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Much has been said about this issue in construction of high-end audio loudspeaker systems. It is very important when it comes to accurately reproducing the sound stage, as well as the spatial relationships of the various instruments, and reproducing the overall "presence" of the music. Time and phase coherence add a dimension of clarity and spatial realism that cannot be achieved by other means. Only a very few of the top-end speaker manufacturers properly address this problem, and Linn Audio has sought to improve on all the solutions, to provide the best overall performance of any high-end audio speaker system available today.

In order to achieve this desired effect, all the frequencies of the music must reach the listener at the same time, that is, in the same "coherence" as that of the original source. This is a problem with most speaker systems that 1.) use complex crossover networks, with many components in the signal path, and 2.) mount all the drivers flat onto the front baffle, all in the same plane (see diagram below) and therefore do a poor job of preserving time and phase relationships.

Crossover components create phase shifts in the audio waveform, so that the sound is "smeared out" relative to the original signal, and different frequencies are reproduced by the drivers at different relative times than in the original source. And different speaker drivers have voice coils and/or dispersion points, that are at different depths from each other, so when the audio signal reaches all the drivers at the same time, the distance from the driver source, for the different frequencies, reach the listener at slightly different times. Both these issues, though not contributing to distortion of the signal, can adversely effect the "presence" of the music, as well as the breadth , depth and height of the sounds stage. Timing errors also create the loss of much directional or imaging information. Also effected is the placement of the various instruments within the sound stage, in comparison with the original performance. Outputs of the various drivers must be heard in unison to preserve the original structure of the sound.

Linn Audio's solutions to the first problem, that of phase incoherence, is to reduce the number of components of the crossover in the signal path to a bare minimum, thus eliminating the phase shifts associated with these components. (See the "crossovers" link for more information on this issue.) Linn Audio also uses very wide bandwidth drivers, so that more of the frequencies are reproduced in synchrony with each other from the same source/dispersion point.

The solution to the second (driver placement) problem, is to step the drivers forward or backward on the cabinet baffle, so that the voice coils (and/or the principle dispersion points of the cone or horn) so that they are aligned in space, and hence reproduce the various frequencies at the same distance from the listener. As a general rule, the woofer has the most depth in its dispersion point, so needs to be stepped out the furthest, while the midrange has its point further in front of the woofer, but forward from the tweeter, which has its dispersion point very close the its front mounting plate.

So in the Linn Audio Reference system, the woofers are stepped out a full 3-4" from the front baffle, while the midrange horn is stepped out 2 1/2" and the tweeters are mounted directly to the front baffle, i.e., not stepped out at all. In addition, the woofers are "canted" so that the sound emanating from this source is aimed directly at the position of the listener, which further reduces any problems with time coherence, and creates optimal dispersion for the typical listening position. The midrange horn and tweeters are nearer the center of the cabinet, and hence are already aimed at the typical height of the listening position, and do not need to be canted (see diagram below)

In conventional systems, drivers are mounted in a flat baffle such that the dispersion points are positioned at a different distance in relation to the listener. So audio signal from the tweeter arrives at the listening position in advance of the midrange, which in turn arrives before the bass signals generated by the woofer. The problem of time and phase incoherence is only worsened by large speaker systems, where the height of the speaker cabinet puts the drivers increasingly out of range with the listening position.

With the Linn Audio Reference System the drivers are mounted to achieve optimal driver dispersion for the listeners position, both in time and phase relationships. The "canted" woofers especially compensate for the height of the cabinet, by aiming this base and lower midrange driver directly at the listeners position, thus overcoming the problems with time and phase relationships.

Home |  History |  Design Overview |  The Cabinet  |  The Drivers  |  Crossovers and wiring  |  Bi-amp Capability  |  Time and phase coherence  |  Specifications  |  Finishes