How to Choose Loudspeaker Enclosure Design, Material & Type

Choosing the Right Speaker Enclosure Type and Material for Your Application

Every part of a speaker is important to its sound, but the beauty of great loudspeaker design is that you can alter almost any of them to meet the needs of your specific application. The speaker enclosure is also a crucial part of loudspeaker design- the choices you make about its material, size, and shape are instrumental in getting the right durability, sound quality, and performance from your loudspeaker system.

You can make the search for the right loudspeaker enclosure design a little easier by considering a few of your options and how they make sense (or don't) for your needs. Read on for an overview of basic speaker enclosure types, materials, and how to find the right design for your application.

What is a Loudspeaker Enclosure?

A loudspeaker enclosure is the housing in which a speaker driver (woofer or tweeter) is mounted, sometimes along with other elements like circuitry and amplifiers. Loudspeaker enclosures are also called loudspeaker boxes or loudspeaker cabinets.

Enclosures are important not just for the aesthetic appeal of the speaker (if it is visible) but also because they play an important role in how the speaker sounds and works. For one, the enclosure separates the speaker's front-facing sounds from its rear-facing sounds, which prevents wave cancellation that happens when two out-of-phase sound waves interact with each other. Loudspeaker boxes also manage the tuning, sound vibrations, moving air mass, and heat that result from the driver's operation.

Speaker Enclosure Types and How They Affect Sound

Loudspeaker enclosures come in all shapes and sizes, depending on how they're used. The material, shape, use case, box size, and driver size are all factors that affect what loudspeaker enclosure design is right for your application.

Generally, a speaker enclosure should be fairly rigid and resistant to vibrations. A concrete speaker enclosure would be great for resisting vibration, while a flexible plastic enclosure would be terrible. When it comes to enclosure types, loudspeaker designers have many options to suit the needs of their projects. 

Fundamentally, loudspeaker enclosure design comes down to a few key factors:

• Enclosure material (wood, aluminum, or plastic composite). 
• Speaker enclosures are traditionally made from wood because it's durable, relatively lightweight, and able to absorb vibrations. Wood enclosures (MDF works great) also have the benefit of aesthetics through the use of different colors or finishes.
• At some thicknesses and by using the correct composite materials, rigid plastic speaker enclosures flex less than very thin wood enclosures, making them an attractive option for loudspeaker design. They're also more durable than wood and more cost-effective in high manufacturing volumes.
• Enclosure type (sealed, ported, or passive radiator).
• A sealed speaker enclosure moderates the movement of the speaker’s cone at low frequencies by acting as an air spring inside the enclosure.  Because this helps to tune the low frequency of the driver, there must be no air leaks. A ported speaker enclosure (or "reflex port") essentially adds a ported tube to the enclosure, creating a mass that can allow a lower tuning in a smaller enclosure than a sealed box. Ported enclosures may have to be deeper than a sealed box to accommodate the length of the port but changing the length and diameter of the port lets designers "tune" the box to different resonant frequencies based on the application.
• A passive radiator enclosure operates similar to a ported enclosure but may allow for a more compact box than one needing a long port. Because passive radiators can achieve comparable resonance to ported boxes but take up less space, they're ideal for shallow home audio and car audio applications.

The physical makeup of the speaker box is instrumental in its resonance, resistance to vibration, and durability.

Choosing the Right Speaker Enclosure

When designing a speaker enclosure, it's important to remember there's no universal "right" choice for every speaker application. Even between similar applications, the many factors of a loudspeaker's use and specifications will change what type of enclosure will best achieve the sound, durability, and longevity you need. You should speak to your loudspeaker manufacturer about your specific needs rather than choosing based solely on one or two factors. An enclosure can be designed to optimize a given driver, or the driver can be designed to optimize the space available for the enclosure.

That said, you can narrow down your options by starting with what you need out of the end product and working backward from there. For example, if you know the speaker will be a typical square or rectangular shape, you might limit your scope to wood enclosures. On the other hand, if the shape of your loudspeaker is more complex with recesses and unusual shapes, plastic molding is often more effective and cost-efficient.

Other considerations include making them out of flame-retardant material or being manufactured to meet certain material, loudness, or power ratings. Or, if your quantity needs are at odds with the cost-effectiveness of the materials, you need to get them made to spec.

The important thing to remember is that a properly designed speaker requires both the right enclosure and the right driver working together to create the right audio system for your application. Speak to your speaker designer and manufacturer about the solution that best balances and addresses your loudspeaker needs.