This tutorial will be slightly technical in nature. I haven't prepared this in my head and I type as I think, so it might be slightly disjointed. The facts might be correct, but not represented clearly. You'll are welcome to ask me as many questions as you'll want.
As most people visiting the ICE section know, I have designed, built and configured a Carputer for my car. What is a CARPUTER?? It's a computer, a simple personal computer, installed with a purpose built power supply in a car, in order to take the place of a normal head unit.
Carputers or Car PCs are known to perform a variety of tasks like playing music, videos, internet surfing, checking occasional emails, monitoring engine diagnostics, satellite navigation aided by GPS and the screen could also serve as a reversing camera output.
Most carputers are configured with a touchscreen sitting in the center console, enabling one to operate the carputer and configure it if required. The operating system can be a myriad of choices, but my choice of operating system is Windows 7, only because it's universally accepted, easy to use, and most devices work without a fuss on it. Added benefit of Windows 7 is how easily and well it handles audio, and also the speed with which it boots up from hibernation, which is very important in a car, since there might be times when one needs to switch off the ignition or restart a car that might have stalled. Startup with Windows 7 can be between 30-40 seconds on a cold start and once set to hibernate, you can expect 10 seconds to start the unit up. Not bad, considering that is the amount of time a fully featured Caska, Kenwood or Alpine dual din touchscreen unit takes to start. Computers can also be configured to start when the ignition is turned on, and hibernate when the key is removed.
There are THOUSANDS of things one can speak of, when it comes to Carputers, but today I shall speak about the MOST important aspect that one installs a carputer for. AUDIO. Music is something NO one can drive without, unless you drive a Ferrari or a Lamborghini or a Maserati and you love listening to your engine. Well, that can be a little boring after a few months, and music is really integral to ensure that a driver stays alert over long distances, for relaxation and sometimes, to quell road rage (in my case, LOL)
So, what does one need for a carputer to sound good???
By good, I mean the whole shebang that you can do in a professional head unit.
Time alignment, active crossover management, channel cropping, phase shifting, equalization, the works.
To be honest, a year ago at this time I was lost. There was hardly any data on team-bhp and international sites didn't lay much importance on audio processing in the car. In most cases they would use on board audio on their PCs and provide a single output (headphone out: EP jack) to an amplifier, which would then power their speakers. The signal from this onboard sound card would be weak, noisy and lossy, leading to what we can safely call, MP3 sounding audio. Compressed digital audio can really be made out with eyes closed at times, and this basic onboard output with a low preout voltage and zero processing would more often than not, lead to sound quality that would be trounced by better than average head units. Well, it would serve it's purpose, but we are not here to discuss that. We are here to talk about what it takes to build a carputer that outputs a signal of SUPREME quality to the amplifiers, after which they can take over in powering the speakers.
Let's come to the hardware. You can install ANY PCI or PCI-E soundcard to take advantage of this audio processing, and you will be surprised as to how much of a difference it will make from onboard audio when you first power your system up. You will have to drop the gains considerably, since the signal voltage from a good soundcard is almost double that of onboard audio. Which is what we require.
The soundcard must have atleast 6 outputs (5.1) in order for us to distribute the signal correctly to the different speakers, and assign processing values for each speaker.
I will take the example of an Asus Xonar D2X card currently installed in my car right now.
It is a 7.1 card with 6 outputs, front, rear, surround and subwoofer out.
HOW does the soundcard know whether a particular output is connected to a front midbass or a rear fill speaker or even a subwoofer??? Well, I shall come to that, don't get confused. The following explanation will iron things out.
Coming back to the connections part, my soundcard has 4 primary outputs, front out, which provides output for the front tweeter amplifier. rear out, which provides output for the front midbass amplifier. side/surround out, which provides output for the rear fill amplifier, and subwoofer out which provides output for the subwoofer amplifier. Now someone will ask. HOW does a REAR out power a front midbass?? Well, this is the beauty of a carputer. You can ASSIGN ANY SOUNDCARD OUTPUT TO OUTPUT A SIGNAL TYPE OF YOUR CHOICE!! Hence, you can power even 5 subwoofers at a time, or 10 midbasses at a time from a single soundcard, since you can assign each channel to digitally alter and output the frequencies of audio YOU want it to. Simple as that. And beautiful!!
If this makes your head spin, please don't tear your hair out. This tutorial will actually make this sound like child's play and even egg some of you to actually go out and venture into a project like this.
I shall start with simple software talk. Here are the ESSENTIALS you will need, for your system to process audio the way it is mentioned in the tutorial. There might be more ways to do this, but this is a sureshot method since I have personally tried and failed with many other methods over the last year or so, but this one has consistently done what it was supposed to.
Here goes. You need: (It's ok to not know the functions (or even names) of most of the softwares mentioned below. I shall explain each one in detail soon)
1. Windows 7
2. Your soundcard driver. In my case, Asus Xonar Drivers.
3. Centrafuse
4. Audiomulch/Console
5. ASIO4ALL
6. Virtual Audio Cable
7. VST Plugins.
Here goes:
1. Windows 7: Operating system of choice for reasons mentioned earlier.
2. Your soundcard driver. Make sure you have the latest drivers, and make sure you have the version right (32 bit or 64 bit) I realized this the hard way when I was using the wrong version for a long time, and getting dirty mono sound out of the computer.
3. Centrafuse: The front-end of choice, this makes it easy to play music and operate other functions via a simplified touch interface and is the CORE software that helps to operate your carputer without taking your eyes off the road for too long. Big large finger friendly buttons to use the functions of the computer.
4. Audiomulch: This is where all the complex software meets and communicates and co-exists with each other. This is the meeting point, and like the command centre for audio processing in your computer.
5. ASIO4ALL: Audio Stream Input/Output (ASIO) is a computer-sound card driver protocol for digital audio, providing a low-latency and high fidelity interface between a software application and a computer's sound card. ASIO drivers are generally bundled into a soundcard driver, but sometimes the drivers might just not communicate well with the soundcard. Which means, you need to get ASIO4ALL, which is a universal ASIO driver, simplifying things, and making the software (processing) and the soundcard 'talk' better with each other.
6. Virtual Audio Cable: Virtual Audio Cable software allows you to transfer audio (wave) streams between applications and/or devices (in our case, from Centrafuse to Audiomulch, and then to the soundcard)
It creates a set of virtual audio devices named "Virtual Cables", each of them consists of a pair of the waveform input/output devices. Any application can send audio stream to an output side of a cable, and any other application can receive this stream from an input side. All transfers are made digitally, providing NO sound quality loss (a bitperfect streaming).
IF this sounds difficult, just gulp it down with a pinch of salt. It's ok to not know what this does. JUST MAKE SURE YOU DON'T ELIMINATE IT FROM YOUR EQUATION though.
7. VST Plugins: Now these are small .dll files (remember Windows 98 onwards?) that are available by the TON around the internet, and these plugins are the ones you use, inside Audiomulch to add ANY FORM OF processing to the audio. Time alignment plugin, crossover assignment plugin, channel trim plugin, phase control plugin. You name it, we have it. Free or paid, whichever works for you.
HOW DOES ONE DO THIS?!! IS this complex wizardry?? Do you need to be cleverer than your friendly neighbour who is a level 4 electronics engineer at IIT??? Noway. It's simple. I did it. Why can't you?? It's as simple as DRAWING LINES. (Mark my words. Drawing lines is not a joke or an analogy. At some point in this tutorial, audio will emit from the speakers ONLY if you draw these lines in Audiomulch. YES, LITERAL drawing of lines!)
1. First, go to your soundcard and configure it to output 8 channels (just do what I am saying, even if it has only 5 channels). Then go to windows control panel and set VIRTUAL AUDIO CABLE as the default audio device, NOT your soundcard. (you will understand why as you read on)
2. Go to start>programs>virtual audio cable, and click on control panel. Enable volume control. (there is an option, tick on that box. This will allow you to control the system volume from Centrafuse. If not checked, raising or lowering the volume from Centrafuse will result in NOTHING, and you will have to go to the windows audio control panel, which is a pain on such a small screen, esp while driving)
3. Start>Audiomulch>
after opening audiomulch, go to EDIT->SETTINGS.
under settings, click on audio driver-- it should be set to "ASIO4ALL" (note that these pictures are from a WRONGLY explained thread elsewhere, but since I don\'t have pictures from my PC, I illustrate these. DO not set it to windows multimedia. Set it to ASIO4ALL.
IMPORTANT STEP: Now that you have enabled ASIO4ALL, a green coloured icon will appear in your windows taskbar (next to time, volume and antivirus icons).
Double click on that, and there will be a lot of settings. On the bottom right hand side, click on ADVANCED.
Setup ASIO4ALL with VAC set as the only "INPUT" (light turns on in the interface) and Xonar as the only "OUTPUT". DISABLE ALL OTHER LIGHTS THAT ARE TURNED ON IN THE INTERFACE.
4. Now go to AUDIO INPUT, and set it up like the picture for VAC:
5. for audio output, setup your audio card, and its respective channels. HERE he shows 6 channels, I say setup 8 channels.
6. Click ok to exit out of the settings window, and you will have the basic screen-- under the inputs/outputs area, you can drag the input/output plugins onto the layout screen, and then connect them by clicking and dragging between the 'nubs' on them-- this will create 'wires' between them... (TOLD YOU, we gotta draw lines!!)
if you set it up like i have on the screen shots, you will almost have re-enabled audio on your computer..
there is a speaker button in the top row-- right above auxin4 on the screen shot that need to be enabled-- after enabling that, you should have a computer that with audio that acts normally-- if you 'ding' the volume slider in windows, or play a song, it should come through fine now.
7. for the Plugins: you should see it near the bottom of the list on the lefthand side under vstplugins:
8. drag it onto the screen, delete the 'wires' connecting the input and output, and then reconnect the input/output to the plugin. it should look something like this: This is where you can do your frequency segregation via crossover, time alignment, phase control etc. Just drop the plugin between the output and the input.
9. now double click on the plugin, and it will pop up with the adjustment menu on the right hand side-- that you can use to tweak till your hearts content(i assume that you have a enough experience with stereos, i don't need to explain all the knobs, but in case you run stuck, there should be a manual that was included with the plugins-it will be in the vstplugins folder):
IMPORTANT TIPS:
1. Remember to assign inputs and outputs well. TYPICALLY, not thumb rule,
MAIN INPUT will be soundin, (in my case, tweeters) aux 1 will be input 1 and 2, (in my case, Midbasses) aux 2 will be input 3 and 4, (in my case rears) aux 3 will be input 5 and 6 and (in my case, subwoofer) aux 4 will be inputs 7 and 8.
Accordingly set the outputs,
soundout, auxout1, auxout2, auxout3 and so on, depending on the number of outputs.
2. Think of audiomulch as a drawing board. Just draw the channels (left and right) from the main source to wherever you want in real time and feel the sound stop or move accordingly.
IT's simple. Not rocket science. This tutorial should get you started up. This should be the primary thread for audio processing on a car pc, so start with all your questions here. Will try to answer as many as I can!!
Cheers!!
Could not have been a more appropriate thread title.
Very well written Frank. With so much research done by you, I am going in for a Carputer in my next car for sure. Thanks!
Frank. I read the specs. of Xonar and it says Output/Input Full-Scale Voltage - 2 Vrms (5.65 Vp-p). How is it compared to CD7200MKII ? Have you used any Line Driver ? For e.g. JL Audio CL-RLC Preamp.
I know XONAR has definitely higher Output voltages than Onboard Audio. But After installing xonar did you turn down your Gain on Amp ?
At traffic lights when you can swtich off the engine, does it keep switching between hibernation and active?
Also, unlike a HU during such circumstances, it wouldn't continue playing the same music after a engine restart, right?
Maybe the computer should be connected directly to DC (remembering to shutdown/hibernate when needed) and the amps to the key mechanism?
Quote:
Originally Posted by jinu_joseph
(Post 2353173)
You can take care of this by using SSD disk. This will ensure and improved boot and respone times and no impact due to vibrations. Its expensive but worth the price.
Can wait to see the pics..
|
I am using a laptop hard drive. Supposedly they are better at taking shocks than the huge Desktop drives.
Quote:
Originally Posted by nisarg86
(Post 2353341)
Frank. I read the specs. of Xonar and it says Output/Input Full-Scale Voltage - 2 Vrms (5.65 Vp-p). How is it compared to CD7200MKII ? Have you used any Line Driver ? For e.g. JL Audio CL-RLC Preamp.
I know XONAR has definitely higher Output voltages than Onboard Audio. But After installing xonar did you turn down your Gain on Amp ?
|
Don't read much in the VRMS. The Eclipse was destined to put out 8 VRMS according to it's specs. It didn't. Probably put out half. Or slightly less. 8 VRMS is quite a wild figure and all gains must be turned down to ZERO if it was actually 8 VRMS. Turns out, it wasn't. Almost all gains in all the amps were on half, when I had the eclipse.
After installing the Xonar, BELIEVE IT OR NOT, I had to turn down the gains on the amp.
So this VRMS bull and cock story is far from true, and once again cements my belief in the fact that figures never speak the truth!
No line output, nothing! Running directly from the soundcard.
Besides, even if you do use cards with low VRMS, you can always bump the gains on the amps, most of them can play well even with .5 VRMS with Gains almost on full.
Quote:
Originally Posted by bullboy
(Post 2353375)
Frank, Does this mean one stereo amp needed for each channel or a 4 channel + mono will suffice?
|
No no, 2 channels required for each speaker. So the number of amps doesn't matter. It's how many speakers you need, and how many channels of amplification you have.
Normal headunits have 3 preouts, the soundcard has 4, (or more, depending on what you assign to it)
4 channels + mono is perfect for a setup with one component set, one rear fill and one/two/xx subwoofers.
Quote:
Originally Posted by srishiva
(Post 2353485)
At traffic lights when you can swtich off the engine, does it keep switching between hibernation and active?
Also, unlike a HU during such circumstances, it wouldn't continue playing the same music after a engine restart, right?
Maybe the computer should be connected directly to DC (remembering to shutdown/hibernate when needed) and the amps to the key mechanism?
|
Yes, as long as you have the key in the ignition, the computer doesn't get a SHUT DOWN/HIBERNATE signal. Hence, when you are in the car, and you have to shut it at a signal, the computer stays on.
Switch it on while music is playing, and there is no break. The computer stays on. DC-DC Car power supplies are very clever. Almost like a mini UPS, but without storing electricity as such.
Quote:
Originally Posted by greenhorn
(Post 2353542)
a 4 channel + mono should be fine. the third pair of channels is teh center and sub - I'm not sure if you need a center, given that the soundstage is pretty decent already.
If you are planning to go active bi way or more, you'll need more amp channels :)
|
You don't need a center, unless you plan a 5.1/7.1 setup in the car. Which is ALSO possible IMHO. In a very grand way. With a Lot of DSP. That is something for someone who has a lot of 5.1 digital content and likes to feed it to his carputer. Not me. I love my music. And I listen to mp3s, FLAC and the like.
MODS: Wouldn't it be appropriate to change a single word in title. "Idiot's" to "dummies".
Raab Rakha.
