We focus on developing an effective Direction Of Arrival (DOA) estimation method for wideband sources based on the gridless sparse concept. Previous coherent methods have been designed by dividing wideband frequencies into a few subbands which are transferred to a reference subband using focusing matrices. In this work, as opposed to the previous techniques, we propose a convex optimization problem that leads to an accurate wideband DOA estimation method with no need for any focusing matrix. Moreover, in this method, no initial DOA estimates are required and it can be used for any arbitrary linear arrays. Numerical simulations show that in comparison to some well-known techniques, the proposed method generates outstanding accuracy and better robustness to noise. The effectiveness of the method is also verified in presence of close adjacent sources.