audio-intl

A.E.C. Soundlab Series

The Sound-Lab Philosophy

All of our speakers are „line sources“ by nature. Two beneficial aspects of our line sources are, first, the proximity effect and, secondly, the fulfillment of the reciprocity principle. Unlike the „point source“ which disperses energy in all directions the line source disperses only in the horizontal plane. Energy density from a line source varies as the inverse of distance whereas with the point source it varies with the inverse of the square of distance. Thus, as one moves toward or away from a point source the apparent sound level varies quite noticeably. However, with the line source such movements produce variations on sound pressure level that are virtually indiscernible psychoacoustically.

From a pragmatic viewpoint we have chosen to base our product on the line source because of the latter phenomenon. The listener is free to move about in the sound field in all directions and the „stage“ remains very stable. One can stand up or sit down or walk to and fro and still enjoy proper sound balance and staging. In contrast, the point source requires that the listener sits at equal distance between the speakers to achieve good balance. Philosophically, it is argued that many musical instruments can be considered point sources (that is, the wave lengths that they produce are large compared to the size of the virtual source). However, at a live presentation the listener is usually far enough from the instruments that the sound rays are nearly parallel (this is similar to the sun being regarded as a visual point source but, due to its distance from earth, the rays appear to be parallel). Thus, as an audience participant the line source produces basically the same proximity effect as an orchestra from a normal listening distance (ie: in the farfield). Therefore, when one attempts to recreate the staging of an orchestra in his living room the line source provides a proximity effect similar to that found in the orchestra hall.

Another invalid criticism of the line source is that it does not give proper vertical imaging because it does not disperse energy in the vertical plane. One need only remember that standard two-channel recordings have staging cues only in the horizontal plane. Therefore, pretense to vertical imaging is a delusion.

The principle of reciprocity states simply that in order to recreate a three-dimensional sound field not only does the frequency response and phase response of the recreation have to match the original source but also the spatial dispersion of the enery must match. For example, the combination of a microphone with a narrow acceptance angle and a loudspeaker with a wide dispersion angle would tend to stretch the sound stage. The reverse affect would occur with a wide acceptance angle and a narrow dispersion angle. Obviously, professional microphones vary in their spatial characteristics, but usually microphones are used that have a cardiod charcteritic. We have „avaraged“ the acceptance angles of the more common professional microphones and have adopted this avarage as the dispersion angle for all of our speakers to fulfill the principle of reciprocity as nearly as possible. This angle is approximately 90 degrees. An important side benefit of wide dispersion is that in reflective listening rooms the wide dispersion if energy helps to avoid annoying room modes caused by strong direct reflections.

To summarize the reasoning of our technology, the line source recreates in the home listening enviroment the same type of spacial effects as one would experience sitting in the audience of a music hall. Furthermore, due to wide dispersion of the entire audio spectrum the room acoustics have less effect on the sound field and set-up is easier. Also, due to a tall projected field with no vertical dispersion troublesome floor and ceiling reflections are virtually eliminated. In brief, whether one is sitting or standing, or positioned to the left or to the right of the listening room, or far or near to the speakers the sound stage remains stable and accurate.