The design of antialias and reconstruction filters has traditionally presented a dilemma. Minimum-phase filters suffer from increased group delay at high frequencies, which is considered undesirable. Linear phase filters suffer from pre-responses, also sometimes considered undesirable. At high sampling rates, it is possible to ameliorate these effects by suitable tailoring of the response above 20kHz. The paper presents some designs intended for use at 96kHz and 192kHz that are simultaneously optimised in the frequency domain in the range 0-20kHz, and in the time domain wideband. Pre-responses can be penalised more heavily than post-responses, resulting in an asymmetrical impulse response somewhat similar to a minimum phase analogue response. The paper also considers briefly the use of a filter of this type at the end of a recording and reproducing chain that may contain an unknown combination of conventional bandlimiting filters.
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