Im looking at putting my two ID Max D2's in a 5.1 cu ft box.
From what I understand It is not the size of the port it is the length which tunes it. correct?
I was therefore going to go by your advice of 16sq in per cu ft ad have 80sq in of port surface area.
Image Dynamics recommends porting at 28hz for this box which requires a 15inch long port, however as it is going to be a false floor setup in my trunk the whole box is only 12 inches deep. how can I get around this?
oh also when measuring the length of the port is it measured from the outer edge of the box or the inner edge of the box (ie minus the thickness of the MDF?
Tuning frequency depends mainly on three things: net internal volume, port length(measured to outside of box), AND port cross sectional area. It also depends slightly on cross section geometry and whether the port is externally flanged(baffled) or not. These last two parameters both determine the effective mass of the collumn of air oscillating in the port, but the differnece is generally considered negiglible and calculations are usually based on the first three alone.
If you've got no room to fire a port horizontally and are depth limited the easiest way to get around this problem is to use an L-shaped slot port(s)as is shown in the box diagram in this .pdf:
[edit] "net internal volume" should read "net enclosure volume".
Blair
Unregistered guest
Posted on
Ok thanks that does help but I have a couple of more questions.
With the L shaped port how do I measure the length of the port ie. the length of the L through the centre of the cross section I presume?
Also if this is the case can someone confirm my calculations. 2.55cu ft per sub with a 4x10(cross section) x 15 in port, to create a 28hz tuning frequency? is this right?
Also does any one have a link to a port/box size calculator program.
Also do you think 28 hz is to high frequency? I dont want to be cutting off any typical musical notes.
Sorry for all the questions, but I want to get it perfect the first time.
Blair
Unregistered guest
Posted on
anyone....
By the way i just found out that if i want an 80 sq in cross section port for this box it is going to have to be over 3.5 feet long!!!
Does this sound right? Has anyone here built a box like this?
