Why does a dent to a tweeter not affect sound quality?

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.

Depending on the moment of "denting", the voice coil could have been compromised which may or may not change the sound audibly.  It's possible that over time this may or may not cause a larger problem for the voice coil / driver.

This is an excellent question. I had a pair of Celestion Kingstons whose aluminum dome tweeters were exposed. Two nephews visited and damaged the tweeters, one much worse than the other. I was pretty heartbroken, because Celestion was out of business by then. I waited a couple of months before I had the heart to listen to them, and surprise, I couldn't hear a difference. 
Had them for years after that, not using them and trying to sell them with no luck. I finally found an interested party, a British gent who had connections with one of the speakers designers in Ipswich and could have it repaired. He had previously owned a pair of them for years and knew them well. When he got them home, he emailed me and said that he couldn't believe that they sounded fine to him, just as I had told him.
Yes, you would think that a badly damaged metal dome would sound terrible, but apparently that's not always the case.  

I have pair of JBL 4311's with one tweeter with a slight dimple. and one that does have a side push. You know what? They sound fine. And they will bring $400-$600 just the way they are.

This all depends on what speakers, and the severity of the dent.

It is mainly for protection and air leaks. When the cone is modified a phase plug either fixed to the cone or stationary can be used. There is a place for weezer tech too.

Very interesting phase plug tech, I use it. Mine are stationary.
The cone bore vs phase plug gap is very important (air leaks cause noise) Phase plug length and the tip configuration is # 1 in mechanical distortion control for any inverted cone driver

I always thought domes in the center of a cone were for the the sound waves coming back on the cone. Just like covering the WHOLE surface with a dome. Its not so much for the waves going OUT but more so for what’s coming back. That is where the measurements will get wiggy if they are crunched.

As far as fixing domes I’ve fixed hard domes that have cracked and soft domes (or rings) that were torn. Nail polish makes quick work of that problem. A few strands of insulation fiberglass and cover the crack.

DENTS pull them out with tape and if they are bad use a sharp dental pick (or two) and if you manage to poke a hole, a little dab will do ya, of what ever you like.. Nail polish to Flex Seal, it ALL works fine.

I repaired 2 different set of QLS1s. I got pretty good at fixing some weird ones.. I think they were ringed mids. 20 + years ago. That was a great speaker Infinity QLS1 Ribbons and domes.. The wires would delaminate from the domes and of course 50% were smashed in and a few 10 penny nail holes. I think they are still in service. Surrounds 4-5 times. They had a servo model too.. These weren't

Wait when weezers come back they will be all the rage, how to add a weezer to your speaker.. :-)

Regards