Introduction: How to Choose a Subwoofer for Your Car Audio System (to Place in the Trunk of Your Car)

This instructible will give an idea of how to choose a suitable subwoofer/s for your ride. This has a lot of information regarding selection of your beloved 'woofer. I have a lot of friends who have taught me a lot of stuff about sound systems, as well as magazines and internet articles, which have developed my knowledge heaps as of late.
I hope this helps you people unsure about what to get. Enjoy.

Step 1: Your Car

Firstly you need to have an idea of what car your subwoofer/driver is going into, because the size of the car and amount of space will directly affect the size and/or amount speakers you can install. If youre like me, you wont have a car at the moment, but it wont stop you if you have a little knowledge about cars (I didnt have a car at the time of writing, but I had a very good idea of one that I wanted).

Step 2: Measurements

Once you've decided what car your driver is going into, you can just go out and buy a speaker, but it's best to do some research first, whether it be simply to talking to some friends in the know, or going to a local auto electrician and getting someone with experience to voice their opinion. Or you could simply get on the internet, and get some info on your car (if you don't have one). When I did my research, I got a few measurements of the car which were: rear width, rear track, total trunk capacity (in litres). I'll explain these later.

Having these measurements can help you to calculate the dimensions of the trunk (if that's where the speaker is going), which will better help determine what drivers you're buying. The depth and width, while still necessary, arent as essential as the height of the trunk. This particular measurement becomes less important to get right if you're looking at getting smaller drivers, such as an 8" driver, or a 10" driver. I had already bought two 12" drivers, which meant, coupled with the size of the enclosure (I was building my own), there was little room for error in terms of the height of the box.

Step 3: Enclosure Types

Next is choosing which type of enclosure you will use to house your speaker. There are two common types:
"Sealed: A completely airtight enclosure, very basic in design, good speaker performance, improved bass response
"Ported/Vented: Similar to a sealed type, but with a vent/port installed, used to emphasise a particular frequency, improved reproduction of low bass frequencies, low distortion
How you want your subwoofer to perform will mostly likely decide for you which type of enclosure you will choose. I can't recommend either, because I have only ever heard any subwoofer used in a ported enclosure, but I really do love the loudness that the ported type provides.

Step 4: Buying the Subwoofer

Once you've gotten all necessary information about your car, and what enclosure youre going to use, you can go out and purchase a subwoofer. When you first get your eyes on a speaker of interest, you're immediately going to see a few things that may confuse you, but dont worry, help is at hand.

The things that hit you first will more than likely be the following:
"Power Handling (Watts RMS and Max)
"Size of the subwoofer (8", 10", 12", 15")
"Amount of voice coils (SVC or DVC)

We'll start off with explaining Power Handling:
This is basically stating how much power your subwoofer can handle before it starts damaging itself. Generally, the higher the power, the better it can handle bass when your system is turned up to its loudest.

Note: Most manufacturers will try to entice a customer into buying their product by giving them the wrong impression about their speaker's power handling abilities. On the box, power handling will be specified, but it will more than likely be the Max power rating. Don't be fooled, most subwoofers can only take this amount of power for short amounts of time, but not continuously.

The power rating measurement that you're looking for is the Watts RMS rating. This shows exactly how much power your subwoofer should take to make satisfactory (and often amazing) bass. If you can't find an RMS rating, but a Max power rating is evident, generally you can simply divide this amount by two to get an idea of the WRMS rating for the particular speaker.

Next is the size of the subwoofer.
Fairly self-explanatory, it's just the size of the driver. The most popular ones seem to be the 12" type, because they have a decent cone size without being massive.

Finally, the Amount of Voice Coils.
The amount of voice coils can help decide which type of amplifier to purchase, but I won't explain that now. Basically, the amount of voice coils is the amount of inputs to your speaker. If your subwoofer has only one voice coil (Single Voice Coil, or SVC), it has one input for you to wire the sub to the amp. If your sub has two Voice coils (Dual Voice Coil, or DVC), it has two inputs for you to wire the sub to the amp.

People will generally try to get a DVC sub for multi-sub projects, because it gives them more options when they come to wiring their subs to their amp.
But, if youre only going to be using one subwoofer (which is often enough), you should show more interest in an SVC subwoofer. It doesn't have any significant advantages over a DVC sub, while still maintaining comparable performance attributes. They're also easier to install if you're doing the whole thing yourself too.

Step 5: Conclusion

This is probably the easiest step in the process of upgrading a sound system, which is...
Installing it! The installation will more often be done by a professional auto electrician, which means that it will work first time, and generally satisfy the customer. But, it can also be the hardest step if you do it yourself, which is why I would recommend the auto elec. Option if you're not confident about doing it yourself.

If you read the first part of step 2 again, you remember these measurements:
"Rear Width
"Rear Track
"Trunk Capacity

Rear width is pretty easy; it's simply the width of the car at the rear

Track is a little trickier though. Track is commonly referred to as the distance from the centre of one tyre to the centre of the tyre on the opposite side. If you've ever been driving in rural areas with lots of sand, or you've driven through mud, you will have seen an excellent example of how track looks. It just looks like the number 11: II.

Trunk capacity is also pretty obvious. It's essentially how water/air your trunk could hold if you filled it up. The measurements to calculate this are:
Width of Trunk x Length of trunk x Height of Trunk, or LxWxH. It is best to measure the height of the trunk against the back seat, because that's normally where the subwoofer and enclosure will be placed.

Enjoy the results of your new speaker peoples!
Feel free to comment on this instructible so as to help me improve my writing of other instructibles.