Disappointed- went from sealed to ported (Tempest) (1 Viewer)

[Patrick Sun]

Damn you, Cam, damn you and your double-speak!

 

[Greg Monfort]

>just a 6" pipe has twice the volume of 2-3" of same length.
====
What's the relevance? I mean for a given alignment, a 6" diameter pipe requires 4x the Vb of (2) 3" diameter vents.

GM

 

[Kyle Richardson]

Thats my favorite party trick! Its even better if it gets sucked back in while in mid air too

 

[Cam McFarland]

I was only questioning his use of a 6" port on a box
smaller than the one Adire says you need 2 - 3" ports for.

Or...are you just kidding & saying the EXACT same thing myself & Patrick said in triple-speak....lol

 

[Patrick Sun]

The wider the port, the less compression/chuffing noise will eminent from the port. Using multiple ports doesn't always equate to same performance as the equivalent single port under stressful condition.

 

[Cam McFarland]

Thanks Patrick......

 

[KyleGS]

I didn't adjust the phase when I moved the ported cabinet in. I'll try that and see how it sounds. I don't know why I didn't think to try that.

I don't know if I can fit an elbow in the box. The bracing is very close to the port and doesn't leave much room for anything.

Thanks for the ideas.. keep 'em coming and I'll let you know my progress.

 

[Cam McFarland]

You could always extend the port "outside" of the box if you ran out of room inside.




Hey.....you are the one that told us to keeep the ideas coming.....

 

[Paul Spencer]

I find that multiple ports are more difficult to fit in a box. I have made up a spreadsheet on excel based on the forumulas on diysubwoofers.org, and it is helpful to see the impact of changes in diameter, number of ports, box size etc.

Here's an example:
100L box
20 Hz tuning

4" vent >>> 520mm long, 4.1L volume
2 x 2.8" vent >>> 540mm long, 4.2L volume
note: the area is the same, the volume and length of the smaller vents is slightly more.

What is annoying is that in practical terms they take up more space, require more effort to build, add complicaton, and probably don't perform quite as well at the extremes of operation regarding turbulence.

My spreadsheet can be downloaded here:

Sub design spreadsheet

It includes quick vent design, and also does a few other handy calculations to compare drivers etc.

 

[Greg Monfort]

>Or...are you just kidding & saying the EXACT same thing myself & Patrick said in triple-speak....lol
====
No, I'm way too simple-minded to be witty. I just didn't understand what point you were trying to make.
====
>What is annoying is that in practical terms they take up more space, require more effort to build, add complicaton, and probably don't perform quite as well at the extremes of operation regarding turbulence.
====
Correct, the most efficient vent is a single round one. Using multiple smaller diameter vents and/or other than round has the benefit of flexibility in placement and adds acoustic resistance. I assume this is why Adire spec'd them.

GM

 

[Brian Bunge]

Good lord, Patrick Sun and GM posting in the same thread, on the same day when we haven't seen or heard from either of them in months?

Howdy guys! Great to see you both around here again! I miss the ol' timers sometimes!

 

[Patrick Sun]

I'm here everyday...

 

[Justin Ward]

Here's another theory. Perhaps the presence of deeper bass is creating the "slower" impression you are getting. Perhaps similar to the way an 8" woofer cna sound "faster" merely because it is not attempying deeper bass?