SpeakerObjects
1. Overview of SpeakerObjects
SpeakerObjects, a customized version of SoundObject, specializes in binaural reproduction of stereo speaker-based sound fields.
Headphone monitoring of stereo sound that is assumed to be play-backed from speakers degrades sound localization. Similarly, stereo speaker sound mixed by headphone monitoring leads to sound imbalance. In these cases, it is necessary to compensate for the acoustic characteristics of the listening room during monitoring or mixing, which is supported by SpeakerObjects.
SpeakerObjects is provided as a VST 3 plug-in for digital audio workstations (DAW) and supports 44.1KHz, 48KHz, and 96KHz sampling rates. OS environment is 64bit Windows 11.
SpeakerObjects binary distribution is licensed under Creative Commons Attribution 4.0 (CC BY 4.0) at no charge.
SpeakerObjects source code distribution is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 (CC BY-NC-SA 4.0) at no charge.
2. Operation of SpeakerObjects
Coordinate system
Coordinate system of SpeakerObjects based on the spatially oriented format for acoustics (SOFA) defined by AES69-2020 [1] specification is shown in Fig. 1.
As shown in the figure, in SpeakerObjects, the center of the sphere (listener's head) is located at the origin. And x, y, and z-axis directions are the front, leftward, and upward directions respectively. In the polar coordinates system, radius r is the distance from the origin to the left speaker, elevation angle θ [−90, 90] deg. is measured from the x-y plane, and azimuth angle φ [0, 360) deg. is measured counterclockwise from the x-axis. The depth, width, and height of the reverberation room are the distances of x, y, and z-axis directions respectively. And distances to the center of the sphere are measured from the point shown in the figure.
Note: The definition of elevation angle in AES69-2020 is different from the typical definition.
User interface
User interface of SpeakerObjects is shown in Fig. 2.
The position of the left speaker indicated by the white dot colud be set from any of the rectangular coordinates, the polar coordinates, the x-y pad illustrating the top view, and the y-z pad also illustrating the rear view. The red dot indicates the position of the right speaker which is automatically positioned symmetrically to the left speaker. They are constrained by the inside of the reverberation room shown by the rectangles.
The reflectance slider indicates the reflectance of the reverberation room. Typically, it is set to less than 0 dB, however, in a large reverberation room, it may be set to over 0 dB because the level of reflected waves decreases due to distance attenuation.
The LPF cutoff frequency slider denotes the cutoff frequency of the LPF for reflected waves. However, in the case of ∞ KHz, the LPF function is invalidated.
The distance attenuation slider indicates the distance decay of direct and reflected waves. −6 dB means decreasing by half when the distance to the left speaker is doubled (i.e., point sound source) and 0 dB means no attenuation (i.e., plane sound source).
The HRIR option menu selects the HRIR database used by the pinna scattering effect filter.
Descriptions for dimensions of the reverberation room and center of the sphere are explained in the coordinate system. It is strongly recommended that the center of the sphere be placed in an asymmetrical position in the reverberation room. In addition to these, settings for acoustic speed and radius of the sphere are updated during the DAW is not playing, that is, not updated in real-time.
References
[1] Audio Engineering Society, "AES standard for file exchange - Spatial acoustic data file format," AES69-2020, December 2020.
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