Alesis M1 ACTIVE - Port Plugging for Room Acoustics

Sporker
lnrtellffon
Plugging the
ports
to adjust for room acoustics
The low frequency
response of
the Ml Actives can be
custom tailored by plugging
the ports.
If the speakers
must be placed less than
one foot from a front wall,
or if
they are too
close to a comer, then
the bass may
become exaggerated and inaccurate
The rules of
thumb for these
situations are as follows:
The
"plug"
can
be wad
of cloth to
completely block
the port(s)
or
a more
porous
material like
fiberfill
whidr will give
less bass
attenuation.
The bass output
of the
Ml Active
is thus
easily variable
depending
on in-room positioning
and/or
personal
Prererence.
If
the M1 Actives
are to
be used in
a system with
a subwoofer,
the proper
blmd of
the two
systems is
critical if low-bass
accuracy
is to
be
maintained.
Here
again, your
ear is your
most
important
piece of
test equipment.
If the
subwoofer
(such
as the
Alesis Point
one) or preamplifier
has
80Hz high-pass
filters
built-in for connection
to
the other
amplifiers,
then no port
plugging
is necessary.
The proper
match
will have
already
been taken
care of electronically.
In
the absence
of an 80Hz high-pass
filter
feeding the M1
Actives, you'll
need
to experiment
with various
degrees
of port
plugging
to minimize
the cancellations
and nodes
that can occur from
bass sources
placed
several feet apart
in a room.
In practice
we've
found that a
single
port
plugged
with cloth is
usually
the best
compromise.
See Figure
5 below. It shows
the
approximate
bass attenuation
that can
be expected
with one port plugged.
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