Ojgalli's explanation is a good one. It all has to do with the relationship of the compliance of the driver and that of the air in the box.
In layman's terms, a sealed box can be either acoustic suspension (AS) or infinite baffle (IB). A small box, with a very compliant suspension will tend to be AS, a larger box and/or less compliant driver will tend to be IB.
By the way, AS is truly one of the landmark developments in the history of audio. In my mind, nothing has eclipsed it, and is probably the biggest reason we have 2 channel (as opposed to 1) audio.
In layman's terms, a sealed box can be either acoustic suspension (AS) or infinite baffle (IB). A small box, with a very compliant suspension will tend to be AS, a larger box and/or less compliant driver will tend to be IB.
By the way, AS is truly one of the landmark developments in the history of audio. In my mind, nothing has eclipsed it, and is probably the biggest reason we have 2 channel (as opposed to 1) audio.