-The closed-box or "acoustic suspension" enclosure, rather than using a large enclosure to avoid the effects of internal air pressure changes caused by cone motion, uses a smaller sealed enclosure, generally much smaller. The enclosure must have a very small leak so internal and external pressures can slowly equalise over time, allowing the speaker to adjust to changes in barometric pressure or altitude.- taken from Wikipedia

'The enclosure must have a very small leak so internal and external pressures can slowly equalise over time, allowing the speaker to adjust to changes in barometric pressure or altitude'

Is this true? Do sealed designs need a small hole or 'leak'?
cheers