Help with subwoofer design

[vipul982]

Hi everyone,
I've decided to build a subwoofer of my own and the circuit is as follows



All the circuits which i went through in the internet uses dual power supply of either 12v or more whereas the proffessional 2.1 channel systems uses single 12v supply. can u give me a circuit with single power supply. Also have a doubt, should this circuit be connected at pre amp stage or post amplification stage. how to match it with speaker impedance??
thank you in advance

 

[Audioguru]

I've decided to build a subwoofer of my own and the circuit is as follows

it is not a sub-woofer. a sub-woofer is a low frequency speaker. the circuit you found is a second-order variable frequency butterworth lowpass filter for a sub-woofer's amplifier.

All the circuits which i went through in the internet uses dual power supply of either 12v or more whereas the proffessional 2.1 channel systems uses single 12v supply. can u give me a circuit with single power supply.

Any opamp circuit can work from a single supply if the opamps are biased at half the supply voltage.
The (+) input of the first opamp should be connected to two equal-value resistors in series (100k each) connected from the positive supply to ground so that their junction is at half the supply voltage. Add a filter capacitor (10uF) from their junction to ground. Add input coupling capacitors and an output coupling capacitor.

Also have a doubt, should this circuit be connected at pre amp stage or post amplification stage. how to match it with speaker impedance??

This filter circuit feeds the input of the power amplifier that drives the sub-woofer speaker. The original TL062 dual opamp was replaced by a much better TL072 dual opamp.

 

[vipul982]

audioguru, do you have a circuit for a 2.1 channel system?

 

[Audioguru]

A 2.1 channel system has highpass filters for the left and right channels and a lowpass filter for the sub-woofer channel. The frequency of the filters depends on the spec's of your speakers.

Then you don't need filters with adjustable frequency.

 

[u_husain88]

hi audioguru,
i need a circuit for subwoofer low pass filter for producing a deep bass.my speaker specs are 4ohms 40W.i have built a power amp using tda7294.it performs realy good.thanx

 

[Audioguru]

A lowpass filter will not help poor speakers produce bass sounds. The filter simply reduces high frequencies.
A sub-woofer speaker is usually 10" or bigger with a low resonance frequency. The enclosure must be designed using the detailed spec's of the speaker.

Usually an opamp is used to make a Sallen and Key lowpass Butterworth filter.

 

[u_husain88]

A lowpass filter will not help poor speakers produce bass sounds. The filter simply reduces high frequencies.
A sub-woofer speaker is usually 10" or bigger with a low resonance frequency. The enclosure must be designed using the detailed spec's of the speaker.

Usually an opamp is used to make a Sallen and Key lowpass Butterworth filter.

hi audioguru,thanx for your reply.
as u said that a subwoofer should be usually 10" or bigger,can u provide me with a good subwoofer driver circuit along with dimension and watt of subwoofer that i can buy(assuming 10" or so).thanx

 

[Audioguru]

A sub-woofer driver circuit is a power amplifier. Make one. Also make a lowpass filter circuit for it and highpass filters for the stereo amplifiers.
I don't know which speakers are available in your country.

 

[u_husain88]

A sub-woofer driver circuit is a power amplifier. Make one. Also make a lowpass filter circuit for it and highpass filters for the stereo amplifiers.
I don't know which speakers are available in your country.

ok about the power amp i have already made one using tda7294 and about making a low pass filter will the image given in url below ...i.e. the sallen and key butterwoth low pass filter be useful?
i have a variety of speakers available in my country.
thank u for your immediate response

 

[Audioguru]

You show the Sallen and Key 103Hz second-order Butterworth lowpass filter that I posted somewhere. It will work as the lowpass filter for a sub-woofer.

 

[u_husain88]

You show the Sallen and Key 103Hz second-order Butterworth lowpass filter that I posted somewhere. It will work as the lowpass filter for a sub-woofer.

yes audioguru this is one of your posted image.i also found one in this url

**broken link removed**

can you advice which one will be better performance wise .thank you

 

[Audioguru]

The Subwoofer Controller project uses a 15" very powerful woofer in a sealed enclosure that is too small for it. The small enclosure increases the resonant frequency. The frequency response of the speaker drops at 12db per octave below resonance. The filter circuit makes bass boost at 12dB per octave so the amplifier needs a very high amount of power and the speaker must survive a lot of motion then the speaker performs well down to 25Hz and up to about 100Hz.

The lowpass filter circuit is used with an ordinary subwoofer and a normal size enclosure for it. The amplifier power can be normal. the lowest frequency depends on the speaker and enclosure.

 

[u_husain88]

ok audioguru i got it.u mean that the subwoofer controller ckt will be a powerful controller for for audio applications with heavy duty woofers and the one that suits me would be a low pass filter like a sallen & key low pass butterworth filter.m i correct?
thankyou

---------- Post added at 06:20 ---------- Previous post was at 06:15 ----------

audioguru, i also found an ic pt2351(subwoofer cross-over low pass filter ic) and pt2353(3-way speaker(satellite+subwoofer)system ic).will this be helpful to me if i use pt2351 in place of sallen and key low pass filter.thanx

 

[Audioguru]

ok audioguru i got it.u mean that the subwoofer controller ckt will be a powerful controller for for audio applications with heavy duty woofers and the one that suits me would be a low pass filter like a sallen & key low pass butterworth filter.m i correct?

Correct.

i also found an ic pt2351(subwoofer cross-over low pass filter ic) and pt2353(3-way speaker(satellite+subwoofer)system ic).will this be helpful to me if i use pt2351 in place of sallen and key low pass filter.thanx

You probably want to use the PT2353 since it adds highpass filters for the stereo channels.
But the Princeton datasheets have no detailed spec's.

These two ICs are not mentioned on Princeton's website so maybe they are obsolete and are not made anymore.