Kofferraumaubau! subs vice versa?!

huhu! my problem or my question is a little bad to describe but I try to find a picture in the internet afterwards. so the following: many people have a subcase with beveled wall on the back wall of the seats in the suitcase room. in the whole tuning magazines you can see it but also often that you have 2 times 30 cm bombs hanging there, only those are then not directed with the membrane but with the magnet to the eye of the viewer. so the magnets have yes g ar no own volume. my question now: is such a thing useful? in how far does it affect the performance? that it looks good I know but I can not imagine that a sub with membrane in the volume can be so good?! would like to have a better teaching, especially since I plan to build something similar, if I feel it makes sense. I would have about 45 liters volume, is that enough for 2 times 30 cm subs at all? and what would they have for klan g properties with such small volumes? as I said everything difficult to explain but I’m still looking for nem pic. thanks for all the inspirations, excitements and other until then, hekko!