Have a master filter installed, but was using Naked DSL, so it is probably not needed for Naked DSL anyway.
Now back to Broadband bundle with phone line now, seems my speed dropped a little, and I can have phone signal in the same jack with my ADSL jack (as I connected the phone and it can make phone call fine), so I think therefor that particular jack still need a filter for some reason otherwise the phone signal still going to interfere with ADSL signal?
For completeness, I just switched to Telecom with ADSL2+ plan, was using Slingshot with Naked DSL.