1. An apparatus comprising: an enable generator to assert a sparse update enable in response to detecting at least one of a double talk condition and an impulse response change in an echo channel, the echo channel receiving a far-end input and a near-end input; and a main weight updater to transfer shadow weights of a shadow filter to N sets of sparse weights in N sparse filters of a main filter according to the sparse update enable, the main filter filtering the far-end input non-adaptively to generate a main output, the shadow filter filtering the far-end input adaptively to generate a shadow output, and estimating delays of peaks of the sparse weights.