The advantage of this design is the ability to the speaker’s primer pdf a smaller area, hence their popularity in car audio. The low frequency sound waves from the woofer are not reduced too much by the drivers in their path. This design was popularized in the 1970s with Electronic Industries, Inc.
813 model based on a 15-inch coaxial augmented with a plain 15-inch driver. The blue rectangles show where blue foam rubber has been applied to the edges of the high-frequency horns to attenuate undesired anomalies. Coaxial loudspeakers in professional audio enable sound from two drivers to come from one source. As well, the pattern of response is symmetric around the axis of the loudspeaker.
Dual Concentric design assumed the same role across Europe from the 1950s onward. The Tannoy also used a 15-inch woofer and a compression driver for high frequencies, but differed in that the woofer itself served as the final horn flare for the high frequency driver. Thus, its output pattern was radially symmetric, not just mirror-image symmetric as in the Altec. The high frequencies arrived at the listener’s ear slightly later than the low frequencies. One drawback of the design is the production line difficulty in mating the two drivers, and in replacing or reconing the woofer. The Tannoy style of coaxial, with the woofer forming part of the high frequency horn, had greater intermodulation distortion.
Designs similar to the Altec 604 have further problems with diffraction of the low frequencies around the central horn, and with rearward emanations from the horn body reflected forward by the woofer out of time with direct sound. Time Alignment crossover design to fix the long-standing problem of the two bandpasses not being aligned in time at their crossover point. The Altec 604 was given this elaborate new crossover feature and incorporated into the UREI 813 studio monitor, which also had a second woofer physically separate from the coaxial pair. This design dominated recording studios of the 1980s, and time alignment became a feature of competing manufacturers. Fulcrum Acoustic to reduce some of the coaxial drawbacks such the diffraction of the woofer’s upper range around the central horn, by filling in this “shadow” with low frequency sound from the compression driver, and by countering the out-of-time reflections bouncing off of the woofer. As well, the enclosure may be made more compact. 12- or 15-inch woofer, and having a projecting high-frequency horn as in the 604.