speaker port tube trade-offs

[taj]

What are the trade-offs if one was to use more smaller ports instead of one larger one.

For example: (sizes approximate as examples only).

One 4-inch port x 8-inches long
or
Four 2-inch ports x 9-inches long

Both would tune the system similarly, but would one system present less chuffing, less audible tube resonating, etc., etc?

Thanks!

..Todd

[badman]

Use the four, flare the termination inside and out, this may require some figuring for the inner piece. I'd use wood and a large roundover or bevel for a flare. This reduces turbulence and adds slightly to the effective length (take half the depth of the flare and add it to the pipe length for "actual" length).

You should also distribute the lengths of the port tubes. So long as the total length remains 36" you're good- keep the shortest at least a few inches though, and don't go "crazy" long with the longest.

[taj]

Well, thanks for the construction advice Badman, but this isn't a real project; just a curiosity about the differences (the physics involved), so I can make intelligent decisions going forward.

I don't have a good grasp of the Helmoltz physics, so I've always wondered about that question... Does one work better than the other, and if so, in what regard, and why?

Now I'm curious about using different lengths like you mentioned. Intuitively, I would have expected that to (try to) tune the box to multiple frequencies, causing all sorts of weird interactions and phase cancellations, not act as a single tuning. I guess I don't completely understand the concepts behind vented enclosures.

..Todd

[Wavebourn]

Fill all pipes with sand; it sounds better.

[Don Hills]

I'm sure badman's just pulling your leg.
If a single port needs to be 2 square inches and 12 inches long, you can use 2x 1 square inch, 12 inch long ports. But you cannot use one 6 inch long port and one 18 inch port.

This was discussed in great detail right here:
http://www.diyaudio.com/forums/showthread/t-144331.html