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Single SI HT 18 build

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18 build single
34K views 72 replies 26 participants last post by  Billy13 
#1 ·
Hey. Thought I'd make a build thread of my new sub beings that I like reading them and maybe others do too. This is my second DIY speaker project, but I'm far from being much good at it. Im still learning woodworking and about as far from an engineer as you can get. I've been reading threads here and elsewhere for quite awhile now and have learned a lot. This is a great forum.

So I picked up an SI HT 18 on preorder, seemed like a good deal. I've modeled all of the 15's and 18's in my price range and decided on a single 18 in a sealed box. I know I lose some SPL down low compared to ported, but the simplicity of the build as well as knowing how a sealed box in this room sounds steered me in this direction. Im replacing an old Velodyne F-1200 which did surprisingly well. I think I'm fortunate to have some nice room gain here.

I went with a box with outside dimensions of 34"h X 24"w X 21.75"d. Using .75" thick mdf sandwiched to .75" plywood for sides and back. Double .75" mdf for top and bottom. Baffle is 2 layers of .75" ply plus a .75" layer of mdf for the front. All bracing is double .75" mdf. After calculating the bracing volume I end up with about 5.75 cubic feet inside. I know its probably overkill and will be heavy, but my design philosophy is if its worth building, its worth overbuilding.:T

Now for some pics.

Beer and power tools.
Tool Machine Toolroom Wood shaper Table saw

Gluing the baffle
Workbench Wood Table woodworking Tool accessory

ply from home depot. Had to squeeze a bunch of glue in and clamp up.
Wood Plywood Table Furniture Hardwood

Workbench Wood Machine Table Tool

Gluing in bracing
Workbench Wood Table Plywood Furniture

White Architecture Black-and-white Line Monochrome

Machine Machine tool Photography

Machine

Metalworking hand tool

Black-and-white Monochrome Machine Monochrome photography Photography

White Black Black-and-white Monochrome photography Monochrome

More pics to come.
 
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#35 ·
I have only had a few subwoofers that did have the holes match up. Most did not. Although I feel SI will correct the problem where as the other companies still dont have the holes matching up. And this is a first run.
 
#36 ·
I never thought of using a larger bit for routing out the hole. Beings that I would have had to buy one I would have just drilled an extra hole in my jig anyway. Im cheap that way.

As for the non matching holes on the woofer, it wasnt so much the curling of the surround when tightening the bolts down. I figured out that a small washer would help with that, but it was just the difficulty that it created in seeing the actual holes and pushing a bolt through. A little trimming and all is good to go now, so no harm no foul. Its nice to see someone from the company reading the forums and acknowledging an issue with their product. I have to say other than that small issue the driver seems very well put together and very impressive, especially considering the price.

Glued up the baffle today. First the double layer plywood inner baffle.


Then the outside mdf piece.
Scale model Naval architecture


I really need to get some more bar clamps, I hate relying on all those screws. Oh well maybe next time.
I weighed the baffle pieces before I glued them up. Taking the 135 lbs I had before the baffle, then adding the 29 lbs for the baffle then the 52 lbs for the driver, Im looking at 216 lbs. Uhg.

Im really getting amped to get this thing rumbling. I picked up a Beringer EP 4000 on Amazon Prime for $275 shipped awhile back. Its more power than I need but for that price I figured I could only use one channel for now then possibly run another 18 later on with the other channel. I'll probably pick up a mini DSP too, though Im going to try it without just so I know the difference.

Tomorrow night I'll start on the finish; filling screw holes with wood filler and sanding. I bought some bondo and meant to try it out but man, the smell. My garage is also my studio, so I work in there during the day so I try to limit noxious vapors.
 
#46 ·
Thanks audiocraver I appreciate that. As I start the finish, as it were, I realize that there have been some lapses in the attention to detail though. I knew that having the plywood showing with butt joints instead of designing with rabbet joints and having only mdf on the outside was going to create finish problems. Mdf and plywood just sand at different rates even using a hard sanding block. That and all of the screw holes. I knew this going in and opted for strength over a perfect finish beings that the sub will be behind the mains stuck in a relatively dark corner. The finish doesnt have to be perfect. Ill leave that for when I build some new mains and center.

Heres a shot of the back before I started with the primer.

Plywood Wood Box Furniture Pedestal


After the first coat of primer.

Product Wood Audio equipment Subwoofer Loudspeaker


I decided to use a good spackle to fill the smallest holes that the wood filler left.

Table Wood Plywood Furniture Material property


This is a better shot of it.

Audio equipment Subwoofer Loudspeaker Concrete


After sanding and another coat of primer.

Technology Electronic device Package delivery Gadget


After 5 coats of primer.

Subwoofer Audio equipment Loudspeaker Plywood


Ill probably give it a few more coats because you can still see the color difference between the plywood and the mdf.
 
#50 ·
I used Kilz 2 latex. I just used a foam brush as I didnt want to go to the trouble of making a separate spray tent in my garage, or move it outside. I didnt have a problem with brush strokes that even a foam brush leaves as it will blend in with the paint method I plan on using, and as I said before, the sub will hide in the corner anyway. I put it on vertically in long even strokes from top to bottom except for the top, there I went from front to back.
I painted the back today just to see how it will look and I think it will turn out OK. I'll post pics when I get it further along.
 
#52 ·
Overkill - isn't that one of the required characteristics of being an A/E enthusiast? "Overkill is in the eyes of the beholder?" "Overkill is the mother of invention?" "One person's overkill is another person's just good enough?" Just funning with you. It is SO easy to get carried away on a project like that. I still say the basic woodworking quality is to be greatly admired.
 
#53 ·
Overkill? Yeah probably. I agree with audiocRaver, its all relative. I was looking around the webs the other day at speakers to get ideas for new mains I plan on building. I came across these: http://stereophile.com/floorloudspeakers/magico_q5_loudspeaker/index.html They are a modest sized floorstanding speaker that weigh 387 lbs each and cost about 60t thousand a pair. I realize that the importance of a dead cabinet is probably more important in a full range speaker, but even in a sub it just makes sense to me to make it resonance free as possible. Plus I just like making things really solid.:D Also, I own a good hand truck.:T
 
#55 ·
Paint. I had a color in mind when I started this project, a dark gray-brown with a subtle metallic champagne quality.

Art Paint Sculpture Still life


It came out a little darker than the photo shows.

Wood Circle


Big rubber feet.

Wood Floor Architecture Games Metal


Again its actually darker than the photo shows.

Plywood Wood Table


Tomorrow I hope to get a top coat on, then get the binding posts on and wiring done. After that I'll stuff it with poly fill and move it to my living room. Then pop the driver in and test it out. Beers will probably then be hoisted.
 
#59 ·
I use a wide soft artists brush. I use a water spray bottle to mist the paint while applying to control consistency. I apply in thin layers a section at a time and let that layer dry thoroughly before adding another layer. I brushstroke in the same up and down direction for each side. The result is a subtle faux wood grain effect that the pic doesnt show very well.
 
#61 ·
So looks like you custom made your paint. Can you describe how you did that, specifically how you made it metallic. I wanted a metallic paint for a recent project but didn't like any of the premade colors. Would love to know how to make my own. I would have never thought to do that.
 
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