MartinLogan 20 Speaker User Manual


 
6
amplification directly connected to the high- and
low-frequency sections of the crossover. There are
two different methods for bi-amping with two stereo
amplifiers. The first and most common is referred
to as Horizontal Bi-amping. The second method is
referred to as Vertical Bi-amping. With either meth-
od you may use two stereo amplifiers or four mono
amplifiers, or two mono amplifiers and one stereo
amplifier. Get the idea? With either form of passive
bi-amplification, your preamplifier must have dual
outputs. If your preamplifier is not so equipped, you
must either purchase or construct a “Y” adapter.
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Horizontal bi-amping allows you to use two differ-
ent types, models or brands of amplifiers (i.e. tubes
on top, transistor on the bottom). However, we rec-
ommend that you use two identical amplifiers (i.e.
same brand and model). If you must use two differ-
ent amplifiers, it is essential that they have the same
gain or that one of the two have adjustable gain
so that you can match their gain characteristics. If
the amplifiers of choice do not have the same gain
characteristics, then a sonic imbalance will occur.
With horizontal bi-amping, one amplifier drives the
high-frequency section of the speaker while the sec-
ond amplifier drives the low-frequency section. To
horizontally bi-amp your speakers you must loosen
the binding posts and remove the jumper clips.
Connect the low-frequency amplifier to the lower
set of binding posts of both speakers. Connect the
high-frequency amplifier to the upper set of binding
posts. Next, connect the left and right preamplifier
outputs to the appropriate left and right inputs of
both amplifiers (Fig. 3).
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The very nature of vertical bi-amping dictates that
both amplifiers be identical. With vertical bi-amp-
ing, each of the stereo amplifiers is dedicated to
one speaker. For instance, the left channel of each
amplifier drives the low-frequency section while the
right channel drives the high-frequency section. To
vertically bi-amp your speakers you must loosen the
binding posts and remove the jumper clips from
both speakers. Starting with one speaker, connect
the right channel to the lower binding posts and
the left channel to the upper binding posts. Repeat
the same procedure for the other speaker. Connect
the left preamplifier outputs to both inputs of the left
channel amplifier and the right preamplifier outputs
to both inputs of the right channel amplifier (Fig. 4).
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We do not recommend active bi-amplification. The
internal crossover can not be bypassed. This con-
nection method seriously degrades performance.
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Allow approximately 72 hours of break-in at 90
dB (moderate listening levels) before any critical
listening.
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Although your speakers are designed to deliver a
superb sonic performance when placed close to a
wall, you may notice improved imaging and detail
if you are able to place the speakers (measured
from the tweeter and woofers) 2–3 feet from the
front wall and 2 or more feet from the side walls
(Fig. 5).
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To achieve superior stereo imaging we recom-
Assembly And PlACement