Weird trigger behaviour....
First of all I have to thank you for all the information and help I already got from this forum. This time I have a specific question which I were not able to answer using the search function.
It's a little complicated and I hope that my English is good enough to describe my 'problem'.
Here I go: What I intended to do was to tie a heavier sound (plus an env_shake) to a cube. What I mean is that it is supposed to give the impression to be heavier than the usual sound when it hits the ground.
I made a trigger (multiple) which covers the ground and each time exactly does what it is supposed to do. It fires the sound plus the shake.
Since I wanted the sound (and shake) only to occur after the cube had reached a certain height (and not after being dropped by the player), I added a second trigger multiple above the ground its purpose was to enable the trigger on the ground which it usually does, but sometimes it fires the sound/shake itself instead of only enabling the trigger on the ground. Why does this happen??? It has only an output to enable the lower trigger.
I have to add that the trigger on the ground resets (disables) itself each time it is triggered by the cube via logic_relay (could be also had with a !self command. I don't know just occured to me while writing).
I uploaded the said file in the WIP category.
Here's a second one. How can I update and edit the uploaded file and or add files like the .vmf to it.
Thank you in advance and wait............mooooore questions to come 
Thanks for the tip!
You're right the .vmf file isn't included. Thought it's not worth it until it's finished. I meant the WIP-map which uses the described triggers and effect.
I will update the file as soon as I make some major changes to the first chamber. Seems as if it is solvable in way I wouldn't have thought of.
The map is called 'sp_momentum' you can find it here:
http://forums.thinking.withportals.com/downloads.php?view=detail&df_id=1089
Will post a small test chamber file demonstrating the effect ASAP.
Is it possible to upload example files here or should I use a free hoster???
Edit:
You can hear/see the effect on a YouTube video which was kindly provided by 2CAE7256 here:
He has torn my debut map to pieces 
I don't know whether this would solve it, but you can set trigger_catapults to only check the velocity of the activator. Combine this with a filter for cbes and threshold check, and you can set the catapult to fire an output, I.e., the shake and sound, whenever the cube hits the ground at a certain speed.
By the way, completely irrelevant, but, for a debut map, that is looking PRETTY good! If you'd like more play testers for it, you can sign me up! 
Either way, I intend to play it when it's done.
Hello Rubrica,
that sounds marvelous, can't wait to give it a try. Hope I can figure it out. I love gimmicks like this.
Glad you liked it so far. It's full of errors, yet. Of course I would like a bunch of testers before I upload another WIP version and would love to count you in. Unfortunately I'm not allowed to use the PM feature (yet??) to let you know.
It's time to trigger_catapult the authoring tools......
Thank you!
Hello Rubrica,
unfortunately your suggestion to use a trigger_catapult as a detector didn't work for me. It was too tedious to find the right values and percentages for threshold and speed.
I found a solution which works quite fine so far. Instead of enabling/disabling the triggers I used logic_branches and a logic_branch_listener to achieve the effect. The entity names are quite self-explanatory and I can't imagine that it should be difficult to understand.
The upper trigger_multiple detects the start_touch resets the lower trigger_multiple each sending values to the respective logic_branches. The logic branch_listener if both cases true fires the result via relay to an ambient_generic and an env_shake.
Problem is that when the player jumps holding the cube both branches are set to true which fires the logic_relay when the player drops the cube after having landed.
This can be easily circumvented by additionally detecting the player if needed and setting the logic_branch values to zero.
Should anybody be interested and find it useful or usable elsewhere, feel free to download the vmf-file.
http://forums.thinking.withportals.com/downloads.php?view=detail&df_id=1098
The biggest advantage of this solution is that you can visually adjust the height.
Edit: Ooops, I've forgot to describe the scene file. The catapult next to the wall has a target above the desired height while the target of the other one is below and thus the cube lands without the shake and sound effect. Well, you would have found out but anyways.............
I uploaded a attachment.
It's my variant how to solve your problem.
You can use it.
Be careful: The group with the logic_compares and sensors with the point_template must be always at groundlevel!
The entity_maker must be on groundlevel too!
The sensors have to be spawned with the cube in the same template to keep their relations.
To change the value when the impact can happen, just change the value in the logic_compare "Cube_Velocity_Compare" to any value. It's the only value you are allowed to change.
What have I done?
I'm measuring the velocity of the cube. The impact is now depending on the velocity (logical I think).
If the velocity is at a custom level, it activates a distance sensor. It will measure when the distance is less than 31 units to the ground (cube landing on just 1 corner). If this happens, the compare will activate the impact.
Moin moin Skotty,
have to take a closer look at it today. Right now it ummmmmm, looks like rocket science to me, honestly
I don't understand almost anything of the mechanism/entities involved. But hey it works and looks pretty damn good.
Thank you for your effort. Others might like to give it a try as well. I however have to have a extra dosis caffeine first.
Will come back to this later..........with many many questions I suppose