Bit of an update -
At first I got put off by the metal sheet and did not have any metal cutting equipment
Cue 1 hour later and a jigsaw and metal cutting blade, I followed your guide above and carefully went ahead and cut an opening. I am glad the metal sheet was not too thick but made sure I covered everything up as I did not want the metal bits scratching the leather.
I still need to make the baffle to mount the sub which will be done next weekend. So far I have the sub in a sealed box firing through the hole.
A couple of things I have noticed (I admit I am not an expert just like listening to good quality sound)
no ski hole/sub facing back of the seat = bass was muted could not feel the low notes
no ski hole/sub facing back of seat/arm rest down = slightly increased presence of the sub and could hear some of the low notes
With the above, I got out of the car and outside around my boot/fuel filler cap/numberplate holder was vibrating like mad and annoying imo
With the ski hole cut/sub firing into the cabin = I could feel the warmth of the bass notes, it wasnt overpowering but just nice not to loud to make my ears bleed
Went back outside and noticed a lot less rattle from boot area
Sub - JL audio W3V2 12" and Im only feeding it 250wrms (which I amhappy at the moment)
Now I really want to try to make a IB similar to what mob17 has done to see the difference.
Can anyone give me any tips when making an IB?
I have seen other threads and from what I can gather 2 square pieces of MDF 18mm thick each, cut circular hole, mount sub onto the MDF and the whole MDF board onto the back seat?
I did take some pics if anyone is interested but its similar to the DIY thread