sonosub tempest question (1 Viewer)

[Bob Bartlett]

I will be doing my first sonosub using a tempest and really didn't want to use a 24"diameter tube. Has anyone used a 20" or 18" tube. I know it would have to be taller. Are there any other trade-offs?

 

[James W. Johnson]

Are there any other trade-offs?>>>>>>>
None at all, use whatever diameter tube you like. The only drawback to using 18" dia. sontube with a Tempest would be very little baffle space to work with for applying the port, feet and binding posts..but it can be done.
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James' DIY speakers

 

[Dustin B]

I built one using 18" sonotube. You can see a detailed write up and some pictures of it here.
http://ht.s5.com/Sonosub.html
There is no way you can put the port on the bottom with 18 or 20 inch sonotube so it would have to go on the top. 1.5" sqaure legs fit with no problem. If you mount a plate amp to the sub like I did then binding post space isn't an issue. If you want to use them though, it shouldn't be a problem as long as you don't get a large cup.
With 6 1/4" legs my sub ended up 5'11" tall in order to get a net volume of 260L with it's 6" ID port.
This created two problems. One was the length of the tube is long enough that in the 110hz range a half wave length standing wave could form. 6' would be about 90hz and 5' would be about 110hz. From Dr. Hyre's suggestion I placed about a foot of insulation at the top of my tube around the port. I haven't noticed any resonances. The second problem isn't really that much of a problem, just makes things a little more difficult. That is an 18" tube is a tight fit to crawl into in order to caulk the endcap from the inside. I did it the hard way crawling into the tube and succeeded. From another post on this forum if I did it again I would try a different method. I'd draw a line where the end cap should end inside the tube and then run a thick bead of caulk on that line so that when the end cap is pushed on, it should push nicely into the caulk forming a nice seal.
Except for the possibility of resonance created by hieght there are no trade offs sound wise when using 18 or 20 inch sonotube. And with my insulation I haven't noticed any.