Methods and systems for filtering include accessing first and second signals produced from an input signal and producing first and second filtered outputs, which correspond to the first and second signals, based on a filtering characteristic. The filtering characteristic can include a first filtering coefficient weighting the first and second signals. The filtering characteristic can include a second filtering coefficient weighting third and fourth signals, the third and fourth signals being produced prior to the first and second signals. The first and second filtering coefficients can include matrices which have non-symmetrical terms.