According to one embodiment of the present invention, a thermoacoustic device has a complaint enclosure which includes a rigid portion and a compliant portion. The compliant portion includes an oscillating member and a flexure seal with a pair of ends and a flexure body extending between the ends. One of the ends is sealed to the rigid portion and the other end is sealed to the oscillating member. The flexure seal has an average cross-sectional area and an end-to-end equilibrium length. A flexure volume is defined as the product of the average cross-sectional area and the end-to-end equilibrium length. A thermal core is disposed in the complaint enclosure and includes at least a first and a second heat exchanger. A working volume of gaseous working fluid fills the complaint enclosure. The working volume of gaseous working fluid has an equilibrium pressure. A motor is operable to oscillate the oscillating member such that the end-to-end length of the flexure seal is increased and decreased with respect to the equilibrium length. Therefore, the pressure of the working volume of gaseous working fluid is oscillated between a peak pressure greater than the equilibrium pressure and a minimum pressure less than the equilibrium pressure. In some embodiments, the working volume is less than or equal to four times the flexure volume, while in other embodiments, the working volume is less than or equal to two times or one times the flexure volume.