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LCD vs. SDC

Large Diaphram Microphone vs Small Diaphram Microphone

When choosing microphones for this kind of work, you need to find the right balance between two virtues: 1) low self-noise, and 2) good off-axis response.

As the diaphragm gets larger it is capable of collecting more sound energy and therefore has lower self-noise - i.e. the microphone is quieter. But the larger diaphragm (and the housing around it) creates a larger obstacle to sounds arriving off-axis, resulting in poorer off-axis response. The result is a coloured sound. LDCs are fine for close-miking, but not so good when you're miking from a distance and need to capture all sounds cleanly.

As the diaphragm gets smaller it becomes less of an obstacle and so the off-axis response improves, resulting in a more natural sound when miking from a distance. The downside is that there is less surface area to collect sound energy, resulting in higher self-noise.

SDCs from 10mm to 15mm or so generally provide the best compromise between good off-axis response and low self-noise. Hence they are very popular with people who record acoustic music.

To give two examples from DPA's stable: their 4060 series of omnis use 5.4mm diaphragms and have a textbook omnidirectional response, but their self-noise is 23dBA or thereabouts. At the other extreme, their 4041 omni has a 24mm diaphragm and offers a self-noise of only 7dBA, but it's off-axis response deviates considerably from omnidirectional, especially at higher frequencies.

Horses for courses. If low noise is a priority, there are few mics that can come close to DPA's 4041. But if excellent off-axis response is a priority, it's hard to beat their 4060 series.

Most DPA owners have the models with the 16mm diaphragms, such as the 4006 or similar, which offer a good compromise between off-axis response and self-noise.

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