Loudspeaker in a sealed enclosure
Loudspeaker mounted in a sealed enclosure sees:
on a front surface: radiation impedance
on a rear surface: discontinuity impedance (acoustic mass) in series with an acoustic impedance of a box
at low frequencies, sealed enclosure is seen as acoustic compliance
at highest frequencies, the eigenmodes of the box reveal internal resonances modifying the impedance seen by the loudspeaker. In general, electroacoustic models take into account the resonances existing along the largest dimension of the enclosure using waveguide models (see section 2.3).
Response of a complete system (loudspeaker + sealed enclosure) is as follows:
electrical impedance has a single resonance with frequency and quality factor that are higher than for a screen-mounted loudspeaker.
pressure response is a high-pass filter of order 2 (12 dB / octave slope) with higher resonance frequency and quality factor than for screen-mounted loudspeaker. At high frequencies, pressure response may involve bursts due to the internal resonances of the box (which can be damped with absorbent material).
