no problem

 

So are you dead set on doing the Type E? The reason I ask is because Type E and ports don't seem to like each other... pretty far from a flat response.

But if you're gonna do it 2 cu ft tuned to 20hz gave a very similar curve to the sealed box but with a nice gain. FYI you'll have a definate hump in your frequency responce from about 40-80hz which will make some music sound unbalanced but hey if you listen to rap that's where most of the bass happens anyway. It just depends on what your after...

BTW that's 2 cu ft after speaker and port displacement. And a 4" diameter port must be 39.23" long to be tuned to 20hz in a 2 cu ft box. So you're port will displace .277 cu ft and your sub will displace .086 so make your internal dimensions for a gross volume of 2.4 cu ft

 

why would you ever want to port a sealed box?you may have tp much flo ande your subs underlow bass will sound like shit and popping,i mean and in a big airspace like a Suv a sealed is better and give you that hit in the chestBass everyone wants

 

so i should just stick with the sealed type E 's? I just really wanted to go ported because i was gonna spend all this money on a amp and i wanted to get the most sound out of my shit. I guess ill jus build one huge sealed box for 4 12's and go with that

 

if you want to build a ported box, build a ported box, dont just cut a hole in a selaed box.. tun on the subsonic filter and lets have fun

ported is awesome in a big suv, since you have the ROOM to make a 3 or 4 cube box without a problem

 

If you are gonna continue to be into car audio... it would be wise to get to learn WinISD, also read about T/S parameters. Jesse gave me this link...

http://www.welcometotheden.8k.com/ca...parameters.pdf



To elaborate on what was said earlier in teh thread by MDIFYTD...
Since the Type-E don't give a flat responce and don't seem to be ported well, you will probably have to tune to a low frequency. The lower frequency you tune the ported box to, the longer the port length have to be since lower frequences have a LONGER wavelength. Making room for that long port requires a much bigger box.

You also have to take into account "port noise" from the air pumping in and out. Speakers with more volume displacement (Cone area x Xmax) require wider ports... and the wider the port the LONGER it must be. So you want the minimium port diamter so decrease the port length. Here is a quote taken from one of Adire Audio's webpage HERE.

For a Helmholtz resonator to work requires two reactive acoustical elements: an acoustical compliance, supplied by the volume of air in the box; and an acoustical mass, supplied by the port. As you may know, the acoustical mass in the port is directly proportional to the length of the port and inversely proportional to the square of the port's diameter. This is why when you increase the diameter of the port, you must increase its length to maintain the same acoustical mass.

But to behave as an acoustical mass, the air in the port must essentially he moving as one. Implicit in this is the requirement, then, that all port dimensions must be substantially smaller than a wavelength of sound. As one of the dimensions starts to approach a wavelength, the port no longer acts as an acoustical mass, but begins to exhibit the behavior of an organ pipe or even a transmission line. Not all the air is moving in the same direction, and the port no longer behaves as a single mass.

So, clearly, we have a set of limits imposed by the requirements that the port act as a single lumped acoustical element. The diameter must be small enough so that it is a tiny fraction of a wavelength in the region of the Helmholtz resonance. At the same time, port length resulting from the diameter must also be a tiny fraction of the wavelength at these same frequencies. Using an arbitrary notion of "tiny" as less than 1/10 of a wavelength, this would suggest that the largest dimension of a port operating at 50Hz (wavelength is 20') would be a 2'.

I would, personally, adopt an even more conservative figure, such as 1/15 or 1/20 the wavelength, suggesting that a port tuned to 50Hz should not exceed about 16" in length. This is because the port is not just acting at 50Hz, but over a substantial range of frequencies above and below this. Imagine, also, that a 2' long port will exhibit its first standing-wave resonance at the low frequency of only 250Hz, where the output of the port increases substantially.


What a Helmholtz resonator is...

 

First of all IM BUILDING A WHOLE NEW BOX. Im not using existing sealed boxes. I want to put 4 12" Subs in my car but im going to make 2 different boxes. I was thinking of making each box 4 cu/ft before all the displacement. Tune it to 20 Hz using a 2" Diameter port. In order to get 20hz it would need to b 5.29 inches long. Now how much louder would this box get over a sealed box, all i listen to is rap. BTW thank you So much everyone for all the help. I have had SOOO much trouble with all this ported box stuff thats why i always made sealed but thank you everyone for the help. I also didnt know if u used a smaller diameter port that it would require a less amount of tube to get the hertz as comparded to a larger sized port.

 

Also another option for me might be getting two of the brand new 12" Polk MoMo subs and port them ( http://www.polkaudio.com/car/specs.php?name=mm2124 ) . I would make each chamber 1.5 b4 displacment and port to 30 Hz? And run them off the 600 watt xtant amp or should i get the 1000 Watt MTX like i was going to? I mean if the alpine type E's wont sound good id rather get these Mo Mo's and port 2 if they would slam even more. Again i wanna thank you guys so much for puttin up with my newbieness

 

"You also have to take into account "port noise" from the air pumping in and out. Speakers with more volume displacement (Cone area x Xmax) require wider ports... and the wider the port the LONGER it must be. So you want the minimium port diamter so decrease the port length."

So if the Xmax is a larger number i need to make the ports wider? Cant i jus use 2" ports the whole time or i have to make it larger

 

Im at school, so I cant runthe specs thru WINISD, but why not like type R's or somethign ofthe like..i know youre stickign with CC stuff..