"J" notanymore wrote ...
I'm building a snake box for my rca gear.

"gear"? audio? video?

I'm going from rca female on the box to a multi cable and
probably back again

"back again"? not sure what that means? back where?
"the box"? can you give us a better hint what you are doing?

and I can use a panel-mount rca, solder a shielded (or
unshielded?) wire to an output connector (below)
(db 25).

What is the signal? audio? video? something else?
"output connector"? output to where? what kind of cable
does the db25 connect to?

What about a Double shielded twisted pair DB25?

DB25 connectors are neither shielded or non-shielded.
DB25 connectors are neither twisted pair or otherwise.
You seem to be describing some sort of cable which
connects to the DB25?

if not please recommend an available cable/connector.

You have left out too many details for us to have any idea
what you are trying to do here?

If I use plain unshielded cable inside the (metal) box, could
I run into problems?

What kind of signal? audio? video? something else? How far?

Do I have to worry about shielding, say, composite video
from component

If they are the same picture, probably not.
If they are different video signals, then, probably yes.

or audio (-10 or +4) inside the box?

Depends on how far from the video.
I would use shielded cable just to be safe.


What do you think my distance limitations will be for component video,
composite, -10/+4 audio, digital coax, svideo on the DB25 cable??

Impossible to answer.
We have no clue what your "DB25 cable" is.

I'm thinking 3f patch +1ft in box + 10ft +1ft in box + 3f patch
for a total of 18 Feet.

You have provided only ~40% of the details necessary to answer
your questions properly. I would be far more concerned about
the nature of the 10 ft of snake cable than about the details of the
boxes and connectors.