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ALL-FET Crossover |
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The EB-1102/215, EB-1102/216 and the EB-802/214 family of ALL-FET crossovers are designed for 2-way, 3-way and 4-way speaker systems, including subwoofers. |
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 |  | | The EB-1102/215 Basic Crossover Board |
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EB-1102/215: Basic Crossover Board
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The EB-1102/215 board, shown in fig. 1 provides a balanced input buffer, two filter buffers and an independent output buffer. The input buffer is configured to operate as a unity gain buffer, with both plus and minus inputs available. It can be used for normal, unbalanced input, both in non-inverting (-INP is grounded to SGND, the input signal is connected to +INP), and in inverting mode (+INP is connected to SGND and the input signal connected to the –INP). It can also be used for balanced signals, with the plus side of the balanced input signal connected to the +INP and the negative side connected to -INP. Finally, it can also be used to sum two channels into one for a common subwoofer, both in unbalanced and in balanced mode.
There are also two filter buffers marked BUFFER1 and BUFFER2 on the board, each with its field for the filter components. Both filters can be configured as Low-pass (LP) and High-pass (HP) filters with 6, 12 and 18 dB slope. 24-dB/octave slope can be achieved by connecting the two filters in cascade.
The independent output buffer can be used as a straight unity gain or +6dB gain output buffer with a volume control in front of it, or it can serve as an inverter to create a balanced output.
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 | | | Fig 1. Block Schematic for the Basic ALL-FET Crossover Board EB-1102/215 |
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EB-1102/216 Extension Board
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The block schematic of the ALL-FET Extension board EB-1102/216 is shown in fig. 2. It contains two filter buffers, the same buffers as the ones on the EB-1102/215 board. Both filters can be configured as LP or HP filters, with 6, 12, and 18 dB slope. The filters can be cascaded for 24 dB slope. |
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 | | | Fig 2. Block Schematic of the ALL-FET Extension Board EB-1102/216 |
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The extension board can be used together with the EB-1102/215 basic board to make 3-way and 4-way crossovers. It can also serve as an experimental board to work out the best combination of filters for your speaker. |
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 | | | Fig 3. Block Schematic for the ALL-FET Bass-Extender Board EB-802/214 |
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The EB-802/214 is a Bass-Extender board. It contains a Bass Extender circuit, an LP filter which can be used as a crossover filter and a subsonic filter. The Bass-Extender board allows you to extend the low-frequency response of your speaker, by providing a 12dB/octave boost. Linkwitz described the calculation of the components in his original article (1). An Excel program, provided by True Audio, see www.trueaudio.com, can also calculate the components.
The crossover filter provides a 12dB or 18dB/octave LP for the subwoofer. Because the Bass Extender boosts the low frequencies significantly it is strongly recommended to use the subsonic filter to cut off the frequencies below 18 or 20 Hz. This is especially important when used with records, which generate rumble.
Normally the Bass-Extender board is used together with the basic EB-1102/215 crossover board; the input buffer on that board providing the input signal. However, it can also be used stand-alone, as long as the source impedance of the driver circuit (usually your preamp) is low (<100 Ohm). Alternatively a SUPER BUFFER can be used as an input buffer. |
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 | | | The EB-802/214 Bass Extender board, with Bass Extender circuit at right, LP filter in the middle and subsonic filter at left. |
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1.Siegfried Linkwitz: A Three-Enclosure Loudspeaker System: Part 3. Speaker Builder, 4/80 p.16 |
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