The seat was a non-folding factory seat with factory hardware brackets. The front brackets were removed but the rear bracket that ran across the rear and held the seat belt bolts was left on and used in the project.

Height was a factor. I didn't want to raise the passengers too high so I decided on the height by raising the rear seat and sitting in it.  I found that 4 inches was acceptable (under the roll bar) and actually increased the height towards the front which gave a more relaxed seat and more storage AND made room for the 6x9 speakers which was a priority.

Four pieces were cut.  A front, a rear and two sides. The dimensions were approximately as follows (measure your own tub as it may be different than mine)

• Front: 36" x 7" (measure your tub width)
• Rear: 36" x 4"
• Sides: 24" tapered from 4" (rear) to 7" (front), the rear was cut square while the front was cut at a 7 degree angle. Also when ripping the wood in the table saw, I angled the blade to 7 degrees so the top was angled into the sides.

The four sides were pre-tapped and screwed together using 3" wood screws forming the main box.  The floor of the box is a sheet of aluminum tacked to the bottom.  Pioneer 6x9 speakers were purchased earlier and carefully measured to locate the speaker holes which were then cut out using a jigsaw.

Mounting the Seat - Hinges and lock-down

A few more requirements were that the seat had to hinge forward so the space under the seat could be accessed. It also had to be able to secure down in the rear safely. That required the rear of the seat belt bracket to firmly secured to the Jeep tub and not rely on the wood structure for the latch-down to the tub.

Here's what I came up with:

The Hinge located at the Front of the Seat

The seat's brackets up front were removed leaving four threaded holes.

A Stainless steel 1¼" x 36" x  ¼" piece of steel was cut, the length of the top of the wooden box. The seat was slightly narrower than the box.  Two heavy duty steel door hinges were fastened to each end of the steel bar.  The 36" bar was then secured to the seat.  As you can see to the right, the hinges were offset from the bolts that go into the seat, which also helped to make clearance for the speakers.  I also ended up cutting the inside corner off the hinge to make room for the speakers leaving 3 holes to anchor the hinge to the box.   The seat was then flipped over and secured to the wooden box.

Rear Bracket bolt down

The seats rear bracket that ran the width of the stock seat was left on to utilize the seatbelt anchors that are part of this stock mounting bracket.  When the seat closes down over the box, this rear bracket actually hangs to the rear of the box (see picture below). When closed this bracket was now 2 inches above the floor of the tub.  This gap was bridged using three 2 inch pieces of steel square stock. The square stock was attached to the box in the locations of the three stock floor holes so that they lined up with the holes in the stock seatbelt bracket.
  

Mounting the Speakers

A lot of planning went into the location and size of the speakers.  I wanted to use the largest speakers possible without raising the seat too high.  What I ended up using was a pair of 6x9 Pioneers.  Once the speakers were decided upon, the storage box was basically build around the speakers.

When the holes were cut into the storage box, they were cut, not oval to expose the whole speaker but a smaller (narrower) opening to keep as much wood as possible above and below the opening for strength. The speakers would be mounted inside the cabinet.

Once the cabinet was built and assembled, it was then taken apart and painted.  The pictures below were taken when it was being re-assembled.

Speaker Protection The storage cabinet's job is to store stuff.  Tools and spare parts bouncing around inside the cabinet aren't too friendly with speakers so I had to come up with a way to protect the speakers.  Two things were used, metal screening and aluminum coil. The screening was stapled to the wood, covering the speakers.  The aluminum coil was then tacked in to act as a barrier. later silicone was used to secure the aluminum to the floor of the box and sides to reduce vibration caused by the speakers (I figured this out later when the speakers were in use). See pictures below.
This was a bad idea.  Thinking that mud or rain or whatever could splash in on my speakers, Using silicone I glued plastic wrap over the speakers opening.  Not a good idea for sound quality.  Good thing it came off easily.

  
Thinking I may someday need to tie-down something to the seat like an ice chest, I installed a military surplus tie-down between the speakers and used large washers to prevent the bolts from pulling through the wood. 

Securing the Storage Box 
to the Tub Floor

Front - For the front a simple piece of angled steel was used.  It was bent on the same angle as the front of the box.  I actually took a piece of steel that originally was 90° and lessened the angle using a 5 pound sledge and a railroad tie, pounding the steel to reduce the angle.  The steel was about 2 inch by 2 inch and something like 16 gauge.

When planning the size of the box, I took into account the ORIGINAL seat mounting holes on the floor. This bracket would use the front mounting holes on the floor.

Finishing Touches

For the speaker covers, they were mounted outside the box, and over the lower mounting bracket. This picture also demonstrates why the corner of the hinges were cut off.
Picture of the Seat mounted to the box, speakers installed.  For the most part, it is completed.  Later four stainless steel kick protection bars were installed over each speaker to prevent damage.       Later, these speaker guards were made from some stainless steel rods.  I bent then into a u shape, drilled holes in the wood and pressed the rod ends into the wood.  Works great to protect the speakers from feet and it looks good. Location of speaker wires outlet
Above and left, a few interior pictures.