This is 2 way speaker box design for audio system. I’ve used this design for my home audio system, the sound quality is good. Two speakers used for this speaker box that are tweeter / high frequency speaker and woofer / low frequency speaker / subwoofer. Alternatively you may replace the woofer with fullrange loudspeaker.
The ventilation is used for this 2 way speaker box design, you can find speaker box plastic ventilation at electronic part store.
For better audio performance and protect the loudspeakers, you may use passive crossover circuit. Just mount this circuit inside the speaker box.
Below is the example of tweeter loudspeaker, woofer loudspeaker and crossover circuit:
Woofer Speaker
Tweeter Speaker
2 Way Passive Speaker Crossover Circuit