interesting multielement, snap-together loudspeaker construction. Al- though many of its novel features are intended to simplify assembly, perfor- mance benefits are also set forth.•GLA

4,598,178

43.88.Ja MEANS FOR CRITICALLY DAMPING A

DYNAMIC LOUDSPEAKER

WHlinm L. Rollins, Monroe, WI 1 July 1986 (Class 179/115.5 VC); filed 16 December 1983

If voice coil 24 is driven by a signal powerful enough to push it com- pletely out of the magnetic gap, then auxiliary coil 30 moves in to take its r .................... ....• or •,,.,.;.•;u to a. network to provide damping. This suggests three questions: ( 1 ) Is this really an electro- dynamic snubbing action rather than critical damping? (2) What happens if a signal overload draws the voice coil into the gap? (3) Would a suitable centering spider (none is indicated) provide the desired snubbing action at lower cost? It may be that the answers to these questions are buried in the text of the patent. After all, it explains that "at resonant frequency, current in the drive coil and the drive of the speaker cone will be maximum for a

4,525,857

43.88.Lc CROSSOVER NETWORK

Robert A. Orban, as•iguor to Orban Associates, Incorporated 25 June 1985 (CI• 381/100); filed 4 September 1984

Writing newspaper headlines is a specialized occupation, and the same may be true of patent titles. In both cases arcane procedures sometimes produce identifiers having no obvious relation to the subsequent text being identified. This patent is a borderline case. An audio signal is split into two bands and then recombined, but the complete circuit functions as a low- distortion audio peak limiter. The patent is interesting, easy to understand, and brief. "The limiter effectively provides radio-frequency clipping of low frequencies and audio-frequency clipping of high frequencies. Thus, little or

no harmonic distortion occurs for voice, whereas harmonic distortion is permitted for high-frequency signals." Why this should be subjectively de- sirable is then explained in some detail.--GLA

•O

24 25

ZZ

4,566,119

43.88•Lc, 43.85.Kr EQUALIZER NETWORKS AND METHODS OF DEVELOPING SCALING COEFFICIENTS THEREOF

Richard W. Peters, mignor to Industrial Research Products, Incor- porated

21 January 1986 (class 381/103); filed 12 October 1983

People interested in audio filter designs or signal processing in general will want to get a copy of this interesting patent. It describes a multiband audio equalizer in which the base is a ladder delay chain rather than a set of tuned LC filters. The delay chain is made up of simple first-order allpass networks, and the total circuitry required is not much more complicated than that of an equivalent active filter bank. The main advantage of this seemingly more esoteric approach to equalization is that ripple between adjacent bands is virtually nonexistent even at maximum settings. Commer- cial versions are now in production, and have been generally well re- ceived.---GLA

17

16

15

given signal voltage with the result that distortion in the reproduction of signal energy as acoustic energy occurs." If this is a misprint, and I failed to understand the rest of the patent, I apologize.•LA

4,453,809

43.88.Md SOUND MIXING SYSTEM FOR FILM SOUND EDITING

James W. HHI and Eugene N. Finley, Corte Madera, CA 12 June 1984 (Class 352/11); filed 5 August 1981

The first two-and-a-half pages of text in this patent are devoted to a succinct (and, in the reviewer's experience, all too accurate) description of accepted audio dubbing and editing practices in the motion picture indus- try. A relatively simple arrangement for control and routing of various signals is described. It interfaces directly with other equipment found in editing rooms, and seems to be well thought out in terms of signal flow and operational features.•GLA

211 J. Acoust. Soc. Am. 81(1), Jan. 1987; 0001-4966/87/01211-01500.80; ¸ 1987 Acoust. Soc. Am.; Patent Reviews 211

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