Since a spawner will activate if a player is within 16 blocks of it (in a sphere, not a cube) there DOES seem to be an area at Y=14 (+/- a couple) that may activate all three spawners.
I think, you'll have to try it, that if you stand at -74, 14, 405 you will activate all three spawners.
If you de-activate the spawners in pairs and then go to that location and spiders appear then you are close enough for the one not deactivated.
Try this with all three possibilities to establish where you need to stand.
I've never done an elevator/drop for spiders so I don't know how one would be built.
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There are no dangerous weapons. There are only dangerous people. R.A. Heinlein
If you aren't part of the solution, then you obviously weren't properly dissolved.
I wouldn't worry about dropping them it you have a diamond Sharpness V, Sweeping Edge III, Looting III sword. One hit should kill most of them. You'll be overloaded with string!
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My short story-like journals; quick-and-easy reads:
Triple cave spider spawners in mineshaft pretty close to spawn.
Seed:-636242970150697
Locations: -58/15/403
-70/13/417
-91/14/407
I don't think its possible to link all three for a grinder but if anyone finds a way let me know. A double grinder is easily possible thou.
Since a spawner will activate if a player is within 16 blocks of it (in a sphere, not a cube) there DOES seem to be an area at Y=14 (+/- a couple) that may activate all three spawners.
I think, you'll have to try it, that if you stand at -74, 14, 405 you will activate all three spawners.
If you de-activate the spawners in pairs and then go to that location and spiders appear then you are close enough for the one not deactivated.
Try this with all three possibilities to establish where you need to stand.
I've never done an elevator/drop for spiders so I don't know how one would be built.
There are no dangerous weapons. There are only dangerous people. R.A. Heinlein
If you aren't part of the solution, then you obviously weren't properly dissolved.
The latest release of Amidst, version 4.6 can be found here:
https://github.com/toolbox4minecraft/amidst/releases
You should probably also read this:
https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-tools/2970854-amidst-map-explorer-for-minecraft-1-14
You can find me on the Minecraft Forums Discord server.
https://discord.gg/wGrQNKX
I wouldn't worry about dropping them it you have a diamond Sharpness V, Sweeping Edge III, Looting III sword. One hit should kill most of them. You'll be overloaded with string!
My short story-like journals; quick-and-easy reads:
My Quest for Elytra Complete! (Pic Intense, End-Game Spoilers)
[Journal & Pics] After a Year and a Half, I Finally Found a Jungle
FrozenCore: Hardcore Death; 3/20/15 to 5/3/15; Eight Weeks on a Frozen World in Pictures