Magnitude/Frequency Graphs Magnitude/Frequency Graphs Measurements
The Bohlender-Graebener Corporation Planar Magnetic Ribbons are long line sources with some very special properties.
Drivers working as a line source behave differently than the "traditional" point source drivers. (cone speakers) The latter produce sound from a single point expanding in all directions using a spherical wave. As such the sound will bounce off floor, ceiling and sidewalls The many reflections from a 2 to 3 way point source speaker system add time smear to the signal and suffer from lobing and time distortion because of the spherical propagation of the different waves in overlapping patterns.
A line source however radiates sound using a cylindrical wavefront. Hardly any energy is radiated above and below the driver except for the low frequencies with wavelengths longer than the length of the line source driver. Those low frequency waves are omni-directional in nature anyhow.
The natural vertical directivity from a line source eliminates most of the floor and ceiling reflections, increasing the ratio direct to reflected sound the listener experiences with an improved clarity and intelligibility as an immediate result.
When applied in a dipole fashion, these line source further minimize the side wall interaction as the dipole eight pattern has minimal energy propagating perpendicular to the listening axis. The BGC Radia ribbons can be used as monopole drivers also which makes them the most versatile planar magnetic ribbon drivers on the market.
Further advantage of a line source system over a point source system is the 3dB attenuation over doubling of distance for line sources (and planar sources) versus the 6 dB number for point sources. This provides much more consistent coverage in the listening environment which minimizes long term listening fatigue.
Add to this the almost full range operation of these drivers (8 octaves) and it becomes obvious that these drivers are special indeed. There is no crossover required in "singing" range to utilize these drivers which aids greatly in voicing speaker systems utilizing the BGC Radia ribbons. Mating with a stereo (sub)woofer to cover the full spectrum is very much possible.
Magnitude/Frequency Graphs Magnitude/Frequency Graphs Measurements Crossovers and passive notch filters component values can be found in the FAQ.May 5, 1998:
Copyright (c) 1997-2000, by Rudi A. Blondia, ALL RIGHTS RESERVED. Last update: January 21, 2000.