Specifications
9
PASSIVE 6 dB LOW-PASS PASSIVE 6 dB HIGH-PASS
A 6 dB x-over filter has a 6 dB slope / octave. The
output from an amplifier is only a quarter after falling
with 6 dB. A 6dB filter is also called 1:st order filter.
A common use for a 6 dB low-pass filter is for a
subwoofer to stop frequencies over, as for example,
100 Hz.
A 6 dB low-pass filter consists of a coil. The x-over
frequency is decided by the inductance value
measured in the unit Henry (H) and parts of a Henry.
For speakers we normally use coils with the unit mH.
1 H = 1000 mH.
+
-
CALCULATION FORMULA:
L (mH) = 160 x Z
Fc
Z = speaker impedance in Ω
Fc = x-over frequency in Hz
L= Coil inductance in mH
Speaker impedance
X-over fq. 2Ω 4Ω 8Ω
Hz L (mH) L (mH) L (mH)
65 5 10 20
80 4 8 16
100 3,2 6,4 12,8
130 2,5 5 10
200 1,6 3,2 6,4
360 0,9 1,75 3,5
500 0,65 1,3 2,6
800 0,4 0,8 1,6
1000 0,32 0,64 1,28
X-over frequencies at given values:
10 mH 6,3 mH 1,75 mH
2Ω 32 Hz 50 Hz 183 Hz
4Ω 64 Hz 101 Hz 365 Hz
8Ω 128 Hz 203 Hz 730 Hz
Inductance values for different x-over frequencies:
A 6 dB high-pass x-over filter consists of a capacitor.
The crossover frequency varies with the capacitor
value that is measured in the unit Farad and parts of
Farad. Normally we use µF values for speakers.,
1 F = 1000 000 µF
Capacitor values from approx. 10 µF and up are
normally of bipolar electrolytic type. For lower values
we often use polyester capacitors. A capacitor as in
the drawing below let the high frequencies pass and
stops the lower.
+
-
C (µF) = 160000
Fc x Z
1:st order 6 dB low-pass filter:
1:st order 6 dB high-pass filter:
C
L
CALCULATION FORMULA:
Z = speaker impedance in Ω
Fc = x-over frequency in Hz
C = Capacitor value in µF
Capacitor values for different x-over frequencies:
Speaker impedance
X-over fq. 2Ω 4Ω 8Ω
Hz C (µF) C (µF) C (µF)
80 1000 500 250
100 800 400 200
130 600 300 150
200 400 200 100
500 160 80 40
800 100 50 25
1000 80 40 20
2000 40 20 10
5000 16 8 4
X-over frequencies at given values:
300 µF 200 µF 150 µF 50 µF 6,8 µF
2Ω 266 Hz 400 Hz 533 Hz 1,6 kHz 11,7 kHz
4Ω 133 Hz 200 Hz 266 Hz 800 Hz 5,85 kHz
8Ω 67 Hz 100 Hz 133 Hz 400 Hz 2,92 kHz
Treble
Bass
=
When connecting coils in series the values are
added.
Use this formula when connecting in parallel:
1 1 + 1 + 1
L L L L
=
When connecting capacitors in parallel the values
are added. Use this formula when connecting in
series.
1 1 + 1 + 1
C C C C
DLS SOUND HANDBOOK - PASSIVE X-OVER FILTERS