Capsule Size options

When shopping for microphones, you’ll often see specifications like 3mm, 4mm, or 6mm listed in the product description. These numbers refer to the capsule size, which is the diameter of the tiny microphone element inside the mic head that actually captures sound. While it may seem like a small detail, capsule size has a meaningful impact on how a microphone looks, sounds, and holds up in real-world use. Understanding this one spec can make it much easier to choose the right mic for your performers and your space.

Capsule size mainly affects four things: visibility, durability, output level, and overall sound character. Smaller capsules are easier to hide and are lighter on the performer, but they tend to be more delicate and have slightly lower maximum volume before distortion. Larger capsules are more visible, but they are tougher, naturally louder, and often produce a fuller sound. Choosing a capsule size is always a balance between how discreet the mic needs to be and how rugged it must be for repeated use.

Very small capsules, such as 3mm, are designed for situations where the microphone must remain nearly invisible. These are commonly used in wigs, hairlines, and professional stage or on-camera environments where appearance is critical. They deliver clear, natural sound but are more fragile and less forgiving of rough handling. A step up, 4mm capsules are considered the theatre “sweet spot.” They are still small enough to hide easily while offering improved durability and a fuller sound, making them ideal for school productions, dance-heavy shows, and general stage use.

It’s important to note that capsule size does not affect wireless range, transmitter compatibility, or whether a mic is omnidirectional or cardioid. Those factors depend on the transmitter and microphone design, not the physical size of the capsule. Capsule size is primarily about the physical footprint of the mic and how it behaves acoustically and mechanically in everyday use.

For most theatre programs, a simple rule of thumb applies: smaller capsules for hidden placement, larger capsules for visible use, and 4mm as the best all-around option. It offers the best balance of concealment, durability, and sound quality for typical stage productions.

There is no single “best” capsule size for every situation—only the best size for your application. By understanding what capsule size really means, you can choose microphones that look better on stage, last longer in your inventory, and deliver consistent sound for every performance.