In my last blog about listening optimisation I started on the topic of supports and microphony. I got up to the point of discussing how individual circuit components are microphonic, so the next piece to cover is about structures and how structures can conduct damaging vibrational energy into those microphonic circuit components..
It goes hand in hand really. The fact that our components are microphonic and that they have to be mounted on, secured to and fixed within various structures. We can see the casework externally, and internally see mounting bolts and circuit board supports that all make a complex network of highly conductive acoustic pathways.
But then we have to consider how efficient these structures are at conducting acoustics. In our mind we think of acoustics in the air around us. Sound moving across our listening room and maybe out into other rooms, or bass travelling to another floor. Now that’s an interesting point, bass being conducted around walls. We’re getting warmer. Solid materials, it turns out, conduct acoustics thousands of times more efficiently than a gas, and at much higher speed too. Right, you’re at a hifi show, in a very noisy corridor full of people, and I’m right down the other end of the corridor. It would be almost impossible for you to hear me if I was to shout your name. But you instinctively know that if we were holding up a very long steel bar and you were to press your cheek bone against one end and I was to scratch the other end with the tip of a screw driver, you would easily hear the scratching noise. So consider the mains transformer that is vibrating, sending its vibration down its mounting bolt into the chassis that all the circuit boards are screwed to as well. That’s it. That’s the essence of what we’re talking about.
But we can start to tackle this problem with some simple hifi husbandry. For example, how you have components stacked perhaps. Maybe you have a pre and power combo stacked one upon the other. The vibration from the large power amp may well be acoustically polluting the delicate preamp, so see if you can separate them. But there are bigger gains to be had with the way you might have mains and signal cables routed. Often we end up with our components quite close up to the back wall, with cables tightly curved and pressed up hard against the rear wall, or parts of our component stand. So have a good listen first, then re-position everything with more room and maybe disconnect cables and re-route them better – always mindful that you want to significantly reduce as many hard contact points in the cable loom as possible. Then fire up and listen again, remembering to let everything settle down for a while.
This is the essence of decoupling, or isolation. And we can do some of that with the way we set up our systems. And there are other times when we can do the reverse – for instance we can couple speaker cabinets to a solid floor with a good set of spikes, and improve the way vibration is drained away from the drivers for improved clarity in the sound. In my next blog I'll go into more detail about coupling and isolation in equipment supports.
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