How to make perfect crunchy popcorn?

Over the years, I've microwaved, air popped, and tried a pot on the stove...even tried over an open fire. Once I found the Whirley Pop, I never returned to any other method. You can't beat it. Perfect "crunchy" (maybe crisp is a better description?) popcorn every time.

Not truly and answer, but I am trying for an explanation of what likely you are seeing:

Popcorn pops because there is a small amount of water it those try kernels that when heated goes from liquid to gas and because it is contained it does so explosively. Key is getting the proper amount of heat to go boom. Too much, burned. Too fast, incomplete boom. Too little, no boom. Poor corn, be it too dry or too wet, no boom or incomplete.

Now, sogginess? Well, the boom releases that water as steam. If it gets trapped, soggy popcorn. Also, many applications as you noted use oil. Too much and soggy popcorn. Why oil? Because it helps distribute the heat more efficiently and uniformly for a better boom. Some think it also helps trap the water for a more complete explosion, I will just say maybe, but not the prime reason if so. It also flavors and helps any seasoning stick.

Air popper: I have never had soggy from it though those cheap models are notorious for uneven heating, kicking out unpopped kernels, overloading and burning, etc. I could see the soggy issue though if it is not properly exhausting the vapor especially if overloaded, but I find it odd because their claim to "fame" is specifically dry popping os that one if a bit odd.

Dry stove-top, that is usually going to burn due to uneven heat. I have heard of people being able to pop on a stove with little to no oil, but I have never seen it. Normally need oil to have a chance on the stove to get even heat.

Microwave: The pre-packaged stuff has a ton of oil. In addition, the microwave works by vibrating the water molecules, to popping corn in a way is almost what it was designed for. Know, you can also pop corn without the oil quite nicely especially with gadgets to help focus the microwaves well, but the pre-packaged bags are convenient and the companies make more selling those than the gadgets. ;) Note though the bag is vented. It is actually a key thing. Also, you typically will open the bad fairly quickly when done, which lets out the steam. If you fail to do this while still fairly hot you may find the microwave corn can get soggy too.

Key things for stovetop tends to be even heat and venting. Theaters use a larger version of a popper on which the device @moscafj mentioned is designed. Those designs stir the corn which increases the uniformity of the heating, so less chance of scorching, fewer inclomplete pops, but also they have hinged lids. This lets steam escape and is important to your experiment. Tight fitting lids on the stove equal trapped vapor which condenses and dumps water back onto the corn, instant soggy.

On popping in butter, there you are dealing with a lower smoke point so getting the right temp for popping without scorching the oil may be tough, and the butter itself will release some of its water so may produce some good tasting, but soggy mess.

I can't imagine how you made the corn (# 4) oil on stovetop soggy. When I shake mine the lid movement lets steam escape. The oil needs to be hot enough to barely smoke before putting the corn ( too hot for butter).

Alton Brown's recipe (https://youtu.be/byqaZhMTwAs) :

Take a stainless steel mixing bowl (around 6 quart size) and add 3 oz popcorn kernels and 3 tablespoons of peanut oil ( or similar). Toss in some fine salt (you can use kosher, but it's better if you grind it down smaller). Cover tightly with foil and stab the foil with a kitchen knife about 6 times or so. Continuously shake over a medium high gas stove flame until popping stops (no pops for a over 2 seconds). Keep in mind it takes a while of shaking before you'll get the first pop, this is normal. Toss in some melted butter if desired (this will make it less crunchy though).

Gives me perfect crunchy popcorn every time.

Some notes:

• You can use a non gas stove but it's a bit harder.
• You don't need a mixing bowl but it's better. I've done it with a stock pot however.
• The kernels matter. Some brands and colors turn out much crunchier than others. Usually the standard stuff you can find at your local supermarket works fine. I've found the more exotic kernels (like a red mix) are less crunchy.