Iv recently got hold of a Rockshox dual crown Domain. IM happy with the rebound adjustments however the compression damping has confused me a little… It has a high speed compression adjuster in the form of an intergrated speed stack???? and a crown mounted low speed compression damper. Could somebody explain how I should set this up and which damper to use if the fork feels harsh or too soft?

High speed compression is needed for bumps you ride over.

Low speed compression is needed for you pushing down.

How you set up the RS, I’ve no idea – but on my RC2 Fox I just rode across a big plank, fast to understand how the high speed reacted.

For the low speed, just push down and judge it.

It sounds like you cannot adjust your hsc on the fly. Hsc is generally there to sort out the big landings or the harsh square edge hits you might get. It helps to manage the high speed stuff I.e. how quickly your fork needs to move to cope with what it has just been ridden into or dropped onto and to help keep things nice and comfy for you and to not bottom out too harshly or indeed too often.

Your lsc will help with brake dive and bobbing at the front end for example when you are standing up and pedalling up a steep climb. It will also help with cornering or indeed not if adjusted poorly to suit you.

Find a piece if trail that you are familiar with that has some decent corners and braking zones and set the fork to the middle setting. If you get to much dive under braking you want more lsc. If you feel the fork does not give you enough support you can reduce the rebound compression and increase the lsc.

Make notes of the changes you make and only make small changes. But before you do any of this set the sag correctly!

Of course you could just go and ride the shit out of your bike and not worry about any of the above.

As far as I’m aware, the domain dual rc only has low speed compression damping via the blue dial on the top of the right leg. I didn’t see any adjusters for high speed on mine and I had them apart for servicing a few times.

They are simple beasts consisting of a spring in the left leg and the compression and rebound damping in the right. That’s about it.

as above, low speed, steps/lean on fork stuff
high speed riding along hits.

Not sure how much you can change on the fly but the old routine of ride adjust ride repeat works well. You will understand how your suspension works after a bit and be able to change dependent on the conditions. It can take a bit of practice but it’s a skill worth learning.
It’s much easier if you have a good local trail you can push up and down.

Set and leave both in the middle.