{"id":6086,"date":"2016-12-10T20:15:22","date_gmt":"2016-12-10T20:15:22","guid":{"rendered":"http:\/\/www.audioexcite.com\/?page_id=6086"},"modified":"2017-01-11T15:28:57","modified_gmt":"2017-01-11T15:28:57","slug":"bowers-wilkins-685-review-part-2","status":"publish","type":"page","link":"https:\/\/www.audioexcite.com\/?page_id=6086","title":{"rendered":"Bowers & Wilkins 685 review part 2"},"content":{"rendered":"

Technical Specification:<\/strong><\/span><\/h3>\n

 <\/p>\n

This is Bowers & Wilkins official technical specification for the B&W 685 loudspeaker. Let’s see how correct it is.<\/p>\n

Technical features:\u00a0 <\/strong>Nautilus tube-loaded aluminium dome tweeter, Kevlar fibre cone mid-woofer and flowport.<\/p>\n

Description:\u00a0 <\/strong>2-way vented-box system<\/p>\n

Drive units:\u00a0 <\/strong>1x 25mm aluminium dome tweeter, 1x 165mm woven Kevlar cone mid-woofer<\/p>\n

Frequency response:\u00a0 <\/strong>-6dB @ 42Hz \u2013 50kHz<\/p>\n

Dispersion:\u00a0 <\/strong>Within 2dB of reference response<\/p>\n

Sensitivity:\u00a0 <\/strong>88dB @ 2.83v\/1m<\/p>\n

Harmonic distortion:\u00a0 <\/strong>2nd<\/sup> and 3rd<\/sup> harmonics @ 90dB\/1m, <1% 110Hz \u2013 22kHz, <0.5% 150Hz \u2013 20kHz<\/p>\n

Nominal impdedance:\u00a0 <\/strong>8\u03a9<\/p>\n

Cross-over frequency:\u00a0 <\/strong>4kHz<\/p>\n

Dimensions (HxWxD):\u00a0 <\/strong>340x198x331mm<\/p>\n

Net weight:\u00a0 <\/strong>7.0Kg<\/p>\n

Impedance measurements:<\/span><\/strong><\/h3>\n

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<\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Blue:<\/strong> Left loudspeaker<\/p>\n

Green:<\/strong> Right loudspeaker<\/p>\n

Excellent consistency between the left and right loudspeaker. It doesn\u2019t get better than this.<\/p>\n

Impedance minimum of 4.79\u03a9 @ 197Hz and 3.59\u03a9 @ 20kHz.<\/p>\n

The impedance plot shows a bass-reflex and port tuning frequency of 48Hz, which is slightly higher than normal for a medium sized stand-mount loudspeaker. Using two 4\u03a9 drivers, I would consider this loudspeaker a 4\u03a9 system rather than an 8\u03a9 system according to the official specification.<\/p>\n

Frequency measurements:<\/span><\/strong><\/h3>\n

 <\/p>\n

If nothing else is noted in the comments, the following frequency measurements of the B&W 685 loudspeaker are made at a 2m distance at tweeter height.<\/p>\n

All frequency response charts are presented in a 50db scale with 1\/24 octave smoothing and the measurements are valid down to 375Hz.<\/p>\n

 <\/p>\n

<\/a><\/a><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Frequency response on-axis:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Frequency response 15deg off-axis:<\/strong><\/p>\n

Blue:<\/strong> Left Loudspeaker @ 2m<\/p>\n

Red:<\/strong> Right Loudspeaker @ 2m<\/p>\n

Minor differences between left and right loudspeaker.<\/p>\n

 <\/p>\n

<\/a><\/a><\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Upper left:<\/strong> On-axis frequency response.<\/p>\n

Lower left:<\/strong> On-axis frequency response, tweeter reverse polarity.<\/p>\n

Upper right:<\/strong> 15deg off-axis frequency response.<\/p>\n

Lower left:<\/strong> 15deg off-axis frequency response, tweeter reverse polarity.<\/p>\n

Here we can see a cross-over frequency of 4kHz which is true to the official specification. We can also see that the loudspeaker uses a shallow sloped cross-over topology where the drivers initially rolls-off at roughly 6dB per octave.<\/p>\n

On the other hand we can see approximately a 5dB boost at the cross-over point compared to the frequency response above and below the cross-over point.<\/p>\n

We can also see from the reverse polarity test that we have an unsymmetrical null, which indicates less than optimal individual phase tracking between the driver units below and above the cross-over point. The tweeter response is boosted about 4-6dB above 10kHz.<\/p>\n

 <\/p>\n

<\/a><\/a><\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Upper left:<\/strong> On-axis, 15 and 22.5deg off-axis frequency response.<\/p>\n

Upper right:<\/strong> 30, 45 and 60deg off-axis frequency response.<\/p>\n

Bottom:<\/strong> On-axis frequency response. Blue<\/strong> = Front cover off. Red<\/strong> = Front cover on.<\/p>\n

The peak at the cross-over frequency smooths out from 30deg off-axis and above as well as the boosted tweeter level.<\/p>\n

The front covers should be off when listening to this loudspeaker. In order to achieve the flattest and smoothest frequency response, the loudspeaker shouldn\u2019t be toed-in. Instead let it as a starting point straight forward and toe-in until the tweeter level is according to personal taste.<\/p>\n

Distortion measurements:<\/span><\/strong><\/h3>\n

 <\/p>\n

Measurement setup:<\/strong><\/p>\n