How much clearance for bottom port

[hobbyhands]

So my simulation on my latest project are saying I need 8.25" port length. My box is not that deep. I have three choices as I see it.

1. L shaped port
2. Port on the top
3. Port on the bottom
How much clearance would I need for the bottom?

[wogg]

Approximately the diameter of the port. You can go smaller, but you're tuning frequency will be affected a bit.

[Chris Roemer]

I put some screen around the bottom to make it easier to dump out stuff that "falls" in there.

[jhollander]

The proximity of the port to the cabinet wall and floor can increase the effective length of the port. If you have the ability to measure the tuning you can make adjustments as you go. I also did a project where the port exited the bottom of the cabinet and I used the space under the cabinet to extend the length of the port.

[hobbyhands]

So let me clarify. Not internally but externally. So if the port opening were on the bottom of the box.

[PWR RYD]

If you had a port with a 2" internal diameter then you would want to have 2" tall feet on the bottom of your enclosure.

[fpitas]

I've always wanted to do bottom ported, just so I could use that cool cone-shaped aerodynamic device that I've seen used.

[jhollander]

If you had a port with a 2" internal diameter then you would want to have 2" tall feet on the bottom of your enclosure.

To use the bottom of the cabinet and stand top as the port I calculated the same area as the port, like a slot port and ended up with 1/2 inch feet for my 1-3/8 inch port tube. That was probably a bit higher than needed, but I was able to adjust the inside port tube to get the tuning I wanted.

[AEIOU]

. . . . cone-shaped aerodynamic device that I've seen used.

POLK Audio Power Port.

[fpitas]

POLK Audio Power Port.

Thanks! Whatever the pros and cons of bottom porting, I've always liked the look of that thing.