Thanks for the answers. I basically thought that there would be little
loss. What I want to do is add a 25' hose to my Shop-Vac so I can go out in
yards and vacuum up pecans without having to move the damn vacuum so much.
I get them free, and they sell for up to $6 per pound.

WHERE?
That's worth the gas to get there. They started at 50 cents a pound
and went to 40 here.
Using a vac, something like a dust collector chip separator in between
would be helpful to keep the leaves and pecans separate. A leaf
sweeper works if the pecans are not buried in the grass too far -
then you shake the basket to get the pecans on the bottom.
A dedicated wife and 5 galllon buckets is what I use.
On the original question:
Theoretically, the ribs on the hose create friction and there's loss.
I got some plastic ribbed extension hose from the plumbing section
of Big Orange thinking it would go on the vac and DC. The flowing air
sounds like a train whistle. Not a good idea.
J