>>106292214
You have no idea because you've never opened a set of headphones
Here are 2 examples how openback headphones are usually built
On the left your ear is closed off by the driver and driver cap
On the right two types of acoustically transparent material highlighted in green, the paper one looks like it will allow airflow but it doesn't, unless you try to directly blow trough it, and even then it's negligible. As an example I also have dt770 (they also use velour pads) and I don't feel any difference between them and hd560 when it comes to airflow.