Abstract – The ITU-R BS.1770 multichannel loudness algorithm performs a sum of channel energies with weighting coefficients based on azimuth and elevation angles of arrival of the audio signal. In its current version, these coefficients were estimated based on binaural summation gains and not on subjective directional loudness. Also, the algorithm lacks directional weights for wider elevation angles (|| ≥ 30°). A listening test with broadband stimuli was conducted to collect subjective data on directional effects. The results were used to calculate a new set of directional weights. A modified version of the loudness algorithm with these estimated weights was tested against its benchmark using the collected data, and using program material rendered to reproduction systems with different loudspeaker configurations. The modified algorithm performed better than the benchmark, particularly with reproduction systems with more loudspeakers positioned out of the horizontal plane.