Derivation of the Quasi-Butterworth 5 Alignments
The use of adequately designed second-order high-pass filters, such as Butterworth (B), Chebyshev (C), and sub-Chebyshev (SC) alignments, to improve the low-frequency response of fourth-order loudspeaker systems is well known. Characteristics of the filter and enclosure are derived fro the poles of the desired transfer function. In the case of quasi-Butterworth 5 (QB5) alignments, which actually are sixth-order alignments, this procedure leads to very complex equation systems. Because these were difficult to solve, they have generally been discarded. In this paper, a successful alternative method is introduced for calculating QB5 alignment parameters, and some comparisons with analogous B, C, and SC alignments are given. Systems using QB5 alignments are characterized by a small diaphragm displacement, a small enclosure, and a high power handing capacity.
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