To determine the appropriate type of power amplifier for your DIY speaker, you'll need to consider a few factors: the impedance of the speaker, the desired power output, the type of music or audio you'll be playing, and your budget.
If you're building a speaker with a low impedance (e.g. 4 ohms or less), you'll need a power amplifier that can deliver a lot of current. Class D amplifiers are a good choice for low-impedance speakers because they are highly efficient and can deliver a lot of power.
If you're building a speaker with a higher impedance (e.g. 8 ohms or more), you'll need an amplifier that can deliver more voltage. Class A, Class AB, and Class H amplifiers are good options for high-impedance speakers because they can deliver more voltage.
It's also important to consider the power output you need. If you want to drive the speaker at high volumes, you'll need an amplifier with a high power output. On the other hand, if you only need to drive the speaker at moderate volumes, you can get by with a lower power amplifier.
The type of music or audio you'll be playing is also a factor to consider. If you'll be playing music with a lot of bass, you'll need an amplifier with good low-frequency response.
Finally, consider your budget. Power amplifiers can range in price from a few hundred dollars to several thousand dollars, depending on the features and quality you need.
I hope this information helps! Let me know if you have any other questions.