In this paper, a new direction-of-arrival (DOA) estimation method for wideband signals is introduced. This new method uses both the signal subspace projection and the reference frequency selection in squared test of orthogonality of projected subspaces (Squared-TOPS) and estimates DOAs by measuring the orthogonal relation between the signal and noise subspaces of multiple frequency components of the signals. The signal subspace projection and the reference frequency selection reduce some error terms in the matrix used for testing the orthogonality between signal subspaces and noise subspaces. The resolution and root mean square error (RMSE) of the proposed method are compared with those of the coherent signal subspace method (CSSM), test of orthogonality of projected subspaces (TOPS) and test of orthogonality of frequency subspaces (TOFS) through computer simulations, respectively. The simulation results show that the resolution of the proposed method is better than that of the others except CSSM in whole signal-to-noise ratio (SNR) ranges. They also show that RMSE of the proposed method is the best in whole SNR ranges.