The field of the invention pertains to electroacoustic loudspeakers for home and concert stereophonic music reproduction. In particular, the invention is directed to modifications of such loudspeakers to reduce the effect of the loudspeaker's electroacoustic configuration on the sound signal and thereby to produce a more accurate reproduction of music.
Recently, a variety of loudspeakers have been introduced that are directed to creation of ambient sound fields in addition to the direct sound fields generated by drivers directed at the expected listener position. Such loudspeakers incorporate rear facing drivers and upward or downward facing drivers.
Loudspeakers such as the "TIME WINDOW" from DCM CORPORATION of Ann Arbor, Mich. employ a prismatic or dihedral front with drivers in both panels. The drivers in the panels facing the listener provide the direct sound field and the drivers in the panels facing away from the listener provide the ambient or reflected sound field.
Reference is made to applicant's U.S. Pat. No. 4,315,102 which discloses improvements in electric crossover circuitry and methods to adjust loudspeakers for flatter amplitude and phase response within and beyond the pass bands of the electroacoustic networks. Reference is also made to applicant's pending U.S. application Ser. No. 146,254 which discloses improvements in crossovers incorporating delay lines, coaxial drivers and methods to adjust loudspeakers for flatter amplitude and phase response within and beyond the pass bands of the electroacoustic networks. The above applicant's disclosures are incorporated herein by reference.
U.S. Pat. No. 2,053,364 and U.S. Pat. No. 2,259,907 illustrate early forms of coaxial high and low frequency driver combinations for incorporation in a loudspeaker. The high frequency driver is located in front of the low frequency driver which unfortunately accentuates the difference in time of arrival at the listener's ear of sounds generated simultaneously by the two drivers of the coaxial driver.
The delay lines disclosed in applicant's above noted pending application are directed toward overcoming some of the distortions in the acoustic signals reaching the ear that arise from the use of coaxial drivers. The disclosure below comprises further improvements to the direct and ambient time/space coherent sound approach pioneered by applicant with the original "TIME WINDOW" loudspeakers and with other loudspeaker products of DCM CORPORATION.