[DRG-ler]

Hi folks, I guess that's more of a question now for a hot rod forum, but I'll give it a try anyway.

I'm a very big fan of Model A's, but I'm also a very big music fan. Fortunately, today you can combine both in modern cars. I would now like to have this luxury in my 1930s Tudor.
The first ideas have emerged, but I'm still looking for some detailed solutions, and I hope for tips from like-minded people.
A very important point for me is that I don't want to change the original appearance of the car if possible. This means that the entire system should be hidden as possible.

For this purpose, NO car radio is installed, but the mobile phone or an MP3 player with Bluetooth is used. A small digital amplifier with 4x50W is installed under the rear seat, and the loudspeakers are to be hidden in the front in the footwell in easily exchangeable side panels. Covered with acoustic material so that you cannot see them.
Everything should be easy to retrofit, and I don't want to make any changes to sheet metal parts of the body that can only be removed with great effort.

My problem now is that I am looking for a hidden solution for a subwoofer. I admit that I am also a fan of very low audio frequencies, and I am aware that the small speakers in the footwell will probably not meet my needs.
The possibilities in Model A are very limited. I don't want to make a rolling disco out of the car, but I want to get the best result out of the least possible.

Who has ideas where you can install the largest possible woofer in the car without being seen?
A solution to put a bass box behind or on the seat is out of the question for me. How did other people solve the problem?

I'm looking forward to the lively discussion.

Greetings from Berlin
Andy