Boston A200 loudspeakers

The A200 is a high performance three-way loudspeaker system designed for optimum reproduction of music under actual home listening condition. Its design takes particular advantage of recent research about the colorations which can be caused by off-axis sound radiation when it reflects off parts of the speaker, is diffracted at cabinet edges, and is strongly reflected off floor and wall surfaces near the speaker.

These reflections have been controlled in the A200 by the shape of the cabinet and careful attention to the placement of the drivers, yielding a speaker system which exhibits a remarkably uniform and accurate tonal balance, exceptionally good stereo imaging, and relatively high efficiency.

The 10" woofer is mounted near the floor and the shallow cabinet permits convenient placement near a wall behind it. Consequently the woofer behaves acoustically as if it were flush-mounted at the floor-wall intersection, radiating uniformly into the 90-degree solid angle formed by that intersection with all reflections remaining in-phase with the woofer's direct output, preserving its smooth response and raising its efficiency.

The 4-1/2" midrange and 1" soft dome tweeter are positioned near  ear level for realistic musical imaging. They are flush-mounted in an unusually large and smooth front-panel area, so that the nearest cabinet edge or reflecting object is more than a half-wavelength away at any frequency in their operating range.  Consequently the drivers radiate essentially a hemispheric wave front, and the control of early reflections permits their smooth response to be heard to full advantage.

The infinite plane enclosure

The A200's enclosure design isn't a cosmetic "sales feature". It is calculated specifically to restrict the amount of sound than can reach the rear wall and floor, especially at the crucial midrange frequencies that determine a speaker's tonal character and imaging capability.

The A200's unusually large and smooth front panel makes the midrange and high frequency drivers behave as if they are mounted into an infinitely large plane extending beyond the baffle. As a result, they acoustically "see" only the hemispheric space in front of the cabinet, eliminating the early reflections that can color their sound and blur the stereo imaging.

Dealing with bass frequencies and their very long wavelengths required a different solution. By mounting the woofer close to the floor, floor reflections remain in phase, reinforcing the woofer's output and preserving its smooth response.

Another benefit of the A200's tall, slim cabinet is the opportunity to mount the midrange and tweeter near ear level to enhance the sonic perspective. Mid and high frequency information emanates at the proper height in space, eliminating the "highs-at-knee-level" phenomenon of typical cabinet shapes.

Specifications:

Drivers:

Low-frequencies  :  10" (250 mm) acoustic suspension woofer

Mid-frequencies :  4-1/2" (120 mm) midrange with ferrofluid

High-frequencies ;  1" (25 mm) soft dome tweeter with ferrofluid

Crossover Frequencies:  450 Hz and 3000 Hz

Sensitivity:  1 watt produces 90 dB at 1 meter

Impedance:  8 Ω nominal

Low Frequency Response "  -3 dB at 36 Hz

Driver Fuses:

Tweeter :  1,5 A

Midrange :  2 A

Dimensions (H x W x D):  1040 x 530 x 160 mm (41" x 21" x 6-3/8")

Weight:  27 kg (58 lbs)