Products Tech Talk (Designer's Notebook)
  09. P3ESR circuit board layout  
  At Harbeth we take in-house control over the entire design process, from concept to production. This includes the design of the cabinet, the woofer, the crossover and the printed circuit board (PCB) onto which the crossover components will be soldered.

The crossover's electrical circuit is what sets the tone or voice of the entire speaker. The crossover doesn't just divide the signal between the woofer and tweeter, it optimises the energy level of each drive unit. This optimisation cannot be achieved with just one or two simple components and so, if a neutral, flat system voice is needed, the crossover becomes necessarily more complex.

After the prototype 'bread-board' circuit is finalised, the next step is to layout those components to sit neatly on a custom-made high-quality a fibreglass PCB. The board obviously has to be big enough so that the components aren't cramped but not so big that it won't fit inside the cabinet. Also, crossover inductors (chokes or coils) must be spaced apart so that they don't interfere with each other. Components that could run hot need air around them. These constraints mean that the layout of the board needs thought and care by the designer. Alan narrates as he proceeds so you will need to turn on your PC's sound to be able to hear him explain what he's doing.

Feel free to jump over the more specific details - our objective is to give you just the flavour of what's involved in the design of a modern Harbeth loudspeaker. Three days work on the crossover layout (but not the circuit design which took many months) has been condensed down to just a few minutes of video at key points in the design ....

'Medium' resolution screen-cam videos to play on 1024 x 768 screens or bigger:

Part 1 (about 6 minutes) -  A mock-up and first steps

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Part 2 (about 4.5 mins.) - Using components from M40.1 crossover in P3ESR

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Part 3 (about 3 mins.) - Checking the layout  before PCB manufacture

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Part 4 (about 3 mins.) - Conclusion:  the production-ready PCB is born!

Play (Medium resolution video)

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