About speaker box.

[jst]

Is Woofer/low frequency the only speaker part that needs box ? Does mid or tweeter also need box ?

Because for car speakers, tweeter doesn't need box, it's usually put on dashboard, and the mid or full range is put at the door, sure there is room for air there but it's not boxed like woofer, and there's also small box for mid too, so the size for mid probably also doesn't matter ?

Spoiler

Is there a universal speaker box dimension for woofer ? like 25x25x25cm (not actual calculated box, I just made it up) for example would work for all kinds of 8" woofer. Or 30x30x30 cm would work for all kinds of 10" woofer. Something like that.

 

[alex-z]

Tweeters still need an air volume behind them, but this is built into the cup on the back.

Mid-range drivers are available in open and closed back configurations. If you buy an open back mid-range, it needs an air volume behind it.

The air volume controls how much damping is provided to the speaker cone. It is important that you use the correct amount for both your mid-range and woofer. T/S parameters are used to describe electrical and mechanical properties of a driver, so that you can determine the ideal air volume with software.

Driver size is not directly related to air volume, because drivers can be used/designed for different purposes. Subwoofer, mid-woofer, and mid-range can all be the same size yet behave much differently. Further complicating matters, some drivers are intended for ported enclosures. Again, refer to the T/S parameters.

Baffle size is another important conversation. How your drivers are positioned changes the frequency response, especially for the tweeter. This impacts your crossover tuning heavily. Small or large baffle, the most key element is smoothness of the edges. In your example picture, that tweeter pod is a bad design. It has a ring all the way around, and the tweeter sits in the centre, amplifying the edge diffraction.