Cabinet Resonance

Any box-like construction will resonate at one or more frequencies. In the case of a loudspeaker, such resonances are likely to be undesirable as they may obscure or interfere with the wanted sound from the drive units. As resonance also involves the storing and releaseing of energy over time, cabinet resonances can result in 'time smearing', causing a sharp impulsive sound like a 'thud' to be reproduced as a prolonged 'boom'.  Cabinets are usually braced and damped internally to minimise resonances.