A headphone type acoustic apparatus, comprising: a headband having two end portions; a pair of slider blocks , wherein each slider block of the pair of slider blocks slidably retains a respective end portion of the headband ; a pair of housing blocks , wherein each housing block of the pair of housing blocks is coupled to a corresponding slider block of the pair of slider blocks via coupling portions, and wherein each housing block of the pair of housing blocks includes a headphone unit ; and a pair of speaker units , wherein each speaker unit of the pair of speaker units is disposed in each slider block of the pair of slider blocks , wherein each of the pair of speaker units is arranged to transmit sound to a user by vibrating air in a surrounding open space, and wherein each headphone unit is arranged to transmit sound to the user by vibrating air in a space closed by the housing blocks , characterized in that , each of the pair of the speaker units further comprising: a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block ; a magnetic circuit that is configured to drive the diaphragm ; a case that retains and houses the diaphragm and the magnetic circuit; and a lid that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block , wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user. a headband having two end portions; a pair of slider blocks , wherein each slider block of the pair of slider blocks slidably retains a respective end portion of the headband ; a pair of housing blocks , wherein each housing block of the pair of housing blocks is coupled to a corresponding slider block of the pair of slider blocks via coupling portions, and wherein each housing block of the pair of housing blocks includes a headphone unit ; and a pair of speaker units , wherein each speaker unit of the pair of speaker units is disposed in each slider block of the pair of slider blocks , wherein each of the pair of speaker units is arranged to transmit sound to a user by vibrating air in a surrounding open space, and wherein each headphone unit is arranged to transmit sound to the user by vibrating air in a space closed by the housing blocks , characterized in that , each of the pair of the speaker units further comprising: a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block ; a magnetic circuit that is configured to drive the diaphragm ; a case that retains and houses the diaphragm and the magnetic circuit; and a lid that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block , wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user. a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block ; a magnetic circuit that is configured to drive the diaphragm ; a case that retains and houses the diaphragm and the magnetic circuit; and a lid that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block , wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user. <EOS>