B&W Modifications for 600 series?

[biomed_eng_2000]

I was wondering if any of you have modified your 600 series B&W's?...like upgraded crossover components, speaker, or cabinet mods or tweaks.

Any specific 600 series mod links that you know of?

Thanks!!

[Aussie Geoff]

Biomed,

This link HERE is one of the most complete speaker design and modification link lists that I know... You may find what you want there.

Also THIS Article shows some of the most common changes people do to speakers such as:

• Internally re-wiring with very high quality wire (some even use Silver for the Tweeter)
• Upgrading selected or all parts in the crossover (e.g. air core indictors, high quality capacitors etc)
• Lead lining the boxes with thin lead sound absorbent sheet.
• Specially mounding the speakers with washers and gaskets.
• Extra cabinet bracing

However you should be aware that:

• It is easy to spend so much money that you would be better off upgrading the speakers. Anyway with newer models
• You may get many improvements via things like bi-wiring, different speaker cables etc
• B&W have a view on this: HERE in their FAQ section.

  The most common questions about component upgrades refer to crossover components and internal cables, but occasionally people ask if they can substitute a more recent driver in an old system.
  
  Cables are not really a problem as long as you can actually feed the cables where they have to go. Some of the routes are narrow. The hollow rod joining the Matrix 801 midrange enclosure to the main cabinet is a case in point. Beware of getting rattles when laying the cable. Make sure it cannot vibrate against drivers or the enclosure walls. In this respect it is better to use cable with a soft insulation.
  
  We usually find that customers who alter crossover components are not fully satisfied with the results. They find that some aspects are improved, but others made worse. A classic case of this is when a polypropylene or other very low-loss type substitutes an electrolytic capacitor. We all know that polypropylene capacitors can sound inherently better, but the change in internal losses changes the response of the filter, which is designed assuming the losses of the electrolytic component. What usually happens when the low loss component is fitted is that the corners of the roll-off are sharpened, giving a peak in the combined response that can make the sound unpleasant in various ways depending on the crossover frequency. One way of getting round this is to wire a small resistor in series with the capacitor to approximate the original losses. I say approximate because the loss factor is a frequency dependent resistance. The actual value you need depends on the original capacitor loss factor and its capacitance value. The larger the value, the lower the resistance for a given loss factor. The formula for the equivalent resistance is:
  R = d / 2ðfC
  where R = resistance in ohms, d = loss factor, f = frequency in Hz and C = capacitance in farads.
  Loss factor is usually expressed as a percentage at 1kHz. For a "low-loss" electrolytic such as the values between 1µF and 20µF found in tweeter circuits, d is of the order of 0.025 (loss factor of 2.5%). For values in the hundreds of microfarads it may be of the order of 0.07 or 7%. Typically therefore a good electrolytic capacitor of 5µF would have an equivalent series resistance of 0.8Ω. If the capacitor has a much larger resistor in series with it anyway, it's probably not worth altering.
  
  The same argument applies if you substitute a cored inductor with an air core type. Always try to duplicate the DC resistance as well as the inductance. Sometimes inductors are deliberately wound with relatively fine wire to give a certain resistance to add damping to the circuit. Iron dust cores (sometimes called P-cores) have higher losses at higher frequencies than at lower, due to eddy current effects. Substitution of an air core, even of the same DC resistance, may give a steeper ultimate slope in the stop band that can alter the phase relationship between the two drivers. That can also mess up the overall response and skew the optimum listening angle a little.
  
  The term crossover is a little misleading. The networks add equalisation in the driver's pass band as well as dividing up the frequency range. Substituting a different driver more often than not needs a change in the crossover to give the appropriate equalisation for that particular unit. Simply plugging in a different (even nominally better) driver without attending to this often disappoints.
  
  As you can see, it's a potential minefield and difficult to get the optimum result without proper measuring facilities. Adjustment just by ear tends to give good results on limited programme material and you can usually come across some other piece that sounds less than acceptable.

Geoff