Resource to calculate, building and measuring Hi Fi Loudspeakers and more...

Sunday, January 20, 2019
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   Serial Resonant Circuit Calculator (Tube Amplifier)

The primary function of the circuit is to dampen and eliminate the effects of driver resonance on crossover networks.
If the driver has an undamped resonance pea wich is located less then two octaves from a highpass crosspoint, this circuit will greatly improve driver performance.

It's usefull on tweeters and midrange drivers.

It's possible to use the circuit on resonances in the lower octaves, but it usually calls for some extremely large value inductors.

Let's say you have a loudspeaker with 6 Ohm, with a maximum impedance of 19 Ohm at 1200 Hz.
The impedance rise is no problem on a Solid-State-Amplifierd.

But, if you connect this speaker to a Tube Amplifier, then this impedance rise leads to an excessive level at 1200Hz.
Therefore, this impedance rise has to be compensated.

To achieve this, a R-L-C element should be connected in parallel to the crossover.

The R,C & L values are calculated by entering by entering the following data:
  • nominal impedance of the loudspeaker (Nominal impedance)
  • increased impedance that needs to be corrected (Maximum impedance)
  • frequency where the maximum impedance occurs (at frequency)
  • neighbouring frequency where the impedance drops exactly to the calculated value (½ the impedance)

  Frequency ½ the
  at at



Values Rmin of Ohm at Hz

R in Ohm: 10 Hz 12 Hz 15 Hz 20 Hz 25 Hz 30 Hz
L in mH: 40 Hz 50 Hz 60 Hz 70 Hz 80 Hz 90 Hz
C in uF: 100 Hz 120 Hz 150 Hz 200 Hz 250 Hz 300 Hz
  400 Hz 500 Hz 600 Hz 700 Hz 800 Hz 900 Hz
1000 Hz 1200 Hz 1500 Hz 2000 Hz 2500 Hz 3000 Hz
4 kHz 5 kHz 6 kHz 7 kHz 8 kHz 9 kHz
  10 kHz 12 kHz 15 kHz 20 kHz 25 kHz 30 kHz
* R is the sum of resistance-value (R) and DC-resistance of the inductor (L)

Standard R-L-C Circuit