How to Choose a Subwoofer

The time has come and you want to add some bass into your vehicle, so you start looking into purchasing a subwoofer. A subwoofer is a loudspeaker component designed to reproduce low bass frequencies. You do not get very far into your search before you realize that the options available to you are abundant. So how do you know what to look for in a subwoofer before purchasing it? When it comes to choosing a subwoofer for your vehicle, there are many factors that are important to take into consideration. Things such as what your budget is, what your goals with the setup are, how much space you have available in your vehicle, how much power you are able to provide the subwoofer, and your installation capabilities.  

Budget 

There are many different subwoofer manufacturers available at Down4Sound: Ampere Audio, Audio Dynamics, Cerwin Vega Mobile, Crossfire Car Audio, DC Audio, Deaf Bonce, DS18, Hutchinson, Incriminator Audio, Skar Audio, Sundown Audio, and Wolfram Audio. Each manufacturer offers various subwoofer models and thus has subwoofers that fit into many different budgets. These blogs may prove useful in helping you to find subwoofers in a budget range that fits your needs.  

Goals 

Other than budget, it is important to consider what is the most important to you in your setup. Do you prefer superior sound quality, the maximum output possible, or a blend of the two? A subwoofer’s Thiele/Small (T/S) parameters will help you choose a subwoofer that fits your needs and wants. T/S parameters are a good indication of the subwoofer’s capabilities and what it was designed to do or what kinds of applications it was designed for. If you are unfamiliar with T/S parameters you may find this blog to be helpful. Some generalizations are: 

• Lower Fs = Better reproduction of lower frequencies.  
• Lower Qms = Ability to dampen decreases.  
• Lower Cms = Stiffer movement of the cone. 
• Lower Mms, Mmd = Higher Fs. 
• Lower Sd = Less air movement.  
• Lower Xmax = Less cone movement and less air movement.  
• Lower Qes = Ability to dampen increases.  
• Lower Le = Better reproduction of higher frequencies and the faster the response to changes in the signal. 
• Lower Sensitivity = Less output, based on the same input power.  

Space 

Another factor that is important to consider is the amount of space available in your vehicle. It is crucial to first measure the amount of space you have available then pick the size and quantity of subwoofer(s) based on that measurement. To measure the amount of space you have available you should measure the space’s depth, width, and height (in inches). Then, multiply these three figures together. After that, take the product and divide it by 17.28 to calculate the overall volume available (in cubic feet). This will tell you your maximum dimensions, which can then be used to select the size and quantity of subwoofers (and eventually – the enclosure type and air volume of that enclosure). To find the air volume of an enclosure you follow the same steps to calculate the overall volume available, but you also take into account displacements from the subwoofer(s) and port(s).  

Subwoofers come in various sizes. The most common sizes are 6.5”, 8”, 10”, 12”, 15”, and 18”. Each subwoofer model and size take up its unique amount of space (depending on the size of the soft parts and the motor). Please note that the size of the motor itself is not a fair indication of the subwoofer’s capabilities. In order to properly understand the capabilities of the subwoofer, you should look into the subwoofer’s Thiele/Small (T/S) parameters. Though, as a general rule of thumb the larger the subwoofer is the lower the frequencies that can be produced. 

Another factor to take into consideration is how many subwoofers to choose. Again, as a general rule of thumb, the more subwoofers there is the more air movement that will occur. However, the larger the subwoofer and the more subwoofers there is the more internal airspace that the subwoofer(s) will need. It is very important to provide the subwoofer(s) with the amount of airspace needed so it performs at its best. Most commonly, a sealed enclosure or ported enclosure will be needed.  

A sealed enclosure is an enclosure in which the internal airspace is completely isolated from the outside environment. Generally, a sealed enclosure will give a tighter, more articulate bass. A ported enclosure is an enclosure in which the internal airspace is not completely isolated from the outside environment, instead, it is purposefully ported to the outside environment. Generally, a ported enclosure will give a looser, efficient boost of bass.  

To figure out which enclosure type you should choose, you can calculate the subwoofer’s efficiency bandwidth product (EBP). You can do so by taking the subwoofer’s Fs and dividing it by its Qes. An EBP less than 50 indicates the use of a sealed enclosure or a 4th order bandpass enclosure. A 4th order bandpass enclosure is an enclosure in which a sealed section is on one side of the subwoofer and a ported section is on the other. An EBP between 50 and 100 indicates flexibility in which enclosure can be used. An EBP greater than 100 indicates the use of a ported enclosure or a 6th-order bandpass enclosure. A 6th order bandpass enclosure is an enclosure in which there are two ported sections on both sides of the subwoofer. EBP is not a hard and fast rule for selecting which enclosure to use. Though, it is a useful indicator for which enclosure the subwoofer might perform the best in.  

Another parameter that can be used to figure out which enclosure type you should choose is the subwoofer’s Qts. A Qts less than 0.4 is optimal for a ported enclosure. A Qts between 0.4 and 0.7 is optimal for a sealed enclosure. A Qts greater than 0.7 is optimal for an infinite baffle.  

Power 

Power is another factor that is important to consider when choosing subwoofer(s). Subwoofers come in various impedances. A single voice coil is a speaker design in which one length of wire is wrapped around the former and has a single positive and negative terminal. The most commonly used impedances with single voice coil subwoofers are 1-ohm, 2-ohms, and 4-ohms. A dual voice coil is a speaker design in which two lengths of wire are wrapped around the former and have a double positive and negative terminal. The most commonly used impedances with a dual voice coil subwoofer are .35-ohm, .5-ohm, .7-ohm, 1-ohm, 2-ohms, and 4-ohms.  

There is not necessarily an advantage to a subwoofer having one or two voice coils, other than flexibility in wiring options. The impedance chosen will determine which ohm load your amplifier will see. The ohm load your amplifier sees will determine how much power the amplifier puts out. It is ideal for the amplifier to be rated to generate 75% to 100% of the subwoofer’s maximum RMS (while also taking into account the number of subwoofers) at an ohm load that is deemed SAFE by the manufacturer for that specific amplifier. This information can typically be found on the manufacturer’s website or in the amplifier’s owner manual. It is a crucial piece of information, because wiring an amplifier too low may result in equipment failure.  

It is also generally not a good idea to pick out a subwoofer based only on its power handling abilities. This is because some manufacturers list a peak or max rating, which is usually not a true representation of the power the subwoofer can handle consistently over a long period of time. Furthermore, there is a limit to a vehicle’s stock charging capabilities. This means that upgrades to the electrical such as the alternator, battery, and the addition of the Big-3 will eventually be required to utilize an amplifier that can power certain subwoofers properly.  

Installation Capabilities 

There are reasons why someone might need to choose a powered subwoofer or a loaded subwoofer enclosure. If you are new to the car audio scene and are unfamiliar or uncomfortable with pairing equipment and wiring it. Or if you just don’t have the interest, time, or tools to build your own enclosure and hookup subwoofer(s) and amplifier(s). In these scenarios, it may be a good idea to consider a powered subwoofer or a loaded subwoofer enclosure. The advantage to these options is that the manufacturer provides you with a combination of equipment that they know pairs and performs well together.  There are many loaded subwoofer enclosure options available at Down4Sound. 

In conclusion, there are many different factors that can influence the way your setup will sound and perform. That is why it is important to be tactful in choosing subwoofers for your vehicle by taking all these factors into consideration! 

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