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Porting a Sub Box
- Thread starter Leivon
- Start date
isaac
The Isaac
- Joined
- Nov 13, 2002
- Location
- Hurricane River Street, FL
I'm with Jack on this one. Porting a box will make it sound a little louder at the tuned frequencies, but otherwise the SQ sucks compared to a sealed one. You get better cone control with the sealed one too, which makes the bass tighter, more responsive, and can increase the subs' wattage capacity due to the air suspension effect that the sealed box causes.
- Joined
- Nov 12, 2002
Ya, mine is ported, sounds rather good. Its a big box with a pretty decent sized port. Bumps nice and loud.
Ussualy I do prefer sealed boxes... justin wanted to do it ported.
Ussualy I do prefer sealed boxes... justin wanted to do it ported.
Doug, does your trunk rattle like crazy? Especially the gas door on the side of the car? Mine did so I had to stuff towels in between the trunk hing and the walls. It was hella ghetto, but it worked. If you have any rattle, I recommend using a towel if possible, otherwise there's this stuff called brownbread which is like Dynomat, but is better for CA cuz the hotter it gets, the better it outperformes Dynomat. So in the summer it will still sound good.
Jack
Jack
DEM80240WGN
Member
- Joined
- Mar 25, 2003
- Location
- Whitby, Ontario
my gas door rattled too. i put a tighter spring and a thin layer of foam between. never had a problem since.
davidmacq
Bored Member
- Joined
- Feb 17, 2003
- Location
- Clarksville, TN
O.K. I used to read all sorts of audio stuff back in HS.
The deal with ported installs is that they are very easy to get wrong. Pipe size and length is very dependent on the Sub. You calculate using the Thiele-Small parameters which you get from the manufacturer.
A port has a resonant frequency based on the length and size, below this frequency the woofer is unsupported. You will get a boost in sound level at the frequency of the tube, but due to the woofer being upsupported...undamped, it will not sound as tight or have the sound quality as the others mentioned.
A basic sealed box sounds much better, but will take more power and a larger box and may sound muffled.
There are some tricks around this. Stuffing the box with pillow stuffing will make it act like a larger box.
Another bigger secret is something called an aperiodic membrane. This is the simplicity you are looking for with porting. If you want to have a ported install get a professional to calculate the lengths and size of your box for you. Ported is very hard to get right, and doesn't sound great anyway. Sealed is very hard to get wrong.
Aperiodic has the best of both worlds and sounds great. You can have a large or small box, doesn't really matter. You can also install a door speaker in a small location and make it work.
How it works is this, you create an opening for airflow, and stuff it pillow stuffing. You can buy pillow stuffing at walmart. What you are wanting to do is tune the speaker with the stuffing. You want to put enough stuffing so that the speaker doesn't sound like a box with a hole cut in it, like a poor ported design. You want to keep adding stuffing until.
I could see this box shown in this thread sounding very good, by removing one of the small end caps. The one that looks like 12 x 24. Stuff the whole box tightly with stuffing and remove add to taste. Might need to add something to the end so the stuffing isn't blown out.
Btw, I'm not really buying that that box is too shallow too promote standing waves and good bass. A speaker box design requires a certain volume of air. Standing waves inside the box are bad. They bounce off the back wall and come back and hit the woofer, not good really. Stuffing the box with 1.5 or so pounds per square foot can lead the woofer to see a 20 percent or so increase in apparent box size. The stuffing slows down the air movements and the friction heats up the air. The amount the waves are slowed down is what leads to the apparent increase in box size.
Perfect box design is the 'golden square' dimensions. Unless you are doing a 1/4 wave horn standing waves in a sealed enclosure just aren't something that helps, and box design seeks to minimize them.
Expert installers will say install a small speaker in your kick panel, with custom fiberglass enclosure, and create a small channel for air to escape. This alone is very bad, and what an amatuer might try to free up the muffled sound. Add stuffing and tune it by adding removing to taste and you have super high end install
secret.
refs
CarAudioForum.com - What is an "aperiodic membrane?"
http://www.caraudioforum.com/vbb3/showthread.php?t=97326
talks about traditional trunk setup, only hinting at the many applications
http://www.maximacar.com/aperiodic.htm
Good article with pics
http://www.mmxpress.com/technical/apmats.htm
The deal with ported installs is that they are very easy to get wrong. Pipe size and length is very dependent on the Sub. You calculate using the Thiele-Small parameters which you get from the manufacturer.
A port has a resonant frequency based on the length and size, below this frequency the woofer is unsupported. You will get a boost in sound level at the frequency of the tube, but due to the woofer being upsupported...undamped, it will not sound as tight or have the sound quality as the others mentioned.
A basic sealed box sounds much better, but will take more power and a larger box and may sound muffled.
There are some tricks around this. Stuffing the box with pillow stuffing will make it act like a larger box.
Another bigger secret is something called an aperiodic membrane. This is the simplicity you are looking for with porting. If you want to have a ported install get a professional to calculate the lengths and size of your box for you. Ported is very hard to get right, and doesn't sound great anyway. Sealed is very hard to get wrong.
Aperiodic has the best of both worlds and sounds great. You can have a large or small box, doesn't really matter. You can also install a door speaker in a small location and make it work.
How it works is this, you create an opening for airflow, and stuff it pillow stuffing. You can buy pillow stuffing at walmart. What you are wanting to do is tune the speaker with the stuffing. You want to put enough stuffing so that the speaker doesn't sound like a box with a hole cut in it, like a poor ported design. You want to keep adding stuffing until.
I could see this box shown in this thread sounding very good, by removing one of the small end caps. The one that looks like 12 x 24. Stuff the whole box tightly with stuffing and remove add to taste. Might need to add something to the end so the stuffing isn't blown out.
Btw, I'm not really buying that that box is too shallow too promote standing waves and good bass. A speaker box design requires a certain volume of air. Standing waves inside the box are bad. They bounce off the back wall and come back and hit the woofer, not good really. Stuffing the box with 1.5 or so pounds per square foot can lead the woofer to see a 20 percent or so increase in apparent box size. The stuffing slows down the air movements and the friction heats up the air. The amount the waves are slowed down is what leads to the apparent increase in box size.
Perfect box design is the 'golden square' dimensions. Unless you are doing a 1/4 wave horn standing waves in a sealed enclosure just aren't something that helps, and box design seeks to minimize them.
Expert installers will say install a small speaker in your kick panel, with custom fiberglass enclosure, and create a small channel for air to escape. This alone is very bad, and what an amatuer might try to free up the muffled sound. Add stuffing and tune it by adding removing to taste and you have super high end install
secret.
refs
CarAudioForum.com - What is an "aperiodic membrane?"
http://www.caraudioforum.com/vbb3/showthread.php?t=97326
talks about traditional trunk setup, only hinting at the many applications
http://www.maximacar.com/aperiodic.htm
Good article with pics
http://www.mmxpress.com/technical/apmats.htm