New crossovers for BOWERS & WILKINS 683 S2
Loudspeakers from the world-famous British manufacturer Bowers & Wilkins came to my workshop to upgrade crossovers
Configuration. These are mid-size floor-standing speakers. 3-way with a pair of 6.5-inch low-frequency drivers (with aluminum cones), the same size mid-frequency driver with a proprietary Kevlar diffuser and a high-frequency speaker with an aluminum dome membrane. An interesting solution with a “floating” high-frequency speaker – it is on elastic mounts and is not rigidly connected to the main body. I can’t say what the advantage of such a solution is, but it is also a proprietary engineering solution that is used in many B&W speakers. The design of the case is quite traditional: a rectangular box made of chipboard, medium-high-frequency section isolated in a separate volume, low-frequency section has several stiffeners and a phase inverter port. Sheet sound-absorbing material is glued to the inner walls of the box.
Sounding. In short, not very good. The dominance of the bass and lower middle frequencies is clearly audible. Which makes the sound sound dark, heavy, gloomy with a viscous slow bass.
There is a lack of more expressiveness, more drive, more bright tones and lighter sound in general.
Measured characteristics of speakers with original filters:
frequency response of original B&W 683 S2 
transfer functions of the original B&W 683 S2 filters 
impedance of the original B&W 683 S2
Scheme of original crossovers. Crossovers are structurally divided into 2 units. The first unit is a 3rd order low pass filter. The second crossover unit is responsible for the midrange (2nd order on both sides) and high frequency (1st order).
As we can see from the graphs of the frequency response and transfer functions of the filters, it is the parameters of the filters that form the nature of the sound described above. Due to the tuning of the filters, a huge gap is formed in the upper-middle frequency range (-10 dB!) And a large unevenness at high frequencies. The total non-uniformity of the frequency response is ± 5 dB.
Honestly, I can’t understand what the engineers who designed the filters for these speakers were guided by. But I can assume that they did not take into account the characteristics of the drivers that are connected to these filters. And I can also assume that the engineers did not care much about the uniformity of the frequency response and the sound of these speakers. That is, the filter scheme is not optimally designed. Although the crossovers are made quite well with the use of components of decent quality.
Original crossovers B&W 683 S2
New crossovers for B&W 683 S2. Developed taking into account all the characteristics of individual drivers. They provide a more uniform amplitude-frequency response, a much wider direction at high and medium frequencies, and most importantly – a full and transparent sound to these speakers.
Scheme of new filters. Low-pass filter for 2-order bass drivers. 2nd order midrange filter on both sides and complemented by frequency response correction circuit. 3rd order high-frequency speaker filter and electrically connected in antiphase to the midrange speaker. Filter distribution frequencies: 500 Hz, 3.7 kHz.
Filter components. Monacor inductors are used, their denominations are adjusted to the required. Monacor capacitors in the low-pass filter are non-polar electrolytic, in medium-frequency and high-frequency filters film with polyester and polypropylene dielectric.
Structurally, crossovers are also divided into 2 blocks and their boards are installed exactly on the standard places of the original filters.
Frequency response B&W 683 S2 after upgrade 
transfer functions of new filters for B&W 683 S2 
impedance B&W 683 S2 after upgrade
The uniformity of the frequency response of B&W 683 S2 after reconstruction is ± 3 dB in the frequency range 45 Hz – 16 kHz
Resistance 4 Ohm (minimum value of 3 Ohm in the frequency range 150 Hz – 800 Hz).
Option of performing crossovers with Vajd Audio coils:
And Monacor coils:
The characteristics of the filters are absolutely the same, regardless of which manufacturer of inductors is used.
You can make crossovers yourself according to the schemes given above. Or you can order the crossovers to be made and you will need to install and wire them instead of the factory crossovers into your B&W 683 S2.
The cost of making a set of crossovers for one pair of speakers is €250
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