BillFitzmaurice.info

New THT build to be mounted under the floor firing up. Since it won't be taking up any floor space, I am going to make it as big as possible. 33" wide will just fit into the house to test and will also just fit the crawl space door. I will build it, test it above the floor to find the best spot, then move it under the floor in the crawl space, which is about 7' tall where this cabinet will go. This will be the second THT to supplement my other THTLP. I will move the THTLP, to the other side of the living room.

Driver will be a Dayton Titantic 1200, old school goodness.
Specifications:
• Power handling: 350 watts RMS/ 450 watts max
• Voice coil diameter: 2"
• Voice coil inductance: 1.96 mH
• Nominal impedance: 4 ohms
• DC resistance: 3.66 ohms • Frequency response: 16-400 Hz
• Magnet weight: 84 oz.
• Fs: 16 Hz
• SPL:90dB 2.83V/1m
• Vas: 9.894 cu. ft.
• Qms: 8.22
• Qes: 0.42
• Qts: 0.407
• Xmax: 14.2 mm
• Net weight: 14.6 lbs.
• Dimensions: Overall Diameter: 12-1/8", Cutout Diameter: 11-1/8", Mounting Depth: 6-9/16", Magnet Diameter: 6", Magnet Height: 2-3/4"

Yes, it is a 12" driver in a 33" wide cabinet but the Titantic 1200 has specs very similar to the Dayton Audio RSS390HF-4 15"
and with a Fs of 16 Hz, it will favor a wider box.

Build Pictures:


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This thing is a beast, going to need a step ladder to nail the last side panel.

Crap, made a mistake and put panel 4 in backwards Didn't notice until panel 6 was going in and the 4/6 brace cut out didn't match the speaker opening. Panel 4 and 5 were already dried, but a sawzall and some more PL, it is all good.
Panel 4 with the opening correct:


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Triple braces needed for this wide a cabinet, the braces need their own temp braces while the PL cures :

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Trying a new tool with this build, the Harbor Freight 1/4" stapler and brad nailer. This tool works slick with the 1/4" staples, really has strong panel holding power. Definitely worth $20, hasn't jammed yet. The staples are easily countersunk with a flat bladed screw diver. This THT doesn't need an outside finish, but the throat will be finished since it will be seen.


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Homestretch


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Braces and throat primed:

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This thing is a beast.


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Very cool....I love seeing these builds. If I had the room, I'd love a wide THT. My narrow THTLP was big enough sounding...!

Awesome. I considered doing something like this a few years ago and went another route.

I'm anxious to see the final product.

Part II-

Front braces installed:

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Looking at the speaker and taking outside dimensions, I noticed the speaker access panel will be on the wrong side in the orientation I will need it. Asbuilt, the opening will be only 6" from the wall. I need to put the access on the other side.

Glued the original access panel in using screws as spacers and PL. Obviously, I am not too concerned about finish on the outside


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Opening moved to other side. I made this new opening 1" smaller all around.
Dayton 1200 installed. Looks kind of small and tiny in there This photo makes it look like a 6" speaker.
I seriously thought about using two Dayton 1200s in this build since I have another, but that would be overkill and not match my other THTLP.


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Access panel installed, speaker tested for leaks, now the fun part. Testing in place .

I mounted a Harbor Freight furniture mover dolly underneath and drug this monster into the house. It barely fit, even scraped paint off the box by the door latch plate squeezing through.
Here is the monster in place in the living room where it will be lined up with the floor joist but below the floor. I wanted to listen to it and make sure it would sound good in this exact spot, since I won't be able to move it once I cut the hole in the floor.


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When I drug this into the house my kids gave me the look.......I think Dad needs help with this speaker addiction

Testing went awesome, this will put my THTLP to shame in lower frequency extension and is much more sensitive. I used it for a week like this powered by a Dayton 250 plate amp. My THTLP is not moved and hooked back up yet.

Part III

Now for the fun and sawdust in the house. Time to cut the hole in the floor after careful measurements and some pilot holes to find the I-beams. The goal is not to cut any part of the I-beams.


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Mini Sawsled works perfect for this cut:


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Now it is done. No Turning Back Now!


Here is what we are looking at for existing framing: You can see these are composite I-beams on 16" centers with 14" between the flanges. I need to finish these to match the THT when viewed from above.

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I will need to build a support "floor" for the speaker to sit on, and box in the I-beams with plywood so the THT throat will match the finished opening in the floor. Luckily, the standard plans THT throat opening exactly matches the space between the I-beam flanges, but I will have to frame out the web to match the I-beam flange.

I started with framing up a floor for the speaker to sit on with 2" by 4" in the crawlspace, that way I could stand on it while working on boxing the beams. I just used 2" by 4" for a "floor" tied to the existing walls by the corner and used one 4" by 4" post on a concrete pier block. It is important to leave more than 36" between the floor and the bottom of the joist to fit the 36" tall THT, or you will never get that box in there. I left the front of the support down 1.5" (37.5" clearance) and the back down 0.5" (36.5" clearance) so the box will sit on the platform with about 1" clearance in front and 1/2" clearance in back for positioning and adding caulk. I will shim the box into final height.


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With the support floor built, I can stand on it and wrap the inside of the I-beams with 3/4" plywood. A 3/4" plywood fits on the side of the I-beam and matches the I-beam flange perfect. Here it is test fit before I nailed it flush.


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Now filling in the ends between the I-beams: the ends are each three pieces and nail to the side pieces like a box. The three pieces are:, the top piece between the flange, the middle between the webs, and the bottom piece will be a 2" by 4" since the speaker top opening will mate with it, I want the bottom mating surface wide for a good seal. I glued and nailed everything. PL not needed, since I will cover all this surface with formica countertop material.


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Here is the bottom flange created with the 2" by 4" material: In hindsight I should have tacked a ledger around two sides of the bottom flange to line up the speaker perfect to the opening, since it is impossible to see what is going on below when positioning it. I ended up with many trips up and down to check for alignment.

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Working around fiberglass insulation always makes it more fun !

Finished framing waiting for the THT.

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At this point I wrapped the inside of the plywood opening with some formica I had. It doesn't match, but I can sand it with 240 grit and paint it to match if needed. I used formica so I didn't have to finish the plywood, sand it, bondo it, sand it again, prime it, paint it. I am done with sawdust inside the house.

Now I don't have any photos of the giant THT being dragged, strained, cursed, and wrestled into place 3' up onto the support floor, since I did it myself and couldn't hold the camera, but use your imagination what it looked like. It took many trips up and down to get the throat of the THT to line up with the opening before setting it. I had it perfect, then shimmed the THT box up tight to the floor after applying some clear latex caulk for sealing. Sometime during the final shim placement, I was too eager and hammered in one shim in too much and it moved the box 1/8" out of alignment. I wasn't able to move it back without pulling out shims, but it is not real visible from above so I left it.

Here are the finished in place pictures from above.

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With amp on wall hooked up and up and running. I may move the amp over by the stereo, it was already placed here when I had my THTLP in this location.

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I am toying with the idea about adding a light down in there, firing up for affect. I still need to weld a floor grate to keep pets from falling into that chasm. My welding skills are horrible and those photos may not be posted.

That turned out really well !

You know ... I have a crawl space ..

CoronaOperator wrote:That turned out really well !

Yes indeed!
Great work on the cab and the fitout to make it all happen

This is awesome. Suck it up, IB guys.

Looks great, love the idea

If it were mine, I'd put some speaker grill cloth under the floor grate to keep small items from falling down in.