how long need a port be away from sidewalls?

[hugo stiglitz]

hi there,

I am about to finished my first DIY speakers. ATC SCM100 clones.
Now I am thinking about the bassreflex tube.
I am using an elbow piece and its a tricky to let the tube go 90 degrees up.
Since there is not enough space I have to either let the elbow go to the right or left. Now I was wondering what the distance between a sidewall and the inner port should be minimum?
Any suggestions?

Lenght ca. 14cm
Diameter 10cm

 

[Qts]

I have told many times the diameter of the port. I would say it could be even little closer. If you have calculated length with some software, in real life pipe would be shorter. Something like 70-80% of calculated.

 

[moray james]

I have read, though it was year ago so I have forgotten where that the air in a reflex vent will at full resonance moves 1.5 times the vent length both in and out of the vent. well worth remembering when designing a build/ The top panel of a cabinet is probably the very best pace to mount a reflex vent so long as you don't have little kids or wives with knick nacks or plants.

 

[hugo stiglitz]

so you say 1.5 times the length of the port should be the minimum distance between port and any wall?

 

[chris661]

I have read, though it was year ago so I have forgotten where that the air in a reflex vent will at full resonance moves 1.5 times the vent length both in and out of the vent. well worth remembering when designing a build/ The top panel of a cabinet is probably the very best pace to mount a reflex vent so long as you don't have little kids or wives with knick nacks or plants.

That depends entirely on the SPL being produced.

Chris

 

[Jerms]

hi there,

I am about to finished my first DIY speakers. ATC SCM100 clones.
Now I am thinking about the bassreflex tube.
I am using an elbow piece and its a tricky to let the tube go 90 degrees up.
Since there is not enough space I have to either let the elbow go to the right or left. Now I was wondering what the distance between a sidewall and the inner port should be minimum?
Any suggestions?

Lenght ca. 14cm
Diameter 10cm

Have looked online for images of ATC SCM100s. The port is offet as are the mid and tweeter. I assume their port angles towards the middle of the enclosure. Assuming a built baffle with port hole made...

It is what it is. do the best job you can to find free space in the enclosure for the end of the port away from the walls.

Depending on anticipated SPL, you might want to experiment with a smaller diameter port. Small diameter = smaller length and more room to play with.

J.

 

[Pano]

Darn, I used to know this. You can put it against the side wall, but it will change the length needed. But I can not remember by how much or even which direction. Someone here ought to know.

 

[Qts]

14 cm elbow tube? Why not straight one?

 

[mark100]

I know this is a pain to do, but I find that port tuning nuances matter enough, that building a throw away prototype box for trial and error tuning (around modeled design) is the only way to really dial in a port.
Sure, we can get lucky sometimes, with modeling working exactly.....but being able to tinker and measure rules IME. Plus, you get to try anything...

I can't specifically answer OP's question, other than to say I measure a port lengthening effect when running close to, and parallel with wall. And a can't predict effect pointing into a wall...although usually lengthen.

 

[hugo stiglitz]

14 cm elbow tube? Why not straight one?

for reasons

 

[Jerms]

This?
Calculating Subwoofer Port Length - Not So Simple - AVS Forum | Home Theater Discussions And Reviews

For a round port coming somewhat close to a boundary or two? Try to keep it a radius away from the sides of the enclosure IMO. Also build it that the port may be trimmed back if measurements determine it is too long (most likely case).

 

[hugo stiglitz]

Today I've worked on the damping and installed 8cm pyramid basotect in the cabinet. Behind that you'll find bitumen sheets.
In the upper compartment I will still install some polyster wool or the like.
The lower compartment won't show that, since it will have a BR-tube (see cut-out)

Do you think what I did is viable?

 

[hugo stiglitz]

no thoughts?

 

[Brett]

If they're dimensional clones as well, put the port on the bottom as they'll need to be raised to get the tweet at ear height.

 

[hugo stiglitz]

of course the port is at the bottom. did I say anything else?

 

[Brett]

^^ Have it exit on the bottom panel, not at the bottom of the baffle. Then you won't need to bend it either. It will also make tuning easier, if you use round tubes, as you can attach them temporarily, measure and adjust the length to get it right.

 

[Jerms]

of course the port is at the bottom. did I say anything else?

Have the port tube exit the main enclosure from the bottom face. It can then bend forwards if you like. The speakers need a small stand. Make the stand integral to the speakers with the port exit integrated to the stand?

J.

 

[hugo stiglitz]

I won't integrate the port exit on the bottom of the speaker.. everything is already built.
I only need to glue the tube to the cut out hole on the baffle.