[ironglen]

I live in a city of 200,000 and after calling around- for 12' lengths I found a 24" tube @ $102.80 (Associated Supply, I think) and only $74.16 at another! (Shepler Concrete, I believe) Shop around...and they do vary in dia as they ship them inside one another (alot of difference in volume I think for the length you'll use)

 

[goonstopher]

they do come in different thickness. The one I found for 105 was really thin. The one I have now just feels more solid and is a bit thicker.

 

[PhilipW]

As I'm in the process of building a couple 18" sonotube subwoofers, with the terrific help from the forum here, I thought I'd mention something that's not obvious about the sonosub.exe program I found while using it.

By default, the program has endcaps of 3/4" x 3 layers, for a total of 1.5" inside and .75" outside each end. If you just plug in the volume, tuning and port size dimensions as shown earlier in the thread, and you plan to have the more common one x 3/4" piece inside each end, your tube will be too long.

To get an accurate tube length using the more common one x 3/4" plate inside, you need to go to the endcap tab and change the height of the endcaps from the default 2.25" to 1.5" each (both E & F), then go to the main screen and make sure your volume and tuning are still set to the desired numbers. If not, change them back and you'll get a new shorter length.

Comparing the screen grab from earlier in the thread to the ones below, this changes the overall height dimension from 5'-8.39" to 5'-7.0". Almost 1.5" shorter.

I went over this detail yesterday with Mike P, who is helping as well, and he concurred on the need to change the endcap dimensions to get the correct length.

I don't know what you plan to do for a port and flares, but on Mike Ps recommendation I bought Precision Sound Products ports with flares from parts-express.com. According to Bill who makes the sonosub.exe program, if you use PSP ports you will want to use the port length calculation that they come with, or plug in the numbers in the ports tab in his sonosub.exe program. In my case they came out essentially the same and Bill said they were so close either would work. Both were about 1" longer than winISD showed without flares.

While it's a small detail, if you also put in the driver volume occupied number, your length calculation will be even more accurate.

Having said all this, I'm on my first Sonotube build, and by no means an expert. But I have been careful with my understanding of how the program works.

 

[goonstopher]

Yeah the program confused me but I do need some help, let me explain the numbers that my tube is so you guys can point me in the right direction:

One way across is 24.3 internal, the opposite way is 24.7 and a third in the middle was 24.7

My tubes are 70 inches tall each (had to trim them)

The port is 8" across and I will use a flare that goes out to 12" at its taper with a 14 inch lip and is 3 inches long from the opening to the top.

If it helps my wood worker is using 2 layers of 3/4" MDF (part will be outside the tube) so that will take up half of the 3 inches from the flairs length.

I want to tune it around 15hz.

 

[PhilipW]

Well, you're going to have to figure out that internal diameter somehow. Just guessing it at 24.5", I ran sonosub.exe using your diameter, tuning and port size. I didn't know if you were planning to flare the inside of the port as well, so these numbers how flares on both ends. Holding these numbers, the tube needs to be a bit shorter at 5' 8 11/16". The first image below.

If you hold the tube as cut to 70", then the tuning only changes a bit to 14.8 Hz. The second image below.

Both assume your endcaps are a sandwich of .75" outside and .75" inside.

 

[goonstopher]

Phillip,

I think there is an error there somewhere, maybe I am wrong (this is why i need help ha). It says 2' 1/2 for internal diameter which seems like it would mean 30 inches to me... I keep messing this program up so I am probably wrong.

***Editing my own post, i see how the program works now, it assumed 2 feet from 24" then added the half inch. Definitely weird.

I probably wont get a port for the inside as well, they cost $15 + shipping each, if it will help then I will but the 14 inch lip inside might slow air flow.

 

[PhilipW]

Phillip,

I think there is an error there somewhere, maybe I am wrong (this is why i need help ha). It says 2' 1/2 for internal diameter which seems like it would mean 30 inches to me... I keep messing this program up so I am probably wrong.

That's just how he formatted the dimension. it's actually 24.5" written oddly. I just picked a number between your measured numbers.

 

[goonstopher]

I see and I edited above and about my ports.

 

[PhilipW]

You can calculate the OD of the tube if you measure the circumference with a flexible tape carefully. Then take off the thickness of the wall x 2.

 

[goonstopher]

How about internal batting or dampening?

Is it worth doing for such a large enclosure?

 

[PhilipW]

How about internal batting or dampening?

Is it worth doing for such a large enclosure?

Somebody else should probably answer this, but the inherent strength of the round tube should be plenty strong.

 

[goonstopher]

Sorry I didn't mean bracing I meant dampening like stuffing.

 

[PhilipW]

Sorry I didn't mean bracing I meant dampening like stuffing.

This is what Mike P. had to say in my sonotube thread about lining the inside of the enclosure:

"As for the "lining", it's to damp the back wave of the sub so it doesn't sound "boomy". Some say it has no effect, some say it does. I say it does. I build all my subs with it. I use egg crate foam, cheap and very easy to install. It's sold at WalMart as a mattress pad, less then $20."

"For your build the sonosub.exe program states "the driver to box top resonance is 178 hz. Add some damping material to the inside of top endcap" 3 or 4 layers of egg crate foam on the top endcap should do if that's what you're using to line the sub with."

Hope this helps.

 

[goonstopher]

Thanks man,

I hope mike will chime in and let me know how much to use for this build.

I think I will post some pics up soon to show everyone how insane 2 of these will be in my small room.

 

[Mike P.]

Here's how I did mine. Also put a couple layers of foam on the top end cap. That will help with any "driver to box top resonance".

 

[goonstopher]

I didn't want to take over cind3r's thread with questions so I came back here.

I should be prepping the tube soon and working on it while I wait for the woodwork but want to know. Do you treat the inside at all to make sure it is leak proof?

I have been told to fill in any gaps but I don't see any and I have also heard that people treat the inside with something to make an air seal

 

[Mike P.]

The only place it will leak is the end cap to tube joint. On mine I made sure it was a tight fit and used wood glue, never had a problem.

 

[PhilipW]

The only place it will leak is the end cap to tube joint. On mine I made sure it was a tight fit and used wood glue, never had a problem.

I'm planning to epoxy my tube to endcap joint more for strength than an air seal, but will do both.

In general, wood glue is designed for a wood to wood bond that takes advantage of the chemical makeup of wood. When you are bonding wood to something else you should generally pass on wood glue and use epoxy or a polyurethane glue, like Gorilla glue. Just remember, epoxy will fill a gap, wood glue and polyurethane glue will not and if you use a polyurethane glue, do not get it on your hands. Nothing but time or sandpaper takes it off.

 

[goonstopher]

Could you use spray foam to after glueing to make sure it is air tight?

 

[SturmMD]

if you use a polyurethane glue, do not get it on your hands. Nothing but time or sandpaper takes it off.

I've had a tube of polyurethane glue burst on me while using it. Luckily, I knew how important it was to get it off right away. Coleman white fuel (camping) worked well for washing it off, you just end up with pretty dry skin afterwards.