software for port

[kelticwizard]

Using this I get a different answer again.
http://www.loudspeakers101.com/VentCal1.htm

Buster:

For rouond ports and square ports, you should get approximately the same answer. Don't worry about minor differences is length.

For example, in WinISD, a port size of 76mm, (3 in) by 503mm, (20.2 in) tunes a 60 liter, (2.1 Ft³) box to 19.6 Hz. In the link you gave me, the same size port tunes the box to 20 Hz. That is simply a negligible difference, and is to be ignored.

A square or rectangular port with the same area as the 76mm diameter port will give the same tuning.

If you go to that link you gave, you will get a shorter length for a slot port-a rectangular port that uses the bottom or sides of the enclosure as a side-than for the round or square port stuck in the middle of the box. That is good.

In this instance, a slot port with the dimensions of 150mm wide, by 30.2mm high, will have to be 461mmlong to tune the box to 19.6 Hz. That is slightly shorter than the 535mm it would have to be if you used a round or square port that was not located along the bottom or sides of the box.

So everything checks out, approximately.

 

[busterno1]

thanks for the help . by the way the port measurment is 19.87 inchs how do you get a different answer to me when I changed it too metric

 

[kelticwizard]

thanks for the help . by the way the port measurment is 19.87 inchs how do you get a different answer to me when I changed it too metric

I didn't use WinISD to calculate the change from 503mm to inches.

503mm¸25=20.12 inches which I mistyped as 20.2 inches

503 ¸25.4=19.8 inches.

The difference is whether you want to say there are 25 mm per inch or 25.4 mm per inch. I'm not an engineer, so it's 25 mm per inch for me.

The differences here are incredibly tiny-less than 1 Hz difference in tuning. Nothing to be concerned with.