How loud it will be depends on the efficiency of the speaker, not on some theoretical max power rating.
Leo..
1 Like
ClassD is for constant amplitude input. It is non-linear.
Add 1 more transistor.
Google "lm386 transistor" and you will see schematics.
You don't, just feed it the output of the 386 and listen, you won't kill anything.
Tom.... 
???
All car stereos are class-D nowadays, and all subwoofers and all bluetooth speakers.
Leo..
Please explain.
Output of an amplifier is restricted by it's supply voltage.
Yes, you can add a transistor pair, but that won't increase output power, unless you use a speaker with lower impedance (4 Ohm).
Most class-D amps are used in bridge mode, which quadruples power for the same supply voltage.
Leo..
Use 2 LM386's, one with inversed input, and build bridge amplifier... (will not bring you 80W!)
I don't know how car amplifiers work. Class A amplifiers for for AM radios, Class D for FM :).
??? Add an BJT , connect your speaker to its collector. Offset its base voltage to shift its working point (sorry I don't know english wqords for this term) to linear area and thats it.
Class A amplifier.
@mactonight
See post #6
Odd that after 31 posts, you have not had even one piece of further information from you. Have you gone away?
No, they all amplify sound. It's just the way they are constructed.
Leo..
1 Like
Key characteristic of any amplifier is its linearity. Class A amplifiers are designed to offset working point to linear part. As a side effect of this is that BJT is always open -> heating, lower efficiency. Class D is very non-linear: it is ok to amplify signals where we can dismiss that non--linearity, for example if we are amplifying signal whose amplitude is more or less constant but frequency changes, i.e. output cascades of an FM trnsmitter. Amplifying sound with Class D probably require some signal manipulation, like turning it in some sort of PWM (PDM), then amplifying and then having a filter which turns your PDM into audio.
Thats what I have learned 25 years ago :). May be it is all wrong informattion these days, I dont know.
You are not wrong. However over the years Class D has incorrectly become synonymous with Class D Audio amplifiers which involves the modulation of the audio
1 Like
Possibly the teacher wants to insure that their speaker survives all the students attempts. Going to be hard to permanently damage an 80W speaker even with a direct connection across the power supply at the voltages being used.
2 Likes
the "80Watt" specification is an upper limit of the speaker. 80watts is not a functional requirement but a statement that if you power with 81 watts you will damage the speaker.
While 81W is a little tongue-in-cheek it describes the concept.
So build is a see what it does. If it's listenable then you are successful.
1 Like
No IC's then I would switch to tubes 
and an output transformer.
1 Like
@mactonight
See post #6
Or perhaps the teacher or student has plenty of LM386's. And is not currently teaching PWM Audio.