View Full Version : I know... Asked too many times - regarding PORT

12-23-2002, 08:19 PM
I have 2 Alpine type-r's dual 4ohm.... in the next week i will be building a ported box for them. I called alpine to get some help with the tuning frequency and so on. They told me that for each sub the "Internal" volume should be 1.25 with a port 4 inches in diameter and 14 inches long. This will tune it at around 35hertz. With all these box building programs, I have not been able to figure out how this tuning frequency thing works.
So here is my question.... With both subs in one common chamber if the box is about 2.5cf... if i want to use only 1 port, what would be the dimensions for the port?
For this question to be answered, i think i left out to many variables, so just ask me what you need (number wise)

I really appreciate the help:)

Randy Savage
12-23-2002, 10:17 PM
I got a port of 4"x8.13" for a box with an internal vol of 2.5 cu ft tuned to 35 Hz, but my #'s might be wrong, somone back me up here.

12-24-2002, 07:57 PM
first off Merry Christmas.... if you celebrate it of course.... if not happy holidays.

These are the exact dimensions of the box I worked out. it's a wedge design, so the bottom will be 16inches deep, the top is 10 inches. Height is 15inches and the length is 33 inches. Taking into account the the 3/4inch mdf, after doing the measurments the box will be 3.05cf. the volume of each sub 0.23cf

per sub, the port requierment 4" diameter and 14 inches in length. making it i think .10cubic feet per port

If I want to go this way, I will need to put a partition in the middle to seperate the two chambers (why else);)

What I want to do is make one box containing 2 subs and 1 port.

My amp unfortunately does not have a subsonic filter. "it's a USA 400X" for the subs

After doing all measurment, without the partition, including the ports and the subs, the total cubic feet will be 2.4... something along those lines.

So here is my question.... what size port should I use if I want to tune to about 35htz. I would like to use i port for both sub in one box. The type of music i listen to is mainly house music, some trance..... but mostly house music.

Thanks for the help,

Any more info neaded let me know

12-24-2002, 09:25 PM
before I go on, I don't want you to go out of your way for this... I appreciate the replies thus far.
The subs are 12 inches. Although a simple cube design box would simplify things, I would prefer the wedge design given the dimensions of my trunk. I know the wedge along with the slot type port will make construction more difficult, but I would prefer to do it right the first time.

Going with the wedge design would save whatever room I have left in my trunk.

Thanks again

ohh yeah, regarding the tuning frequency, i'll take your word for whatever you recommend, going through various threads, I have learned to trust your judgment ;)

12-24-2002, 10:24 PM
wow... that was quick.... I really appreciate the help. I will get to the drawing board right away. I'm pretty what the answer is, but just incase I will ask it anyways. Did you take into consideration the volume of the subs etc.... I'm sue you did, but it doesn't hurt to ask.

Thank you very much for your help..... you just resolved an issue that has taken me weeks to figure out in a matter of an hour.

Thanks again

12-25-2002, 10:25 AM
great thank you very much! much abliged:D