So my 18watt clone is crackling when i hit like big open chords and stuff similar
it even does it at very low volumes so i don't think it's a bad speaker
some people have told me it's the tubes but i don't think it is
maybe i am wrong
some people say bad speaker
some say bad speaker connection
i will take it to a shop soon but i want to know what to expect and how much to expect to pay
what do you guys think?
What kind of crackle? Low frequency is probably a blown speaker (usually the paper will be visibly torn though not always.)

High frequency crackle is an electrical arc, probably caused by a bad connection usually in the input jack.

Since you plug that cord in and out of there all the time it makes sense for it to get loose over time. Open it up and have a look.

New jacks cost, like, $1.00 at Radio Shack.

It would make sense that you'd get the crackle with loud chords because the amp physically vibrates. This is my diagnosis given the information above.

A blown speaker will sound fine except it just won't do it anymore on the low end at loud volume. You'll get more of a farting sound.

Trust me, I've blown a lot of speakers, some on purpose.
"Virtually no one who is taught Relativity continues to read the Bible."

it's a combo BTW
it also almost completly drops out the volume sometimes if that helps
i have a feeling it's a bad connection somehwere