Bang & Olufsen BeoLab 90 loudspeaker
Ever since I returned from visiting Bang & Olufsen's factory in Struer, Denmark (footnote 1), and listening to a final prototype of the BeoLab 90, I've wanted to hear it againthis time in my own home. Sure, I heard the production BeoLab 90 at its unveilings at a 2015 press event in NYC and the 2016 Consumer Electronics Show, but only in uncommonly large rooms. While the sounds in those space seemed to impress others, I was haunted by memories of what I'd heard in Denmark.
Then, last spring, by chance, my wife and I happened on B&O's London showroom. A brief listen to the BeoLab 90s there confirmed that they were something specialno, something uniquethat should make a big splash in the audio world. Yet I saw no print reviews in the US audio press, and barely any ripples on the Web. This must not stand.
The raison d'être of the BeoLab 90its name refers to B&O's 90th anniversary, observed in 2015is its designers' efforts to control the speaker's radiation pattern throughout the audioband, thereby minimizing the listening room's influence on the direct sounds from the speakers.
A brief reminder: In addition to the soundwaves a pair of speakers beam directly at our ears, the waves of sound spread more widely throughout the room, and are reflected off all of its surfaces, to arrive at our ears slightly later: all that bouncing around takes time. If the delay is relatively shortthat is, if the soundwaves are reflected off a surface close to the speakerthe listener doesn't hear the reflected sounds as coming from a separate source, but as a temporal and spatial smearing of the direct sound. In addition, various types of surfacea hard, flat wall, shelves filled with books, etc.will reflect some frequencies better than others, ultimately affecting the direct sound: even soundwaves that are only briefly delayed by reflection can corrupt tone and timing when they and the direct sounds from the speakers combine at the listener's ear.
Anechoic or even highly deadened rooms are no solution, as we depend on the later reflections to provide a generous and wide soundstage. A live-end/dead-end (LEDE) setupin which the speakers stand at the Dead End, surrounded by highly absorbent surfaces, and the listener sits near the Live End, surrounded by more reflective boundariescan quash briefly delayed reflections while leaving longer-delayed reflections intact. Of course, that presumes that the speaker's off-axis radiation and the room's absorptions and reflections all behave in an equal and linear fashion across the audioband.
Which is a big presumption. Take a look at John Atkinson's "Measurements" sidebars, which accompany every review of a loudspeaker published in Stereophile, and read through his graphs of lateral and vertical dispersion to see the range of variation in performance. With almost every speaker tested, the frequency response of the speaker's off-axis radiationthe soundwaves reflected from the room's near and far surfacesdiffers from the direct, on-axis frequency response. Some off-axis responses are non-linear, but in almost every case the difference between the off- and on-axis radiations varies with increasing frequency from the low midrange up. Such behavior almost ensures an unfortunate in-room response.
For decades, B&O and other manufacturers have tried to design speakers whose off-axis radiation is as smooth as their on-axis, direct sound. We have seen external pads of absorbent materials, narrow and/or curved front panels, and pyramidal and boxlike enclosures stacked like the Towers of Hanoi in attempts to minimize box reflections and edge diffraction. We have seenand still seehorn loading and acoustic lenses, but extending the outputs of speakers so equipped down into the lower midrange comes with complications. We have appreciated that dipole speakers, through the interference of their front and rear radiations, cancel laterally dispersed soundwaves and mitigate some room effects.
Given carte blanche in celebration of the company's 90th anniversary, B&O's engineers mounted a full frontal attack on these challenges. The goal was a speaker with a smooth on-axis frequency response that also had the same off-axis response over a specific lateral span, and little or no output beyond that span.
The 18-driver loudspeaker that resulted is very roughly triangular in cross-section, and vertically tapers from its wide bass cabinet to a smaller midrange box to a still smaller tweeter enclosure. Each individual enclosure contains multiple drivers, and each driver has its own DAC and ICEpower class-D power amplifier. However, the heart of the system is a DSP engine that controls all of the drivers individually.
Three front driverswoofer, midrange, and tweetercomprise a more or less standard three-way system, to be aimed directly at the main listening position; for these, the DSP engine provides a phase-correct, three-way electronic crossover. For the remaining 15 drivers per loudspeaker, it provides signals whose content depends on the setting of the speaker's Beam Width Control: Narrow, Wide, or Omni. At the Narrow settingwhat might be called the "audiophile" Beam Width modeeach driver gets a highly specialized, bandwidth-limited, phase-controlled signal that has one task: to interact with the acoustic output of the three front drivers, so as to redefine the BeoLab 90's off-axis radiation at all frequencies. Thus, each of these 15 drivers will be summing or interfering with the off-axis radiation at different frequencies, to reshape the dispersion to be uniformly controlled over most of the audiobandmuch as a sculptor might add clay at one place and remove it at another.
The BeoLab 90's DSP and multiple drivers also allow the user to change the speaker's radiation axis, directing its output at different listening positions using the Beam Direction Control, and to implement Active Room Compensation. I didn't try the former; the effects of the room equalization are described below.
The appearance of the BeoLab 90 is pleasantly domestic. While the speaker is undeniably big, the use of multiple curved panels of fabric and wood, with aluminum accents, distinguishes it from the monolithic appearance of most large speakers, even those that have some curved contours. The BeoLabs didn't overwhelm my 24' by 14' room, nor did they change the overall feeling of the space. Instead, they became a welcome design element (footnote 2).
Setup, Part 1
Setting up the BeoLab 90s required more brute force than sophisticated tweaking. Three B&O employees unboxed and positioned the large, heavy speakersone hopes that a regular purchaser would receive at least as much consideration I did. They used a custom-made trolley to move each speaker into positionthe only constraint was that we wanted the BeoLabs equidistant from and aimed precisely at my head as I sat in my preferred listening spot. Their considerable size meant that each BeoLab 90 ended up less than 18" from a sidewallbut if the raison d'être of B&O's Controlled Beam Width is relief from room influences, positioning shouldn't be critical.
Each pair of BeoLab 90s comprises a Master and a Slave (B&O's terms). The Master speaker was connected to my home network with one CAT7 Ethernet cable, and to the Slave by another. Since the speakers sat at the opposite end of the listening room from my Baetis music server, I needed long cables. Sure, I could have used the long XLR cables that usually run from my equipment rack to my power amps, and let the BeoLab 90 convert their analog signals to digital at 24-bit/192kHzand I did use the analog RCA outputs of my exaSound e28 DAC directly, as well as the analog XLR outputs of my Parasound Halo P 7 preamplifier. But unless I want to play vinyl (which I don't), why not send the digital source, to avoid unnecessary D/A/D conversions and any attendant variables? Well, long runs of digital cables are problematicUSB tops out at about 16' without active drive, and S/PDIF is usually unhappy with really long runs.
I asked for help from two sources. First, Baetis's John Mingo hooked me up with Shunyata Research, who sent along 30' of their Anaconda S/PDIF BNC-to-RCA cable and assured me it would do the job. It did. Second, I asked Corning Optical for their shortest (10m!) USB 3.0 optical cable. Unfortunately, the BeoLab 90's USB input was not yet functional at the time of my listening, so I arranged to borrow a Peachtree Audio X1 USB-to-S/PDIF converter.
Not so fast! Corning's optical USB cable doesn't carry the 5V required to power the Peachtree X1. So I added to that run an UpTone Audio USB ReGen, with its independent power supply. I now had two routes to the BeoLab's S/PDIF input: one from the server's S/PDIF output via the Shunyata cable, and the other from the Baetis server's USB output (footnote 3) via the Corning cable, the UpTone USB ReGen, and the Peachtree X1. Both hookups worked.
Footnote 1: See "Industry Update" in Stereophile's October 2015 issue.
Footnote 2: The BeoLab 90's 42-page manual states that it was designed by Thorsten Frackenpohl and André Poulheim, who, I assume, are responsible for the speaker's handsome appearance. However, I believe that at least equal prominence should be given to those at B&O who were in charge of its technical development and implementation: Gert Munch, Technology Specialist in Electro Acoustics; Jakob Dyre, Technology Specialist in Electro Acoustics; Geoff Martin, Tonmeister & Technology Specialist in Sound Design.
Footnote 3: By means of its accessory SOtM tX-USBexp.