Audio Crossover For Three-Way Loudspeaker Enclosure Using Digital Wave Filters

Cilj prvog dijela rada je napraviti trosmjernu aktivnu digitalnu skretnicu s točkama skretanja od 200 Hz i 2 kHz, optimiziranim IIR odzivom u programskom alatu FilterShop. Tri su zvučnika koja se nalaze u zvučničkoj kutiji – niskotonski, srednjetonski i visokotonski te na svaki od njih treba doći audio signal odgovarajuće frekvencije. Potrebno je također kompenzirati propade u točkama skretanja, što se radi koristeći razne mogućnosti i opcije programskog alata FilterShop. Također, dizajnirana su tri pasivna ljestvičasta RLC filtra koji dokazano imaju manju osjetljivost na tolerancije elemenata u pojasu propuštanja. Oni su pretvoreni u digitalne valne filtre koji imaju manju osjetljivost na kvantizaciju koeficijenata, a dizajn je provjeren u programu MATLAB. Uspoređena je osjetljivost klasičnog IIR digitalnog filtra s ljestvičastim digitalnim valnim filtrom i dobiveni rezultati su u skladu s Fettweis-Orchardovim teoremom – digitalni valni filtar pokazao je puno manju osjetljivost promjena njegove amplitudno-frekvencijske karakteristike na efekte kvantizacije koeficijenata u pojasu propuštanja.The objective of the first part of the thesis is to get a three-way active digital crossover with crossover points of 200 Hz and 2 kHz, optimized IIR response in design tool FilterShop. There are three speakers in the box – woofer, midrange and tweeter, and therefore on each of them an audio signal of the corresponding frequency has to arrive. It is also necessary to compensate for the dips in crossover points, which is done using a variety of features and options of the software tool FilterShop. Also, three passive RLC ladder filters are designed, that are proved to have lower sensitivity to component tolerances in the passband of the filter. They have been transformed into digital wave filters having lower sensitivity to coefficient quantization and the design has been tested and verified in the program MATLAB. Sensitivity of the digital wave filter has been compared to the sensitivity of the classical IIR digital filter and the obtained results are along the Fettweis-Orchard theorem – digital wave filter is less sensitive to changes of its amplitude-frequency characteristic due to coefficient quantization effect in the passband