Sound improvement: 2.1 Subwoofer

Discussion in 'General Electronics Chat' started by ranatungawk, Dec 3, 2015.

  1. ranatungawk

    Thread Starter Senior Member

    Oct 30, 2008
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    Hi Friends,
    Subwoofer_1.JPG

    I found Circuit of my 2.1 Subwoofer is built with two KA2206B amplify ICs. One is used for left-right speakers (as a stereo amp) and the other one is used for the subwoofer (Bass speaker) as a mono amp. Input stage of this circuit is attached herewith. I need to increase the sound of my Subwoofer kit. So I hope to replace the existing resisters with new resisters in RED ( 2x 47k with 2x 10ks and 2x15k with 2x 3.3ks ). Please tell me, will this reduce the sound quality of my subwoofer while increasing the volume ? Specially the bass sound (boom) of the subwoofer?
     
  2. wayneh

    Expert

    Sep 9, 2010
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    You might get more volume, but I would predict a large loss of sound quality and possible destruction of the amplifier.

    Why do you think the original design can be so easily improved?
     
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  3. ranatungawk

    Thread Starter Senior Member

    Oct 30, 2008
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    Thanks wayeh;

    actually the reason is this : this sub woofer comprised a fm radio, USB , mp3 card module. due to a faulty of it , i installed a new card. now all the functions are working but with the new card , sound volume is not as high as the old one. so i decided to increase the sound by changing the resisters i have mentioned.

    please help me to understand that : have these resisters been used as frequency filters ( like Low-pass ) in this design ? if so it will be a big impact for the sound quality as u had explained
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,031
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    Why don't you make a small booster from the sound card to the 2.1 system? If it has enough power with the old sound card, it is not the fault of the 2.1 system that the input signal is too low. As wayne said, you will likely kill the performance of the 2.1 system with any changes. Remember, that feedback systems and input resistance is there mostly to filter unwanted sub-sonic or ultrasonic frequencies. If you change the resistors, you risk moving the filter into the audible frequencies. You will need to do a detailed analysis of the filter network.
     
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  5. ranatungawk

    Thread Starter Senior Member

    Oct 30, 2008
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    Thank you for the advice ! can you pls show me how to make a simple bass booster circuit for the woofer ?
     
  6. bertus

    Administrator

    Apr 5, 2008
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  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Changing the 15K resistors to 3.3K will significantly decrease the max volume of the stereo speakers while not affecting the bass speaker. Decreasing the 47K resistors to 10K will increase the bass without affecting the stereo outputs, but also change the base crossover filter characteristics. How did you come up with these new resistor values?

    ak
     
  8. ranatungawk

    Thread Starter Senior Member

    Oct 30, 2008
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    Thanks Ak :) ;

    "Changing the 15K resistors to 3.3K will significantly decrease the max volume of the stereo speakers" ...???? is this correct ??? not decrease but increase , i'm i wrong ? how ??
     
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    My mistake, I misinterpreted your schematic symbol for the amplifier.

    ak
     
  10. Techno Tronix

    Member

    Jan 10, 2015
    140
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    I agree. When designed and used appropriately, subwoofers can be extremely effective and very convenient. Equally, though, it is very easy to destroy any chance of good monitoring quality with an inappropriate or badly set-up subwoofer. It can effect on bass.
     
  11. ranatungawk

    Thread Starter Senior Member

    Oct 30, 2008
    147
    0
    Thanks for all the valuable advises, can you please tell me whether these resisters are used as filters ? to select a certain frequency ?
     
  12. Dodgydave

    Distinguished Member

    Jun 22, 2012
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