MartinLogan 20, 40 Vertical Passive Bi-Amplification, Active Bi-Amplification, Placement, Toe-In

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.

Horizontal Passive Bi-Amplification 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).

Vertical Passive Bi-Amplification

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).

ACTIVE BI-AMPLIFICATION

We do not recommend active bi-amplification. The internal crossover can not be bypassed. This con- nection method seriously degrades performance.

Assembly and Placement

BREAK IN

Allow approximately 72 hours of break-in at 90 dB (moderate listening levels) before any critical listening.

PLACEMENT

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).

TOE-IN

To achieve superior stereo imaging we recom-

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