This is a simple treble-midle-bass (3-way) crossover Circuit, intended for triamping Hi-Fi systems. This is a conventional 12dB / Octave unit, and cannot be expected to have the same performance as a Linkwitz-Riley aligned filter network. It will still be a vast improvement over nearly any passive crossover, and is ideal for beginners or those who want to experiment further with multi-amping, but without the complexity of a major project. The retuning (to (sub)-Bessel / Linkwitz-Riley alignment) is recommended, as the performance will be more in line with modern standards - see information below.
Low-mid range: Low pass filter, fh = 300 Hz.
fh = 1 / (2 * π * R1 * C1), assuming R1 = R2 & C1 = C2 = 10nF. This yields R1 = R2 = 53K (used 56K).
Mid range: Low pass filter, fh = 3000 Hz, followed by a high pass filter fl = 300 Hz.
Assuming R1 = R2, R3 = R4, C1 = C2 = C3 = C4 = 10nF.
For the low pass, fh = 1 / (2 * PI * R1 * C1), yields R1 = R2 = 5.3K (used 5.6K).
For the high pass, fl = 1 / (2 * PI * R3 * C3), yields R3 = R4 = 53K (used 56K).
Mid-high range: High pass filter, fl = 3000 Hz.
fl = 1 / (2 * PI * R3 * C3), assuming R3 = R4 & C3 = C4 = 10nF. This yields, R3 = R4 = 5.3K (used 5.6K).
In the above schematic are shown the low-mid range, mid range mid-high range filters. The x'over frequencies chosen are 300Hz and 3000Hz. Thus the low-mid range filter has a cut-off frequency of 300 Hz, the mid range has a lower cut-off at300 Hz and an upper cut-off at 3000Hz, and the mid-high range has a cut-off frequency of 3000 Hz. Please see references (2) for the x'over frequencies.