cannot change the Constitution without a referendum in Australia.
ttbn,
And, who can instigate a referendum ?

To be pedantic it actually requires a special sort of referendum in that it is not just a simple standard majority of eligible voters that approves an amendment. Instead it requires a double majority: where the double majority is a majority of states by each state's registered voters (so there is a majority in at least 4 of the 6 states), and by a majority of voters overall nationally. Voters in the territories count towards the national majority (since the 1977 referendum) but don't count (obviously) towards any particular state.

[Also, the actual proposed change is first a formal a bill of parliament which has to be successfully passed by special rules above and beyond what normally applies to ordinary bills.]

it actually requires a special sort of referendum
thinkabit,
So, who can actually instigate a special referendum ? Two drunks in a Pub ? A High Court Judge & a Politician ? Lawyers, Academics, Builders & Labourers?
I say let's look at the flaws or rather no longer relevant parts of the Constitution & adjust them accordingly !

I say no Public office holders should be allowed to have a say !

individual: "So, who can actually instigate a special referendum ? Two drunks in a Pub ? A High Court Judge & a Politician ? Lawyers, Academics, Builders & Labourers?"

I'm not certain if your asking this for an answer. But as I said in the last post: "Also, the actual proposed change is first a formal a bill of parliament which has to be successfully passed by special rules above and beyond what normally applies to ordinary bills." So a referendum to change the constitution can only be initiated by a politician in parliament.

The process is similar to how normal bills (ie: potential future laws) are introduced but does however have a few additional/different requirements. Most importantly it requires an absolute majority* of both houses or it requires one house to pass it twice by absolute majority with at least a few months (3?) between the votes.

*(absolute majority here means : a majority of all the members of the house. Not just a majority of those present at the time of the vote.)

Whoops, I did it again: "your" in my last post is "you're". Why do I continually make this mistake only to find it immediately after posting?

Voting is an important activity in a democracy. Elections decide the fate of a country for a specific period apart from its long term impact. In most countries the voting age is around 18 years.The youth are a volatile group who are swayed by personal considerations rather than public good. In my opinion these young people are not mature enough to choose the right candidate. Being children themselves how can they choose a suitable adult who is going to govern. Youth are fascinated by money, cinema and other entertainment. They may not understand what public good is.
Age is the only variable which can be universally applied. All other specifications such as "married people" etc. etc. may become highly subjective. When people reach certain age say 21 years or more it is likely that they might have been exposed to the complexities of life and therefore will be in a position to understand what is personal and how it affects the interest of the public. Understanding the functioning of societies is the most important aspect that will decide the quality of voting.