Do I have enough port?

[OB/GYN Kenobi]

First off im pretty new to car audio, well at least recently. I haven't had a system for over ten years, and back then it was all sealed boxes and if you had more than a more than 1000 watts it was a big system. (At least around here lol) So anyway i got a new ride in Oct and ever since ive been planning out a system for it. Ive been doing my homework going through 100's of builds on diffrent sites and trying to educate myself the best i could before starting my build. I finally decided on running 3 15" DC Audio Level 4's with possibly the level 5 upgrade. Amp would be a DC 3.5k. So i started the box. Internal Volume is 9.75 cubic feet after displacement, and tuned to 28hz, using two 6" Aeroports, flared at both ends. DC site calls for 3.25 cubic feet per sub. Got them from parts-express in case your wondering.

But now upon reading more im worried, and confused on how much port i need. If I add another aero port i will lose box volume, because i cant go any higher do to trying to stay under the window line. I can add power and step up to a DC 5.0k which is what i wanted to do later on anyway, just means it will take a bit longer for funds. Any help is appreciated guys.

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[Kangaroux 5,000+ posts]

I would add a third 6" port and raise your tuning up to 31-32hz. From personal experience, if you want to tune to anything below 30hz, you should be looking into a bandpass instead (I recently made the switch and the lows are so much better)

 

[OB/GYN Kenobi]

Well i was thinking of a bandpass but not till the rebuild lol. This is going in an 05 escalade esv. Its the suburban of cadillacs, and for this first build im building behind the d pillar, wifes decsion. I guess im just cofused on the math. People say 12-16sq " per ^3, i guess im not sure how thats calculated. Like i said i have two 6" flared aero ports, 17" long not counting flares, which according to the pnp calculater would tune me at 28 hz. Which is where i wanted to start at, as i could to my understanding always trim my port length to raise my tuning. I guess i just dont understand how my port area is calculated or how much i really have

 

[RangerDangerV2 5,000+ posts]

do four dc level fours in a fourth order on 7k.... I sat in a blazer that has that same system and he plays 155 flat from 26-53 hz.

 

[Buck 5,000+ posts]

You need more than 2 6" aeros. I would personally go with slot in your situation.

 

[DukeNut 10+ year member]

Well i was thinking of a bandpass but not till the rebuild lol. This is going in an 05 escalade esv. Its the suburban of cadillacs, and for this first build im building behind the d pillar, wifes decsion. I guess im just cofused on the math. People say 12-16sq " per ^3, i guess im not sure how thats calculated. Like i said i have two 6" flared aero ports, 17" long not counting flares, which according to the pnp calculater would tune me at 28 hz. Which is where i wanted to start at, as i could to my understanding always trim my port length to raise my tuning. I guess i just dont understand how my port area is calculated or how much i really have

port volume formula is

radius^2 (squared) * pi (3.14) * length

so 3^2*3.14*17 = 9*3.14*17 = 480.42 * 2(ports) = 960.84 cubic inches / 1728 (12"*12"*12" #inches in cubic ft) = .556 ft^3