About thc
Mt ActiYe
The
cabinet and
port
design
The
M1 Active cabinet construction
employs vinyl
composite
material laminated
to a
.625" MDF
(medium
density
fiberboard) core for the
four
sides
and the rear.
The
front
panel is 1" thick MDR to withstand
the gteater demands
of the
drivers
mounted on
it.
The entire
cabinet is braced extensively in
random
fashion to
dissipate
intramodal vibration.
Why the tureeters ane o'ftset
The Ml
Active
speakers
have
been developed
as a rnirror-imaged
pair with dual
front
mounted ports and an offset tweeter. In some applications,
an extremely wide
dispersion tweeter, such as used in the M1 Active, will exhibit
response dips
if
mounted exactly on center. Wave-guide style tweeters, used
in other products,
purposely limit dispersion and thus can be center
mounted. But as hi-end audiophile
speaker companies have found, a high quality dome tweeter,
offset in the cabinet
towardthe stereo
"imagecenter"
(betwemtheleftandightspeakers)
willhaveaflatter
characteristic frequency and power response. This
(flat
power
response) more closely
characterizes
the
way humans hear.
On a horizontal
polar
response curve of the ML Active, with
the cabinet placed
vertically, the tweeter response at one meter stays essentially symmetrical on
either
side of the cabinet's centerline. This is because the angle subtended
between the
cabinet-centerline-to-tweeter-centerline
(.5"),
and the nominal
nearfield listening
distance
(1
meter or 39.375"), is only 1.27 degrees. Thus, acoustically speaking, the
offset tweeter design has no negative effects, only the positive of smoothing
the
frequency response in the 2KHz-4I(Flz range.
In the tradition of the Alesis Superport design, which uses the energy
from
the
back
of the speaker to enhance bass performance, the Ml Actives use dual, front baffle
mounted, long folded ports. The dual ports on the M1 Active
are also non-
symmetrical
with relation to their distances from the woofer. In developing
the M1
Active,
Alesis engineers
deterrrined that dual
ports,
offset
to the outside of the stereo
image center
gave
the
rrost
coherent and extended low bass
augmentation. The
ports are
flared
on the front baffle to provide smooth and quiet exit airflow while
inside they are cut with a 45o angle
and
faced
toward the amplifier's
intemal heat
sink.
This arangement aids in keeping
the
intemal amps
working
at a nore constant
temperature. At the same time, this 45o angle increases the port's air enky efficiency.
II]| ACTTUI
REERENCI
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