The Design of a 2 way crossover for 8 Ohm loudspeakers    4 Ohm crossover

Frequenzweiche für 2-Weges-System oder Subwoofer If you want to calculate the crossover yourself:
2 way crossover calculator

For a 2 way system or to separate satellites from a subwoofer a 12 dB / octave filter according to the picture on the left should be used. For 8 Ohm systems the values of the following tables are applicable.

To choose a capacitor is straight forward: select the value from the table below and choose a capacitor according to the desired quality level. Standard means: a MKT in series to the tweeter and an unetched electrolytic capacitor in parallel to the woofer (in high powered PA application possibly a MKT). Please take into account the maximum voltage Vac:

Selecting the right coil is a bit more complicated. Important aspects are:

Taking these aspects into consideration, we suggest the coils listed in the table below, indicating coil type, order no and DC resistance.

The colour code indicates the coil's material:
- iron, high power handling
- ferrite, low distortion - even at low volume
- ferrite, T-Core with extremely low distortion
- air, type 1 or 2 with lowest distortion
- large air core coil, type 3 or 4, with lowest distortion

For 8 Ohm loudspeakers:         ... 4 Ohm calculation  

Frequency in Hz 120 180 270 400 550 800 1250 1800 2300 3100
Cap. C in uF 100 82 47 33 22 15 10 6.8 5.6 4.7
e.g. ClarityCap PWA EUR 30,32 excl. VAT: € 25.48 / $ 29.27 EUR 25,54 excl. VAT: € 21.46 / $ 24.66 EUR 16,18 excl. VAT: € 13.60 / $ 15.62 EUR 9,65 excl. VAT: € 8.11 / $ 9.32 EUR 7,41 excl. VAT: € 6.23 / $ 7.15 EUR 4,97 excl. VAT: € 4.18 / $ 4.80 EUR 4,00 excl. VAT: € 3.36 / $ 3.86 EUR 3,51 excl. VAT: € 2.95 / $ 3.39 EUR 3,13 excl. VAT: € 2.63 / $ 3.02 EUR 2,53 excl. VAT: € 2.13 / $ 2.44
Coil L in mH 15 10 6.8 4.7 3.3 2.2 1.5 1.0 0.82 0.56
Coils
up to 25 Watt
H71
15 mH
1,2 Ohm EUR 15,01 excl. VAT: € 12.61 / $ 14.49
H71
10 mH
0,87 Ohm EUR 11,21 excl. VAT: € 9.42 / $ 10.82
H71
6,8 mH
0,70 Ohm EUR 9,94 excl. VAT: € 8.35 / $ 9.60
H71
4,7 mH
0,46 Ohm EUR 8,99 excl. VAT: € 7.55 / $ 8.68
L100
3,3 mH
1,1Ohm EUR 18,72 excl. VAT: € 15.73 / $ 18.07
L100
2,2 mH
0,83 Ohm EUR 15,89 excl. VAT: € 13.35 / $ 15.34
L100
1,5 mH
0,62 Ohm EUR 13,06 excl. VAT: € 10.97 / $ 12.61
L100
1,00 mH
0,49 Ohm EUR 11,31 excl. VAT: € 9.50 / $ 10.92
L100
0,82 mH
0,44 Ohm EUR 10,33 excl. VAT: € 8.68 / $ 9.97
L100
0,56 mH
0,36 Ohm EUR 8,94 excl. VAT: € 7.51 / $ 8.63
Coils
up to 50 Watt
H100
15 mH
0,83 Ohm EUR 27,39 excl. VAT: € 23.02 / $ 26.45
H100
10 mH
0,64 Ohm EUR 23,59 excl. VAT: € 19.82 / $ 22.78
H100
6,8 mH
0,46 Ohm EUR 18,62 excl. VAT: € 15.65 / $ 17.98
H71
4,7 mH
0,46 Ohm EUR 8,99 excl. VAT: € 7.55 / $ 8.68
H100
3,3 mH
0,27 Ohm EUR 14,91 excl. VAT: € 12.53 / $ 14.40
L100
2,2 mH
0,83 Ohm EUR 15,89 excl. VAT: € 13.35 / $ 15.34
L100
1,5 mH
0,62 Ohm EUR 13,06 excl. VAT: € 10.97 / $ 12.61
L100
1,00 mH
0,49 Ohm EUR 11,31 excl. VAT: € 9.50 / $ 10.92
L100
0,82 mH
0,44 Ohm EUR 10,33 excl. VAT: € 8.68 / $ 9.97
L100
0,56 mH
0,36 Ohm EUR 8,94 excl. VAT: € 7.51 / $ 8.63
Coils
up to 100 Watt
BS125
15 mH
0,59 Ohm EUR 53,61 excl. VAT: € 45.05 / $ 51.76
BS125
10 mH
0,46 Ohm EUR 45,33 excl. VAT: € 38.09 / $ 43.77
BS125
6,8 mH
0,37 Ohm EUR 43,48 excl. VAT: € 36.54 / $ 41.98
BS125
4,7 mH
0,30 Ohm EUR 41,53 excl. VAT: € 34.90 / $ 40.10
H100
3,3 mH
0,27 Ohm EUR 14,91 excl. VAT: € 12.53 / $ 14.40
H100
2,2 mH
0,21 Ohm EUR 10,82 excl. VAT: € 9.09 / $ 10.45
H100
1,5 mH
0,17 Ohm EUR 9,39 excl. VAT: € 7.89 / $ 9.07
L140
1,00 mH
0,30 Ohm EUR 18,72 excl. VAT: € 15.73 / $ 18.07
L140
0,82 mH
0,26 Ohm EUR 17,74 excl. VAT: € 14.91 / $ 17.13
L140
0,56 mH
0,2 Ohm EUR 15,99 excl. VAT: € 13.44 / $ 15.44
Coils
up to 180 Watt
PA-Trafo
mo-123200
0,12 Ohm EUR 72,56 excl. VAT: € 60.97 / $ 70.06
PA-Trafo
mo-125490
0,19 Ohm EUR 26,12 excl. VAT: € 21.95 / $ 25.22
PA-Trafo
mo-125470
0,16 Ohm EUR 24,94 excl. VAT: € 20.96 / $ 24.08
H140
4,7 mH
0,26 Ohm EUR 28,37 excl. VAT: € 23.84 / $ 27.39
H140
3,3 mH
0,19 Ohm EUR 26,51 excl. VAT: € 22.28 / $ 25.60
H140
2,2 mH
0,14 Ohm EUR 20,67 excl. VAT: € 17.37 / $ 19.96
H140
1,5 mH
0,11 Ohm EUR 17,74 excl. VAT: € 14.91 / $ 17.13
L140
1,00 mH
0,30 Ohm EUR 18,72 excl. VAT: € 15.73 / $ 18.07
L140
0,82 mH
0,26 Ohm EUR 17,74 excl. VAT: € 14.91 / $ 17.13
L140
0,56 mH
0,2 Ohm EUR 15,99 excl. VAT: € 13.44 / $ 15.44
Coils
up to 330 Watt
PA-Trafo
mo-123200
0,12Ohm EUR 72,56 excl. VAT: € 60.97 / $ 70.06
PA-Trafo
mo-125490
0,19Ohm EUR 26,12 excl. VAT: € 21.95 / $ 25.22
PA-Trafo
mo-125470
0,16Ohm EUR 24,94 excl. VAT: € 20.96 / $ 24.08
PA-Trafo
mo-125450
0,14Ohm EUR 22,32 excl. VAT: € 18.76 / $ 21.55
BT140
3,3 mH
0,22 Ohm EUR 75,64 excl. VAT: € 63.56 / $ 73.03
BS140
2,2 mH
0,16 Ohm EUR 35,77 excl. VAT: € 30.06 / $ 34.54
BS140
3,3 mH
0,12 Ohm EUR 32,95 excl. VAT: € 27.69 / $ 31.81
H140
1,0 mH
0,08Ohm EUR 15,89 excl. VAT: € 13.35 / $ 15.34
L200
0,82 mH
0,16 Ohm EUR 37,72 excl. VAT: € 31.70 / $ 36.42
L200
0,56 mH
0,11 Ohm EUR 30,22 excl. VAT: € 25.39 / $ 29.18
Coils
up to 550 Watt
PA-Trafo
mo-123200
0,12Ohm EUR 72,56 excl. VAT: € 60.97 / $ 70.06
T250
10 mH
0,16 Ohm EUR 193,98 excl. VAT: € 163.01 / $ 187.29
T250
6,8 mH
0,12 Ohm EUR 184,24 excl. VAT: € 154.82 / $ 177.89
T250
4,7 mH
0,08 Ohm EUR 170,59 excl. VAT: € 143.35 / $ 164.71
T200
3,3 mH
0,10 Ohm EUR 103,33 excl. VAT: € 86.83 / $ 99.77
BT140
2,2 mH
0,12 Ohm EUR 69,89 excl. VAT: € 58.73 / $ 67.48
BT140
1,5 mH
0,09 Ohm EUR 58,44 excl. VAT: € 49.11 / $ 56.42
L200
1,0 mH
0,18 Ohm EUR 42,40 excl. VAT: € 35.63 / $ 40.94
L200
0,82 mH
0,16 Ohm EUR 37,72 excl. VAT: € 31.70 / $ 36.42
L200
0,56 mH
0,11 Ohm EUR 30,22 excl. VAT: € 25.39 / $ 29.18
Coils
up to 1000 Watt
T250
15 mH
0,17 Ohm EUR 235,90 excl. VAT: € 198.24 / $ 227.77
T250
10 mH
0,16 Ohm EUR 193,98 excl. VAT: € 163.01 / $ 187.29
T250
6,8 mH
0,12 Ohm EUR 184,24 excl. VAT: € 154.82 / $ 177.89
T250
4,7 mH
0,08 Ohm EUR 170,59 excl. VAT: € 143.35 / $ 164.71
T200
3,3 mH
0,10 Ohm EUR 103,33 excl. VAT: € 86.83 / $ 99.77
T200
2,2 mH
0,09 Ohm EUR 88,61 excl. VAT: € 74.46 / $ 85.55
T200
1,5 mH
0,09 Ohm EUR 75,94 excl. VAT: € 63.82 / $ 73.32
L250
1,0 mH
0,12 Ohm EUR 61,41 excl. VAT: € 51.61 / $ 59.29
L250
0,82 mH
0,10 Ohm EUR 58,39 excl. VAT: € 49.07 / $ 56.38
L250
0,56 mH
0,08 Ohm EUR 48,64 excl. VAT: € 40.87 / $ 46.96

Both, the two coils and the two capacitors, should have the values indicated in the table. A subwoofer filter requires only one capacitor and one coil.

The coil in parallel to the tweeter or satellite needs to handle only half / a quarter of the power, if the crossover frequency is higher than 400/800 Hz.

Hint:

1) 18 and 24 dB / octave crossovers only make sense when the driver's exact characteristics are known!

2) This is certainly not a high-end-crossover. Such a crossover needs to be designed according to the drivers used. A good example is the Cauchy-crossover.
 

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