hey i was wondering if somone tryied to connect seccond monitor to macbook pro buy a USB adapter?
looks like it should work but i wondering how is input lag when you working in ableton
What do you want to do? If you want the same thing on both sets of monitors:
If you want different things on both monitors you need an audio interface with 4 outs (2 stereo).
Hold on, do you mean monitors or a monitor like this: :w00t:
uupssssss!
i mean computer screens 
sorry
i didnt think ableton had dual monitor support?
Was thinking of getting another monitor and mouse over at my controller so i don’t have to keep switching back and forward.
As Phil mentioned you need adapter that extends your laptop monitor. “Extends” being the important word. Some adapters just duplicate. Technically Ableton doesn’t need 2 screens. None of Abletons devices have the option to detach from Abletons GUI. (I could be wrong on that haven’t tried every device in ableton) Where 2 screens come in handy are with VSTs. You can move your VSTs to the extended screen and have Ableton on your main screen.
Edit: Im not a Mac guy but on PCs there isnt any noticeable lags.
I use a Matrox DualHead2Go with my MacBook Pro, it basically lets you plug in two extra external displays via USB giving you a total of three displays when you include the MacBooks own display.
[url=http://www.matrox.com/graphics/en/products/gxm/dh2go/]http://www.matrox.com/graphics/en/products/gxm/dh2go/[/url]
There is no noticeable lag when running with the extra monitors, the two external displays are basically treated like one extra widescreen monitor by the mac.
If two monitors aren’t enough for you they also do the TrippleHead2Go
i have adapter to, but i have 3 24 inch screens at my desk and 2 of them i use for my Windows computer, but it would be nice to have a 2 screens conected to mac isted of using a mac book pro screen and one .
I have a 27" Apple Cinema Display plugged into the mini video port on the Macbook Pro. That’s the simplest solution.