Hole in the box? (1 Viewer)

[Mark Larson]

I read an article about Bass Reflex in Secrets (i think), and they said that the effect can be achieved with both a 'hole in the box' and a port. Can anyone tell me how this works? What kind of hole are we talking about for a 4" dia 33" long port?
Thanks!

 

[Mark Tranchant]

A very small one. The "hole" isn't strictly a hole, but a port using the thickness of the box as the port length.

This is usually useless except for tuning large boxes with thick walls to comparatively high frequencies.

To answer your question, tuning a 1.64 cu ft box to 24Hz with a 4" diameter pie requires 33" port length. To achieve a 0.75" port length (3/4" box thickness), you'd need to use a 0.765" diameter port. The similarity of these two numbers is a coincidence. The "port" would be very sensitive to "end-effects" at such a short length, and the theoretical calculations will be approximate at best.

Such a small port would generate significant port noise with even small driver movements.

 

[Jack Gilvey]

He's just using the term "hole-in-the-box" to refer to a port. Same thing. Even a hole drilled into a box will have a diameter and length, it's just a small "port".