subwoofer filter circuit schematic

Subwoofer Filter Circuit

This subwoofer active filter circuit is a 24 dB octave filter with a Bessel character and cutoff frequency of 200 Hz. So, if you are interested in experimenting with audio circuits in subwoofer range, this circuit is for you.

In subwoofer range, all audio frequencies below 200 Hz can be fed to a single speaker box since the human directional perception of sound diminishes at this frequency range. The normal stereo signals above 200 Hz can be fed to 2 satellite speakers.

How does the subwoofer filter works: A1 and A2 buffer the signals coming from right and left channels. Opamp combinations A2/A4 and A9/A10 function as the highpass filters. The outputs are then connected to the final amplifiers of the battelite boxes. Signals from both channels are fed to A5. Opamps A6/A7 function as the lowpassfilter, A8 as the output amplifier for the subwoofer signal.

The signal level can be balanced between the subwoofer and the satellite lines. The power needed for this filter circuit must ne a symmetrical power supply. The opamps can have either JFET or bipolar inputs.

Active Subwoofer Filter Circuit Diagram

subwoofer filter circuit schematic


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  • Name *kingdedon

    pls indicate the individual ICs seperately

  • siva

    Can this be used as a 2.1 Channel speaker system.
    Please forgive my foolishness if it is already one.

  • anu

    my 10 inch sub woofer & I m build 30watts amplifier is good working but these connected to old 2.1 amplifier 10 watts subwoofer 2.5inch this small .these 2.1amplifier power on then not connect to input (mobile.etc) so the sub woofer build a blur sound (harmonica sound) only vibrating . these problem how to reduce or hew to forget . plzzzzzz. help.

  • anu

    I want 5.1 or 5.2 3d originality circuit plzzzzz help urgent

  • Maika

    what modifications should I make to make this a 100 watt rms output?

  • k.manjunath

    sir i want to ckt dia of audio mixer to camera input wich has sterio ep. using gain controller.

  • dan mainza

    what are the equivalent op amps to these LM833 TL072 NE5532 & LF3F3 i cant find any

  • ramakrishnan

    I am very sorry to say that most people wanted to learn everything on in one cup. It is much appreciable that Mr. Joseph Perkins has patiently replying the entire question. The question raised by somebody has to take much effort spending time to read more books.

    I would like greet Mr. Joseph Perkins for his efforts.

    • Joseph Perkins

      I am always willing to help folks understand electronics when I can.

  • Stefan

    Hello, thank you for this circuit
    i have a question…can i use NE5532 ic’s without modifying the circuit?
    those are powered by a nomal power supply(10V-15V) like an LiPo battery(11,1V), which i intend to use…so no need to simetric power suply!!
    Thank’s for the attention!

    • Joseph Perkins

      The supply only needs to be symmetrical to prevent clipping. So long as the “virtual ground” is the same for both the positive feedback point and the negative, the operational amplifier will keep the output pin at that same DC level, regardless (that’s sort of the definition of an OPAMP).

      In the sorts of circuits you are seeing, the (+) lead of the OPAMP is the DC reference, or virtual ground. The (-) lead is DC connected to the output. So whatever DC level is at the (+) lead will be what the OPAMP output will settle at.

      If your incoming AC signal voltage exceeds the supply, in either direction, it will get clipped to that voltage.

      You can make a pseudo virtual ground that is symmetrical by using two resistors of equal value from the +DC voltage to the -DC voltage in series. The center connection is a virtual ground. 10K each is useful at these voltages. Then bypass the 10K resistor that connects to -DC with a 47UF or 100UF capacitor where the NEG of the capacitor is on -DC and the + of the capacitor is on the new virtual ground. That capacitor prevents motor boating. Connect the GND leg of all inputs and outputs to the virtual ground.

  • Deepu....

    the circuit is good…but the capacitors mentioned ,such as .15 uf are not available in the market…how can i get it???

    • Joseph Perkins

      This type of circuit will output at about 1VRMS that would be typical for a power amplifier input.

      This is an active subwoofer circuit so you will need to size the subwoofer and its amplifier to match the rest of your system.

      I would recommend making the subwoofer 4 times the wattage of the right/left pair (200W subwoofer with 50W left/right) and getting either a “mono” amplifier that size or one that can be operated in “bridge” mode. A single ported subwoofer at 200W is typically 4 Ohms.

    • Deepu....

      Thank you Joseph…..Will you please tell me what’ll be the rms output of the circuit..?also please give me the specification of the woofer speaker should be connected to it…

    • Joseph Perkins

      Capacitors can be paralleled to make any arbitrary value you need. Use a 0.1UF (100NF) in parallel with a 0.047UF (47NF) capacitor and you will get 0.147UF (147NF). If you can find 0.05UF, then you can get 0.15UF within the 5% or 10% most capacitors are rated for. Don’t forget also that there are other types of capacitors that will work in this circuit besides ceramic disc types. Mylar or Polystyrene are usually preferred for audio.

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