Port shape round vs ported question
 

Ok guys I need some help here. I am getting some conflicting #'s from winisd. So I am making a ported box for 2x 10" Clarion SSW1001. I was told to make it 2cu' total tuned to 30hz with 2 round ports 2.5"dia x 12.79"long. Does it change the volume of the port if I went with slot ports? If I put in winisd it gives me a length of 12.5" or so long. Which works out to around 61cu". Now when I change to the square port and try to get the same area it makes the ports twice as long???? 2"wide X 6"high X 5.25"long = 63cu" but winisd changes the length to like 11" WTF? Does the shape of the port make that much of a difference? Does a slot port need to have 2x the volume of a round port to get the same tuning? Or was I right first time and just take the volume of the round port and make a slot port of the same volume? These are the T/S specs I was working with BTW
FS- 33.5
QMS- 4.27
VAS- 0.539cu'
MMS- 190.7g
Xmax- 24mm
SD- 0.083sqmeters
QES- 0.753
RE- 1.6 paralel
LE- 6.067mH paralel
BL- 9.236Tm paralel
QTS- 0.64
BD- 0.071cu'
2.8v SPL- 87.75 paralel
recomended 1.0cu' each port 2.5"dia X 12.79" long tuned at 30hz
Thanks for any help this is the first attempt at a ported box.
Nick

Don't use VOLUME to compare vents. As a vent increases in area it also increases in length. For a given area though the length will be more or less the same regardless of the shape of the vent (round, rectangle, other).

Also, two 2.5" diameter ports are way too small for your setup. You need at the very least a pair of 3" diameter ports, aeroports would be a good idea.

Oh - and where did that tuning frequency come from? Never tune below FS. Never. I would tune to 35hz at the very lowest.

It was recomended by the owner and installer at the shop I am buying them from. So if I take the volume of the round port and make a slot port the same volume it will keep the same tuning? Winisd shows a little more output at 35hz so I think I will go with that.
Thanks
Nick

Area. Keep the area of the vent the same and the length will be the same in 99% of the cases.

I'm kind of surprised at their recommendation. Very few people (ie nobody) use 2.5" ports an 1cuft at 30hz sounds really generic. Sounds like something off of a manufacturers spec sheet.
Good on you to be modelling it on WinISD.

two 3 inch, or one 4 inch aero ports would be suffice, but definatly not 2.5 inch ones

Anyways, i'll design something for those woofers.
give me about 25 minutes

1.1 cubic feet per chamber @ ~34.5hz


32"w x 18"d x 13"h

Awesome dude thanks. Thats exactly what I needed. Looks good too.

Smaller ports are fine (to an extent) if u use multiples. If you are trying to move too much air through a too small port the venturi effect of the air movement will get messed up and thats when you get chuffing/farting/port noise (pick your own word). Multiple smaller ports coupled together (close proximity to each other) will split the load of air and get the job done as efficiently as a larger port.