View Full Version : soo im building a new box again, quick question.

01-16-2007, 01:53 PM
well after sub displacement its 8.66cubic ft.

wanted it tuned to 30hz. minimum area for the slot port would be 100.55inches.

so i did 16.5in. by 7in giving me 115.5in. area.

so when using http://www.carstereo.com/help2/Articles.cfm?id=31

i put in 1 port and the rest of the info and it gives me 27.57in. in length.

But if i wanted to do 2 ports, lets say one on each side of the box towards the back couldnt i just do two ports at 16.5x3.5 at 13.78in. in length?

or am i doing that all wrong?

Mr Bojangles
01-16-2007, 01:56 PM
you will need to enter 2 ports and it will recalculate for you.. Not exactly sure if it will be exactly half if you go with two ports instead of one big one. You would think, but i'm not sure if that's right

01-16-2007, 02:32 PM
well if i do enter 2 ports then would i enter only half of the width of a single port in the Area section?

01-16-2007, 11:15 PM
anybodyyyyyy??? lol come on i know this is probably a noob *** question but i knew absolutely nothing about car audio up until half a year ago and i think im doing pretty good. this part is just buggin the hell outta me. I thought i knew the answer but then im like hmm what if im wrong.

01-16-2007, 11:59 PM
Since you're using 2 ports, my understanding is that you divide the volume of your box by 2. Use the half-sized volume, and use the half sized single port dimension as well. Then your volume becomes 4.33, the number of ports is still 1, Each port (at 16.5 by 3.5)should end up being 32 inches long.

Actually, it also works if you just enter 2 ports using your complete volume, and enter the half-sized port dimension(16.5 x 3.5) as well.

01-17-2007, 11:30 AM
I don't get the same output based on your inputs. First you want to make sure that you are using the volume of port displacement and substracting it from the gross internal volume. If this is not done your tuning will be way off.

As far are your data given I get
Length Slot=31.05" @ 7" port opening

01-17-2007, 08:13 PM
RP, make sure you click "yes" on the "slot port" button. I also noticed that if you switch height for width on the square vent dimensions(in other words, input a port height of 7 and width of 16.5 versus 16.5w and 7h), the port length changes. To me, it doesn't seem like it should, but using this calculator, it does.

Also, using that particular calculator, you can't take your port volume into account( in order to subtract it from your box volume) because you don't have a port length yet. I was assuming you would keep the net volume a constant(8.66 total AFTER speaker and port displacement), but then your box would need to be bigger(8.66 plus the volume of the port(s)).

01-17-2007, 08:29 PM
when using more than 1 port you dont just divide the length of the port into 2 separate ones, dual ports will have to be longer than a single one