Speaker box design

[Jonny69]

I'm trying to design a small enclosure that I want to tune like a bass-reflex speaker cabinet. I know the volume I want to use and I know the frequency and I know the sizes (diameter) of port I have available.

How do I calculate the length of the port?

It's not got a speaker in it so the Thiele and Small parameters don't count, I can't find a website with basic tuning charts anywhere!!!

 

[phykell]

Just as an aside, have a look at this:

http://www.ee.vill.edu/~cdanjo/voigt.html

I've been intending to make one of these for years just to see how good they really are

Much more detail here:

http://fullrangedriver.com/

 

[Jonny69]

I think I found the post T&S equation I was after:

The port length required to tune a volume of air to a specific frequency can be calculated by using the following equation:


Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)


where,

Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of each port (cm)
Np = number of ports
k = end correction (normally 0.732)

Looks about what I can remember it looking like when I used to make speaker cabs!

 

[DRZ]

Have a look at BoxPlot or WinSpeakerz too if you want to check the frequency response of the box before you build it.