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Key to Crossover Diagrams

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Crossover schematics and wire colors provided are taken from whatever original documents are available to me, or from actual speakers.

Parts marked "unk." are usually on crossovers I analysed in customer speakers, where the values were not visible, and due to the circuit topology, were not measureable in situ.

It is important to remember that the map is not the territory. A schematic diagram simply shows how something works, not how it is put together. For example, devices that are in series can be physically assembled in any order and it does not matter at all. Capacitors are very often made up of smaller values in parallel, and, rarely, in series.

Note! What is actually in your speakers may vary from the schematics published here.

Symbol and Description

These are the actual parts that produce the sound. Note that passive radiators do not appear in the schematic since they are not wired.

Value given in microfarads. Rated for at least 50, but usually 100 volts. Aluminum electrolytics are common in older speakers. Capacitance values simply add up when they are used in parallel, and are equal to [(C1*C2)/(C1+C2)] when wired in series.

Air Core
Value given in millihenries, followed by the specified wire gauge, if available. Although this is not always done, choke coils should be mounted with their axes at ninety degrees to any others that are within six inches or so of them.

Iron Core
Value given in millihenries, followed by the specified wire gauge, if available. "Cored" choke coils, which are wound around a ferrite slug or laminated steel, can achieve a much higher inductance for a given number of wire turns, which lowers costs and series resistance. Unfortunately, they also exhibit saturation at a lower power level. The laminate core design (similar to what is seen in transformers) is preferred.

ResistorValue in ohms/power rating in watts. The non inductive type should be used. Mounting position should take heat dissipation into account.

A number of different protection devices turn up in speakers - circuit breakers, fuses, light bulbs (which have a negative temperature coefficient and can be used to limit current), and solid-state NTC devices.

Three and two position switches

It was the height of fashion in the 70's to provide switches (and potentiometers, below) to allow "frequency contouring" to the owner's taste, or to compensate for room acoustics. In my opinion, these should be set to "normal," or bypassed (see below). This is the flat setting, the way the speakers were designed to sound.

PotPotentiometers (usually wire wound, high power types) are prone to corrosion and dirt, resulting in poor signal transfer and "crackling" sounds when adjusted. They are sometimes seen wired as simple variable resistors, with one end not connected.

When bypassing potentiometers or switched resistive networks with fixed, soldered parts, if the "normal" position is indicated to be somewhere in the middle, or keeps some of the resistors in the circuit, a network of equivalent power resistors should be soldered into the crossover in their place.

Wire and
color codes
In cases where the wire color code is known to me I have colored the appropriate part of the circuit diagram to represent this information. Most original wiring in affordable speakers is a bit thin. Replacement with at least 16 AWG is highly recommmended.

JunctionsI have not used visible dots to indicate the places where 3 conductors meet and are connected to each other, as is standard in schematics. This is because crossover networks have a circuit topology that makes it easy to draw them with no "crossing" of current tracks. Thus, everywhere that the lines of a diagram meet, there is actually a connection.

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