OVERVIEW
The Bose 901 series speakers, which have been manufactured since 1968, probably qualify as having the longest tenure of any currently made hi-fi product. Although they have undergone a continuing process of design modification— and the new Series V differs in almost every detail from the original Model 901—the basic concept of the system remains unchanged to this day.
The design of the Bose “Direct/ Reflecting” speaker is based on the fact that most of the acoustic energy reaching a listener in a concert hall has been reflected at least once from the ceiling, floor, or walls. Dr. Amar Bose, president and founder of the Bose company, decided that in order to give a subjective effect more like that of a live performance, a similar proportion of a speaker’s sound output should be reflected from a home listening room’s walls.
To that end, every Series 901 speaker, from the first model to the new Series V, has used nine identical full-range drivers, with two groups of four on its angled rear panels and a single driver facing forward. Before reaching the listener, the output of the rear drivers is reflected from the wall a foot or so behind the speaker, and usually from a side wall as well. The front driver, which provides only 11 per cent of the system’s output, supplies the early-arrival information needed for stereo localization.
Each of the 4-1/2-inch drivers can be viewed as a miniature woofer rather than a large tweeter. The total radiating area of the drivers in each Bose 901 is roughly equal to that of a 13-inch-diameter speaker, but the high-frequency performance of the small drivers is far superior to that of a large single-cone driver of equivalent area. The 901 uses no crossover network, and an electronic active equalizer is required to generate a flat response in the listening room. The equalizer, which is furnished with the speakers, normally operates in an amplifier’s tape-monitor loop, whose functions are duplicated on the equalizer.
The Bose 901-V differs from the earliest versions, which had acoustically sealed wooden cabinets, in using an unusually sophisticated form of venting. The cabinet is a very complex plastic molding that Bose calls an “Acoustic Matrix” enclosure. Although the drivers are isolated from each other, their outputs are combined through a network of nine chambers, two couplers, and three reactive air columns.
The nominally 8-ohm Bose 901-V is efficient enough to be driven by a 10-watt amplifier. Because of its multiple drivers and flat-wire voice coils, the speaker can also handle very high power levels.
The front and much of the rear of the speaker cabinet are covered by a non-removable dark-brown cloth grille. The cabinet is 21 inches wide, 13 inches deep, and 12-5/8 inches high, and each speaker unit weighs 35 pounds. Black steel speaker stands, 18 inches high, are available as options.
The 901-V equalizer is 13 inches wide, 4-7/8 inches deep, and 2-3/4 inches high. Its exterior is gold satin-finish aluminum with a dark-brown plastic front panel and side plates. Price: $1,400 per pair (including equalizer). The optional speaker stands are $120 per pair.
LAB TESTS
Because of its multidriver configuration, the quasi-anechoic FFT frequency-response curves from the Bose 901-V are much less regular than the actual response of an individual driver. Actually, an averaged room-response measurement is probably a more meaningful indication of this speaker’s performance in a real listening room. We still used our digital IQS FFT signal-analysis system, with close microphone spacing, to gain some insight into the performance of the drivers over limited frequency ranges. Measurements were made first with the equalizer controls centered and then repeated at their limit settings to evaluate the equalizer’s effect on the system response. We also measured the equalizer’s response with a swept sine wave, as we would with any amplifier or preamplifier.
SPECIFICATIONS
| Drivers | 9 x 4.5" Full-Range Helical Voice Coil Drivers per Cabinet |
|---|---|
| Dispersion | Reflected: 89% Direct: 11% |
| Impedance | 8 Ohms |
| Maximum Power Handling | 10-450W RMS (Rated 250W IEC) |
https://www.erinsaudiocorner.com/loudspeakers/bose_901_series_v/
https://www.hifi-classic.net/review/bose-901-series-v-499.html
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