3-way Vented Floorstanding Speaker - Crossover

The crossover was designed by Madisound for a $35 USD fee. They use LEAP and measured driver data to predict frequency, impedance and phase response. A schematic for the crossover is also provided. In my particular case, the AC-10 woofer could not be measured by Madisound since this is not their stocked item. Instead, the published T-S parameters were used.

I mounted all crossover parts onto a piece of 9x12 inch peg board. Inductors were carefully placed to avoid mutual inductance. Components were purchased from Madisound and consists of air and iron core inductors of varying gauges (Madisound), polypropylene (Solen), mylar and electrolytic capacitors, sand cast and non-inductive (Lynk) resistors. Inexpensive parts are used only in non-critical areas and could be replaced with premium parts at additional expense and board space. Refer to the schematic for circuit details. All parts are tied to the board with plastic ties when possible. Caulking is used on all parts for adhesion.

The tweeter circuit consists of a 3 ohm non-inductive 10 watt Lynk resistor in series with a 8 mfd Solen polypropylene capacitor. Parallel to the tweeter is a 23 ohm 15 watt 5% power resistor and a 0.15 mH small gauge air core inductor. For the midrange, the 70 mfd capacitor is really a 60 mfd and a 10 mfd Solen polypropylene cap in parallel. Both the 1.3 mH and the 6 mH are medium gauge inductor; the former is air core while the latter is iron core. The 4 ohm resistor is two 8 ohm Lynk non-inductive resistors in parallel for more power handling. The 6.8 mfd cap is mylar. The woofer has a series 6 mH heavy gauge air core inductor. The 12 mH inductor is iron core. The 800 mfd capacitor is a 200 mfd and 600 mfd non-polarized electrolytic in parallel. Another 200 mfd NP parallels the woofer. Lastly, the 8.3 ohm resistor is three 25 ohm 25 watt 5% power resistors in parallel. The remaining parts are not critical and consist of a 0.35 mH small gauge air core inductor, a 30 mfd NP capacitor and a 7 ohm 15 watt 5% power resistor.

The midrange was tested in both normal and reverse polarity. Under reverse polarity, a 10 dB dip appeared at the woofer/midrange crossover region. Thus all three drivers are wired in normal polarity.

29-September-2000

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