Frequency at which a speaker vibrates in unison with the audio signal creating vibrations in the enclosure and driver with very little input. A speaker driver is easier to drive at its resonant frequency because that is the frequency it is naturally attuned to. However, the resonant frequency may cause standing waves and other sound anomalies. vibrating speaker enclosure tends to “color” the sound or change its tonal characteristics. For this reason, speaker enclosures are built to resist vibration, and this is why resonant frequencies create difficulty with audio reproduction. ll instruments have a resonant frequency that allows them to make sound. For instance, a piano string has a certain resonant frequency that enables it vibrate and create sound for an extended period of time with a small input (it resonates amplifying the input). This is desirable in nature, but speakers are supposed to accurately portray the sound of instruments and other sound sources not their own resonances.