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Elite Shackster , HTS Moderator Emeritus
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Discussion Starter #1
It's been over a year since I started this, but the paint is finally dry on my DIY subwoofer project.

It's a dipole subwoofer design with a Linkwitz alignment (spooning, not mirrored).

As you can see my finishing booth setup is not ideal :)


Material is MDF, first part of the finishing was to spray and sand liberal amounts of Zinsser BIN primer (shellac) on the MDF to seal it.



Spray setup is a Wagner HVLP conversion gun. I like the spray setup because the fine mist dries very fast and you can get multiple coats in the same afternoon. Spraying inside the labyrinth was a bit tricky with such a large spray gun.

Next step was to spray flat black acrylic latex paint. I bought the expansion projection set that had the wider nozzle. The latex sprayed fine without any thinning. I was going for a slight orange peel effect, so it was okay. If you are looking for glass smooth, then a viscosity agent or in some cases just plain water is required to thin it out.



I put on about 5 or 6 coats of paint. It dried completely in about an hour, so I just kept recoating until the finish looked very smooth.

The final coat was water based poly. It's nicer than standard poly in that it won't react funny with the latex paint and it's a lot thinner, which makes it better for spraying. Plus it cleans up with just soap and water. I put on three light coats of it, sanded with 220, and put three more on top.

The result:


and



I had the only visible T nut stripped out (after being painted over), so there was some cursing last night. But I got another one to fit in just right and you can't tell anything went wrong.

I've been listening to it unfinished for months now and it sounds great. I have a line level passive EQ circuit that takes it pretty flat all the way to 20 Hz and it's plenty loud to keep up with my Magnepans in our small townhouse theater.

:jiggy: Nice to have another project completed.
 

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Elite Shackster , HTS Moderator Emeritus
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2,216 Posts
Discussion Starter #3
Exodus Audio Tempest one-offs. Kevin had an order of messed up surrounds that were way too stiff for spec. Rather than return them, he sold them as IB/dipole use and mentioned that these were limited run. So I bought two and decided to design the cabinet later.

The cabinet is about 18" tall, 29" wide, and 21" deep.

Here's the discussion with the FR (passive EQ, one parametric filter (amp), in room). Tan curve is the current best. http://www.hometheatershack.com/forums/bfd-electronic-equalization-devices/16950-passive-6db-oct-filter-results.html
 

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Man, there is a lot of talent on this website. I can't get over the work and craftsmanship you guys put into your builds. Very nice work!
 

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Elite Shackster , HTS Moderator Emeritus
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Discussion Starter #5
I was once told that a true craftsman just knows how to hide his mistakes. This project is the perfect example of that :D

One T nut came off, the complete bottom (where I started dialing in the sprayer) looks like garbage -- but I made sure when it came to the top, front, and sides, that I did everything perfect and took no chances. Also not pictured is the chunk of paint that came off behind one of the drivers that was filled in by a sharpie. You'd have to look in there with a flashlight to see it -- but I knew it was there and fixed it anyways :dizzy:

Thanks for the kudos. I definitely could not have done this without help from guys here, DIY Audio, Kevin (Exodus audio), and the Linkwitz site. That and woodnet.net for woodworking advice.
 

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Elite Shackster , HTS Moderator Emeritus
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Discussion Starter #8
Thanks.

Simple butt joints with pocket screws for the top and direct screws from underneath for the bottom.

I did a rabbet joint for the end caps of the labyrinth. Everything except the bottom is glued too.

It is very solid and very heavy.
 

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Elite Shackster , HTS Moderator Emeritus
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Discussion Starter #10 (Edited)
Thor is a U baffle sub ( <--error, see discussion below). This is a larger and deeper version of the Phoenix woofer, which is a w baffle in a spoon alignment. It goes deeper hence a subwoofer.
 

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Elite Shackster , HTS Moderator Emeritus
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Discussion Starter #12
You are right. I just saw the picture and forgot he used a sealed one on there. He talks all about U baffle, H baffle, and W baffle subs and woofer sections elsewhere on his site, so I just blended it all together.

Originally I remember Linkwitz published/posted a whitepaper a while back about this "spoon" alignment and how the drivers cancel their non-linear distortions. At the time, I did not understand the physics of it but I got the point: front to back drivers good, albeit harder to build. I tried to find it online -- the original link was over at diyaudio.net -- but am drawing a blank. I'll see if I saved it on my laptop when I get home.
 

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Considering the state of your paintbooth, the finish looks really good!
You also sound happy with the performance, so it's a bit of a shame the drivers are so "custom"...
 
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