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Review by LOUIS CHALLIS It’s got the looks. It’s got the sound. It’s got the technical magic! Nautilus 801 B&W’s massive new monitor speakers are not for the faint-hearted. They are very big, very efficient, very expensive and their looks are hardly conventional. But according to Louis Challis, they are one of the very best loudspeaker systems ever made. He was so impressed he just had to buy a pair. The Nautilus 801s are large and heavy loud-speakers. Note the curved construction of the cabinet. Top of page is the exploded view of the Nautilus 801’s tweeter and midrange drivers. January 2000  11 W hile a few loudspeaker manufacturers do produce ‘monitor speakers’ very few deserve such an accolade. Following my recent involvement in the equalisation of three television sound-dubbing studios, I am aware of just how critical the quality of a pair of monitoring loudspeakers has become to the recording industry. Although studio monitor loudspeakers are expected to offer a flat frequency response, few achieve that aim. B&W’s 801 loudspeakers were first released in 1979. They were an instant success and I was but one of many international technical reviewers who adopted them as my reference against which all other loudspeakers were then compared. B&W’s use of woven Kevlar diaphragms in the mid-range drivers and the application of laser holography to iron out the bugs associated with diaphragm and edge termination reson-ances gave it (and the 801 series speakers) an initially unassailable edge over virtually all its competitors. In the ensuing 20 years, the 801 series 1, series 2 and most recently, the series 3, have been adopted by more than 80% of classical recording studios for their mix-down and dubbing suites. A limitation in the original 801 loudspeaker was the presence of discernible cabinet resonances in the frequency range from 50Hz to 500Hz. B&W resolved that problem in the mid-1980s with their ‘Matrix’ composite foam and internally stiffened enclosure structure. This was featured in the 801 series 2 and 3 and was based on a honeycomb of rigid internal bracing elements filled with foam. The results were dramatic, with the cabinet resonances reduced to a very low level. Then, in the early 1990s, B&W developed its controversial Nautilus loudspeakers. The Nautilus had a decidedly unusual appearance, with a stacked array of loudspeakers in what looked like four spiral conch shells of decreasing size, stuck one above the other. The tapered form at the rear of each loudspeaker driver provided an effective damped termination. This worked but its unusual appearance, weight and cost meant that relatively few enthusiasts were willing to accept it. B&W have now taken a different tack, incorporating the Nautilus system into the 801 series 3 monitor speakers. During my visit to B&W’s factory in Steyning, Kent, work on the development of the Nautilus 801 loudspeaker was in its final phase. On return from England, I was told that I would have to wait at least a year before a pair could be provided for review. When they finally turned up in two extremely large cartons attached to timber pallets, they were so heavy that specialist removalists were required to get them into my living room. Before I could start to review them, I found myself in the perplexing position of having to unpack them myself, even though I had been assured that the carriers would perform that task. Having unpacked them, I can confirm just how time-consuming (and at times daunting) that task was. Each cabinet weighs 104kg and my wife The quality of monitoring loudspeakers in the recording industry is critical. A pair of B&W Nautilus 801s have been chosen for the mixdown room at the famous EMI Abbey Road studio in London. 12  Silicon Chip tapered tail extends to the very rear of the cabinet at which point an aluminium venting cover provides a controlled impedance element for the taper’s exposed exit. The tweeter is centrally housed above the speaker in its own tapered assembly. Foam ring surround Fig.1: 1/3-octave pink noise listening room response of the Nautilus 801s. and I took about an hour to complete the job. There are few visual or functional similarities between the 801 series monitor loudspeakers and the Nautilus 801. The only significant element of the series 3 that was retained is the matrix concept in the construction of the low-frequency driver cabinet. Even the bass driver has been changed, from 300mm (12") to 380mm (15"). The more obvious differences are the curved sides and back for the lower portion of the enclosure. Curved panels are inherently stiffer than flat panels of the same thickness and they also reduce diffraction problems. The extremely thick curved plywood panels in the Nautilus 801 are manufactured by a Danish company. The woofer has a massive diecast aluminium chassis and its rigid cone is a composite of Kevlar and paper pulp. The dust cap is also unusual and is made from carbon fibre. The woofer voice-coil has two separate spider elements at its rear to maintain axial linearity during the extremely high excursions which can occur as a result of the extended low-frequency response. conventional loading ports produce is suppressed. The base of the cabinet also has a thick cast aluminium assembly on which the crossover networks are mounted. The aluminium casting acts a heatsink for the crossover and the base also incorporates four ball-bearing roller glides to enable moving the cabinets across a smooth floor. The roller glides are not intended to provide the final support though and B&W advocate their replacement by four long machined aluminium spikes with stainless steel points that should be inserted in the floor at the selected monitoring location. When I tentatively suggested that approach to my wife, the negative vibes convinced me that it might not be appropriate. . . The most striking feature of the Nautilus 801 is its midrange and tweeter assembly. The 150mm dia-meter midrange driver is housed in a shiny black, extremely rigid tear-drop plastic enclosure. The enclosure’s The mid-range driver utilises what B&W describe as a “fixed suspension transducer assembly”. This has a woven Kevlar diaphragm without the traditional foam or rubber surround. In its place is a 3mm diameter ring of foam that B&W claim removes the dominant surround resonance that plagues most conventional mid-range drivers. Those resonances can result in disturbing peaks and dips in the frequency response curves. B&W claim that the foam ring provides an optimum match between the travelling wave impedance of the bending waves in the cone and thereby minimises reflections that would otherwise occur at the outside of the cone’s rim. The foam edging results in a lower excursion capability when compared with conventional drivers but B&W claim that the driver’s operating frequency range negates the need for a greater excursion. In the place of the conventional dust cap, the mid-range driver has a stationary bullet-shaped cone and this is claimed to improve the off-axis response. Also provided is an alternative bullet-shaped cone with a central screw to which the protective black speaker cloth and wire-framed cover is attached. The mid-range enclosure is actually a long-tail reverse horn. With its carefully shaped internal cavity, it greatly reduces internal reflections, whilst Dimpled loading port The base of the enclosure incorporates an unconventional tapered loading port, with a rectangular aperture at the front and with tapered slots on the two sides of the cabinet. The upper and lower surfaces of the flared port are dimpled. B&W’s research showed that dimpled surfaces in the loading ports reduce boundary layer turbulence. As a result, under high drive conditions, the audible ‘chuffing’ that Fig.2: manufacturer’s frequency response curve for the Nautilus 801. January 2000  13 isolation material, with characteristics more like those of rubber. The crossover has three separate PC boards which are physically separated to minimise any coupling or interaction between them. Each coil is air cored, the capacitors are primarily polypropylene, with supplementary capacitors that are more effective at high frequencies and each thin film resistor has its own heatsink. The crossovers are designed for bi-wireable connections and two pairs of terminal posts are provided at the rear of each speaker enclosure. The gold-plated brass posts are designed to accept banana plugs, spade lugs and bare wires. For those people who choose to use only a single pair of wires for connection, B&W supplies short jumper cables with the speakers to simplify the task. Fig.3: near field frequency response of the Nautilus 801. Objective testing simultaneously providing a smooth, diffraction-free external surface that further improves off-axis response. at their points of fixing to avoid unwanted inter-modulation products. They use a newly developed plastic When reviewing speakers I normally do the objective testing in my anechoic chamber but the sheer weight and size of these Nautilus 801s made The 25mm diameter aluminium tweeter uses a small neodymium-iron-boron magnet assembly with an edge-wound, copper-coated, aluminium ribbon voice-coil and it has magnetic fluid cooling. The tweeter’s frequency response and rear loading is enhanced by a tapered aluminium tube filled with wadding. The tube acts as a heatsink while simultaneously absorbing the rearward directed sound waves. The wadding density behind each tweeter is carefully tweaked during manufacture to ensure the correct frequency response. The tweeter and mid-range assemblies have been carefully decoupled Fig.4: measured impedance curve of the Nautilus 801. 14  Silicon Chip that impossible. As a consequence, I had to do the objective and subjective testing in my listening room. The assessments included a third octave band analysis of the space-averaged pink noise response, measurements of the individual drivers’ frequency response in the near field using MLSSA procedures, impedance characteristics, peak level and distortion. Fortunately, each Nautilus 801 comes with a frequency response graph recorded during final testing in a small anechoic room. This shows the response differences relative to the company’s primary reference speaker which has been separately measured in a large anechoic chamber. The pink noise response reveals an unusually smooth characteristic with a relatively small (±2dB) variation over the critical frequency range from 200Hz to 20kHz. Between 20Hz and 200Hz, the listening room’s Eigentones (standing waves) dominate the peaks and null characteristics of the measured pink a pair of Nautilus 801s was used for the left and right channels of a home theatre system, there would be little measurements showed that the low frequency response was reasonably smooth (even though a flat response noise response. For example, there is a significant 7dB rise in the response in the third octave bands centred on 31.5Hz and 40Hz. Between 50Hz and 200Hz there is another smooth rise in output of approximately 7dB, whose peak is centred in the 100Hz third octave band. There is a discernible droop in the pink noise response above 16kHz, although the speakers still provide useful output at 20kHz (which few people can hear). At the other end of the frequency range, the low frequency drivers in the Nautilus 801 speakers will out-perform the majority of subwoofers that I have recently evaluated. In fact, if point in buying a subwoofer. Objective performance testing with a 12mm Bruel & Kjaer reference microphone, preamp and measuring amplifier coupled to an MLSSA system confirmed that even in the listening room, the frequency response (measured at 1 metre) was still within ±2dB over the frequency range 200Hz to 20kHz. The primary peaks and dips were all attributable to near-field reflections from the floor, ceiling and the walls behind the speakers. Longer path reflections in the listening room make the recording of a quasi-anechoic frequency response impractical. However, near-field could not be confirmed). Even the waterfall responses revealed smooth decays, whose peak-iness is primarily, if not entirely, attributable to room mode responses. Although the B&W literature talks about impedance adjusting elements in the crossover, the measured impedance curve still displays some significant peaks. For example, there is an unusually high peak of 42Ω at 15Hz, with a second peak of 16Ω at 40Hz and still another nominal 16Ω peak at 2.2kHz. The minimum impedance was 3.3Ω at 200Hz. However, the 801’s impedance characteristic would not cause any problems with the vast Fig.5: spectral decay response of the Nautilus 801. These are notably smooth curves. January 2000  15 majority of modern amplifiers. Having completed the objective tests, I had to conclude that the Naut-ilus 801 offers one of the flattest and without a doubt the highest peak output of any monitor loudspeaker system I have ever tested. I was mightily impressed by their ability to provide transient peak outputs exceeding 120dB at three metre distance over the frequency range 100Hz to 10kHz, without my risking the destruction of any drivers. At those extremely high levels, the distortion is both measurable and frequently audibly detectable. In case you’re wondering, I wore earmuffs for that phase of the testing, as peak levels of 120dB are painful and can cause permanent hearing loss. Subjective assessment For subjective tests, I used my listening panel, who were already familiar with the B&W 801 series 1, 2 and 3 loudspeakers. We compared the Nautilus 801s with a pair of B&W 801 series 2 and also with a pair of Quad Electrostatics supplemented by a subwoofer to broaden their low frequency response. In hindsight, that test might be considered patently unfair. In fact, the Nautilus 801s out-performed the other two systems in every single department. With a rated sen- sitivity of 91dB at 1 metre for 1 watt, the Nautilus 801 is one of the most efficient loudspeakers of its class. The difference in efficiency is quite marked when compared to the 801 series 2 – they required a 30° shift in the volume control to provide comparable output. The Nautilus 801’s frequency response is far broader than that of the Quad Electrostatics, even with the supplementary subwoofer and they provide a peak output power capability that exceeds the Quad’s by more than 15dB. More importantly, they provide a smoother and far less coloured frequency response, when assessed with broadband pink noise, than any other speaker I have yet heard. Our subjective assessment then involved a series of vocal and instrumental music. The vocal assessment made use of Ghillian Sullivan’s Vocal Gems (Walsingham Classics WAL 80322) and specifically track 8, Vilja from The Merry Widow and track 15 Voices of Spring by Johann Strauss. The recording and mix-down process adopted during the production of this particular disc has proven to be effective, even though unusual. The orchestral recording was made in the Eugene Goossens Hall, with Ghillian Sullivan’s vocal lead added during a subsequent mix-down. Having heard music and vocals in the Eugene Goossens Hall on many occasions, I know its sound quality very well. When listening to this recording through the B&W 801 Nautilus loudspeakers in my listening room, with eyes closed, I could easily convince myself that I was sitting in a central position in the Eugene Goossens Hall. The second disc I used featured Yo-Yo Ma as a soloist playing various modern works from Zoltan Kodaly, David Wilde, Alexander Tcherepnin and Mark O’Connor’s Appalchia Waltz (Sony Classical SK 61739). The stereo imaging was razor sharp and absolutely brilliant. While much of the music was not to my taste, the reproduction was outstanding. The third disc was a new release entitled Amiel: the chase, “mixes by Josh Abrahams and hifi bugs” (Festival Records D 1936). All five tracks but particularly the last two provide a low-frequency output that sorely tested the two comparison speakers, but presented no hurdles to the Nautilus speakers. And as noted above, the Nautilus 801s provided a smoother, more clearly focussed and less distorted, high-level low-frequency output than the quality sub-woofer that I had been using. Any purist who takes delight in organ recordings or cannons firing in Tchaikovsky’s 1812 Overture will revel in the 801 Nautilus’ sound reproduction. I have yet to test any loudspeaker that can approach or equal their performance. The B&W Nautilus 801s have a recommended retail price of $26,000 per pair. Many people would consider that a lot of money to spend on a car but there are quite a few people who would be prepared to swap that car for a set of these outstanding loudspeakers. I am one of those people. For further information, on the B&W range of loudspeakers, contact the Australian distributors, Convoy International. Phone 1 800 817 787. For a demonstration, visit the Len Wallis Audio showroom at 64 Burns Bay Road, Lane Cove NSW 2006. SC Phone (02) 9427 7655. Fancy a pair of Nautilus 801s in your listening room? You’ll need a lot of space, strong floors, rather deep pockets and a v-e-r-y understanding spouse. 16  Silicon Chip