We consider the problem of extracting the source signals from an under-determined convolutive mixture assuming known mixing filters. State-of-the-art methods operate in the time-frequency domain and rely on narrowband approximation of the convolutive mixing process by complex-valued multiplication in each frequency bin. The source signals are then estimated by minimizing either a mixture fitting cost or a 1 source sparsity cost, under possible constraints on the number of active sources. In

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... article, we define a wideband 2 mixture fitting cost circumventing the above approximation and investigate the use of a 1,2 mixed-norm cost promoting disjointness of the source timefrequency representations. We design a family of convex functionals combining these costs and derive suitable optimization algorithms. Experiments indicate that the proposed wideband methods result in a signal-to-distortion ratio improvement of 2 to 4 dB compared to the state-of-the-art on reverberant speech mixtures.