Port question, fairly complex.....

[kickerlivinloud 10+ year member]

Ok I've been trying to do a lot of reading about the more technical side of audio. I was thinking about different styles of port and how they effect the output of the box.

So on to my main question. What if you had a circular port that started off small and grew into a larger diameter. Say it begins as a 3" port and ends up say a 10" port (pulling numbers out of my butt) What advantages or disadvantages would this have?? If you think about it wouldn't it make it louder?? When you helling into a cone your louder, or when you cup your hands around you mouth your voice is louder then without. Wouldn't the same apply for car audio applications???

Any informative incite would be appreciated!!

Jon

Click to read more...

 

[Blove1991 10+ year member]

Im about to make a complete dummy out of my self but heres my thoughts

If your trying to push the air from a 3" space to 10" wouldnt it still push like around a 3" port since that is all it can take it.....?

 

[kickerlivinloud 10+ year member]

Im about to make a complete dummy out of my self but heres my thoughts

If your trying to push the air from a 3" space to 10" wouldnt it still push like around a 3" port since that is all it can take it.....?

No. Like I said above, think about when you yell, if you yell into a cone which is larger at the exiting end then the original end your louder, or when you cup your hands over your mouth. Your louder when you have a "tube" that expands in area.

Its basically like a simple horn design. I don't under stand horns so obviously I don't under stand this....lol //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

Jon

 

[Immacomputer 10+ year member]

When saying you are going from 3" to 10" diameter, you're bringing in some effects from horn theory and you're heading away from the Helmholtz theory used in ported enclosures.

http://www.quarter-wave.com to learn more about horns and their theory.

 

[kickerlivinloud 10+ year member]

When saying you are going from 3" to 10" diameter, you're bringing in some effects from horn theory and you're heading away from the Helmholtz theory used in ported enclosures.
http://www.quarter-wave.com to learn more about horns and their theory.

Thanks for the link I'll deffenetly be doing a lot of reading, rereading and then reading it all again from there,lol. I'm thinking about building a box and trying this style of port though. Its really the only way to see if it'll work or not. I'm thinking to give a guess at the "tuning" I'll find the volume and compare that to regular ported enclosures as a starting point. From here I'll try shortening it, lengthening and changing its size to see how that effects the output and sound. Should be an interesting attempt at a "complex" ported enclosure. Mostlikly it'll end in failure b/c I really don't know what I'm doing.....lol

Jon

 

[spoonraker 10+ year member]

yeah just build a box and see how it sounds lol, I'm kind of curious.

Just make a whole bunch of MDF rings, start with the big one, and work you way down in diameter until you get the small one. Then just brace them somehow so they stay in position, and fiberglass your custom aero port using the rings as a guideline. That's my idea for building a box like that...do you understand what I'm saying?

 

[kickerlivinloud 10+ year member]

yeah just build a box and see how it sounds lol, I'm kind of curious.
Just make a whole bunch of MDF rings, start with the big one, and work you way down in diameter until you get the small one. Then just brace them somehow so they stay in position, and fiberglass your custom aero port using the rings as a guideline. That's my idea for building a box like that...do you understand what I'm saying?

You must of read my mind. That why my original plan! I've done a little bit of reading and have some other idea's. I won't say what they are just yet, need to do some more reading to see if there even possible. Either way this should be a very "interesting" undertaking!

Jon

 

[spoonraker 10+ year member]

More specifically, I was thinking...

make the rings, and brace them on the outside, then fiberglass inside the rings. Once you get a decent shape going, brake off the rings, and add to the outside to give it strength. Cut the ends off clean, fill the gaps and stuff with bondo, and paint it with some black lacquer paint. Then you'll have basically...a custom aero port with no mdf attached. I think it's doable, you should go for it!

 

[kickerlivinloud 10+ year member]

Bump for someone would more smarts them me!! Helo, maybe denim??? Come on guys help a brother out!

Jon

 

[Volenti 10+ year member]

The trouble with hornloading and bass is the horn length needs to be longer and longer as you go down in frequency (mouth size increases in a similar manner), bass horns start at ~8' long and get bigger from there, small 1'-2' long expanding ports are little more than flares at bass frequencies.

Here's a free horn design program you can get started with http://www.users.bigpond.com/dmcbean/

And here's a usefull wiki on loud speakers/subs including a guide to hornresp http://www.diyaudio.com/wiki/index.php?page=Loudspeaker

 

[Twistid 5,000+ posts]

sounds more like circular flared ports

except being rectangular , its going to be circular... why not try your hand at flared ports instead?

 

[helotaxi 5,000+ posts]

There are equations out there to figure out the tuning, but I don't have them handy, I don't think. It won't work the way you seem to think though. My best guess, and it is only a guess, is that it will act like a port of the smallest diameter and of a longer length than the total length that you have. You will have high port velocity at the small end and the port velocity will decrease as you move toward the mouth. Problem is, if it is a straight cone taper, you will end up with a ton of port noise from the small end that will just carry down and out the mouth. You want a circular or hyperbolic profile on the flare.

 

[Decipha 10+ year member]

a simplistic way to figure out the tuning which won't be at all accurate but around tuning would be to start at the middle of the port diameter and determine the length of the port for that... example

you have a port thats 3" diameter at the mouth and 10" diameter at the end... take the mid-way measurement 6.5" and determine the port length for that... would be 'about' tuning.. and a good starting point

 

[djman37 5,000+ posts]

Ok I've been trying to do a lot of reading about the more technical side of audio. I was thinking about different styles of port and how they effect the output of the box.
So on to my main question. What if you had a circular port that started off small and grew into a larger diameter. Say it begins as a 3" port and ends up say a 10" port (pulling numbers out of my butt) What advantages or disadvantages would this have?? If you think about it wouldn't it make it louder?? When you helling into a cone your louder, or when you cup your hands around you mouth your voice is louder then without. Wouldn't the same apply for car audio applications???

Any informative incite would be appreciated!!

Jon

look at the wicked one on http://www.decware.com (you can access the plans) the dimensions are what is important when flaring ports.

 

[helotaxi 5,000+ posts]

a simplistic way to figure out the tuning which won't be at all accurate but around tuning would be to start at the middle of the port diameter and determine the length of the port for that... example
you have a port thats 3" diameter at the mouth and 10" diameter at the end... take the mid-way measurement 6.5" and determine the port length for that... would be 'about' tuning.. and a good starting point

That doesn't work because tuning freq vs port area is an exponential function.