# First Sonotube Try

Discussion in 'Archived Threads 2001-2004' started by Frank Kanyak, Mar 30, 2002.

1. ### Frank Kanyak Stunt Coordinator

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Here's my specs. 18" sonotube, 41" length before 3" legs. Tempest 15" driver. My question is how long should I make my port to tune it to 16.5hz??? And what diameter port to use? Thank you.

2. ### Patrick Sun Studio Mogul

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5.25 ft^3 (this takes about of the driver and port) is what you get with the 18" wide 39.5" inner length of sonotube (subtracted 0.75" for each endcap inside the sonotube).

If you use a 4" wide port 20" long, that will yield a tune of 16.5Hz for the enclosure. But at the cost of the F3 going up to 27Hz.

The enclosure volume is the problem. If you want to go low, you need a larger enclosure, at least 8 ft^3, or go with a sealed Tempest design.

3. ### Frank Kanyak Stunt Coordinator

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what dimensions would yield the 16hz? EX: 6'length, 18" sonotube, 4" port 20" long??? With 5' being the WAF and 6' probably the best on paper. Thank you for responding.

4. ### Jack Gilvey Producer

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How did you arrive at your box volume (or did you just pick the dimensions of tube you wanted to use)?

5. ### Patrick Sun Studio Mogul

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If you have the WAF constraint, I'm pushing it with a 64.5" inner height for the 18" wide sonotube (66" if you factor in 3/4" layer inside for the top and bottom endcap) which will yield roughly 8.75 ft^3 of internal volume, but you'll need to use a larger diamter port, I'm suggesting one 6" wide port 26" long.

This will get the tune down in the neighborhood of 16.5Hz-17Hz, and the F3 will be around 18-21Hz (depends on room gain/acoustics/etc).

If you need to use 4" wide ports, I'd use two of them 20" long each, and port out on the top endcap. (Note: The single 6" port is a little better on the air speed/port noise than the dual 4" ports).

But feel free to take Jack's sage advice and play around with the numbers with LspCAD. It'll let you see how different sized enclosures will affect the response, and give you insight on the porting options, but you have to use your noggin, and know what your final goal is.

6. ### Frank Kanyak Stunt Coordinator

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Great I will check it out in the next few days!!!

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