To have enough output power if the audio input is sufficient and the supply voltage/current is sufficient. The power supply voltage is higher and the relative power will be larger. The speakers with different impedances will have different output powers. In the case of sufficient voltage and current, the larger the ohms of the horn, the smaller the relative sound power. Please pay attention!

voltage:
12V ------- 8 ohm speakers / 12W (left channel) + 12W (right channel) 4 ohm speakers / 20 (left channel) + 20W (left channel),
15V ------- 8 ohms / 18 + 18W, 4 ohms / greater than 30 + 30W,
19V ------- 8 ohms / 32 + 32W, 4 ohms / greater than 45 + 45W,
24V ------- 8 ohms / 38 + 38W, 4 ohms / greater than 55 + 55W,