Design Matters: Bowers & Wilkins 700 S3 Series
Andy Kerr tells David Price about the thinking behind the company's brand new mid-market loudspeaker range…
The problem with being the loudspeaker giant that is Bowers & Wilkins, is that with success comes pressure. Any new model has to be both appreciably better than the one it replaces and able to provide its peer competition with a major headache. In short, it's got to be seriously good, with no nasty surprises. And this is especially the case in the mid-market, where there is absolutely nowhere to hide, as any failings in the range can't be excused by pointing out the speaker's budget origins…
Talking to the company's erudite Director of Product Marketing & Communications, Andy Kerr, I think it's fair to say that he gets this – as indeed does the Bowers & Wilkins design team. “Nobody in our team has the mindset to hold back. Our approach is always to try to do as much as you can, push as hard as you can, deliver as much as you can. I think we're in a consistent vein of form right now. With the new 700 S3 Series, our intent was pretty straightforward – within the constraints that naturally apply to a more affordable range of loudspeakers, how close can we get to the performance of the 800 Series Diamond?”
Andy Kerr, Director of Product Marketing and Communications, Bowers & Wilkins
I have followed Bowers & Wilkins' progress over the course of more than thirty years, and have attended most of its product launches stretching back to the mid-nineteen nineties. Never before have I seen so much attention to detail go into a new mainstream range as this. You'd expect the flagship 800 Series to spend years in gestation, with every aspect of it measured and assessed for the difference it makes in sound quality. Yet this time, designers have applied exacting theory and practice to deliver the company's best-ever mid-price speaker range. “The 700 S3 is the current state of our art, in this sector”, Andy tells me.
In this feature, we run through every aspect of the new 700 Series design, particularly focusing on the 702 S3 (read our review here) as the range flagship. Prospective purchasers should find this interesting, but speaker enthusiasts, in general, may also enjoy learning about Bowers & Wilkins' current thinking on speaker design…
Everything starts with the speaker cabinet. No amount of fancy drivers or trick crossovers can make up for a duff enclosure that booms, colours the sound, or messes up the time-domain performance. Even the best transducers have the legs pulled under them if the cabinet is sub-par. With the 800 Series, Bowers & Wilkins expends much time building exceptionally stiff, heavy and acoustically inert enclosures; it's a major contributing factor to the very high prices of the speakers in that range. Obviously, you can't go to such lengths with more affordable, 'real world' designs – but still, Bowers & Wilkins has done its best within the constraints that the new 700 S3 operates.
“Going back to 2015,” says Andy, we introduced a significant new form to the 800 Series flagship range; the reverse wrap”. By this, he means the curved front baffles – which confer a multitude of benefits, which he'll go on to detail. “That was a significant undertaking from a manufacturing standpoint because it required entirely new tooling, and changing over a tool typically is a ten-to-twelve week undertaking per model. We decided to phase the process of introducing that new cabinet form into two stages, concentrating on the larger models in the range in 2015, with a view to coming back to the smaller loudspeakers at the next product lifecycle change.”
He continues: “When we went to change the (then) CM Series into the 700 Series in 2017, we felt that for various reasons we couldn't, at that point in time, introduce a curvature to the cabinet. So, we decided to defer that and focus on upgrading everything inside, which is why the 2017-era 700 S2 Series was all-new internally, but with cabinets that were pretty much carried over. Then, in 2021, we were able to introduce that new reverse wrap form to the 805 and 804 D4 models, which has really helped both models from a technical and aesthetic perspective. With that done, the next step for the 700 S3 was to focus on how to introduce some element of curvature into its design…”
“The transducers were already changed in 2017 and have been further refined for the 700 S3”, says Andy. “But first and foremost, it's all about the cabinet”, says Andy. “It's about utilising as much as we can of our COMSOL FEA-based knowledge of cabinet construction and acoustic forms in a more affordable range of loudspeakers. It begins with a subtle curvature to the front of the cabinet; it's engineered and manufactured in a different way, using a machined-profiled form cut from a thicker (32mm) section of MDF. This stiffens up the front of the speaker, which has useful mechanical benefits, and also places the drive units further forward from the baffle of the cabinet, making the latter less audible.”
“We have shaved about 8mm off the width of the cabinet at the same time, so we have a narrower cabinet, with a curvature, which is thicker and stiffer, with the drivers mounted forward within that baffle using aluminium-faced plastic pods. These help minimise the baffle interaction still further. They're not as structurally influential as the solid machined-aluminium pods we use in an 800 Series Diamond loudspeaker, but certainly have considerable acoustic benefits. We've got a velocity plot where you can see the amount of energy moving through the baffle on a 705 S2 versus the new S3, and you can clearly see that the latter's baffle is quieter. This is because of the new form and materials, so we get less unwanted radiation from the structure and the sound from the drive units propagates better into the room.”
As with most modern domestic loudspeakers, Bowers & Wilkins' 700 S3 models are reflex-loaded – but the company has spent a serious amount of time getting the best from this arrangement. Not everyone is a fan of bass reflex ported speakers, because of the time domain issues they can create, not to mention bass boom. But as ever with hi-fi, it's a case of 'it ain't what you do, it's the way that you do it'. A properly designed reflex loading system can give many of the benefits of sealed box – also called 'infinite baffle' cabinets – but with none of their drawbacks, such as reduced sensitivity or less extended bass.
Andy explains: “If you look at the new down-firing port on the bottom of the 702 S3, it's pretty substantial compared to the rear-firing ports used on the other models in the range. The new orientation allows us to use a much bigger port in a more optimal location compared to the 702 S2. This has let us tune the bass down to go really low. The plinth is now a mandatory-use item, but in turn this gives us a constant surface/distance to tune the port with. This makes it more consistent in a wider range of rooms, as well as making it sound bigger – because crudely, we can push a lot more air through it because it's a longer length of tube with a wider output than we could have used before, and we now know for certain where that result of that output is going.”
“The other big lesson from 800 D4 that's rolled straight into 700 S3,” explains Andy, “is about the length of the tweeter tube loading systems. Over time we've got better at modelling those and understanding how they behave; and if you look at the 800 D4 tube loading system next to a D3, you'll notice that it's quite a lot longer – on an 805 it essentially runs from the front to the back of the cabinet. This gives a more cohesive knit between the lower portion of high frequency output, and the upper midband. That lack of individual drive unit audibility is really strong now, there's much more of a sense of there being one unified driver. This approach is now carried into the new 700 S3. The Tweeter-on-Top models have a significantly longer tube loading system – around thirty five percent – and even with the in-baffle tweeters used on the 704 S3, 706 S3 and 707 S3 it's pretty much forty percent longer than it was.”
Although much thinking has been taken from the latest 800 Series Diamond, this does not extend to the Matrix bracing system inside the cabinet, the Diamond Dome tweeter or the so-called Turbine Head – the substantial metal enclosure for the midrange driver, which is hideously expensive to make and fit to larger 800 Series Diamond models. Andy says: “The 700 Series has to be more affordable, it doesn't have the Turbine Head, it doesn't have significant aluminium reinforcement on the internal face of the baffle and there's no Matrix assembly, although it is of course braced. It doesn't have the aluminium top plate or bottom plate you find on an 801 D4, either.” But in fairness, given the dramatic price differential between the 800 Series and the new 700 S3, this shouldn't come as a surprise!
He elaborates: “The 700 S3 is more domestically friendly; one shouldn't lose sight of the fact that the 705 S3 is a £2,599 loudspeaker and 805 D4 is a £7,000 loudspeaker; that's a very significant difference, and you do get what you pay for. An 800 has a cabinet that's even more likely to 'disappear' acoustically, even though the 700 S3 has been informed by the principles that went into the design of the 800.”
Andy explains that the drive units used for the new 700 S3 range are effectively tweaked versions of the already very capable 700 S2 series. “Although we use the same tweeter diaphragm as before – it's our proven Carbon Dome design – basically everything behind it has been revised. So you're talking a new vented coil, a new magnet system, much longer tube loading system (in both tweeter-in-baffle and tweeter-on-top), the decoupling system, all directly inspired by the 800. The radiating component parts in the system – whether it's a cone or a dome – are pretty much the only carry-over component. The pods are 800 Series all the way, a single piece of solid aluminium machined out. We also have more models in the range that use Tweeter-on-Top: it's in 703 S3 for the first time, and also in the HTM71 S3, our larger centre-channel speaker, for the first time. In terms of the impact it makes to performance, it's huge.”
Bowers & Wilkins designers have also given a lot of thought to the relationship between the 700 S3's drive units and the cabinet. Unsurprisingly, this has involved trickling down the company's technology from the 800 D4 range. “The new range is the first aside from 800 D4 last year to employ the Biomimetic Suspension technology. It's only on models with the dedicated FST midrange – so, the big centre channel and the three floorstanders. So, in the case of the 5” FST unit in the 704, what you have essentially got now is an 804 D4 midrange in a 704 chassis. With the 6” in the 703 and 702, it's basically the same approach, but to 802 D4 spec. It's quite trick, you're getting a lot of high quality firepower!”
Ironically perhaps, with the 700 S3's cabinet naturally being more audible than an 800 D4 Matrix cabinet, the midrange suspension is arguably even more important on the new range. One could argue that the super-quiet enclosure of the 800 D4 is less prone to being excited by vibrations coming from the drivers than that of the 700 S3. Andy expands on this idea: “Whereas the 802 D4 also benefits from the Turbine Head, the fact is that the midrange unit in a 702 or a 703 S3 is still inside a box rather a separate, acoustically optimised structure, and one without the stiffness of a whacking great big lump of aluminium. So the lack of output coming from the secondary suspension, or spider, is arguably even more of a benefit – you can definitely hear how much more this speaker goes quiet, when it's supposed to. The resolution jump is just “wow!”.
Bowers & Wilkins has long been keen on the idea of decoupling speaker drive units from the cabinets – and more specifically, the all-important front baffle, which the company's research shows can be responsible for a multitude of sins. “The decoupling has been refined a lot,” Andy tells me. “It originally came in with the 800 D3 in 2015 but has been refined twice since – 2017 with the 700 S2s and 2021 with 800 D4. The latest version is the most optimised yet: at the front of the cone there are four very small compliant mounts at the bottom and two at the top to centre it, and then the chassis is retained at the back by a sprung rod which bolts into the centre part of the enclosure. It's as 'free' as we think we have yet achieved, in that as far as is possible it helps limit unwanted interference coming from the rest of the cabinet. And that's very important with the 702 S3, which has got three substantial 6.5cm bass drivers and good porting, so it will go low!”
The attention to detail doesn't stop there. The 700 S3's new rear terminals are now arranged in a horizontal grid of four like an 800 Series – and the connectors are from the 800 Series. This gives superior contact with better material, is easier to use and looks better, says Andy. “The plinth on the floorstanding models has been revised too. We've done some more modelling and taken a slightly different perspective how we mechanically couple the plinth into the base of the speaker – we now use very substantial M8 bolts. That in turn lets us scale in the plinth. In the case of the 702s, we now use much more substantial M10 spikes too, not the M6s of before, so the new plinth is better connected to the ground.”
INTO THE FUTURE
As thoroughly engineered as it is, the new 700 S3 range is no 800 D4. Yet it's peppered with the thinking that went into Bowers & Wilkins' flagship speaker line, if not the exact parts. This not only pays off some of the huge investment that the company puts into R&D, but it makes the company's mid-price appreciably better than its predecessor – so there's a double win. “The 700 Series in all of its forms, across all our markets, is one of our strongest selling ranges”, Andy points out. “It is therefore incredibly important to get right. That means that just one year after rolling it out on 800, advanced technology such as the Biomimetic Suspension is making its way to 700. And we wouldn't have got either this or the Continuum Cone into the 700 Series without all that development work we did on the 800”, he adds.
“The 800 is the collective output of everyone in the company, our 'space rocket'; but the advantage is, once you've made your space rocket once it becomes easier to understand how to do it again, but at a more attainable level – that's how you move forward. It justifies all the research done because it's implemented on a wider range of products. We're also in a useful position because we've got our own benchmark for performance, our own reference. For our acoustic team, they've always got the 801 D4 on hand to give them a clear idea of how things should sound – and then they can use that as a reference point to help them get something like a 702 S3 to sound as close to that as we possibly can.”
For yours truly, the strength of the new 700 S3 Series is that you get a good deal of the performance of Bowers & Wilkins' flagship speaker, for far less money. It deserves to succeed.
David started his career in 1993 writing for Hi-Fi World and went on to edit the magazine for nearly a decade. He was then made Editor of Hi-Fi Choice and continued to freelance for it and Hi-Fi News until becoming StereoNET’s Editor-in-Chief.
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