Can i use oboe reeds on an English horn? Would it make much of a difference in the sound? Does anyone know?

Yeah, it`s possible, but your tone is going to sound really small and muffled, and you`re probably going to be playing pretty sharp. Plus you`re going to kill yourself trying to force enough air through an oboe reed to make it sound in an English horn-sized bore. But, it`s possible. I`ve done it... and it sucked.

Yeah I guess I`ll stop being cheap and just buy an EH Reed.
If I use a medium to medium-hard reed on the oboe what size english horn reed should I buy?

does that really work??? so would it work the other way around - english horn reed on oboe??? never seen either done, so, oh well.

Torus is right.....and you should learn to make your own EH reeds.

No, it wouldn`t work the other way around since English horn reeds are made to attach to a bocal and have no cork. But if you could somehow stick one on there, I`d probably expect the reverse to happen. I.e. you`d be playing really flat and the tone would sound really spread out and unfocused.

I see, not that I would buy the wrong reed on purpose, but I was just wondering.

just buy an effing english horn reed, cheapo