I know there have been quite a few different sound system recipes that have been shared on the forum. I came up with something for my new Speedster if any one is interested.
This solution doesn't have any head unit so you will control everything from your phone with music apps like Pandora, Spotify, apple music or various apps that can stream radio. Doesn't help if you want to play CDs, tapes,... or 8 tracks (sorry). It also means you control volume from the phone. I'm looking for a solution to this as there has to be some sort of Bluetooth volume knob that can be enabled and mounted hidden under the dash.
The approach was to install a Bluetooth enabled car amplifier under the dash that isn't too big/heavy but has ample power to run decent speakers and a good Bluetooth connection. I landed on an $83 blaupunkt bluetooth amp on Amazon that has 4 channels and can be bridged 2 if you want. Really good power for any size speaker you would use in our cars and you could even power a small sub if you want. Model AMP1804BT.
I used industrial strength velcro strips that I bought at Walmart and put the soft strip across the entire back of the amp and the same size hook side on the fiberglass wall right of center under the dash -- vertical wall that is up against your frunk. So far mine is holding strong and you can see how I later mounted my speakers so just in case it comes loose it won't go flying at anyone in the passenger seat. Simple wiring setup run from the fuse box with a 30a fuse on the power (tap into the full time power lead from the battery), one for the ignition on power lead, and a ground. NOTE: turn both of the gain settings down to the 1/4 mark before hooking speakers up. Mine were all the way up by default which could blow speakers if you start it up with your phone volume up.
For speakers I didn't want to cut any holes and wanted something that was mostly out of sight. I have seen a couple of solutions where plastic speaker pods were used under the dash with 6.5 or 5.25 car speakers but I wanted it to be a little less noticeable. For my back yard I found outdoor speakers from Proficient Audio years ago and have been really impressed with their sound and build quality. I was able to find a new open box pair of their 4" woofer model on ebay for $62 shipped which is a great deal... typically around $150.
I drilled through the steel bar that runs under the dash and mounted them using the brackets that came with them. As you can see they are a little more to center than I would like. Ideally they would be more to the sides but the hood arm fiberglass bump outs were in the way. Still sounds great but soundstage would be better if the left one could sit left of the steering column and right one symmetrically placed on the other side - didn't work with my build but something to consider. Since they are slightly up under the dash you just adjust them to angle down a little so the speaker is projecting below the dash.
Here are pictures of the finished install. You can see them but barely noticeable with the black covers and no brand emblem to catch your eye. What is nice is that the sound comes through really good realitively speaking. Decent bass out of the 4 inch woofers but as with any setup the bass gets lost first at higher speeds.
For about $145 I'm very pleased with the sound and look. If I want some heavier bass eventually, I may look into building a custom cabinet for a 6.5 inch subwoofer and mounting it in the open cavity under the dash on the passenger side, but stand alone these are heavy 4 inch woofers and hold their own. The 2nd two channels in the amp can be bridged to have plenty of power to run a small sub and it has built in high pass and low pass crossovers that allow you to send bass signals to the sub and highs/mids to the speakers.
Let me know if you have any questions or suggestions.
Paul
