Anchoring port from one end or both ends?

[noamgeller]

Anchoring port from one end or both ends?

 

[stv]

Have a look at the beautiful port supports here:
https://www.diyaudio.com/community/...ead-with-faitalpro-6hx150.316684/post-5299297
Combined with inner roundover!

 

[GM]

Ideally at one end and at some odd harmonic along its length to harmonically damp it, usually at its 3rd or 5th.

 

[profiguy]

It really drpends on the length, specifically the ratio of length to diameter of port tube. There is also concern for radial resonance deflection of the port tube on its open end inside the cab at higher mid frequencies, so its a good idea to strengthen the inner tube lip if thei wall thickness is insufficient to avoid this. If dealing with a subwoofer that only goes up to about 80 -100 Hz, its of little concern but on a big 2 or 3 way it can be an issue. I've had a situation where this was mistaken as an enclosure standing wave resonance. This was on a very large (6") diameter port and it even showed up as a small bump on the impedance plot - it was in fact the inner port tube lip itself resonating like a bell. A quick temporary fix of wrapping it with gaff tape proved it to be the culprit.

 

[noamgeller]

Damn, and I hoped there will be a straightforward answer to this one

 

[Brett]

I brace extensively, so they'll be held at the end as well as multiple other points as they pass through the bracing depending on the length of them. Unless they're really short they're held at at least 2 points.

 

[markbakk]

Equal termination is of far more importance. Bracing… what do you imagine?

 

[wesayso]

Ideally at one end and at some odd harmonic along its length to harmonically damp it, usually at its 3rd or 5th.

I can understand this solution, as supporting it at both ends would stil make it viable to oscillate (mimicking a guitar string).
How about a support in the length of the port?

Ending just shy of the end of the port and fixing it with a rubbery glue to that port?

 

[IG81]

That should be good if the tube is otherwise stiff radially. Personally, I like Ultraflex/Onken shelf-venting schemes.

 

[markbakk]

I can understand this solution, as supporting it at both ends would stil make it viable to oscillate (mimicking a guitar string).
How about a support in the length of the port?
View attachment 1058052
Ending just shy of the end of the port and fixing it with a rubbery glue to that port?

It certainly braces the bottom panel better. But what resonance mode bothers us here (I don’t bother, frankly)?