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Low Pass Filter for Subwoofer

The post explains a simple low pass filter circuit which can be used in conjunction with subwoofer amplifiers for acquiring extreme cuts or bass in the frequency range 30 and 200Hz, which is adjustable.

How it Works

Several low pass filter circuits for subwoofer application are presented all over the net however this one is an upgraded example.

The circuit provided here utilizes the high efficiency opamp TL062 from ST Micro electronics. TL062 is a twin high input impedance J-FET opamp exhibiting minimal power consumption and large slew rate.

The opamp possesses outstanding digital attributes as well as being exceptionally compatible with this circuit.

Between the two opamps inside TLC062, one is connected in form of the mixer with pre amplifier stage. The left/right channels are linked to the inverting input of IC1a for mixing.

The gain of first stage may be tweaked utilizing POT R3.The output of the 1st stage is hooked up to the input of next stage via the filter circuit containing parts R5,R6,R7,R8,C4 and C5.

The second opamp (IC1b) functions as a buffer as well as the filtered output can be obtained at the pin 7 of the TLC062.

Need Help? Please leave a comment, I'll get back soon with a reply!


  1. What is that part of resistors r6 and r7?

  2. those are pots....variable resistors

  3. Very useful circuit, tryin' to build this one asap the only problem is lack of transistor 2N3905,, can i replace those bjt by two-parallel BC547?

  4. Hai sir
    In my area shop 0.47uf available only in 400v 474code....
    Shall i use it sir...
    Audio gain will be loss or not

  5. Hi, Kesav, it will work but it will look quite bulky....anyway you can use it, audio will not get affected.

  6. Thank u sir...
    Sir one doubt...
    I see one low pass filter circuit past 1 year back
    Using 0.56uf , 0.47uf and 39nf..
    In my area shop there is no 39nf till there any alternate...while using alternate any effects will be loss or not..

  7. Kesav, the capacitors in a filter circuit determine the range of the input frequency, if you change it the outcome might get can learn more about it here

  8. what is d function dual pot of 22k? can I use the 10k, 50k,100k dual . *(sir or I can series 12k+ 10k)

  9. I need ur help I build a metal detector. wit 555 and it work but my problem is I need d out to be either high or low state. I even couple d o/p to op-amp no response. but there is variation in d 555 o/p .what I don't like is that the sound is on always... *irritating * .help me out o

  10. it is probably for controlling the high frequency range, you can use 50 k pot or 10+12K pots in series.

  11. help me I want to make metal detector wit high sensitivity. ( that is when ever it detects metal an indicator will glow only.) thanks in advance

  12. sorry jack, I do not have any practical experience with metal detectors.

  13. dear sir
    Low Pass Filter Circuit for Sub woofer
    request answer please
    1.The wattage of resistors quarter watt s enough?
    2. 22k pot is dual gang stereo type?
    3. What is the output woofer impedance and watt ? 4ohm 50w is enough ?
    4. L in and R in lines other wire is connected with ground ?(input)
    output other wire is taken from ground isnt it ?
    Thank you sir

  14. Dear Jayanth,

    I think the R2 link must be removed, the input cannot be dual if the output is a single output.
    So please ignore the R2 link
    1) all resistors are 1/4 watt 5%
    2) 22K pot is a dual ganged pot
    3) impedance will depend on the type of amplifier used, it is not related to the above circuit

  15. thanks for early reply sir
    ok i will do same.
    i will make this circuit recently and let you know sir.

  16. Sure! Wish you all the best!

  17. sir circuit is working perfectly. thanks

  18. Glad it is working jayanth, keep up the good work!

  19. R1 and R2 acts as a mixer of both L&R channels, its important when you are building a 2+1 system.

  20. OK, but how can we get a stereo response using this circuit?

  21. sir this circuit is working fine with 100w amp.but i want to increase the bass effect further more. for that what are the components and values to be change sir?

  22. Hello jayanth, for customized design you can refer to the following article and adjust the values according to your preference


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