18W is rather a low output power to drive a subwoofer speaker. Typically they are at least 50W.

Can you show me that power amplifier cct for the 50W output power?

 

This is the wrong year to answer this thread. Please start one for yourself.

 

This is the wrong year to answer this thread. Please start one for yourself.

sorry, just learned

 

Can you show me that power amplifier cct for the 50W output power?

No, but its easier and generally cheaper just to buy one ready made such as one of these.

 

Can i ask you about the power amplifier cct, does it really have to use the class amplifier such class A, B etc, or can i just use an opamp instead?

 

Hello,

You just hijacked an old existing thread:
http://forum.allaboutcircuits.com/t...ake-a-subwoofer-using-just-tda2030a-ic.88267/

As this is not wanted over here, I moved your posts to its own thread.

You might have a look at some circuits over here:
http://sound.westhost.com/projects-0.htm#pwr

Bertus

 

Can i ask you about the power amplifier cct, does it really have to use the class amplifier such class A, B etc, or can i just use an opamp instead?

No. You need a power amplifier that can deliver many watts into a low impedance speaker load. An op amp can only provide a few tens of milliwatts of power into a high impedance load.