Why does a dent to a tweeter not affect sound quality? You see this statement all the time, when someone is selling an affected piece of used equipment. I’ve never understood it. Can somebody explain?
Not only tweeters, all dynamic drivers. You can’t hear a dented dust cover on a midrange driver or woofer either. Probably speaker designers can measure it, but you never will hear it.
Think about how dynamic drivers work. A voice coil moves back and forth. The voice coil is connected to a cone or in this case soft dome. Most think this dome moves back and forth like a piston. That is the ideal or the way we think of it. In reality, have you ever touched one? They are super soft. How in the world is this ever gonna move like a piston?
It can’t. What happens instead is the piston (the voice coil) moves and this starts a compression wave that travels from the edge of the dome where the piston attaches towards the center of the soft dome. Think of a ripple or wave, like when you make a bed and fling the sheet, the wave travels along the sheet. Like that.
Well now this wave travels just fine no matter what the shape of the dome. So even dented it works just fine.
When they use Be, diamond, carbon fiber and whatnot, btw, all these are just attempts to make the thing behave more like a piston. Doesn’t work. Well it does, sort of. These materials do have a more extended clean and clear sound. But they still have the same wave phenomenon, only now at a much higher frequency. This is why some notice they sound harsh or bright, it is because of this ringing.
Anyway, back to the soft domes. Sound radiates out in a spherical sort of way. The physics of it are that these wavelengths are very short, from around a half an inch to an inch or so. Since this is around the size of the dome and the dent then from a wave and hearing point of view it is all coming from the same location. If the dent was on a driver a foot wide and putting out 10kHz then it would be directional and we would hear it. So again it is a physics thing.
