jwestbury Posted June 19, 2014 Report Share Posted June 19, 2014 I won an embedded motherboard and processor at an event recently, and after a lot of deliberation, I think the most fun way to utilize the parts will be to build a PC in my car. I'd like to keep my existing head unit, because its appearance matches the car, and if I ever had issues with the PC, I'd like to be able to revert back to the head unit. Further, I've already got a Grom bluetooth unit, and it doesn't seem sensible to me to just toss the Grom aside. Besides, I'm somewhat concerned about the reliability of a PC running in my car, so, y'know... best to have failsafes. My car is an S70 T5 SE (unbadged, American model SE), so it's got the SC-901 and factory amp. This should make life easier. On the other hand, I might look into setting up a full surround sound system, in which case life gets less easy. This idea only came to me tonight, and here's what I've figured out so far: I need to build or buy a cable to change the amp output on my HU to RCA outputs. I need a car case for my parts. Mini-Box has an enclosure and power supply designed for this. Total price of the pair is $140. The PSU cuts power to prevent battery drain while the car is off, handles voltage fluctuations, and reduces pops during startup. I need a sound device for the PC which can accept RCA line-in and also one which can output back to the amp, preferably in RCA. More on this momentarily. I need a screen to control the PC from, preferably a touchscreen. Not sure where to mount such a thing. Additionally, there are some ideas I've got and topics I still need to research: I'd like to do surround sound. This could get tricky, as I will likely need to either replace or augment the factory amp to achieve this. I believe the factory amp only supports two channels, left and right. If I replace the amp or add an additional amp, I'm probably looking at replacing speakers, as, if I recall correctly -- and I haven't researched this in a while -- there are impedance issues using the stock speakers with aftermarket amps (I believe the stock speakers operate at 8 ohms?). I'd love to integrate some sort of switch that allows me to flip between the factory setup and my custom setup. If I can retain the stock amp for the front speakers, this is probably doable. If I can't retain the stock amp... well, then it gets a lot more problematic, but maybe still possible. I've never really looked at amps that can handle surround sound setups. The PC only has a single PCI slot. No PCI Express. Are there 5- or 6-channel amps out there with digital inputs, so I don't have to run a crapload of wires to them? Otherwise, I'm probably looking at some really weird adapter setups -- the HU to RCA adapter to go into a line-in on the PC (which would have to be handled by a separate sound card), or HU-to-RCA-to-3.5mm (which could go into the line-out on the motherboard). The motherboard has six-channel out, but only three ports, which means I've got front, rear, and the a single port shared between speaker and sub. I'll probably need a sound card, here, but I need to do more research to figure out what the best setup is. Given that the existing speakers are configured such that there are tweeters up front, mid-woofers in the front and rear doors, and woofers in the rear, it seems like I'm going to need to make some speaker changes regardless. Sound routed to the front speakers will not have sufficient bass otherwise. That's no good. I need to figure out what the rated stats are on all of the existing speakers. I found some info which says that everything is four-ohm (not eight like I said a few bullet points up) except the four door speakers, which are eight. That... that seems like it could be problematic, but there's some confusion about it. More research required. I do know that finding replacement speakers is a pain in the ALL GLORY TO THE HYPNOTOAD due to the low clearance. I need to figure out what platform to run the computer on. Windows is fine and dandy, but I'm not sure how well it'll handle this particular application, especially if it's going to be shut down forcefully whenever I turn the car off. On the other hand, media options if I'm not using Windows are a lot more limited, as is the driver situation. This will require some thought. (Edit: Actually, looks like the PSU sends a shutdown command when the ignition is turned off, then waits for a configurable amount of time before actually cutting power. It also has a feature to automatically cut power any time the battery drops below 11V output. That's really awesome.) So, this should be a fun project. It's gonna last a while. I'll make sure to post updates as it happens. Or I'll give up and never post in this thread again. Could go either way. Link to comment Share on other sites More sharing options...
jwestbury Posted June 19, 2014 Author Report Share Posted June 19, 2014 A snippet from a Facebook post where I discuss moving to 5.1: So moving to 5.1 will be totally custom, and there are some quirks to doing it with my car in the first place -- the rear shelf speakers are woofer/tweeter combos, as I understand it (I haven't popped the grates to confirm there are tweeters in there), so if I want bass from sound going to the front speakers, I pretty much HAVE to add a sub, and I'll probably have to configure the crossover separately for front and rear to get balanced sound (not sure of the feasibility of this from a software standpoint, but it could probably be done from a hardware standpoint at significantly increased cost). Also, adding OBD II would be pretty sweet, right? Link to comment Share on other sites More sharing options...
jwestbury Posted June 19, 2014 Author Report Share Posted June 19, 2014 Rough plan: Grom > HU > PC > 1x 2ch amp & 1x 5ch amp The two-channel amp gets used exclusively for the center channel and the five-channel amp gets used for front/rear speakers and a subwoofer. RCA adapters get dropped in where necessary -- from the HU to the PC, plus three of them from the PC to the amps. Preliminary hardware list: Case for PC Power supply for PC Hard drive for PC (SSD) RAM for PC Sound card for inputs on PC 5ch amplifier (4 + sub) Subwoofer + enclosure (or try some 8", 4-ohm free air subs in the rear shelf wired in series to the 2-ohm sub channel on the 5ch amp? -- this loses the surround effect for rear passengers, though) Possibly a 2ch amp if I can't make the factory one work A handful of RCA adapters Bluetooth adapter for PC? Link to comment Share on other sites More sharing options...
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