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Bowers & Wilkins 686 S2 Spinorama measurements (CTA-2034)

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Ageve

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Here are measurements of the Bowers & Wilkins 686 S2 bookshelf speaker.

It was released in 2014, and discontinued in 2018, and it's two generations behind the 607 S2 measured by Amir. I Think the MSRP was 399.99 USD / pair.

BW686S2.png



My measurements are quasi-anechoic, with near-field port+woofer, corrected for baffle edge diffraction, combined with gated measurements at 1m distance.

I measured at tweeter axis, since that's what B&W recommends:


The first thing to bear in mind is tweeter height. It’s important to ensure that the tweeters are as close as possible to your ear level when listening.


When starting to measure this speaker, the first thing I thought was "What have I done wrong?".

But then I looked at the Soundstage anechoic measurement of the larger 685 S2:


This is my quasi-anechoic result (686 S2) vs Soundstage (685 S2):

BW686S2 vs 685S2 Soundstage.png



The tweeter response is very strange on both of them, and they're actually very similar > 1 kHz (The resonances are at different frequencies due to different woofer sizes, and the larger 685 S2 has more bass).

I then compared the gated response at 1m and 2m in my garage (slightly off-axis. That's why the peaks are a bit different). Basically identical (The difference below 2 kHz is due to lower resolution of the 2m measurement (3ms window):

BW686S2 gated 1m-2m.png



Just as a final confirmation, since I want to get the measurements right, I brought out my trusty M16. Very similar to my old measurement (living room):

RVLM16 living room vs garage.png



Here's the CTA-2034 data:

BW686S2 CTA-2034.png



Early reflections:

BW686S2 early reflections.png



Estimated in-room response:

BW686S2 estimated inroom.png



Horizontal directivity:

BW686S2 horizontal directivity polar.png


BW686S2 horizontal directivity lines.png



Vertical directivity:

BW686S2 vertical directivity polar.png


BW686S2 vertical directivity lines pos.png


BW686S2 vertical directivity lines neg.png



Quasi-anechoic response:

BW686S2 quasi anechoic.png



Near-field:

BW686S2 nearfield.png



Woofer, 6mm (used for quasi-anechoic response) vs 3 cm (used for the near-field image above):

BW686S2 nearfield woofer.png



That's the reason for the weird response. Several huge woofer resonances causing tweeter cancellation.

Just to make sure the speaker was ok, I compared it to the second one:

BW686S2 woofer 1 vs 2.png



Slightly off-axis here. That's why the peaks are a bit different. Good pair matching:

BW686S2 pair matching.png



Both speakers are in excellent condition, and there's no audible distortion. I would still be hesitant to post the measurements though, if it wasn't for the Soundstage anechoic data (685 S2) confirming the problems.


This is part of the problem:

bw686s2_crossover.jpg



A 6 dB/octave crossover...

Distortion, 86 dB @ 1m:

BW686S2 THD 86dB SPL.png


BW686S2 THD 86dB SPL percent.png



Distortion, 90 dB @ 1m:

BW686S2 THD 90dB SPL.png


BW686S2 THD 90dB SPL percent.png



Very low distortion. Bowers & Wilkins is one of very few manufacturers that actually specify the distortion level.

For 686 S2 it's:

2nd and 3rd harmonics (90dB, 1m):
<1% 110Hz - 22kHz
<0.5% 150Hz - 20kHz


The measured performance is very close to matching the specs. The tweeter distortion peaks (still low level) would probably disappear with a real crossover.


I listened to the speaker while writing this, and it doesn't sound terrible, but not good either. No audible distortion or other obvious issues, but it has a very flat (almost non-existent) soundstage, and female voices sound "closed-in" and a bit boring.

You can clearly hear that everything is playing inside a box. The treble is a bit bright and has a bit of "sizzle", but not as much as some newer B&W-speakers.

This speaker is a bit frustrating. It could have been much better than it is, but it seems to be made for the audiophile market.
 

Attachments

  • BW686S2_CTA-2034-A.zip
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Last edited:
First order crossovers as usual for some reason. This would be fine with 4th or even 2nd order slopes. Baffling.
 
Here are measurements of the Bowers & Wilkins 686 S2 bookshelf speaker.

It was released in 2014, and discontinued in 2018, and it's two generations behind the 607 S2 measured by Amir. I Think the MSRP was 399.99 USD / pair.

View attachment 414122


My measurements are quasi-anechoic, with near-field port+woofer, corrected for baffle edge diffraction, combined with gated measurements at 1m distance.

I measured at tweeter axis, since that's what B&W recommends:


The first thing to bear in mind is tweeter height. It’s important to ensure that the tweeters are as close as possible to your ear level when listening.


When starting to measure this speaker, the first thing I thought was "What have I done wrong?".

But then I looked at the Soundstage anechoic measurement of the larger 685 S2:


This is my quasi-anechoic result (686 S2) vs Soundstage (685 S2):

View attachment 414123


The tweeter response is very strange on both of them, and they're actually very similar (The resonances are at different frequencies due to different woofer sizes, and the larger 685 S2 has more bass).

I then compared the gated response at 1m and 2m in my garage (slightly off-axis. That's why the peaks are a bit different). Basically identical (The difference below 2 kHz is due to lower resolution of the 2m measurement (3ms window):

View attachment 414124


Just as a final confirmation, since I want to get the measurements right, I brought out my trusty M16. Very similar to my old measurement (living room):

View attachment 414125


Here's the CTA-2034 data:

View attachment 414126


Early reflections:

View attachment 414127


Estimated in-room response:

View attachment 414128


Horizontal directivity:

View attachment 414129

View attachment 414130


Vertical directivity:

View attachment 414131

View attachment 414132

View attachment 414133


Quasi-anechoic response:

View attachment 414134


Near-field:

View attachment 414135


Woofer, 6mm (used for quasi-anechoic response) vs 3 cm (used for the near-field image above):

View attachment 414137


That's the reason for the weird response. Several huge woofer resonances causing tweeter cancellation.

Just to make sure the speaker was ok, I compared it to the second one:

View attachment 414136


Slightly off-axis here. That's why the peaks are a bit different. Good pair matching:

View attachment 414138


Both speakers are in excellent condition, and there's no audible distortion. I would still be hesitant to post the measurements though, if it wasn't for the Soundstage anechoic data (685 S2) confirming the problems.


This is part of the problem:

View attachment 414139


A 6 dB/octave crossover.

I listened to the speaker while writing this, and it doesn't sound terrible, but not good either. No audible distortion or other obvious issues, but it has a very flat (almost non-existent) soundstage, and female voices sound "closed-in" and a bit boring.

You can clearly hear that everything is playing inside a box. The treble is a bit bright and has a bit of "sizzle", but not as much as some newer B&W-speakers.

I'll post distortion measurements later.
Thanks for the excellent review!
6dB/oct crossover ethos elevates the mess.
 
Thanks Ageve for another speaker measurement!

With a small eq, you get some improvements from this speaker but you will not make it great. You will notice that the eq track
closely the target under 3k and is more and more off. I have been limiting the EQ a lot recently after doing a bunch of listening
tests. So now Q < 3 until 2kHz, q<1 up to 3kHz and 0.5 above 2khz. Let me know if you think that is too strict, I am trained but
not young anymore.

Score goes from 4.0 to 5.5 with the eq below.
With a perfect sub, it would go from 6.7 to 8.0.

Code:
EQ for Bowers & Wilkins 686 S2 computed from Misc data
Preference Score 4.02 with EQ 5.57
Generated from https://github.com/pierreaubert/spinorama/generate_peqs.py v0.26
Dated: 2024-12-15-14:45:11

Preamp: -2.9 dB

Filter  1: ON PK Fc    52 Hz Gain +2.08 dB Q 1.82
Filter  2: ON PK Fc    83 Hz Gain +2.36 dB Q 1.01
Filter  3: ON PK Fc   172 Hz Gain -1.53 dB Q 0.54
Filter  4: ON PK Fc   942 Hz Gain -1.58 dB Q 2.70
Filter  5: ON PK Fc  1429 Hz Gain -2.41 dB Q 2.99
Filter  6: ON PK Fc  2324 Hz Gain +2.99 dB Q 0.81
Filter  7: ON PK Fc  7834 Hz Gain -2.94 dB Q 0.35

ved
filters_eq.png
 
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Distortion measurements added to first post.

@pierre Tried the EQ, and it makes a big difference. The soundstage opens up and it sounds much better, but it only works when sitting in a quite narrow sweetspot.

This would probably be a nice budget speaker if it had a real crossover (maybe a bit of EQ still needed to bring down the tweeter level).

Instead, Bowers & Wilkins decided to compromise just about everything in order to have a 6 dB/octave crossover (It seems to appeal to some audiophiles).


 
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…Bowers & Wilkins 686 S2 bookshelf speaker…. is a bit frustrating. It could have been much better than it is, but it seems to be made for the audiophile market.
The TLDR version

I appreciate your reviews and admire your consistent, accurate measurements.

Classic bat shaped curve there. That was also the generation where B&W did a load of marketing BS about the audiophile credentials of simple 1st order crossovers.
 
Teardown:

The ring covering the woofer screws can be removed by hand.

BW686S2_tweeter.jpg



bw686s2_woofer1.jpg



Cabinet is made of MDF, and the bracing is made of particle board.

bw686s2_cabinet.jpg



Tweeter with "nautlius pipe".


bw686s2_tweeter_back.jpg


And the crossover again.

While it appeals to audiophiles with 6 dB/octave filtering, and a sturdy air core inductor, the sand cast resistor won't impress them. ;)


bw686s2_crossover.jpg
 
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The peaks at 5 khz and 10 khz are classic B&W bright sound.

While the bright sound is shared between all recent B&Ws, the 600 series seems to stand out with a very uneven response.

This is the 683 S2 floorstander, measured by John Atkinson as a comparison. It's actually even worse (30 deg horizontal average for both):


BW686S2 vs 683S2 stereophile 30 deg horizontal average.png




Here's the near-field woofer response with port open vs plugged. 1.5 kHz dip remains:

BW686S2 nearfield 3cm open vs plugged port.png



And here's the tweeter response at 1m distance, with the woofer disconnected (bi-wire terminals):

BW686 S2 onaxis vs woofer disconnected.png
 
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I just read the What Hifi ”review” of the larger 685 S2.


But enough of that – how do the B&Ws actually sound? In a word: good. Right from the start, the 685s burst to life with a powerful, clear and agile sound.

These are hugely talented and enjoyable speakers, and a definite step up from their predecessors. The sense of scale is massive, especially coming from relatively compact standmounters.

The soundstage is wide and deep, enveloping you in a richly detailed, dynamic performance, whether you’re playing Aerosmith, Lorde or a Hans Zimmer soundtrack.


This couldn’t be farther from how they really sound. I mean, it’s all subjective, but what speakers did they compare it to?

I used to own a pair of 685 S2, and they sound exactly like the 686 S2, but with a bit more bass. I bought them without proper listening, before they were measured by Soundstage (I had older B&Ws at the time, and thought they would be ok).

I never liked them. The soundstage was far from ”wide and deep”. It was completely flat, basically non-existant. Before I sold them, I compared them to my Revel M16s, and I know it’s unfair, but that’s what a ”wide and deep soundstage” should sound like. It was like night and day.

You don’t even have to compare it to more expensive speakers. I have a pair of XTZ Spirit 4 that, while far from perfect, sound much better than the B&Ws (both 685 S2 and 686 S2).

End of rant. ;)
 
I wonder how difficult can it be to replace those filter? I know in older times people changed and rebuilt these and made their own cross over
 
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