Princeton University  

Loudspeaker Directivity:
An Ongoing Experimental Survey

This work is sponsored by the Sony Corporation of America


Introduction


Loudspeaker directivity is the extent to which loudspeakers focus the sound in a particular direction (typically towards the listener) instead of broadcasting it in all directions around the room. Highly directive loudspeakers are ideal for 3D audio with crosstalk cancellation (XTC), since room reflections (which are weaker when using more directive loudspeakers) directly degrade the level of XTC. Consequently, the 3D3A Lab is conducting detailed measurements of the directivity of various loudspeakers using the lab's anechoic chamber. This study on loudspeaker directivity is also important for our ongoing Sony-sponsored research on head-externalization of 3D sound through headphones, since some of the relevant techniques rely on emulating the radiation characteristics of real loudspeakers.


Table of Measured Loudspeakers


To generate the table, begin by choosing a "Sort" option.


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Click here to download a .zip file containing all measured impulse responses (in .mat format), directivity plots, and a .csv file containing the tabulated values of all directivity metrics for all measured loudspeakers. (242 MB, last updated May 26th, 2016)

For a description of the how the data files were generated and the storage format used in the database, please also read this manual. (Last updated May 25th, 2016)


Measurement Notes


All directivity measurements are carried out in the anechoic chamber of the 3D3A Lab using a B&K Microphone Type 4189-A-021. The loudspeaker is placed on a rotation stage in the chamber and rotated in increments of 5°. At each orientation, the loudspeaker's impulse response is measured with, unless otherwise noted, an exponential sine sweep at a sampling rate of 96 kHz. To align the microphone, the loudspeaker is placed at 0° (facing straight ahead) and the microphone is positioned such that the barrel of the microphone points straight at the center of the loudspeaker cabinet (or some other logical alignment point). Due to the physical limitations of the anechoic chamber, a time-window is applied to each measured impulse response to remove any reflected sound. The measured data are processed and plotted using custom software developed in-house at the 3D3A Lab.

The measurements shown above have been made by Lukasz Mosakowski, Tim Matchen, Joe Tylka, Rahulram Sridhar, Tony Jin, and Gianfranco Colombi under the direction of Prof. Edgar Choueiri.

If you know of any loudspeakers that may have particularly high directivity, please inform the 3D3A Lab. We will try to acquire these loudspeakers and measure their directivity.


Publications:

R. Sridhar, J. G. Tylka, and E. Y. Choueiri. Metrics for Constant Directivity. In Audio Engineering Society Convention 140, May 2016.

J. G. Tylka, R. Sridhar, and E. Y. Choueiri. A Database of Loudspeaker Polar Radiation Measurements. In Audio Engineering Society Convention 139, October 2015. (pdf, poster)

J. G. Tylka and E. Y. Choueiri. On the Calculation of Full and Partial Directivity Indices. Technical report, 3D Audio and Applied Acoustics Laboratory, Princeton University, November 2014. (pdf)