Jinnie wrote:

I want to use LM386 (http://www.kynix.com/uploadfiles/pdf2286/LM386M-1.pdf) to drive a 5W 8ohm speaker. But the speaker cannot make a loud sound. So I need your suggestions for making the speaker louder.

And here are my guesses:
1.Add a transistor to LM386
2.Reduce the power of the speaker through the circuit?
3.Or should I choose another IC to replace LM386?

I used TDA2005 before, but the 7805 chip was easy to burn during the process. Also it makes a terrible noise.

Now the sound quality is better by using LM386, but it cannot produce a loud sound...
I really need your suggestions. Much thanks if you can help me!

Your speaker is too small to produce the sound level you want.

You need a speaker that is rated for at least 40 watts.

An LM386 cannot put out enough power. You need an amplifier that can put out at least 20 watts RMS.