Port walls?

[sub-FATHER 10+ year member]

To an extent... There's a point of diminishing returns where you can keep adding tons of port length and the tuning only goes down a very miniscule amount. This is because of the volume inside the box that the port takes up. As the port gets longer, the tuning lowers but internal volume is also taken up which tries to raise the tuning and at a certain point they will almost offset eachother.

thats why you calculate how much air space the port will actually take up

and find out how much enclosure you still have left when you have limitations on airspace.

i have mine tuned to 27hz and the port is 38 inches long.

but yeah if you dont have the room to add port lenght then your stuck

 

[PV Audio 5,000+ posts]

the longer the port the deeper the bass.

This idiot strikes again. Stop giving advice because this is not necessarily true.

 

[PV Audio 5,000+ posts]

it lowers the frequency, and the lower the frequency the more power it takes to produce the same spl of a higher frequency with the same amount of power. but if its your daily driver make your port length longer

//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif Where the flying **** do you get your information from? This isn't true at all.

 

[sub-FATHER 10+ year member]

This idiot strikes again. Stop giving advice because this is not necessarily true.

is too is too. come on bud, quit. if my port is 17.5 *10 and 20 inches long. and my enclosure is 15 cubes total. if i add 18 inches length to my port i will lower my frequency.

prove me wrong!//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[DNick454 10+ year member]

you better research that somemore, your giving wrong information on that one bud. you cant just cut the port from 4" to 2" and expect the length to stay the same especially when your cutting the airspace of the enclosure in 1/2 when you calcuate that one.

Dude, this is why you're getting bashed so much man. Before you scrambled to your keyboard in an attempt to prove me wrong, you should've thoroughly read my post. You're misinterpreting what I wrote.

First off, I'm not just cutting the port width in half. I'm explaining to him that having TWO ports as opposed to one would require the other one to be half of the cross-sectional port area, but the same length.

50sq in of port area that is 30 long is the same as TWO ports with 25 sq in of port area that are 30 inches long (roughly, keep in mind... there are a few quirks with multiple ports that don't make it EXACTLY equal, which I explained)

And where did you get the idea that the airspace is cut in half? It's a common chamber //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

4 cubic feet net with 1 port that is 4" wide, 12" tall, and 30" long is roughly the same as 4 cubic feet net with 2 ports that are 2" wide, 12" tall, and 30" long.

 

[DNick454 10+ year member]

is too is too. come on bud, quit. if my port is 17.5 *10 and 20 inches long. and my enclosure is 15 cubes total. if i add 18 inches length to my port i will lower my frequency.
prove me wrong!//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

Until the port becomes so long that it occupies such a large amount of internal space that you only have 10 cubes total. Happy?//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[PV Audio 5,000+ posts]

Please, sub2weeker, just please stop giving advice because this guy clearly isn't very experienced and everything you are saying is simply NOT true. I could post 15 exceptions to each thing that you've said. It's realistically false and theoretically false to say that a lower port somehow means deeper bass because that is entirely driver dependent and it is 100% false that somehow the lower the frequency, the less power it takes to produce that frequency. I don't know what book you read that in but it must have had pictures and a coloring area because that is not true by any laws of mathematics or physics.

 

[sub-FATHER 10+ year member]

Dude, this is why you're getting bashed so much man. Before you scrambled to your keyboard in an attempt to prove me wrong, you should've thoroughly read my post. You're misinterpreting what I wrote.
First off, I'm not just cutting the port width in half. I'm explaining to him that having TWO ports as opposed to one would require the other one to be half of the cross-sectional port area, but the same length.

50sq in of port area that is 30 long is the same as TWO ports with 25 sq in of port area that are 30 inches long (roughly, keep in mind... there are a few quirks with multiple ports that don't make it EXACTLY equal, which I explained)

And where did you get the idea that the airspace is cut in half? It's a common chamber //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

4 cubic feet net with 1 port that is 4" wide, 12" tall, and 30" long is roughly the same as 4 cubic feet net with 2 ports that are 2" wide, 12" tall, and 30" long.

this guy wants seperate chambers

 

[PV Audio 5,000+ posts]

is too is too. come on bud, quit. if my port is 17.5 *10 and 20 inches long. and my enclosure is 15 cubes total. if i add 18 inches length to my port i will lower my frequency.
prove me wrong!//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

If your subwoofer has a bandwidth that has a 3db rolloff point above your tuning frequency, tuning lower offers no benefit whatsoever and can in fact cause your speaker to become undamped at its resonant frequency. If you do not model the enclosure specifically around the speaker, adding port length can yield worse output, or even worse, an undamped environment resulting mechanical damage to the speaker.

 

[sub-FATHER 10+ year member]

Please, sub2weeker, just please stop giving advice because this guy clearly isn't very experienced and everything you are saying is simply NOT true. I could post 15 exceptions to each thing that you've said. It's realistically false and theoretically false to say that a lower port somehow means deeper bass because that is entirely driver dependent and it is 100% false that somehow the lower the frequency, the less power it takes to produce that frequency. I don't know what book you read that in but it must have had pictures and a coloring area because that is not true by any laws of mathematics or physics.

i said it takes more power to produce the same spl at say... 27hz

as opposed to that same power with a box tuned to 45hz

 

[sub-FATHER 10+ year member]

If your subwoofer has a bandwidth that has a 3db rolloff point above your tuning frequency, tuning lower offers no benefit whatsoever and can in fact cause your speaker to become undamped at its resonant frequency. If you do not model the enclosure specifically around the speaker, adding port length can yield worse output, or even worse, an undamped environment resulting mechanical damage to the speaker.

prove that a longer port on my dimensions does not lower the frequency.

my van is tuned to 27 hz and it does play it and everything above

when a box is tuned higher and trys playing the low end that is where your gonna get more damage to your subs.

this is where your ability to crossover everything comes in and plays a part.

 

[sub-FATHER 10+ year member]

as for the only thing i agree on is the single port with internal bracing, unless you are going for the stereo effect. (left and right) from double bass

 

[PV Audio 5,000+ posts]

i said it takes more power to produce the same spl at say... 27hz
as opposed to that same power with a box tuned to 45hz

That is entirely dependent on the enclosure and the speaker. The subwoofer I have in my apartment is tuned to 19hz. It has more output below 30hz than it does above 40 due to the way the enclosure controls the cone's motion. If your speaker is not designed to play in a higher frequency range and if your enclosure is optimized to have maximum output in the lower octaves, then your fact falls on its face. Again, please stop posting vague rules of thumb as facts because there are so many exceptions to the rule to every one of them.

 

[sub-FATHER 10+ year member]

So what would you suggest to get a lower tuning? I believe 38 is too high? Am I correct in thinking this? My goal was about 34 hz. This is a daily driver that I would just like to hit the lows.. I am not aiming for any numbers or competing in any way.

so according to this question you want to tune lower, and am asking how correct?

add length to your port,

thats it thats all....

 

[PV Audio 5,000+ posts]

prove that a longer port on my dimensions does not lower the frequency.
my van is tuned to 27 hz and it does play it and everything above

when a box is tuned higher and trys playing the low end that is where your gonna get more damage to your subs.

this is where your ability to crossover everything comes in and plays a part.

You said a longer port creates deeper bass. Not true. The tuning frequency may be lower, yes, but unless the speaker is supposed to be in that environment, that's about as useful as having the keys to a Ferrari being hung on the top of your chimney: even though it might be there, you'll never be able to use it and could end up damaging something along the way.