Bang & Olufsen Beolab 8000 Floor standing speakers
The Danish firm of Bang & Olufsen (B&O) is well known for the innovative design of its audio and video products. B&O components are designed for people who appreciate attractive styling as well as good listening or viewing quality and are willing to pay for a combination of those features.
The new B&O Beolab 8000 speaker is an excellent example of the company's approach to product design. Its shape is unlike that of any other speaker, resembling an organ pipe tapering to a mere half inch in diameter at its bottom, where it is fastened to a heavy cast-iron base. The speaker enclosure is a polished aluminum tube 3-3/4 inches in diameter and 39.5 inches long. Each speaker weighs 47 pounds.
The B&O 8000's speaker panel, 5.125 inches wide, is covered by a thin, opaque, nonremovable black grille cloth that effectively hides the drivers. At the top of the conical support section is a hinged door that opens to reveal a multicontact DIN socket, a three-position slide switch, a standard phono jack, and the socket for an AC line cord.
Despite its compact dimensions, the Beolab 8000 is a powered speaker, containing two 80-watt amplifiers and an electronic crossover network. A single 3/4-inch tweeter, cooled and damped by ferrofluid, is located about a foot below the top of the column. Below it are two nominally 4-inch woofers (as closely as we could determine by feeling them through the grille, their actual radiating diameter is about 3 inches).
The crossover from the upper woofer to the tweeter (whose centers are only about 3-1/2 inches apart) is at 4,200 Hz, with fourth-order (24-dB-per-oc-tave) slopes for both drivers. The lower woofer operates only below 300 Hz, with a 6-dB-per-octave cutoff slope, and reproduces only the lowest part of the system's range. The aluminum tube serves as a vented enclosure, with a 2-inch port located at the top of the panel.
Below the drivers is the compact dual-80-watt amplifier, occupying the bottom 16 inches of the aluminum tube. The response of the bass amplifier is boosted at low frequencies to compensate for the natural rolloff of the small woofers. B&O says that the maximum bass boost in the range of 30 to 250 Hz is about 8 dB. Minor level corrections for different driver sensitivities are made during manufacturing by trimming the amplifier gain, which is said to keep the variation in overall sensitivity from one Model 8000 to another within 0.4 dB. The amplifier's heat sinks, in the front portion of the tubular column, did not become noticeably warm in normal use.
The B&O Beolab 8000 is designed to be driven from the line outputs of a tuner, receiver, tape deck, or CD player. When used with a B&O receiver, the connection is made through a special cable with eight-pin DIN plugs at both ends. The switch within the support structure can be set to drive each speaker from either channel. With a conventional (non-B&O) source component, a single-channel cable fitted with standard phono plugs is used, and the third position of the speaker's selector switch connects its amplifiers to the adjacent phono jack.
The speaker is designed to be plugged into a live socket at all times, which lights a red LED at the bottom of the enclosure. When a signal appears at the input terminal, the speaker switches on automatically, and the light changes to green. If no signal is present for about 2 minutes, the speaker automatically returns to its standby mode.
For our measurements and listening tests, we placed the B&O Beolab 8000 speakers as we would any conventional speakers, several feet from any wall. They were driven directly from laboratory signal generators or a preamplifier instead of a power amplifier.
With minor variations, the composite frequency-response curve sloped down with increasing frequency from a maximum in the 60- to 120-Hz range to a plateau about 8 dB lower between 2,500 and 12,000 Hz, then rose about 5 dB from 12,000 to 20,000 Hz. The "raw" room response was similar above 300 Hz, where there was a slight peak of about 5 dB. It returned to the midrange level at 180 Hz and was remarkably flat below that point, within +/- 1.5 dB from 60 to 200 Hz. Output dropped precipitously below 60 Hz, at about 24 dB per octave.
Response measurements on the tweeter's axis, with a sweeping one-third octave noise band, roughly confirmed our other measurements, specifically the elevated output at 300 Hz (4 dB in this case). The tweeter's dispersion was very good, with the response 45 degrees off-axis only 2 dB down at 10,000 Hz and 8 dB down at 20,000 Hz.
Quasi-anechoic MLS frequency-response measurements showed a relatively flat response above 4,000 Hz (in the tweeter's range) and a drop of 3 to 5 dB between 1,500 and 4,000 Hz. These response aberrations, it must be realized, are quite moderate for a loudspeaker and should not be compared with the response measurements of electronic components.
The sensitivity of a powered speaker cannot be compared directly with that of a conventional speaker. The Beolab 8000 required an input of 400 millivolts (mV) of wide-band pink noise to generate a 90-dB SPL at 1 meter. That result suggested, and we confirmed it by our use tests, that the speaker can be driven to very adequate listening levels by any normal stereo component.
To measure the woofer distortion, we drove one speaker with a constant-level 400-mV signal stepping from 20 to 2,000 Hz. In a close-miked measurement with our Audio Precision test system, distortion readings- probably exacerbated by the amplifier's bass boost-were rather high below 100 to 200 Hz. We obtained readings in the vicinity of 1 percent from 300 to 2,000 Hz, rising to 10 percent at 100 Hz and a maximum of 30 percent at 50 Hz.
To put these figures into perspective, the bass sounded solid and surprisingly potent-one would never suspect that it was generated by two tiny cones. In listening to a variety of program material, we found the Beolab 8000 to have a very adequate bass response, comparable to that of many compact conventional speakers.
With most music, the Beolab 8000 was able to play surprisingly loud in our listening room (loud enough to interfere with conversation) without sounding strained or distorted. As with almost any speaker, a good subwoofer would be helpful, but we did not find the bass lacking in any substantive respect, and any such deficiency would be more than compensated for by the speaker's remarkable invisibility.
I use "invisibility" advisedly. Not only does this speaker fit almost any decor, but it is certainly one of the most audibly invisible speakers available. The sound simply fills the space at the front of the room, never appearing to come from the slender aluminum and black columns. And, not incidentally, the apparent instability of these relatively tall speakers, each supported by a single 1/2-inch stainless-steel bolt, is also an illusion (although I wouldn't want them to share a room with small children). They can be tipped over, but not easily.
You do pay a price for the combination of acoustical and aesthetic qualities built into the B&O Beolab 8000 speakers. At $3,000 a pair they're not cheap, but the price is quite reasonable when you consider the sophistication of their design, the quality of their construction and sound, and the elimination of the need for a bulky and expensive power amplifier.
