to give credit for a great review. I wish you could find writing like this today.
Here's a few remarks from the writers review(1978):
"The low-frequency portion of the AR9 consists
of a pair of 12-inch acoustic-suspension
woofers mounted on opposite sides of the columnar
cabinet as close as possible to the floor
and rear wall surfaces. The speaker is meant
to be placed as close as possible to the rear
wall in order to prevent the cancellation of
mid-bass response that occurs when a conventional
front-facing woofer is used in a
floor-mounted speaker system. (This is
caused by out-of-phase reflected waves from
the floor or wall boundaries.) At 200 Hz there
is a crossover to a front-mounted 8-inch cone
driver placed 28 inches above the floor on the
center line of the panel. This is installed within
its own sub-enclosure inside the main cabinet,
and the reflections of its output from the
wall and floor occur below its normal operating
range.
Above the lower mid-range driver and on
the same vertical line are two dome-type radiators
at approximately ear height for a seated
listener. The upper-mid-range unit, which
takes over from the 8-inch driver at 1,200 Hz,
is a fully sealed 1½-inch-diameter dome driver.
Its diaphragm is surrounded by a metal
ring that AR calls a "semi-horn": they claim it
provides better coupling to the air in the upper
part of the driver's operating range (above
3,000 Hz). At 7,000 Hz there is another crossover,
to the -Y4-inch-diameter sealed dometype
tweeter. Both of the high-frequency
dome speakers employ high-temperature
magnetic fluid for heat conduction and mechanical
damping of their voice coils.
Below the 8-inch lower-mid-range driver
arje three small toggle switches that adjust, respectively.
the output levels from the tweeter.
upper-mid-range, and lower-mid-range speakers.
Each has three positions and is able to reduce
the output of its driver by either 3 or 6
dB from the maximum (0-dB) level, which is
the nominally "flat" condition."
"The frequency response of the AR9 was remarkably
smooth—within ±2 dB from 25 to
12.000 Hz—even measured by our unconventional
test method. It rose slightly at the high
end, to about +4 dB at 15.000 Hz (which is
the upper limit of our microphone calibration).
We are quite sure that this rise was
caused by an imperfect correction on our part
to the microphone and room response, and we
have no doubt that the true response of the
speaker would fall within the ±2-dB range
shown on the AR reverberant-room measurements
from 500 to 19,000 Hz (and, for that
matter, down into the lowest audible octave).
The low-frequency distortion, as might
have been expected from a pair of 12-inch
acoustic-suspension woofers in a correspondingly
large enclosure, was very low. At a constant
2.8-volt drive level (2 watts into the
nominal 4-ohm impedance), the distortion
was well under 0.5 per cent from 100 to 40 Hz,
reaching I .3 per cent at 25 Hz and 2.5 per cent
at 20 Hz. With a 10-dB power increase (to the
equivalent of 20 watts) the distortion was typically
about 0.5 per cent down to 50 Hz.
reaching 3 per cent at 30 Hz and 6.7 per cent
at 20 Hz.
The AR9 delivered its rated 87-dB SPL at a
1-meter distance when driven by I watt of
random noise in the octave centered at 1,000
Hz. The frequency-balance switches had
approximately the rated effects. The tweeter
switch controlled the output above 4.000 Hz,
the upper-mid-range switch operated between
1.000 and 10.000 Hz with most of its effect between
1.500 and 5,000 Hz, and the lower-midrange
switch affected the output between 100
and 1,200 Hz. The tone-burst response was
very good, especially considering that the
AR9 is a four-way system and therefore has
more than one driver operating over a considerable
part of the frequency range. which usually
causes acoustic-interference effects that
can complicate a tone-burst response.
The impedance curve of the speaker shows
evidence of the tailoring" action of the
crossover network. The maximum impedance
values of 8 and 10 ohms were reached at 27
and 750 Hz. respectively. Elsewhere the
measured impedance was between 3 and 5
ohms. the former value being the d.c. resistance
of the speaker system as seen at the
terminals. Incidentally, this points up the general
futility of using amplifiers with extra-high
damping factors to improve the sound of a
speaker system. With an amplifier damping
factor of infinity (and speaker cables having
zero resistance), the effective damping factor
of the AR9 speaker system would be approximately
one! The usual precautions against
paralleling two of these speakers apply (for
the protection of the amplifier), but, frankly.
we cannot imagine anyone's paralleling two
sets of AR9's! On the other side of that coin,
the low impedance of the AR9 will allow it to
draw the maximum possible power from any
amplifier."
"In view of the response we measured at our
normal listening position, it occurred to us
that we were probably hearing for the first
time what a truly flat frequency response
sounds like in our reasonably normal listening
room. If that is so (and it is admittedly conjectural).
we can report that "flat response"
doesn't provide any special effects (just as a
"flat" amplifier or phono cartridge has no
sound of its own). This may seem anticlimactic.
but it is really quite logical. This speaker
gives the listener an opportunity to hear just
what it particular record, radior broadcast, or
other program source sounds like with a minimum
of modification from the speaker or the
listening room. Judging from our limited experience
with the AR9, these program sources
vary in quality from excellent to terrible—but
we knew that before we started!"
Equipment Test Reports
By Hirsch-Houck Laboratories
