Single SI HT 18 build - Home Theater Forum and Systems -

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post #1 of 72 Old 01-10-13, 10:28 PM Thread Starter
Join Date: Dec 2012
Location: Phoenix, AZ USA
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Single SI HT 18 build

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.

Now for some pics.

Beer and power tools.
Single SI HT 18 build-sub-1.jpg
Gluing the baffle
Single SI HT 18 build-sub-2.jpg
ply from home depot. Had to squeeze a bunch of glue in and clamp up.
Single SI HT 18 build-sub-4.jpg
Single SI HT 18 build-sub-7.jpg
Gluing in bracing
Single SI HT 18 build-sub-6.jpg
Single SI HT 18 build-sub-10.jpg
Single SI HT 18 build-sub-12.jpg
Single SI HT 18 build-sub-13.jpg
Single SI HT 18 build-sub-15.jpg
Single SI HT 18 build-sub-16.jpg
Single SI HT 18 build-sub-17.jpg
More pics to come.
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post #2 of 72 Old 01-10-13, 10:51 PM
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Re: Single SI HT 18 build

Great work! I approve of the beer philosophy. Looks like it will be a solid box, you must have made a lot of dust with all of those routed edges!
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post #3 of 72 Old 01-11-13, 05:31 AM
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Re: Single SI HT 18 build

Looking good!
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post #4 of 72 Old 01-11-13, 06:19 AM
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Re: Single SI HT 18 build

I just love the last three pics in B/W! I say print them big and hang 'em in your HT.

Okay, okay, the build looks nice too...

Slowly building a 9.2.6 HT with 24" SEOS LCR, LLT subs (done) and much, much more...
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post #5 of 72 Old 01-11-13, 07:28 AM
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Re: Single SI HT 18 build

That's your idea of not knowing how to do work with wood?!? I can't wait to see what you build when you feel otherwise...

BTW; keep some of that beer handy. You'll need it to bribe a friend to help you move that beast.


If you take yourself too seriously, expect me to do the exact opposite
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post #6 of 72 Old 01-11-13, 09:22 AM
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Re: Single SI HT 18 build

Gorgeous ply and great looking build so far. Looks like a labor of love there.

"Music is the space between the notes"
[T]o talk well and eloquently is a very great art, but that an equally great one is to know the right moment to stop.
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post #7 of 72 Old 01-11-13, 09:37 AM
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Re: Single SI HT 18 build

Still learning woodworking, huh? It looks like you have a pretty good handle on it... Nice work so far, I'm looking forward to your build progress.
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post #8 of 72 Old 01-11-13, 12:48 PM
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Love how you doubled up on the bracing. I used a single layer interlocking in mine and its not as "dead" as I thought it was going to be.
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post #9 of 72 Old 01-11-13, 10:24 PM Thread Starter
Join Date: Dec 2012
Location: Phoenix, AZ USA
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Re: Single SI HT 18 build

Thanks for the kind words everyone. I think the key for me is to take it slow. As much as I want to hear the end result I really just enjoy making things. Im already thinking about some new mains and a new center. The mains Im using were my first DIY speaker project and I think they turned out good, but they were designed more for music. In heavy duty HT use they could use more power handling, they would make great surrounds though.
Still gluing up the bracing
Single SI HT 18 build-sub-21.jpg
Single SI HT 18 build-sub-22.jpg
Getting there. Im surprised so far with the fit. Im using a $300 table saw and a circular saw, not exactly the best tools for accuracy. Still, I've had no major problems.
Single SI HT 18 build-sub-23.jpg
Gluing up the other side panel.
Single SI HT 18 build-sub-25.jpg
From the back. I used titebond III for all the bracing on to one side and the top(along with lots of 2.5" deck screws) because it was easy to use, but for the other side I used Locite PL fast grab premium. That stuff is like concrete, but I thought it would fill any slight cracks better. Im happy the way it worked, theres a nice bead on all inside seams, though I'll probably still go over everything with caulking just in case.
Single SI HT 18 build-sub-24.jpg
I'll try to get the back on tomorrow, maybe get some caulking in.

The reason I say I'm just learning woodworking is that my grandfather was a master woodworker. My use of butt joints and screws as clamping would have appalled him. He was highly skilled at joinery. Dovetails and stuff that barely needed glue. I doubt he ever used MDF in his life. I also doubt he could have imagined someone wanting an 18" 900 watt high excursion subwoofer in their home. I have no doubt though he could have crafted it with much more skill than I could ever dream of.
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post #10 of 72 Old 01-12-13, 12:33 AM
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Re: Single SI HT 18 build

I bet your grandfather would have whittled one out of hickory if he wanted to, and if he's like mine was, would be proud that you are building it instead of taking the easy path. The build looks awesome so far, enjoy it because it will be over before you know it!
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