changing from sealed to ported in a fiberglass box

[harlemn8ive]

Whats going on everyone? Well i have sticky situation. I a noob looking for some help the issue is since i have joined this page i have done lots of research and been making boxes for friends and what not. the issue is i wanted to try at making a ported enclosure which i did. It came out good... too good this one 12 JL 12w3 sounded good it was tuned at 33 hz. so good i had to question my fiberglass box ( also a first) i made about a year ago. The problem is the box holds 3 infinity kappa 120.1 se. Aftter taking it out i measured it again. it is grossly over sized at about 5.3125 ft^3 So I am sure this attributes to the over all sound when it is suggested to have the enclosure at 1 ft^3. the good news is it is roughly 1.75 ft^3 per sub which is ideal for the sub, My question is if adding an aerial port to this box is feasible i checked it out using torres calculator and it says a 4 inch port 6 inches long would be tuned at 32.28 hz. Or should i just scrap the box? If i should keep it would creating the port be best on the fiberglass or the wood frame(back/ bottom) Any help would be highly appreciated also what would the easiest way to go about doing so?

[timc31610]

You could add a port, but it would need to be external so you don't lose any air space. Also that one 4" port may not be enough port volume for 3 of those subs.

[harlemn8ive]

Would there be a different method of calculating the necessary port volume?

[timc31610]

I think you may be confusing port volume with port tuning. In a box that size a 4" x 6"L port may give you a 32hz tune but the 4" opening isn't enough area so you would end up with port noise and possibly stifling your subs performance. As far as proper port area calculation, I have no clue...lol. I am still learning. I know that when I built my box for a single 12 I initially looked at a 4" aeroport and was told it would be too small. I know my sub has higher power handling and higher xmax than the infinities but I am certain that three of those will need more port area.

[harlemn8ive]

Thanks for the input. I guess i need to do some digging. I found it odd that one 12 had a 2 x 16 port that was about 20 inches long yet this box only need one aero port a few inches long. As far as internal volume i have some volume to play with so i wanna build an internal port. Once again thanx ありがとうございます

[bbeljefe]

Porting a sealed box takes a little time to calculate but it can be done. I usually take the volume that a 12" port would displace and subtract it from the net I already have. Then calculate the port length I will need for a given tuning at that volume. If the port needs to be larger than what I've figured, I subtract that from the net and start over. After a few calculations you can land up on an accurate port length for the tuning you desire. And if you plan to use areo ports, use two 4".

[harlemn8ive]

Lots more research to do i suppose. Thanks for the input