TL Speaker

Lamda/4 = L of pipe for tranmission line speaker such as you have spec speaker at 56Hz. you can calculate L of pipe at
Lamda = V/F => V is velocity of sound in the air ( 3*10^4 m/s)
=> F is frequency
So that Lamda = 30000/56 =...................
L = Lamda/4 =................ m
You can get pipe your speaker...