Help me for box 4th order

[Roby]

Hi,

My name is Roberto,i'm from switzerland and i don't speak english well .

I would like to understand how to design a 4th bandpass box with winISD.

I can not understand the ratio between the closed box and the ported box (example ratio: 1:2, closed 1 ft^3, ported 2ft^3).

In the example 1, the closed box is bigger than the ported box, the curve is flat and should sound good.

In the example 2,  the closed box is smaller than the box ported , but now the curve has a big peak and for what I know is not ideal to play, but more for spl.7

I always see on youtube that you often use the 2: 1 ratio (2 ported: 1 closed) or even 3: 1, but I do not understand why the closed box is smaller, can you explain how the 4th bandpass works?

 

I'm sorry for my english

 

 

[DLHgn]

I can't go into too much detail with the specifics of 4th order bandpass design as I'm not comfortable enough with them but I can elaborate a little bit. The sealed, or "closed",  chamber is used to determine the low end capabilities of the enclosure while the ported is for the higher end. That's why you'll see the ported side tuned to like 50Hz. When you make the closed side smaller than the ported side, you will get that large peak you see and an increase in SPL at that peak. When the closed side is closer to even with the ported side or even larger you will get a larger bandwidth (the big flat portion of the graph) at the expense of total output. Why it does this i'm not going to explain but hopefully that helps and hopefully all of that info is correct. If not, I ask that someone who knows more about these correct me so I don't misinform anymore.