We put music in the rear shelf - Toyota Corolla, 1.5 L, 1989

I'll make a reservation right away. The process itself was not filmed. It took about 6 hours (given the inexperience in this matter). From injuries - a cut finger and a blow to the face with a torsion :-)

I tried different options, carved podiums from wood, etc. Didn't get the desired effect. And it would be more correct that the 6x9 speakers would give bass from the trunk volume.
As everyone knows in the AE91, the trunk torsion bars interfere with this. In fact, torsion bars are needed only for ease of lifting the trunk lid and fixing it in the open position.
Removing the torsion bars was not so easy. We filmed carefully, because we didn’t know what if we would have to put them in place. To remove the torsion bars, I had to constantly pull them down with great force and remove them from the mounts with pliers.
When the torsion bars were removed, they began to wash the shelf and remove all the wires.
After that, I took the plastic speaker casing and made a marking according to its size along which the holes were cut.
We cut the holes with a jigsaw and Boshevsky files. I want to note that the file must be constantly oiled, otherwise it breaks immediately (well, perhaps the fault of our crooked hands).
After we cut the holes for the speakers themselves, they began to cut ovals from plywood onto which the speakers will be attached.
The rear shelf is all "cut" by stiffening ribs, which is why it is not flat but with permanent protrusions. Wooden ovals were fixed on these ledges. But there were significant gaps (due to the ribs) of the order of 2-3 cm in some places. We thought for a long time what to do and how to be. The solution was found unexpected and possibly not correct, but the result seems to tell us that everything seems to be fine. The holes were filled with pieces of Corolla rubber mat. The pieces of rubber were glued to each other and after laying they were once again well poured with glue.
Then we used a car putty, which was tightly sealed with rubber inserts and the whole structure became a solid monolith.
Then the speakers were simply laid down and all the wiring was removed in place of the torsion bars.

This is just the beginning of work. I will post a follow-up from 2 parts:

1. Completion of the shelf with full alignment of the "ovals" with putty and covering the entire shelf with Carpet.
2. Installing pneumatic boot lifters (from VAZ 2108) instead of torsion bars.

Now about the result. I was honestly skeptical about the whole idea. Well, I never thought that it could turn out that way. As a result, it turned out to be so good bass that all thoughts of buying a subwoofer have gone into oblivion. I never thought my car could sound like that.