Vent Match term in WinISD

[blu_line]

Hello all,

I have 2 Vifa 25WN250 which i wanted to check in WinISD.
It will be a vented box.

Checking the vent size, i'd like to have it rectangular, i came across the term "vent match".
What does that mean ?

I also played a little with the numbers. The larger the vent is, the longer it needs to be. Somehow obvious but can some one explain why ?

grtz

Simon

[Ron E]

The air in the port actually acts like a piston. A larger piston displaces more air in the enclosure for the same movement so the box air appears to be a stiffer spring. If it were the same length as a smaller diameter port it would have a higher resonant frequency. When you have a stiff spring, you need more mass, so you make the port longer.

Vent Mach is the speed of the air as it goes back and forth in the port. You want to keep generally below 5% of the speed of sound (~17 m/s) at the higher\st power level you want to use in order to avoid objectionable noises. It helps a great deal to use flared ends on the port - allowing you to bend the 5% rule a bit.