I designed this speaker as a bit of fun. I originally designed it for 4 inch speakers but I got a deal on Amazon for some open box Pioneer 130mm speakers. I designed it for use with the DollaTek Amplifer listed below which was very cheap and actually works really well and is perfect for this project. With some modification, this could be used with a Raspberry Pi and a DigiAmp+ or a HiFiBerry with Volumio, but the cheap amp is much more cost effective and user friendly if you only want Bluetooth connectivity.

I had some bad vibration where the amp is at first, but I cured this by putting some insulation tape on the bottom of the amp. For the 3D printed parts, I found that low infill works best, so used 5%. I printed the frame upside down and the cutout face down using supports for both. Nothing else needs supports. There is a small amount of soldering required and some super gluing. The only electronics knowledge you need is to know the difference between positive and negative.

This ended up costing me around £50 GBP excluding filament. The speakers I used were Pioneer G1330F. Below is a rough step by step guide. I hope this is of help to someone. Here's a quick vid of mine working https://drive.google.com/file/d/1qwi1HMZryxB9LTEKRSs8cs4Kkhm6h10s/view?usp=sharing. I'm very pleasantly surprised by the sound quality.

Step 1. Print all parts, using the plates for the size of speakers you’re using
Step 2. Solder wires to speakers
Step 3. Screw speakers face down to plates
Step 4. Glue plates to frame
Step 5. Terminate speaker wires into amp
Step 6. Glue cutout onto frame
Step7. Feed DC jack wires through top hole in cutout, put nut on the back and solder male end. Plug male end into amp. Put the nut on the front of the knob on amp.
Step 8. Screw bottom onto frame.

You will need:

2x 4 inch or 5 ¼ inch car speakers

DollaTek HiFi Wireless Bluetooth 5.0 Audio Amplifier TPA3116D2
https://www.amazon.co.uk/dp/B083QF164T

6x8mm hinge screws to fix the speaker to the plate https://www.amazon.co.uk/dp/B09W2YTSLX?ref=ppx_yo2ov_dt_b_fed_asin_title

6x20mm hinge screws to fix the bottom to the frame
www.amazon.co.uk/dp/B09W2YSTVP?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

19v DC power supply with 5.5x2.5mm connector. I used this one https://www.amazon.co.uk/ASUNCELL-Connector-Satellite-SatelliteC50-C55-A5245-Black/dp/B0F9F84G3X/ref=sr_1_5?crid=UCTCHHRK78XS&dib=eyJ2IjoiMSJ9.ke0RgWuU9lUfKt3xwlhLuFoLKvORdX9j4cOI3s4q7ON1ltdf8fJyFbHLQYWzYiIERrlxpA6voOjRmJzXvk3QGkkBeFT11RB99aBkmuAdAudPUK4stBzHDrFNAhXvtKimfNT7x9nA5MZs_8i3Uu6LmnccsgRHruxYYCgTkfkcRicPhAnzl96nuN20CUBc7av0Gpa7Ch10K4oX7oIeT8O2OOm6niHb6KBdrCHSXLmQMxw.nPCEEdpmRylUHetVDDd9sjgpwrb8FgKagSN0H7BijpE&dib_tag=se&keywords=19v+5.5x2.1+power+cable&qid=1773430149&sprefix=19v+%2Caps%2C456&sr=8-5

22 AWG wire https://www.amazon.co.uk/dp/B0FR3PJHF1?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Female DC jack https://www.amazon.co.uk/dp/B081MWYT6T?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Soldering Iron

Super Glue

A sh1t ton of filament