diff --git a/lib_enc/ivas_stereo_mdct_core_enc_fx.c b/lib_enc/ivas_stereo_mdct_core_enc_fx.c
index c38494669c8ae4179c34fa7c61a8c7ea49e8a630..646f3e725c747fc6f6b56627138d8884526e094b 100644
--- a/lib_enc/ivas_stereo_mdct_core_enc_fx.c
+++ b/lib_enc/ivas_stereo_mdct_core_enc_fx.c
@@ -458,29 +458,35 @@ void stereo_mdct_core_enc_fx(
             {
                 IF( NE_16( hStereoMdct->mdct_stereo_mode[n], SMDCT_DUAL_MONO ) )
                 {
+                    exp = shl( add( sts[ch]->hTcxEnc->spectrum_e[n], 1 ), 1 ); // 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1)
                     /* power spectrum: MDCT^2 + MDST^2 */
-                    W_tmp = W_mult_32_32( inv_spectrum_fx[ch][n][0], inv_spectrum_fx[ch][n][0] ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]
+                    mdct = L_shr( inv_spectrum_fx[ch][n][0], 1 ); // exp: sts[ch]->hTcxEnc->spectrum_e[n]+1
+                    W_tmp = W_mult_32_32( mdct, mdct );           // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1) (exp)
                     norm = W_norm( W_tmp );
-                    powerSpecMsInv_fx[ch][n][0] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]-norm
-                    exp_powSpecInv[n][0] = sub( shl( sts[ch]->hTcxEnc->spectrum_e[n], 1 ), norm );
+                    powerSpecMsInv_fx[ch][n][0] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1)-norm (exp-norm)
+                    exp_powSpecInv[n][0] = sub( exp, norm );
                     move32();
                     move16();
 
                     FOR( i = 1; i < L_subframeTCX - 1; i++ )
                     {
-                        Word32 mdst_fx = L_sub( inv_spectrum_fx[ch][n][i + 1], inv_spectrum_fx[ch][n][i - 1] );                        // exp: sts[ch]->hTcxEnc->spectrum_e[n]
-                        W_tmp = W_mac_32_32( W_mult_32_32( mdst_fx, mdst_fx ), inv_spectrum_fx[ch][n][i], inv_spectrum_fx[ch][n][i] ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]
+                        /* float mdst = ( inv_spectrum[ch][n][i + 1] - inv_spectrum[ch][n][i - 1] );
+                           powerSpecMsInv[ch][n][i] = mdst * mdst + inv_spectrum[ch][n][i] * inv_spectrum[ch][n][i]; */
+                        mdst = L_sub( L_shr( inv_spectrum_fx[ch][n][i + 1], 1 ), L_shr( inv_spectrum_fx[ch][n][i - 1], 1 ) ); // exp: sts[ch]->hTcxEnc->spectrum_e[n]+1
+                        mdct = L_shr( inv_spectrum_fx[ch][n][i], 1 );                                                         // exp: sts[ch]->hTcxEnc->spectrum_e[n]+1
+                        W_tmp = W_mac_32_32( W_mult_32_32( mdst, mdst ), mdct, mdct );                                        // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1) (exp)
                         norm = W_norm( W_tmp );
-                        powerSpecMsInv_fx[ch][n][i] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]-norm
-                        exp_powSpecInv[n][i] = sub( shl( sts[ch]->hTcxEnc->spectrum_e[n], 1 ), norm );
+                        powerSpecMsInv_fx[ch][n][i] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1)-norm (exp-norm)
+                        exp_powSpecInv[n][i] = sub( exp, norm );
                         move32();
                         move16();
                     }
 
-                    W_tmp = W_mult_32_32( inv_spectrum_fx[ch][n][L_subframeTCX - 1], inv_spectrum_fx[ch][n][L_subframeTCX - 1] ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]
+                    mdct = L_shr( inv_spectrum_fx[ch][n][L_subframeTCX - 1], 1 ); // exp: sts[ch]->hTcxEnc->spectrum_e[n]+1
+                    W_tmp = W_mult_32_32( mdct, mdct );                           // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1) (exp)
                     norm = W_norm( W_tmp );
-                    powerSpecMsInv_fx[ch][n][L_subframeTCX - 1] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*sts[ch]->hTcxEnc->spectrum_e[n]-norm
-                    exp_powSpecInv[n][L_subframeTCX - 1] = sub( shl( sts[ch]->hTcxEnc->spectrum_e[n], 1 ), norm );
+                    powerSpecMsInv_fx[ch][n][L_subframeTCX - 1] = W_extract_h( W_shl( W_tmp, norm ) ); // exp: 2*(sts[ch]->hTcxEnc->spectrum_e[n]+1)-norm (exp-norm)
+                    exp_powSpecInv[n][L_subframeTCX - 1] = sub( exp, norm );
                     move32();
                     move16();
                 }