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Discussion Starter #1 (Edited)
I have a big first in-progress post as I'm well on my way in the project.

After seeking and receiving great advice here in the forum, especially from Mike P, I have started building two 18" diameter Sonotube subs using JL 12w3v2D4 drivers my son had collecting dust from a prior car audio system he had and 2 old NAD THX 2400 Amps I have, which when bridged are limited to an 8 ohm load at 200w, which the dual voicecoil drivers can be wired for fortunately. I have also purchased a Reckhorn B1 filter per recommendation.

The project is really just to get my feet wet without spending much money and determine how much energy I can have inside the shop they will be located. I'm actually a bit worried if I built properly designed subs for the large space, it might be too much for the environment.

Here is the place they will be installed in:



The first thing I purchased was a 12' section of 18" Sonotube from a supplier in Dallas. It was about $4.60 per foot. I took a battery powered circular saw with me so I could cut it for ease of trasnsportation. I had to reject the first piece they brought out as I could tell it had been slightly crushed on one end. No problem getting a better one though.



With help from a friend, I used Chrismas wrapping paper wrap around the tube till the ends overlapped on top of each other to determine the perpendicular line for cutting. It was more difficult than I imagined to get it perfect. Even tiny adjustments in one end moves the other end quite a lot. Propping one end of the tube up on a board made it a lot easier to adjust the paper. After the paper was taped down, I used blue painters tape to mark the cutting edge for the saw.



I used my battery powered circular saw to cut the tube. Cutting the right side of the tape using the left side of the blade I was able to get a near perfect edge.



And it's cut and I plan to use the drop to test the fit on the MDF.



I do quite a bit of work with MDF, and I took a pretty good shortcut on the MDF by having the parts cut on a CNC Router along with some other parts I was having cut at the same time.

This is the main sheet of parts just after cutting, but before we lifted it off the table.



This is the stack of parts after cutting on the CNC Router.



I discovered the top endcaps (dustcovers) were not cut correctly and I had to redo them in the shop, which I did on the router table with an acrylic template and a tip guided router bit (flush trim).



This is after the flush cut.



I used a 1/4" roundover bit to soften the edges of the MDF that's outside the tube. Placing it against the router fence and bit bearing made for safe and easy cutting.



As these subs will live in a woodshop, they won't have a cover around the Sonotube. Because of this, the ends of the Sonotube that join to the MDF will show, which I was worried about looking good. To deal with this, I measured the Sonotube wall at .175" and cut a .1875 groove in the endcaps for the tube to bury in. It turned out the Sonotube wall thickness is not very consistent, varying from .175 to .20" so it didn't fit in the groove which left me a pretty difficult bit of work widening the outside diameter of the groove. Unable to use a centered router circle jig, I had to do this with a plunge router, brass router insert guide and another acrylic template carefully placed.



A couple photos showing the finished .25 groove and test fit.



Here are all the finshed endcap pieces ready for edge treatment, sanding and paint.



This is the uncut PSP 4" flared end tube I bought. Checking the fit. It will be turned inside in assembly.

 

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Discussion Starter #3 (Edited)
Man, what a setup you have there. What a great space. Love the Leia statue!

How tall are the tubes going to be? Not that you don't have plenty of space, just curious. Are you going to cover the tubes?
Thanks.

It's only about 4'-2" overall. I only plan to paint the tube as I don't need any more places to catch dust in the shop.



 

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Discussion Starter #6
Your on your way! Be aware the sonotube has a transparent release film on the inside that glue won't stick to. You'll have to peel if off before you attempt to glue the end caps to the tube.
I forgot about that. Good reminder. I just checked it out. The clear doesn't really peel off, it's more of a thin layer of the spiral cardboard that has the release film on it. There's no getting just the film off this one at least.
 

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Discussion Starter #12 (Edited)
I have an update from work this weekend.

When I was deciding where to put the speaker terminals on the base I noticed they were too large for the available space, so I had to trim them. I'll glue them in after painting the endcaps. Here's a few photos of them and making the pockets for them to mount in.





I had decided early on I wanted the top and bottom gap legs to be aluminum bar anodized blue. On Friday I was able to get a friend with a CNC lathe and mill to set up and run them. The bottom legs are 6" and top legs are 4", each by 15/16" diameter, plus they have a boss that the MDF is milled out to accept. They will bolt through with 3/8" SS bolts. This is a test fit of the top endcaps.



This is a test fit of the completed bottom endcap section.



Whenever I am painting the edges of MDF I use drywall joint compound spread on as thin as possible with my fingers to fill the pores. This, when sanded well, primered and painted results in the edges being as smooth as the uncut surface. Here's four of the endcaps drying from application of the compound.



Finally, I'm gluing up the bottom and top endcaps.



Here's my quick and dirty paint booth where I'm going to paint the MDF. I'm really just trying to control the overspray here as I'm not worried about dust.



I have started painting. Since I'm going with a satin black and I have a good process for doing this with Krylon, I'll be using Krylon primer gray and satin black spray cans. I'll also do each one in turn till finished because you have to recoat finish coats within an hour or wait 24 hours between them.
 

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Discussion Starter #14
I wasn't very happy with the finish on the flat part of the MDF. I've seen MDF not finish out as smoothly as expected before, as though sometimes the board just sucks down finish paint even though the primer appears smooth.

So I'm now using the same process for the flats as the edges, which is to smear drywall joint compound in, and sand it before primer. Here's a series of the steps. Joint compound smeared on, using a palm sander (not a random orbit), sanded with 220, sanded with 400, and the edges handed sanded with 400.



Here's one of the caps ready for finish on the second side. I had to build up temporary legs as I was getting some bounce-back of the spray on the underside of the piece.



Here is the first finished piece. I'm happy with it finally and have started on the rest of them.

 

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My friend who knows nothing about subwoofers but does use joint compound often suggested not using it because it tends to crumble when it vibrates. Your ends look great though!
 

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Discussion Starter #16
My friend who knows nothing about subwoofers but does use joint compound often suggested not using it because it tends to crumble when it vibrates. Your ends look great though!
He would likely be referring to using more of it than I'm using by a stretch. I'm just filling pores with it and I promise, it won't come out.
 

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Wow, we have had some very impressive "first timer" projects lately. Phillip, yours is looking great, and your "quick and dirty" paint booth is nicer than what I used to finish mine! lol.

The shop looks like a fantastic place to spend time, and its about to get even better. No worries with the flatscreen and the dust though?
 

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Discussion Starter #18
Wow, we have had some very impressive "first timer" projects lately. Phillip, yours is looking great, and your "quick and dirty" paint booth is nicer than what I used to finish mine! lol.

The shop looks like a fantastic place to spend time, and its about to get even better. No worries with the flatscreen and the dust though?

Thanks Owen. Much appreciated. I do worry some about the TV. I don't have completely uncontrolled dust, but it certainly is not dust free. I have been checking it and there hasn't been much dust on it based simply on a finger across the top test. Things with fans have forced filtered air on them. You might be able to see the box containing my DVR and PS3 under the TV in its filtered cabinet. I'm not in love with the TV as it's an older Plasma that got burned in while in my office accidentally so its not going to be here forever anyway which is why I didn't already do something to protect it. I recently built a media server and have a client PC now in the shop as a source, so this will probably all get a much larger forced air cabinet. Amps will live upstairs in the equipment / computer room behind my media room.

Getting back to the project, there's not much to this update.

I got back my aluminum legs, now nice and blue.



Paint continues with three pieces done, but it's cold and windy this weekend, so I won't be back on that till next week.

I was expecting to receive my hurricane nuts and some rubber feet today. I want to put the nuts in before I paint those pieces and I need to verify the feet will meet requirements so I can order my capscrews for assembly, but alas, UPS let me down yet again.
 
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