THE DO'S YOU CAN DO!
First and foremost, check whether you really need a sound system or not. Most modern cars already have great sound systems and spending more on it will only give diminishing returns. Even if your car is slightly older, but has a system installed by some previous owner, it isn't always necessary to tweak it unless there is something wrong with it.
If you do decide, however, that it needs changing, then start with the requirements one at a time. Most of your required items will be found in Bangla Motor and Stadium Market. The latter features greater bargains and more exotic parts.
First thing to start with is your entertainment centre, aka head unit, or deck, which have been around since the 60s, featuring radio, and later on, stereo. But as with all things these days, head units have also gotten the digital treatment. Nowadays, these heavy duty things feature LCD panels to eliminate buttons and switches and bring about more innovation such as satellite navigation, online digital radio, DVD movie, climate controls, and so on.
Next, and probably the most important component to consider are the speakers. This single component can make or break your entire system so choose wisely. Expensive necessarily doesn't translate into good, so do your research. Your car's internal space also plays a key factor. For example, putting two tiny speakers in a minivan wouldn't really yield a good result and neither will putting six gigantic speakers in a tiny Maruti hatchback. Your speaker choices should include a set of twitters and full range speakers to give off a clear sound with plenty of mid range flavour and just enough bass to keep most people happy. Subwoofers are an optional addition, but they can add quite a bit of substance to your tracks, but don't go overboard with it. 6-8” woofer cones should be more than enough for just about any car, unless you plan to fit them in a bus, in which case, a 12” can be recommended. An innovative way to install subwoofers would be to install them on sidewalls of your trunk, which saves space for carrying luggage when you do head out for a road trip with people.
After taking care of those two, it is time to address the case of amplifiers. Amplifiers, simply put, amp up your audio signal so that your speakers can produce the sound properly. Any speaker without a proper amplifier would produce very little sound regardless of how much you spin the volume dial. Invest in good quality amplifiers with good venting as these things tend to get hot. One overlooked components are wires. Invest in good high quality wires.
THE DONTS' YOU JUST DON'T!
Whenever people hear car sound systems, they immediately think idiotic cars with loud booming bass and nothing else zooming by. It is as stereotype created by people who only fit subwoofers and amps and very little else. So when building your sound system, please respect the other frequencies and add the full range of speakers and don't place emphasis on the subwoofers too much. They should compliment a sound system, not overrule it.
Also, think about getting proper amplifiers made with cars in mind. There have been cases where people fit amplifiers made for home sound systems. As mentioned previously, these things tend to get hot, and the car is an already hot environment. You don't want to burn your car down while playing Taylor Swift's 'Picture to Burn'.
When choosing a head unit, make sure to only pay for something you need. If you end up buying something supremely expensive with satnav and online radio and so on, but only connect via auxiliary to listen to music, then it is just money down the drain.
Talk to people who have sound systems installed in cars similar to yours and find out what worked for them and what didn't. There is no alternate for trial and error and experience, and getting theirs would only benefit you more.
Audio system installation might seem like a big job to do but with the right amount of knowledge and information, you can get your ideal sound system that you dreamt for and head on a road trip of your life! Happy Vroom Vroom Vrooming!