BOW­ERS & WILKINS 606 LOUD­SPEAK­ERS

Loud­speak­ers

Australian HIFI - - CONTENTS -

A glo­ri­ously rich and warm midrange com­ple­mented by a nicely bal­anced tre­ble thanks to an im­proved tweeter on the new mod­els.

It has been eight years since Bri­tish man­u­fac­turer B&W first de­vel­oped its ‘Con­tin­uum’ cone ma­te­rial for use in its flag­ship loud­speak­ers, the 800 Se­ries Di­a­mond mod­els, and it’s been six years since B&W re­leased its first ‘Six’ se­ries. Why men­tion both events? Be­cause this year, for the first time, Con­tin­uum cones have been in­te­grated into the sixth gen­er­a­tion of the com­pany’s crit­i­cally ac­claimed ‘Six Se­ries’. The first Six Se­ries speaker to ar­rive in Aus­tralia was the B&W 606 and, thanks to the help of Bow­ers & Wilkins Aus­tralia, a sam­ple from the very first ship­ment was sent di­rect to Aus­tralian Hi-Fi Mag­a­zine for re­view.

The Equip­ment

The new B&W 606 is a two driver, two-way, bass re­flex stand-mount/book­shelf loud­speaker. As noted in the in­tro­duc­tion, the 165mm di­am­e­ter bass/midrange cone is made from a ma­te­rial that B&W calls ‘Con­tin­uum’ that’s said to have a ‘ unique com­pos­ite con­struc­tion’ and first ap­peared on the 802 D3. Although B&W rates the over­all width of the Con­tin­uum cone on the 606 at 165mm, the mov­ing part of the cone (cone plus roll sur­round) is 145mm and the cone it­self is only 120mm. The Thiele/Small di­am­e­ter is 133mm, which gives a cone area (Sd) of around 140cm².

Con­tin­uum must be su­pe­rior to Kevlar as a cone ma­te­rial, be­cause B&W it­self pre­vi­ously used Kevlar in this ap­pli­ca­tion… in­deed B&W was the first com­pany in the world to use Kevlar as a cone ma­te­rial—so suc­cess­fully, in fact that it was copied by dozens of other speaker man­u­fac­tur­ers around the world. Some­times these copies were at least faith­ful to the orig­i­nal, and used wo­ven Kevlar in their con­struc­tion, but it must be said that some­times the copies used ma­te­rial that merely ‘looked’ like wo­ven Kevlar!

Ac­cord­ing to B&W the com­pany has spent more than eight years de­vel­op­ing Con­tin­uum, build­ing more than 70 it­er­a­tions be­fore de­liv­er­ing the fi­nal pro­duc­tion cones across a range of dif­fer­ent di­am­e­ters but de­spite this, tech­ni­cal de­tails about the ma­te­rial are very thin on the ground. It has been sug­gested that one rea­son B&W is be­ing so se­cre­tive is that it is try­ing to pre­vent other man­u­fac­tur- ers from copy­ing it, as they did with Kevlar. If this is true, it would sug­gest the rea­son that B&W has not filed any patents for Con­tin­uum, since do­ing so would im­me­di­ately give the game away as to its com­po­si­tion.

What we do know is that Con­tin­uum is a coated wo­ven ma­te­rial whose con­struc­tion is based on the same con­trolled break-up the­ory that made Kevlar so ap­peal­ing as a cone ma­te­rial. The prob­lem with non-wo­ven speaker cones, no mat­ter what ma­te­rial they’re made of—pa­per, plas­tic, metal etc—is that as the cone reaches the lim­its of its re­sponse the cone’s for­ward and back­wards mo­tion will cease be­ing pis­tonic (where all parts of the cone move for­ward and back­ward at the same ve­loc­ity) and will quite sud­denly go into the first ‘break-up’ mode, which is an un­con­trolled ac­tion where some parts of the cone will move for­ward whilst oth­ers move back­wards. This un­de­sir­able ac­tion is fur­ther com­pli­cated by the fact that this sud­den break-up ac­tion will oc­cur dif­fer­ently at dif­fer­ent fre­quen­cies. Us­ing a cone wo­ven with Kevlar will ame­lio­rate these af­fects, but ac­cord­ing to Andy Kerr, Di­rec­tor of Prod­uct Com­mu­ni­ca­tion at B&W, us­ing a cone wo­ven with Con­tin­uum ame­lio­rates these ef­fects even fur­ther. ‘ The Con­tin­uum Cone be­haves quite dif­fer­ently,’ he said.

‘ Its wo­ven com­pos­ite de­sign is based on the con­cept of con­tin­u­ously vary­ing de­grees of flex­i­bil­ity that help it avoid the abrupt tran­si­tions that can dras­ti­cally im­pair the open­ness and neu­tral­ity of a con­ven­tional drive unit. As a re­sult its fre­quency re­sponse is re­mark­ably pre­dictable through­out its range.’ An on-line B&W video ex­plain­ing the Con­tin­uum cone (tinyurl.com/con­tin­uum-clip) says it ‘ doesn’t dis­rupt audi­ble re­flec­tions but works as if the sound waves don’t see the edge of the cone.’ Kerr pro­vided two an­i­mated GIFs to il­lus­trate the dif­fer­ences in per­for­mance at break-up be­tween a Kevlar cone (tinyurl.com/kevlar­break-up) and a Con­tin­uum cone (tinyurl. com/con­tin­uum-break-up).

The tweeter in the B&W 606 is also new for this se­ries, though it is fit­ted to other mod­els in B&W’s range. It’s an up­graded ver­sion of B&W’s 25mm alu­minium domed ‘de­cou­pled dou­ble dome’ tweeter, the up­grade hav­ing en­abled B&W to shift the in­evitable high-fre­quency res­o­nance even higher in fre­quency (to 38kHz) and thus even fur­ther away from the au­dio band. The con­struc­tion of the ‘dou­ble dome’ dif­fers from that of a nor­mal dome tweeter be­cause rather than at­tach­ing the dome di­rectly to the voice-coil for­mer, a sec­tion of dome with a large cen­tral cut-out is first at­tached to the voice-coil for­mer, and then the full alu­minium dome is at­tached to the dome sec­tion. Although an ex­tra step is re­quired, it re­sults in a more rigid dome, sim­pli­fies the assem­bly process and de­creases the chance of mis­align­ment dur­ing man­u­fac­tur­ing. Un­like many of B&W’s ear­lier tweet­ers, the one used in the 606 has the rear of the dome loaded by a ‘Nau­tilus’-like ta­pered tube so that the en­ergy that comes from the rear of the dome sur­face is ab­sorbed rather than be­ing re­flected (the tube is ta­pered to help en­sure uni­form ab­sorp­tion across a wider range of fre­quen­cies).

B&W has not just up­dated the driv­ers in the 606. For the pre­vi­ous five gen­er­a­tions of the six se­ries, B&W has been putting the bass re­flex ports on the front baf­fle. For this sixth gen­er­a­tion, the port is now on the rear, though it still uses B&W’s ‘Flow­port’ tech­nol­ogy.

This ‘Flow­port’ is de­signed to ad­dress a fun­da­men­tal prob­lem with bass re­flex ports, which is that they can some­times cre­ate un­wanted noises when the bass driver is work­ing hard, due to the con­sid­er­able air­flow through the port. Some of this noise is caused by tur­bu­lence as the air mol­e­cules in­ter­act with the sur­face of the port. Bow­ers & Wilkins’ ‘Flow­port’ solves this by ‘dim­pling’ the sur­face of the port, which min­imises tur­bu­lence in the same way that the dim­ples on a golf ball im­prove its flight through the air.

The ‘Flow­port’ on the 606 is im­ple­mented rather dif­fer­ently to any that I can re­call pre­vi­ously, be­cause B&W has in­te­grated the plas­tic ‘Flow­port’ mould­ing with the rear ter­mi­nals, so ev­ery­thing is sup­ported on the same piece of black ABS plas­tic. There are two sets of ter­mi­nals on the mould­ing so the 606 speak­ers can be bi-amped or bi-wired: If you choose to do nei­ther, you’d leave them con­nected by the sup­plied and fit­ted buss-bars. The crossover net­work is mounted to the rear of this mould­ing.

In what is be­come al­most de rigueur on modern bass-re­flex de­signs, B&W sup­plies two-stage foam in­serts that can be used to par­tially or com­pletely block the ports on one or both loud­speak­ers.

B&W’s Owner’s Man­ual ad­vises with re­gard to the use of these bungs: ‘ Mov­ing the speak­ers fur­ther from the walls will gen­er­ally re­duce the vol­ume of bass. Space be­hind the speak­ers will also help to cre­ate an au­ral im­pres­sion of depth. Con­versely, mov­ing the speak­ers closer to the walls will in­crease the vol­ume of bass. If you want to re­duce the vol­ume of bass with­out mov­ing the speak­ers fur­ther from the wall, fit the foam plugs or, for less se­vere bass re­duc­tion, the foam rings in the port tubes.’ The port it­self is 170mm long and 55mm wide so un­like some port/plug con­fig­u­ra­tions, there’s very lit­tle chance of ac­ci­den­tally push­ing the plug though the port so far that it drops down in­side the cabi­net.

An­other im­prove­ment on the 606 is that B&W is now also us­ing mag­nets—rather than steel or plas­tic pegs—to hold the speaker grilles in po­si­tion. B&W says this was to pro­vide a ‘cleaner look’ but it also solves a prob­lem many speaker own­ers will have ex­pe­ri­enced with plas­tic pegs which is that they’re are very easy to ac­ci­den­tally snap while you are re­mov­ing a grille (for the pur­pose of clean­ing it, or for a ‘grille-off’ lis­ten­ing ses­sion). You won’t have the same is­sue with a mag­net­i­cally-at­tached grille.

The B&W 606 is avail­able in only two colours—black and white—of which we were sup­plied the black fin­ish for re­view. The black fin­ish is a matte black and made by us­ing a finely tex­tured vinyl wrap. It’s a very ‘neat’ fin­ish that re­flects light uni­formly ir­re­spec­tive of view­ing an­gle such that it

The tweeter up­grade has en­abled B&W to shift the high­fre­quency res­o­nance even higher in fre­quency…

looked to me to be a ‘char­coal’ colour, rather than a deep black. You get a black grille with the black speaker, but with a white speaker you’re is­sued with a grey grille. Although it’s cer­tainly a very pre­sentable cabi­net fin­ish, it didn’t scream ‘class’ to me in the same way that gloss painted or ve­neered fin­ishes do. And now that B&W has moved most—but not all—of its speaker pro­duc­tion to China, a coun­try that ex­cels at de­liv­er­ing both fin­ishes at very low cost, it rather sur­prised me that B&W has not taken ad­van­tage of this.

In Use and Lis­ten­ing Ses­sions

Since the B&W 606s seem to have been de­signed from the out­set to be used sans grilles—at least from a vis­ual stand­point—I thought one of the first things I should de­cide is whether I pre­ferred the sound of the 606s with their grilles on or off. Since I also had to break in the speak­ers be­fore start­ing any se­ri­ous lis­ten­ing and only had a lim­ited amount of time to do so, the process seemed like an ex­cel­lent way to kill two birds with the same stone. Note that there are two grilles per speaker that can be re­moved: the main rec­tan­gu­lar cloth grille that cov­ers most of the baf­fle, and a smaller cir­cu­lar metal grille that cov­ers just the tweeter.

Af­ter lis­ten­ing to a very wide range of mu­sic across all gen­res, I couldn’t re­li­ably hear any dif­fer­ence be­tween lis­ten­ing with the grilles on or off, or in any com­bi­na­tion. And when I say ‘re­li­able’ I mean that some­times I fan­cied I heard a dif­fer­ence, but when I ran the same trial us­ing the same mu­sic a day or two later, I couldn’t hear the dif­fer­ence I’d heard be­fore. So the re­sult of my ses­sions is that I would strongly rec­om­mend you never— ever— re­move the cir­cu­lar tweeter grilles, and that you lis­ten to the speak­ers with the main grilles in place un­less you pre­fer the ‘look’ of the speak­ers with­out the grilles, in which case I’d rec­om­mend stor­ing the main

A glo­ri­ously rich and warm midrange com­ple­mented by a nicely bal­anced tre­ble

grilles some­where they won’t get dusty or ex­posed to light… such as in the plas­tic sleeves they are sup­plied in, and tucked away safely in a dark li­nen drawer some­where.

As for po­si­tion­ing, I had no doubt the B&W 606s sounded their best and ‘airi­est’ on stands, but the bass is bet­ter if you mount them on book­shelves, so it’s def­i­nitely a case of swings and round­abouts. One work­able com­pro­mise would be to use stands but to place those stands fairly close to the rear wall, which de­liv­ers a bit more ‘air’ than book­shelf mount­ing, but with a bit less bass. You can do fur­ther fine-tun­ing by ex­per­i­ment­ing with the port plugs, but I found that I def­i­nitely pre­ferred the level and sound qual­ity of the bass I heard with­out the plugs fit­ted, ir­re­spec­tive of mu­si­cal genre.

Even with the ports open I found the bass to be a lit­tle on the ‘light’ side, but this is re­ally only to be ex­pected given the size of the bass/mid driver and the vol­ume of the cabi­net. What I did find, how­ever, is that I could crank the vol­ume up to sur­pris­ingly high lev­els yet still be hear­ing clean, ac­cu­rate bass with no audi­ble dis­tor­tion. It was tight, punchy, dy­namic bass too. For mine I thought that the bass was def­i­nitely bet­ter-sound­ing at higher lis­ten­ing lev­els than at low lev­els, but with a longer break-in time, these slight dif­fer­ences at the dif­fer­ent lis­ten­ing lev­els may well have dis­ap­peared.

Lis­ten­ing to Zoe Knighton (cello) and Ian Munro (pi­ano) play Grieg’s Cello Sonata in A Mi­nor, Op.36 I was im­pressed by the way the B&W 606s were able to high­light the dif­fer­ent touches Munro uses when play­ing re­peated fig­ures, so each is not just a straight re­peat but a fresh imag­in­ing. The cello is the hero of this work, and Martin Wright (Move Records) has let his en­gi­neer­ing re­flect this, with the re­sult that we hear clearly the gor­geous tonal­i­ties Knighton is able to ex­tract from her cello, right across the en­tire range from the very low­est notes to the very high­est—at least we hear them clearly if we’re lis­ten­ing though B&W 606’s.

The B&W 606’s re­pro­duc­tion of Munro’s pi­ano was equally good. Lis­ten to the sound of the pi­ano in­tro­duc­ing the sub­lime sec­ond move­ment—the aptly-named An­dante molto tran­quillo— and you’ll be trans­fixed by the ac­cu­racy of the speak­ers’ de­liv­ery.

But although the bass is ex­cep­tion­ally good for such a small loud­speaker, it’s cer­tainly out­shone by the midrange de­liv­ery of the B&W 606. The clar­ity is im­me­di­ately ob­vi­ous and the ar­tic­u­la­tion pre­cise, yet there’s no slur­ring over sibi­lants. The sound is beau­ti­fully trans­par­ent and segues into the tre­ble seam­lessly. I par­tic­u­larly liked that B&W ap­par­ently hasn’t aimed at mon­i­tor-like ac­cu­racy, so the voices of fe­male vo­cal­ists, in par­tic­u­lar, had a slightly warmer sound, whilst bari­tones (but not basses) also sounded a lit­tle more won­der­ful through the B&W 606s than they might in real life. Along with that warmth is a slight up­per-mid for­ward­ness that helps with the feel­ing of pres­ence and im­me­di­acy, so you get the best of both sonic worlds. For ex­am­ple Hay­ley Grace, singing her beau­ti­ful Ghost of a Girl (from her de­but EP), was a truly sen­sa­tional au­di­tory ex­pe­ri­ence, sound­ing su­pe­rior to the many times I’ve heard it on many other loud­speaker sys­tems.

The tweeter de­liv­ered the shim­mer­ing, ex­tended up­per reg­is­ters that have im­pressed me with other B&W mod­els fea­tur­ing ear­lier ver­sions of this alu­minium-domed model, im­part­ing an un­canny re­al­ism to the sound of cym­bals, for ex­am­ple, and re­main­ing to­tally dy­namic when re­pro­duc­ing the sound of the xy­lo­phone and glock­en­spiel, both of which can be heard to mar­vel­lous ef­fect by lis­ten­ing to Sergei Prokofiev’s Scythian Suite, Op. 20, which also calls for two harps!

Con­clu­sion

The B&W 606 costs a lit­tle more than the model it di­rectly re­places, no doubt due to the added cost of the Con­tin­uum-coned low-fre­quency driver and the im­proved de­cou­pled dou­ble dome tweeter—added costs that B&W seems to have tried to ame­lio­rate by economis­ing on the cabi­net fin­ish, which I am not con­vinced was a good econ­omy, as I per­son­ally would have gladly paid ex­tra for high-gloss painted fin­ish.

But in the end, it’s the sound that counts, and the B&W 606s cer­tainly nail that, with big­ger and bet­ter bass—es­pe­cially at higher vol­ume lev­els—than you’d ex­pect from such small cab­i­nets and a glo­ri­ously rich and warm midrange com­ple­mented by a nicely bal­anced tre­ble. Ni­cholas Bossi

Graph 1 shows the fre­quency re­sponse of the B&W 606 as mea­sured by Newport Test Labs. It’s the com­bi­na­tion of two dif­fer­ent fre­quency re­sponse mea­sure­ments, us­ing two dif­fer­ent mea­sure­ment tech­niques. The sec­tion of the trace be­low 1kHz is the av­er­aged re­sult of nine in­di­vid­ual fre­quency sweeps mea­sured at three me­tres, with the cen­tral grid point on-axis with the tweeter us­ing pink noise test stim­u­lus with cap­ture smoothed to 1/12th oc­tave, with the bass re­flex port com­pletely open (no bungs). The sec­tion of the trace above 1kHz is the gated high-fre­quency re­sponse, an ex­panded view of which is shown in Graph 2.

You can see that apart from the small dip in the re­sponse be­tween 4kHz and 7kHz the B&W 606’s fre­quency re­sponse is re­mark­ably flat, for the most part hov­er­ing just un­der the 85dBSPL graph hor­i­zon­tal from around 150Hz all the way up to 4kHz and over­all, even in­clud­ing this dip, the sec­tion of the re­sponse that is vis­i­ble on this graph ex­tends from 68Hz to 20kHz ±4dB. How­ever, the low-fre­quency sec­tion of the graph was mea­sured with the port open. Us­ing the half-bung ex­tends the low-fre­quency re­sponse down to 55Hz. Pre­sum­ably B&W’s low-fre­quency spec­i­fi­ca­tion of 52Hz was mea­sured with the 606 in its ‘sealed en­clo­sure’ mode when the port was fully blocked… a con­fig­u­ra­tion that was not tested by Newport Test Labs.

The sec­tion of the B&W 606’s fre­quency re­sponse above 20kHz (and down to 1kHz) is shown in Graph 2, and you can see that the tweeter’s high-fre­quency re­sponse ex­tends all the way up to 32kHz within the same ±4dB en­ve­lope. So over­all, Newport Test Labs mea­sured the B&W 606’s fre­quency re­sponse as 55Hz to 32kHz ±4dB.

The high-fre­quency res­o­nance peak on the re­view sam­ple looks to be closer to 36kHz than the 38kHz spec­i­fied by B&W, but even at this lower fre­quency it is high enough to be well out of the way of any au­dio fre­quen­cies. There are three traces on this graph and be­tween them they show that you don’t need to worry about re­mov­ing the grilles to ob­tain the best per­for­mance, be­cause B&W’s en­gi­neers have made sure that the grilles are acous­ti­cally trans­par­ent and that you’ll get pretty much the same re­sponse leav­ing the grilles on as you would leav­ing them off.

Low-fre­quency per­for­mance is shown in Graph 3, with the mul­ti­ple traces this time show­ing the out­put of the rear-fir­ing bass re­flex port (red trace) and the out­put of the low-fre­quency driver with the port com­pletely open (black trace), with the port half-blocked by a foam bung (green trace) and with the port com­pletely blocked (blue trace). You can see that the sealed en­clo­sure pro­vides the smoothest, most ex­tended roll-off, but at the ex­pense of los­ing a lit­tle bass out­put. The bass re­flex mode sees the out­put from the low fre­quency driver roll off the ear­li­est, but in this case, there’s quite a bit of low-fre­quency out­put from the port to com­pen­sate. The max­i­mum out­put from the port doesn’t quite co­in­cide with the driver’s min­i­mum out­put, but since B&W is try­ing to ex­tract three dif­fer­ent align­ments from the same cabi­net/driver con­fig­u­ra­tion, I think its en­gi­neers have done pretty well. As you can see, the half-blocked port ex­tends low-fre­quency re­sponse about 10–12Hz lower than the bass re­flex align­ment.

B&W spec­i­fies the im­ped­ance of the B&W 606 as 8Ω with a min­i­mum of 3.7Ω. It does not spec­ify the fre­quency of the min­ima, but you can see from Graph 4 that it’s up around 20kHz and that the im­ped­ance re­mains be­low 4Ω from about 12kHz to at least 40kHz and pos­si­bly a bit fur­ther ( Newport Test Labs did not mea­sure above 40kHz). This means that if you drive the B&W 606 with an older Class-D de­sign you might ex­pe­ri­ence some un­pre­dictable re­sults. How­ever, any new Class-D de­sign—or any Class AB de­sign—will be able to han­dle the low im­ped­ance at these fre­quen­cies.

Else­where across the fre­quency band the im­ped­ance is mostly higher than 6Ω and never drops be­low 5Ω so the B&W 606 should be quite an easy load for any am­pli­fier or AV re­ceiver. The graph shows that the elec­tri­cal crossover takes place at 1.9kHz and that the phase an­gle is be­nign.

Graph 5 shows the av­er­aged in-room fre­quency re­sponse us­ing a pink noise test stim­u­lus with cap­ture smoothed to one-twelfth oc­tave show­ing re­sponse with the port open (black trace) and with the port blocked (dark blue trace). You can see that the dip in the re­sponse that was vis­i­ble in Graphs 1 and 2 is not there, thanks to the av­er­ag­ing. You can also see that the bass-re­flex align­ment ap­pears to give slightly im­proved bass re­sponse, though this would be de­pen­dent on speaker po­si­tion­ing in the room.

The fi­nal graph in the se­ries is a com­pos­ite of the graphs al­ready pre­sented. You can see that there are port res­o­nances at 550Hz and 910Hz that have a tiny ef­fect on the

B&W’s many years of ex­pe­ri­ence are plainly ev­i­denced in the ex­cel­lent mea­sured per­for­mance of the B&W 606

fre­quency re­sponse and above 1kHz you can see di­rectly how the smoothed (green trace) re­sponse (which re­flects how the hu­man ear would per­ceive the B&W 606’s fre­quency re­sponse) com­pares to the high-res­o­lu­tion high-fre­quency re­sponse (black trace) which con­tains de­tails too fine to be re­solved by the hu­man ear.

Newport Test Labs mea­sured the sen­si­tiv­ity of the B&W 606 at 85dBSPL at one me­tre un­der its nor­mal test con­di­tions. As I have noted many times pre­vi­ously, Newport Test Labs’ method­ol­ogy for this test is stricter than that most man­u­fac­tur­ers use, and al­most al­ways re­sults in ‘lower’ num­bers than those claimed by man­u­fac­tur­ers. The test also takes band­width into ac­count, so smaller speak­ers are dis­ad­van­taged com­pared to larger ones. So I was not sur­prised at the test re­sult of 85dBSPL: It’s about ex­actly what I would have ex­pected given the driver size and cabi­net vol­ume. I was, how­ever, sur­prised at B&W’s 88dBSPL spec­i­fi­ca­tion, which seems a tad op­ti­mistic, but both fig­ures sug­gest that an am­pli­fier with a power out­put rat­ing of at least 50–60-watts per chan­nel in 8Ω will be re­quired in or­der to ex­tract the best from this par­ticlar de­sign.

B&W has been at the fore­front of loud­speaker de­sign for a good many years, and these many years of ex­pe­ri­ence are plainly ev­i­denced in the ex­cel­lent mea­sured per­for­mance of the B&W 606. Steve Hold­ing

Rather than at­tach­ing the dome di­rectly to the voice-coil for­mer, a sec­tion of dome with a large cen­tral cutout is first at­tached to the voice-coil for­mer, and then the full alu­minium dome is at­tached to the dome sec­tion

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