Received some feedback and discussion on my head-unit relocation last week, and as I often find, I decided to change it up to the better option.
Below are photos of where the head-unit was mounted, I made a custom MDF piece for that spot too.
But it was obvious that the better position would be in the other corner of the boot, and mounted from above. Overall it looks a lot cleaner and more out of the way.
Started off by half removing some of the rear carpet, I than removed the bottom four bolts of the rear parcel shelf cover. Made it a lot easier to run the harness.
Harness fed through and the head-unit case mounted up!
Everything mounted and connected, works just as well as before.
The new setup was having a few issues with the Bluetooth signal strength, I guess being behind all that metal doesn't help. So I cracked it open to see what could be done!
This is the Bluetooth module, and I found the built in antenna.
I sanded back the antenna trace and soldered a 30cm wire to it. This has greatly improved the range, I can now have the phone a couple meters away from the car. I also don't have any more stutter issues!
I decided I didn't really enjoy the tablet install, so this will now be the 3rd revision of the MX-5's audio setup.
Goal was to create an even simpler interior, might even delete the AFR gauge, by relocating the head unit into the boot/trunk. I still wanted to retain full audio controls as well as Bluetooth and USB connectivity. My old audio setup worked well but the sound wasn't the greatest, probably from the lack of pre-amp/equiliser control.
Although I planned to mount the head unit in the boot, I still wanted full control of the unit, this was achieved using an IR repeater. Normally used in home theatre setups. Simply have the repeater eye in the cabin, and the repeater transmitter in the boot with the head unit.
First thing was to make up an extension harness that goes from behind the tombstone and into the boot. I used roughly 5 meters worth, and I went with something more flexible, conductor is 38/0.15 strands. And I've just terminated the ends with connectors.
Pictured below is the IR receiver unit, I've mounted this just above the rear view mirror. The harness was plugged up, and you can also see the little USB power adapter that's powering the IR Repeater.
This is where the head unit will be mounted in the boot. I've made a cardboard template for that little spot and will make it out of marine plywood and covered in automotive carpeting. You can also see the IR transmitter double sided tape right in front of the head unit's IR receiver, and the right angle USB extension cable.
The completed setup, showing how much simpler it is now. The other end of the USB extension sits in between the driver and passenger seat, and the remote control has some double sided velcro to keep it easily accessible.
Been wanting to do this post for awhile now. It's been a combination of research and a lot of testing to get to this point. Quite pleased with the outcome but would like to make some changes later on, more on that later.
A few goals I had for this project:
- Delete radio/head-unit.
- Keep everything as simple as possible, think minimal.
- Nexus 7 tablet to display all the Megasquirt gauges via Bluetooth.
- GPS with offline maps, pause/resume music on power off/on, wired tether to phone.
- Maintain charge with full brightness, GPS, music and gauges running.
- Easy to remove tablet from the car, one cable to dock.
- Amplifier install that is compact yet has tone controls (bass/treble).
To make it possible for the tablet to dock with just the one cable (USB), and not have to plug the headphone/Auxilary cable in as well, I had to use the tablet's USB OTG Host feature. This basically allows you to plug heaps of USB devices to your Android device, keyboards, mice, thumb-drives, USB DAC, etc...
However, while in OTG Host mode Android doesn't allow the tablet to be charged at the same time. This is where the software comes in to make it all possible. Check out Timur's website for details on his custom built ROM. It is optimised for car installs and enables charging while in USB OTG Host mode, deep sleep mode when power loss is detected (huge power saver), and hot-plugging of audio devices.
You will also need a USB OTG Y-Split cable, I picked up mine off eBay for not much money. While you're there you'll also need a USB DAC, again very little money for these. The USB DAC basically plugs into the tablet via USB and outputs sound for the amplifier.
We're very lucky with Megasquirt when it comes to Android software. MSDroid allows tuning as well as gauges, still in the beta with a new major release soon. ShadowDash is by the same creators as TunerStudio and is a lot more stable but only allows gauges and no tuning features.
For amplification, I decided to go the DIY route. This consists of a pre-amp so that I could have bass and treble control. For the power-amp stage I picked a DIY kit that is built around a IC chip that is commonly used in car radio.
Took me literally under ten minutes to build the power-amp, pre-amp took a bit longer. I than stuffed them both into a plastic case with the USB DAC. The case was picked up from JayCar.
Sound wise, this combo worked very well. The pre-amp gave me plenty of tone adjustments and power-amp was able to keep up with the volume levels I usually listen at. But it did suffer from a "pop" noise on power up, and I may have blown the IC chip because of insufficient heat-sinking!
So the other option I'm look at is this little amplifier, Pyle PLMRMP1B. It's very compact, plenty of power, remote gain control and anti-thump turn on. I'll re-use my current DIY pre-amp though, need those tone controls!
My initial install of the tablet wasn't very successful. Couldn't use my hazard/retractor buttons without removing the tablet, very flimsy, and blocked both centre vents.
I than found a company called ProClip that produce a Nexus 7 holder that was perfect for my requirements.
I used a custom made radio panel, available through my store, and made it a complete blank. This would allow me to hard mount the ProClip tablet holder. Very happy with the qualilty from the holder, sturdy and easy to dock/undock from the car.
For the wiring part, I used new connectors. 4-way connector for the outputs to the speakers, and a 3-way connector for ground, accessory and constant 12V power.
Photos of the finished project!
- Nexus 7 Tablet - $120
- Centre console delete kit - $100
- Stainless steel radio blanking plate - $95
- ProClip Nexus 7 holder - $80
- USB DAC - $14
- Serial to Bluetooth module - $12
- Amplifier TDA7377 - $12
- Pre-amplifier LM1036 - $11
- Narva 4-way connector - $6
- Narva 3-way connector - $5
- USB OTG Y-split charge cable - $5
- Plastic case - $5
- USB car charger - $4