B&W 800 User Manual

A legend reborn Everything moves on. Even

when you’ve reached the pinnacle of technological

achievement, there are always new goals to aim for, new standards to set. In 1979, we redeﬁned what’s possible in sound reproduction with the very ﬁrst 800 Series speaker – the Matrix 800.

In 1998, we re-wrote the rulebook all over again with the Nautilus™ 800 Se ries. But we didn’t stop there. We continued to reﬁne and experiment, and

now we’ve raised the benchmark yet again. The 800 Series Diamond harnesses the unique properties of diamond througho ut the range, producing a sound

of unheard-of accuracy and realism. At Bowers & Wilkins, the quest for perfection never en ds.

The e volution of exc ellence Introdu cing sup erior drive units housed in sepa rate chambe rs, the Matrix 800’s unprece dented s ound quality made the speaker a fixture in to p recordi ng studi os and the h omes of discer ning aud io enthus iasts. W ith th e Nautil us 800 S eries and now the 800 Series Diamond , the tradition contin ues.

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Simulated acoustic Frequency response

The miracle material It can cut stone and grind glass. It’s a superb thermal conductor. And it’s the magic ingredient in every model in the new 800 Series Diamond range. Our acoustic research expert Dr Gary Geaves explains why diamond is the ultimate tweeter material.

Simulated acoustic Frequency response

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Simulated acoustic Frequency response

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Comput er simul ations show that the response of a diamon d dome (right) more closel y matche s the behaviour of th e hypothetical perfect tweete r than an alum inium dome (left).

Tell us about tweeter design – what are you trying to achieve, and what are the main challenges to overcome?

Our aim here at Bowers & Wilkins has always been to design transducers that accura tely reprod uce the signal. It’s really quite easy to create a sound but it’s much more difficult to reprod uce a signal accurately. When it comes to tweeters, th is aim translates into creating a device that moves as a rigid piston over the audible frequency range – in other words, the range below 20 kHz.

As you go up in frequency, you reach a point where the tweeter stops behaving in a nice, controlled way and it starts to resonate. The frequency at which this occurs is usually called the break-up frequency. As you go beyond the break-up frequency, you encounter more and more resonance. The problem with resonance is that it imparts a character to the speaker, which is obviously not what you want when you’re aiming to accurately reproduce a signal.

So the main challenge in tweeter design is to overcome the problem of resonance. And you do this by trying to push the breakup frequency as far above the range of human hearing as it can p ossibly go.

What have you been doing to get around this problem?

For a long time, Bo wers & Wilkins have used aluminium dome tweeters. Aluminium’s a really good material t o use, because it’s relatively light and stiff, and it results in a relatively high break-up frequency. Over the years we’ve be en able to optimis e the mechanical design. For example, for th e second generation 800 Series, we managed to improve the break-up frequency from about 23 kHz to 30 kHz.

It was then that we noticed something odd. We found that, with each improvement in break-up frequency, the resulting tweeter sounded much cl eaner. Not that surprising, you might think – but we found this really curious because, as I’ve already said, human beings can only hear up to 20 kHz. Improving the break-up frequency from 23 to 30 kHz shouldn’t have made any difference to the audible sound q uality. And yet it did. So we started to wonder why this was, and if there might be ways of raising the br eak-up frequency much higher.

How did you go about trying to raise the break-up frequency level? What sort of design approaches did you consider?

We started off by thinking about the size, shape and positioning of the tweeter. Now, the easiest way to improve the break-up frequency is to make the tweete r much smaller. The problem with that approach is that, to get the same output over the same bandwidth, you have to drive the speak er a lot harder. The dome has to move a lot more. And when that happens, you run into problems with linearity, distortion and power compression.

An alternative approach might be to use a supplementary tweeter in addition to your main tweeter. We did consider this, but we found it just complicated the situatio n. Instead of compensating for the deficiencies o f a main tweeter, the su pplementary tweeter just added its own set of problems. There was al so the potential for i nterference between the two tweeters. In th e end, this approach just didn’t seem consistent with our principle of keeping things simple.

How did you hit on the idea of using diamond as a tweeter dome material?

We discovered the benefits of dia mond thanks to a process called finite element analysis. It’s a tool that’s widely used in the aerospace and automotive industries to create virtual computer prototypes, so you can carry out experiments before committing to a real physi cal prototype.

By using finite element analysis we were able to look more closely than ever before at how a speaker reproduces sound. We could examine in deta il how the whole structure vibrates, and t he acoustic field that results from the vibration. We were also able to look at the motor systems i n loudspeakers. This allowed us to come up with new ways to optimise sensitivity, improve linearity, and design better shielding.

It was by using fin ite element analysis that we first simula ted the response of a perfect, rigid tweeter, made from an infinitely stif f material. This is a material that doesn’t exist in reality – but that’s another beauty of finite element analysis; you can do things that y ou can’t do in the real world. So we started to look at tweeter dome materials we could use instead of the aluminiu m – materials that shared similar properties to the hypothetical perfect dome. And we found that t he ultimate material – the absolute closest match in terms of its rig idity and dynamic sti ffness – is diamond.

So what are the benefits of using diamond tweeter domes?

As I said, with aluminium, we were getting a maximum break-up frequency of about 30 kHz. Pretty amazing, when you consider the human hearing threshold is 20 kHz. But by using diamond, we were able to go far, far higher than that, creating a tweeter that breaks up at 70 kHz.

However, diamond doesn’t just have a much higher break-up frequenc y – it also outperforms aluminium within the range of human hearing. When you compare the response of a diamond tweeter with the perfect hypothetica l rigid tweeter, the results are very similar below 2 0 kHz. And this means that you can hear a dramatic improvement in sound quality.

The resulting tweeter sounds more effortless, and yet more detailed, and has a much more realistic soundstage than the standard aluminium tweeter.

Dr Ga ry Geaves, Head of Research, Bowers & Wi lkins

HTM2 Diamond

HTM4 Diamond

Diamon ds all round The 800 S eries Diamond f amily encomp asses sp eakers of all sizes and applications, from mighty studio monitors to booksh elf spea kers that will fit snugly into domestic spaces of an y size. But wh ile every speake r is different, they ha v e two k ey features in common: a twe eter made from pure diamon d, and sound q uality that will leave you speechle ss.800 D iamond 802 D iamond 803 D iamond 804 D iamond 805 D iamond

A diamond is born

Making diamond the natural way takes volcanic temperatures and pressures, and around two billion years. Hardly ideal if you want to produce it for manufact uring purposes, let alone form it into the precise shape required for a tweeter dome. Luckily, scientists have found a way around this. Chemical vapour deposition is a technique tha t allows diamond to be grown, like a crystal, under laboratory conditions.

The process starts with the former – the dome of metal on which t he thin layer of diamond is grown. Each former is meticulously inspected and weighed bef ore being transferred to a specially designed furnace, where gases are super-heated and pressurised. Out of the gases forms a carbon frost (diamond crystals), which grows on the surface of the former to create a super-fine, ultra-hard diamond dome.

Making the cut

Once the diamon d has formed, it is precisioncut by laser to remove any surface irregularities and to make sure that the geometry of each tweeter dome ex actly matches the next. The diamond domes a re then cleaned in four stages in an ultra-son ic tank, before a protective platinum coating is applied to the surface.

Each diamond do me is rigorously tested and inspected for t he tiniest signs of imperfection. Only when a dome ha s passed every test do we give it the fina l seal of approval – its own unique serial n umber. From this number we can trace the entire history of its manufacture, right back to the former on which it was grown.

A head for sound

Nautilus tubes

Not all the sound g enerated by tweeter drive units is good sound. To soak up wayward sound energy an d reduce resonances to a minimum, every tweeter in the 800 Series Diamond is moun ted on top of the cabinet, and uses the taperi ng tube design from Bowers & Wil kins’ trailblazing Nautilus speaker. Added to this, our new quad-magnet design improves sensitivity, which reduces compression and brings music to life. So all the sound you hear is good sound.

The teardrop-shaped midrange head is a distinctive feature of both the top-of-the-range 800 Diamond and the 802 Diamond. Moulded from Marlan™, a synthetic, mineral filled resin, this granite-hard enclosure i s sprayed with seven coats of lacquer and polished by han d until it’s as smooth as glass.

Quad ma gnets For the 800 Series Diamon d we have redefined the science of magnet motor design. In the tweeter, a unique quad magnet design (in red, above) focuses the magnetic energy right where the voice coil sits, and keeps the driver running cool and smooth.

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