Sontube Volume Compensation (1 Viewer)

[Jason Pannell]

I am in the design stage of a tempest sonotube sub and I have a few questions about the box volume. I have decided to use a box volume of 283.5L with two 4 inch ports each 37cm long. Do I need to compensate the tube volume for the area that the pors will take up, and what about the volume that the driver will take up. Is this just being way too picky or should I increase the tube length slightly to compensate for these issues.
Thank you,
Jason Pannell

 

[Patrick Sun]

Your gross volume should include the net volume (that you are modelling) and the volume taken up by the ports and drivers, thus, you should adjust the height of the sonotube to reflect the GROSS volume needed for your design.
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[Dustin B]

Jason, have you considered using a single 6" port instead of two 4" ports. The cross sectional area of two 4" ports is 25.1 square inches while the cross sectional area of one 6" port is 28.5 square inches. So not only do you have more pipe area for air to move through with a single 6", but you only have to cut one port hole in an endcap.

 

[Jason Pannell]

Where did you pick up the 6" tube in town. Every place that I have checked only has 4" as their largest size. I have not gotten a hold of centennial yet. I initially was using a 6" in the design but changed it to 4".
Thanks,
Jason Pannell

 

[Brian Steeves]

Jason,
If you check with any local plumbing/irrigation supply companies you should be able to find some.
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DIY Sono-Sub Page
[Edited last by Brian Steeves on August 22, 2001 at 09:46 PM]

 

[Jack Gilvey]

Hi Jason,
I'd agree with the use of a 6" vs. two fours. The difference is even greater than the area implies due to increased frictional losses from multiple ports. They're a little expensive, but I bought a pair of Aeroport 6" flares, which you can view in Thomas W's Link Removed .
Also, Andrew's site has some very useful sonosub volume calculators which take port volume, endcaps, driver displacement and such into account.

 

[Jason Pannell]

I have been working on 1:1 scale layout tonight and I may have a bit of a problem with the use of a 6" port. with the 14" hole for the tempest and a 6" hole for the port, the amount of material that will be left on the side of the plug will be approx 1.25, and this will probably be smaller once I measure the O.D. of the port tube. Will this be enough material to maintain strength. or will I have to go with 2 4" ports to maintain strength in the endcap.
Thanks,
Jason Pannell

 

[Brian Steeves]

Well Jason usually they say to have at least the port diameter distance from any side wall, but...
On the sonotube subwoofers I've made none have been that far away and sounded fine.
If you look at my latest design the port is darn close to the side. All I did to compensate for this is to add more thickness on the bottom endcap/baffle. Mine is 2+5/8" thick.
Look here to see what I mean. http://home.tampabay.rr.com/bpsdesigns/bottombase3.html
It's a little more work gluing and then routering the holes but I think it's well worth it.
Another thought is you can mount the port on the top.
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DIY Sono-Sub Page

 

[Dustin B]

I got mine at Anderson's Pump House in North Battleford. So if I could find it in NB there has to be a place in Stoon that would carry it. Look under sprinklers in the yellowpages and try those places. I got 3 feet of section 40 for a little over $20 CDN.
So with that talk of not enough space, does this mean you've decided against using the 18" I have left? Or are you still considering it.

 

[Jason Pannell]

I am still considering everything as far as sonotube diameter. I have not made any real decisions yet but I hope to have my plans finalized by the end of the week. I am leaning towards the 24" sonotube because the volume I am shooting for is 10ft^3, and the sonotube that you have left Dustin, would probably not quite give me that volume. I am still playing with different volumes though so I might still buy it from you, if you still have it when I get going.
I assume from what you say Brian, as long as keep as much space as possible from the edge to the driver and port, and keep the plug fairly thick, I should be okay?
Thanks,
Jason Pannell

 

[Patrick Sun]

Jason, take a look at the Sunosub II link in my signature below, it features a Tempest driver in a 10 ft^3 enclosure with a 6" wide port on the bottom endcap for 24" wide sonotube. I used double-thick 3/4" MDF, and didn't have any problems with structural integrity.
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PatCave ; HT Pix ; Gear ; DIY Mains ; DIY CC ; Sunosub I + II + III ; DVDs ; Link Removed
[Edited last by Patrick Sun on August 23, 2001 at 07:56 AM]

 

[Dustin B]

For reference Jason mine is 260L or 9.2 cubic feet. Which resulted in a 5'11" total height that includes 6 1/4" legs and 1.5" thick encaps.

 

[Jason Pannell]

I was trying some numbers out in WinISD beta last night and I think I have decided on a volume of 325 Litres and will tune to approximately 19.5 Hz, so I will probably have to go with the 24" tube or else the thing will just be to tall. Do these numbers seem reasonable for use with a tempest?
Thanks,
Jason Pannell

 

[Dustin B]

You should really go to Adire's site and get LspCAD. WinISD isn't as accurate as it is. It's a very expensive piece of software and Adire has been kind enough to get us a demo version that only works with their drivers. It allows you to do a much better job of designing your sub.