Sound improvement: 2.1 Subwoofer

Thread Starter

ranatungawk

Joined Oct 30, 2008
162
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?
 

wayneh

Joined Sep 9, 2010
16,398
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?
 

Thread Starter

ranatungawk

Joined Oct 30, 2008
162
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?
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
 

GopherT

Joined Nov 23, 2012
8,012
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
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.
 

Thread Starter

ranatungawk

Joined Oct 30, 2008
162
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.
Thank you for the advice ! can you pls show me how to make a simple bass booster circuit for the woofer ?
 

AnalogKid

Joined Aug 1, 2013
8,492
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
 

Thread Starter

ranatungawk

Joined Oct 30, 2008
162
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
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 ??
 

Techno Tronix

Joined Jan 10, 2015
139
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.
 

Thread Starter

ranatungawk

Joined Oct 30, 2008
162
Thanks for all the valuable advises, can you please tell me whether these resisters are used as filters ? to select a certain frequency ?
 
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