Max port air speed will be at tuning, and the port needs to pass that without becoming to resistive, so it needs to be as large as possible to keep the PAS as low as possible. However, the large CSA of a port the longer it will need to be, so some manufacturers use the shortest port possible. When it tries to pass the max volume of air, the CSA will be too low and it will behave like a dynamic filter at port tune, reducing output at the highest levels, but not at lower levels so it still measures well at low levels. Manufacturers won't talk about it because it's their dirty little secret. I try to keep PAS below 15m/s.-Can you please discuss more about 'port-compression'?
I have the understanding that the port does 2 things. 1) It's TUNED to a certain frequency, and 2) it's for air intake/exhaust due to the driver displacement.
The port air-velocity should try to be minimized - or you'll hear 'chugging'. (110 ft/s or less?) You can reduce air-velocity with more vents - or larger diameter vents.
I've never seen 'port-compression' referenced.
Chuffing is more what happens when the air is in a fairly high impedance zone, in the port, and it comes to the open air, their is shear in the flow and this sound can become audible. Where that is and how bad depends upon the tuning and design of the port and box. This why many ports have flared ends, and note that because the port is bidirectional in flow, the intake (inside the enclosure) is also best flared.