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| EB-802/214: BASS EXTENDER BOARD. |
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 |  | | Fig. 1. 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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