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 27,50 excl. VAT: € 23.11 / $ 20.27 EUR 23,15 excl. VAT: € 19.45 / $ 17.06 EUR 12,59 excl. VAT: € 10.58 / $ 9.28 EUR 9,25 excl. VAT: € 7.77 / $ 6.82 EUR 7,16 excl. VAT: € 6.02 / $ 5.28 EUR 4,76 excl. VAT: € 4.00 / $ 3.51 EUR 3,92 excl. VAT: € 3.29 / $ 2.89 EUR 3,21 excl. VAT: € 2.70 / $ 2.37 EUR 3,21 excl. VAT: € 2.70 / $ 2.37 EUR 2,40 excl. VAT: € 2.02 / $ 1.77
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 16,90 excl. VAT: € 14.20 / $ 12.46
H71
10 mH
0,87 Ohm EUR 16,00 excl. VAT: € 13.45 / $ 11.79
H71
6,8 mH
0,70 Ohm EUR 15,00 excl. VAT: € 12.61 / $ 11.06
H71
4,7 mH
0,46 Ohm EUR 13,50 excl. VAT: € 11.34 / $ 9.95
L100
3,3 mH
1,1Ohm EUR 13,40 excl. VAT: € 11.26 / $ 9.88
L100
2,2 mH
0,83 Ohm EUR 10,50 excl. VAT: € 8.82 / $ 7.74
L100
1,5 mH
0,62 Ohm EUR 9,05 excl. VAT: € 7.61 / $ 6.67
L100
1,00 mH
0,49 Ohm EUR 8,05 excl. VAT: € 6.76 / $ 5.93
L100
0,82 mH
0,44 Ohm EUR 7,55 excl. VAT: € 6.34 / $ 5.57
L100
0,56 mH
0,36 Ohm EUR 6,75 excl. VAT: € 5.67 / $ 4.98
Coils
up to 50 Watt
H100
15 mH
0,83 Ohm EUR 29,05 excl. VAT: € 24.41 / $ 21.41
H100
10 mH
0,64 Ohm EUR 27,15 excl. VAT: € 22.82 / $ 20.01
H100
6,8 mH
0,46 Ohm EUR 16,20 excl. VAT: € 13.61 / $ 11.94
H71
4,7 mH
0,46 Ohm EUR 13,50 excl. VAT: € 11.34 / $ 9.95
H100
3,3 mH
0,27 Ohm EUR 14,30 excl. VAT: € 12.02 / $ 10.54
L100
2,2 mH
0,83 Ohm EUR 10,50 excl. VAT: € 8.82 / $ 7.74
L100
1,5 mH
0,62 Ohm EUR 9,05 excl. VAT: € 7.61 / $ 6.67
L100
1,00 mH
0,49 Ohm EUR 8,05 excl. VAT: € 6.76 / $ 5.93
L100
0,82 mH
0,44 Ohm EUR 7,55 excl. VAT: € 6.34 / $ 5.57
L100
0,56 mH
0,36 Ohm EUR 6,75 excl. VAT: € 5.67 / $ 4.98
Coils
up to 100 Watt
BS125
15 mH
0,59 Ohm EUR 42,55 excl. VAT: € 35.76 / $ 31.37
BS125
10 mH
0,46 Ohm EUR 40,65 excl. VAT: € 34.16 / $ 29.96
BS125
6,8 mH
0,37 Ohm EUR 38,75 excl. VAT: € 32.56 / $ 28.56
BS125
4,7 mH
0,30 Ohm EUR 36,75 excl. VAT: € 30.88 / $ 27.09
H100
3,3 mH
0,27 Ohm EUR 14,30 excl. VAT: € 12.02 / $ 10.54
H100
2,2 mH
0,21 Ohm EUR 14,00 excl. VAT: € 11.76 / $ 10.32
H100
1,5 mH
0,17 Ohm EUR 13,40 excl. VAT: € 11.26 / $ 9.88
L140
1,00 mH
0,30 Ohm EUR 14,40 excl. VAT: € 12.10 / $ 10.61
L140
0,82 mH
0,26 Ohm EUR 13,40 excl. VAT: € 11.26 / $ 9.88
L140
0,56 mH
0,2 Ohm EUR 11,50 excl. VAT: € 9.66 / $ 8.48
Coils
up to 180 Watt
PA-Trafo
mo-123200
0,12 Ohm EUR 91,00 excl. VAT: € 76.47 / $ 67.08
PA-Trafo
mo-125490
0,19 Ohm EUR 32,68 excl. VAT: € 27.46 / $ 24.09
PA-Trafo
mo-125470
0,16 Ohm EUR 30,71 excl. VAT: € 25.81 / $ 22.64
H140
4,7 mH
0,26 Ohm EUR 31,05 excl. VAT: € 26.09 / $ 22.89
H140
3,3 mH
0,19 Ohm EUR 29,15 excl. VAT: € 24.50 / $ 21.49
H140
2,2 mH
0,14 Ohm EUR 17,30 excl. VAT: € 14.54 / $ 12.75
H140
1,5 mH
0,11 Ohm EUR 15,30 excl. VAT: € 12.86 / $ 11.28
L140
1,00 mH
0,30 Ohm EUR 14,40 excl. VAT: € 12.10 / $ 10.61
L140
0,82 mH
0,26 Ohm EUR 13,40 excl. VAT: € 11.26 / $ 9.88
L140
0,56 mH
0,2 Ohm EUR 11,50 excl. VAT: € 9.66 / $ 8.48
Coils
up to 330 Watt
PA-Trafo
mo-123200
0,12Ohm EUR 91,00 excl. VAT: € 76.47 / $ 67.08
PA-Trafo
mo-125490
0,19Ohm EUR 32,68 excl. VAT: € 27.46 / $ 24.09
PA-Trafo
mo-125470
0,16Ohm EUR 30,71 excl. VAT: € 25.81 / $ 22.64
PA-Trafo
mo-125450
0,14Ohm EUR 27,00 excl. VAT: € 22.69 / $ 19.90
BT140
3,3 mH
0,22 Ohm EUR 67,90 excl. VAT: € 57.06 / $ 50.05
BS140
2,2 mH
0,16 Ohm EUR 32,85 excl. VAT: € 27.61 / $ 24.21
BS140
3,3 mH
0,12 Ohm EUR 30,55 excl. VAT: € 25.67 / $ 22.52
H140
1,0 mH
0,08Ohm EUR 14,40 excl. VAT: € 12.10 / $ 10.61
L200
0,82 mH
0,16 Ohm EUR 33,85 excl. VAT: € 28.45 / $ 24.95
L200
0,56 mH
0,11 Ohm EUR 28,05 excl. VAT: € 23.57 / $ 20.68
Coils
up to 550 Watt
PA-Trafo
mo-123200
0,12Ohm EUR 91,00 excl. VAT: € 76.47 / $ 67.08
T250
10 mH
0,16 Ohm EUR 199,00 excl. VAT: € 167.23 / $ 146.69
T250
6,8 mH
0,12 Ohm EUR 189,00 excl. VAT: € 158.82 / $ 139.32
T250
4,7 mH
0,08 Ohm EUR 175,00 excl. VAT: € 147.06 / $ 129.00
T200
3,3 mH
0,10 Ohm EUR 106,00 excl. VAT: € 89.08 / $ 78.14
BT140
2,2 mH
0,12 Ohm EUR 64,90 excl. VAT: € 54.54 / $ 47.84
BT140
1,5 mH
0,09 Ohm EUR 49,90 excl. VAT: € 41.93 / $ 36.78
L200
1,0 mH
0,18 Ohm EUR 36,75 excl. VAT: € 30.88 / $ 27.09
L200
0,82 mH
0,16 Ohm EUR 33,85 excl. VAT: € 28.45 / $ 24.95
L200
0,56 mH
0,11 Ohm EUR 28,05 excl. VAT: € 23.57 / $ 20.68
Coils
up to 1000 Watt
T250
15 mH
0,17 Ohm EUR 242,00 excl. VAT: € 203.36 / $ 178.39
T250
10 mH
0,16 Ohm EUR 199,00 excl. VAT: € 167.23 / $ 146.69
T250
6,8 mH
0,12 Ohm EUR 189,00 excl. VAT: € 158.82 / $ 139.32
T250
4,7 mH
0,08 Ohm EUR 175,00 excl. VAT: € 147.06 / $ 129.00
T200
3,3 mH
0,10 Ohm EUR 106,00 excl. VAT: € 89.08 / $ 78.14
T200
2,2 mH
0,09 Ohm EUR 90,90 excl. VAT: € 76.39 / $ 67.01
T200
1,5 mH
0,09 Ohm EUR 77,90 excl. VAT: € 65.46 / $ 57.42
L250
1,0 mH
0,12 Ohm EUR 67,90 excl. VAT: € 57.06 / $ 50.05
L250
0,82 mH
0,10 Ohm EUR 62,90 excl. VAT: € 52.86 / $ 46.37
L250
0,56 mH
0,08 Ohm EUR 53,45 excl. VAT: € 44.92 / $ 39.40

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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