Geometry depended mathematical model of transmission line loudspeaker enclosures and acoustical filter design

The design process of transmission line enclosures always had ambiguous points by means ofgeometrical terms. The effects of bends, rear chambers, placement of terminus, the placementof the speaker unit on the line on the frequency response was not clear. Today, all thesoftware aimed to model these kinds of loudspeaker enclosures, use electro-acoustic model tosimulate the response of the system. It is well know that, electro-acoustic system fails as thegeometry gets complicated and can not bring a reasonable result. When the designer is subjectto transfer the dimensions from software results to real enclosure, it can be seen that the taskhas many pitfalls originating from the uncertainties in the geometry.In this thesis, the influence of geometry over the frequency response has been indicated. Inorder to achieve this aim, alternative methods to electro-acoustic model has been searched andwith parallel to the development in computers, the wave equation has been solved using finitedifference method. With the help of absorbing boundary conditions, it was made possible tosimulate an enclosure inside the solution field. The results received from the numericalmethod have been compared both with the commercial software, FemLab and themeasurement results taken from the test enclosure. In addition to this, the fiber absorber,which is being widely used in the commercial speakers, has been shown to be less efficient ascompared to acoustical filters, which were proposed in this thesis. The results of this searchhave been put forward with the help of measurement results.Keywords: Transmission line loudspeaker enclosures, acoustical filters, numerical solution ofthe wave equation, frequency response of loudspeaker enclosures.xii