[goonstopher]

Trying to design a sub but not sure how bad bends are in the port.

Is there a certain number that is OK if they are kept at 90 degrees and dont do any 180 (double 90's)?

 

[the-jessman]

Vent performance is all about airflow. The less you restrict the airflow, the better off you are.

You want to avoid things like:
1. Sharp edges, round over your corners
2. 180 degree bend, use 90 degree bends if you can
3. Anything protruding into or otherwise obstructing the port, don't run your wires down your port either.

 

[goonstopher]

Vent performance is all about airflow. The less you restrict the airflow, the better off you are.

You want to avoid things like:
1. Sharp edges, round over your corners
2. 180 degree bend, use 90 degree bends if you can
3. Anything protruding into or otherwise obstructing the port, don't run your wires down your port either.

Yeah makes sense...

Real question is can I get away with multiple bends?

Am making a narrow cab, was hoping to use 2 vents that are about 56 inches long.
If I can get away with 3 bends this would work...
Hoped to run them as window braces almost...
Would go:
Front-Back (about 13")
Bottom - Top (about 22")
Back-Front (about 13")
down front (about 8")

 

[the-jessman]

Unfortunately there are no definite answers to what is OK and what isn't. Its not like two 90 corners is totally fine, but three will completely ruin your performance.

In my opinion three 90 degree bends is probably going to be fine. I'd do as much as possible to allow the air to flow smoothly though. This means putting as large as radius as practical on the inside corners of the port, and putting 45 degree angled pieces on the outside corners. At the ends of your port I'd put as big of a flare as practical as well. Here is an example:

Have you modeled your sub in something like WinISD to see what port velocities you are going to have? The lower your port velocities are the more complex port you can get away with.

At 56" your port is getting to be pretty long, I hope you are planning on crossing over to this sub pretty low or you could have port resonance issues.

 

[goonstopher]

Velocity is pretty low.

Peaks at 22.3 at 16hz

1st resonance 127

Dont have a router so cant round off anything

 

[Mfusick]

If the port is fat enough- it should not be a problem.

I assume you mean something like a slot port that runs down the back wall and bend 90 degrees to come out the face???

If so- something like a 4" slot port would be fine- but a 1" might not be. Port volume will play a role.

YOU WANT BIG PORTS

Port compression sucks.

 

[the-jessman]

Velocity is pretty low.

Peaks at 22.3 at 16hz

1st resonance 127

Dont have a router so cant round off anything

22 m/sec is just about my cutoff for home audio use. If you could get closer to 17 m/sec it would be better, but then your port would have to be even longer and you probably don't want to do that.

The general consensus is you want to cross over at least one octave below your first port resonance, so as long as you are crossing over around 60 hz you should be fine.

You don't need a router to round things over, its just makes it a lot easier! You can remove the bulk of the material with a rasp and then finish off with sand paper. It IS worth the effort.

 

[goonstopher]

22 m/sec is just about my cutoff for home audio use. If you could get closer to 17 m/sec it would be better, but then your port would have to be even longer and you probably don't want to do that.

The general consensus is you want to cross over at least one octave below your first port resonance, so as long as you are crossing over around 60 hz you should be fine.

You don't need a router to round things over, its just makes it a lot easier! You can remove the bulk of the material with a rasp and then finish off with sand paper. It IS worth the effort.

hmmm I just sold my router ha.

May scrap this project and buy a horn... ?Just nervous cause it has no bracing.
It was some group design over at DIYAudio

 

[rhodesj]

Yeah makes sense...



Real question is can I get away with multiple bends?



Am making a narrow cab, was hoping to use 2 vents that are about 56 inches long.

If I can get away with 3 bends this would work...

Hoped to run them as window braces almost...

Would go:

Front-Back (about 13")

Bottom - Top (about 22")

Back-Front (about 13")

down front (about 8")

This will probably work fine. Horn designs often have many more folds and even 180 degree turns.

 

[the-jessman]

hmmm I just sold my router ha.

May scrap this project and buy a horn... ?Just nervous cause it has no bracing.
It was some group design over at DIYAudio

Do you have a link to the design? I'd like to take a look.

 

[goonstopher]

Do you have a link to the design? I'd like to take a look.

Thanks - Heres the info I was provided:


http://www.hometheatershack.com/for...ts/61637-tapped-horn-tc-sounds-epic-12-a.html

Would be a local pickup but like i said... was made with no bracing

This is with the epic 12 driver

 

[the-jessman]

If that horn is the direction you would like to head I wouldn't let the lack of bracing stop you. That design shouldn't really need any bracing since all the panels are so narrow and close together.

 

[goonstopher]

Well with my goals...and lack of tools,space and ability plus my huge sub's now.

Guess I can go big and get a new huge toy and get the cap to look small and on its way out for the experiment.