Maybe I can put words on the "Topre feel":
For those of you who have once used a real piano (one made of wood) or a high quality electronic musical keyboard, there is a similarity in my opinion with the Topre switches.
In a real piano, the key is at the end of a lever, and the lever pushes a hammer, which strikes a string or group of strings.
The device has some inertia. When you start pushing the key, you push the key+lever+hammer group. You feel the weight of all these parts. Once the group is set in motion, the pressure on your finger is much lower as the parts continue on their way until they strike the string(s), at which point the hammer bounces back and sends the pressure back on the key. This helps quickly reset the mechanism in its initial position, ready to play another note.
The pressure curve on a piano key is in my opinion somehow similar to the one of a Topre switch.
When you start pressing the switch, the dome still has its semi-spherical shape and resists to the pressure. Then it collapses, and now does not resist anymore. What's left is mainly the force of the conical spring, which is much lower than the force that was needed to collapse the dome in the first place.
The effect is that the key seems to continue on its way to the point where, in a piano, the hammer strikes the string(s).
Now the key bottoms out. The plunger compresses the thickness of the upper part of the dome against the PCB and the completely collapsed conical spring, emitting the "thock" sound. On other mechanical switches, bottoming out is plastic against plastic or against steel, unless they are equipped with O-rings or landing pads. So the pitch of the sound is higher on these, and the feeling is harsher.
Now you can feel a kind of rebound, helped by the elasticity of the upper part of the dome and the conical spring release.
The dynamic of the key press explains why the board has more character than other mechanical switches and feels "alive". It is also the reason why it's good to bottom out (and can't really be prevented) on Topre and why the switch feels more reactive.
When I type on Topre, I notice that I type a little bit harder and that my fingers fly a little bit higher than on a Cherry MX board. Typing harder is not caused by the keys being harder to press, it's just that the reaction is better when your fingers hits the keys with some velocity. This velocity allows the fingers to have just enough inertia to collapse the keys, which react back. And it does not feel hard anyway, it feels like your fingers are bouncing on the board. On Cherry switches, the spring also makes your finger bounce back, but you don't feel the collapse of the key, even on browns. So it's not as easy to know that the key has registered.
A Topre makes you type with some energy in your hands, because the secret is the velocity of the fingers. It's not harder, it's just more playful.
Cherry Browns are better for a "calm" experience, because you need to type differently to feel the small resistance of the brown switch. Type on Browns like you type on Topres and the browns just feel like scratchy reds. Many people say that they do not notice the difference between reds and browns, and I believe their typing style may by much more adapted to Topre than to Cherry MX.
Interestingly, when I type on Cherry MX blue, I naturally adopt the same typing style than on Topres. So while browns are supposed to mimic the slight resistance of domes, they just fail at this. Blue ones, paradoxically, are closer to the dome effect.
Buckling springs have both the "collapse" and "bounce" of Topre, but harsher. And they add the loud click sound. Topres are so much smoother.
One may say that cheap rubber domes can be described in the same way I described Topres. However there are a few notable differences:
- The most important one in my opinion is the travel length. Cheap rubber domes fail to achieve the "piano feel" because you bottom out way too early.
- Cheap rubber domes miss the conical spring. It explains why they have less travel: a higher rubber dome would much more easily "jam" (stay in the collapsed position). Also, the spring helps a lot for the "rebound" feel. But you can put a spring under a rubber dome only if it is a capacitive switch, otherwise you run into too many problems with contacts! Hence the Topre capacitive design...
- The quality of the plunger is probably an important part of the experience. I suspect two different kinds of plastics are used, one for the housing and another one for the plunger. One is harder than the other, which is similar in principle to what is done with metallic moving parts that rub against each other. In cheap rubber domes keyboards, the same plastic is used for both the keycaps and the housings, generally, because it's less expensive to make both the housing and the keycaps from a single mold. It results in more friction between the plunger and the housing. You can feel it on large keys that do not have a stabilizer: they key is hard to press if you do not press exactly in the middle. It may even jam. Doesn't happen on Topre switches.
I hope all of this makes sense. And if I'm wrong on anything I'm saying, I'll be very glad to stand corrected.
