Line array speaker with frequency-dependent electrical tapering optimized for midrange and high frequency reproduction in the nearfield
A speaker system is provided having a line array of drivers wired in parallel and treated with passive or active component systems that serve to electrically taper its effective radiating length with frequency so that it is long/tall at low frequencies and short at higher frequencies, with the effective length of the array determined so as to maintain a listener in the nearfield at typical home and studio listening distances while minimizing the destructive effects of path-length dependent high frequency comb filtering. In alternate embodiments, an array of drivers is provided and wired in series or series-parallel with passive components between the output of one driver and the input of the next. Schemes of active drive and combination schemes of active and passive drive are also contemplated.
1. An audio speaker driver circuit comprising: an input terminal coupled to a high-pass global filter circuit, said global filter circuit configured to attenuate portions of an audio signal that fall outside a predetermined frequency range, and output portions of an audio signal that fall within a predetermined frequency range;
a line array of speaker drivers electrically coupled to the output of said global filter circuit;
a plurality of frequency-dependent filters selectively coupled to a subset of said speaker drivers;
wherein the level of frequency-dependent attenuation applied by said filters progressively decreases inward to the center of the line array.
2. The audio speaker driver circuit of claim 1 wherein said high-pass global filter circuit and said plurality of frequency-dependent filters are implemented actively.
3. The audio speaker driver circuit of claim 1 wherein said high-pass global filter circuit and said plurality of frequency-dependent filters are implemented passively.
4. The audio speaker driver circuit of claim 1 wherein said global filter circuit is a high-pass crossover circuit.
5. The audio speaker driver circuit of claim 1 wherein said global filter circuit is a low-pass crossover circuit.
6. The audio speaker driver circuit of claim 1 in which, at a listening distance of between 2 and 10 meters, the listener is maintained in the nearfield for any frequency above 500 Hz while the path length difference between the listener and different points on said array is limited to no more than approximately 2 full wavelengths for any reproduced frequency above 500 Hz.
7. The audio speaker driver circuit of claim 1 wherein the speaker drivers closest to the center of the array are not electrically coupled to a frequency-dependent filter.
8. The audio speaker driver circuit of claim 1 wherein said speaker drivers are electrically coupled in series.
9. The audio speaker driver circuit of claim 1 wherein said speaker drivers are electrically coupled in parallel.
10. The audio speaker driver circuit of claim 1 wherein said frequency-dependent filters are adjustable.
11. A sound reproduction system, comprising:
a speaker line array comprising a plurality of drivers arranged about a center point;
a housing for said speaker line array;
an input terminal coupled to a global filter circuit, said global filter circuit configured to attenuate portions of an audio signal that fall outside a predetermined frequency range, and output portions of an audio signal that fall within a predetermined frequency range;
a plurality of frequency-dependent filters selectively coupled to a subset of said speaker drivers;
wherein the level of frequency-dependent attenuation applied by said filters progressively decreases inward to the center of the line array.
12. The sound reproduction system of claim 11 wherein said global filter circuit and said plurality of frequency-dependent filters are implemented actively.
13. The sound reproduction system of claim 11 wherein said global filter circuit and said plurality of frequency-dependent filters are implemented passively.
14. The sound reproduction system of claim 11 wherein said global filter circuit is a high-pass crossover circuit.
15. The sound reproduction system of claim 11 wherein said global filter circuit is a low-pass crossover circuit.
16. The sound reproduction system of claim 11 in which, at a listening distance of between 2 and 10 meters, the listener is maintained in the nearfield for any frequency above 500 Hz while the path length difference between the listener and different points on said array is limited to no more than approximately 2 full wavelengths for any reproduced frequency above 500 Hz.
17. The sound reproduction system of claim 11 wherein the speaker drivers closest to the center of the array are not electrically coupled to a frequency-dependent filter.
18. The sound reproduction system of claim 11 wherein said speaker drivers are electrically coupled in series.
19. The sound reproduction system of claim 11 wherein said speaker drivers are electrically coupled in parallel.
20. The sound reproduction system of claim 11 wherein said frequency-dependent filters are adjustable.
21. An audio speaker driver circuit comprising:
an input terminal coupled to a high-pass global filter circuit;
said global filter circuit configured to attenuate portions of an audio signal that fall outside a predetermined frequency range, and output portions of an audio signal that fall within a predetermined frequency range;
a line array of speaker drivers electrically coupled to the output of said global filter circuit;
a plurality of frequency-dependent filters selectively coupled to a subset of said speaker drivers;
wherein said filters adjust the effective radiating length of the array such that a listener at between 2 and 10 meters from the speaker is maintained in the nearfield at a predetermined frequency falling between approximately 2 kHz and 10 kHz;
and wherein said filters adjust the effective radiating length of the array such that the path length difference between the listener and different points on said array remains less than approximately 2 full wavelengths for any reproduced frequency above said predetermined frequency, but such that the effective length of the array tapers to a length shorter than necessary to maintain the listener in the nearfield at certain frequencies above said predetermined frequency.
22. A sound reproduction system, comprising:
a plurality of speaker drivers;
means for housing said speaker drivers;
means for attenuating portions of an audio signal that fall outside a predetermined threshold;
means for delivering said audio signal to said plurality of speaker drivers;
means for selectively applying frequency-dependent attenuation to said audio signal before it is applied to said speaker drivers;
wherein the level of frequency-dependent attenuation applied by said filters progressively decreases inward to the center of the line array.