Center Speaker Research Articles

Experiments and experiences in stereo

A considerable number of observations as well as formal experiments in High Fidelity Stereo sound are reported. Three-channel stereo with corner flanking speakers has been shown to achieve accuracy in both tonality and geometry. A large center speaker with small outriggers is observed to lack both tonality and geometry. A center speaker in the corner with wall outriggers is observed to produce a deeply curved stereo geometry. Limiting speakers to a bass range down to 300 cycles may preserve geometry, but not tonality. Overly large bass speakers lead to a spatial and delay separation of bass and treble events. There is an optimum bass speaker size. Wide spacing of speakers offers improved accuracy of stereo geometry. The array cannot normally exceed the speaker spacing, but because of the focusing effect of the center channel, it may be much narrower than the speaker spacing. Numerous minor observations of radiation angle and polar response point up the desirability of corner speaker placement. Large speakers may be placed at low or high level, but the dynamic range of small speakers is limited. Corner speaker placement affects apparent room size and may be advantageously employed to improve the reverberation effects. Wide Stage Stereo demonstrations using speaker spacing up to 50 feet or more are compared to home applications with 15-foot spacing. High Fidelity Stereo is both high fidelity and stereo, and entails meeting the requirements of both.

Wide-stage stereo

Stereophonic playback systems are studied to determine the accuracy with which they can reproduce the geometry of the original sound. Sounds were generated in a geometric pattern, recorded, and reproduced over a loudspeaker array. The methods used were similar to those used by Steinberg and Snow in 1933. Using two sound tracks, a derived center playback channel, and corner placement of flanking speakers, geometry plots were made with almost as good accuracy as when observers listened to an actual person speaking at the indicated stations in the geometric array. Since wide speaker spacing was used, corner placement becomes natural. An evaluation of corner speaker placement from the tonal standpoint (as contrasted with the geometric) shows that there is a large increase in quality available by taking advantage of the reflections of the floor and walls. It is shown that corner placement of flanking speakers and use of a derived-channel center speaker affords the best reproduction of geometry as well as tonality.