Personally, I feel one off the biggest problems with the site as it stands is it's format.
The home page only shows the latest conversations in chronological order. Unless you know the layout of the site in detail, that's all you see when you first get here.
There are no obvious 'stickies' or articles where visitors can find the stimulating information they might be searching for. Some members make a valiant effort to welcome new members, but where do those folks go next?... Sure, great, helpful information is here, but it's buried deep in long-forgotten threads
To illustrate the situation in real world terms: it's like walking into a musicians/aspiring audio persons' conference...
Someone meets you at the door and says "Welcome, come in, make yourself at home"... So you do, because you love this stuff...but instead of finding signs directing you clearly to seminars, workshops, topical discussions, all you see are little groups of people in huddles, deep in conversations with each other...
What do you do? Break into a conversation? Start talking loudly to attract attention to yourself, hoping someone might join you? Collar someone and ask them where all the action is?
Let's face it: most reasonable, self-aware, generally socially well-adjusted adults want to sit back and observe a situation before jumping in and opining/contributing.
If there is apparently nothing happening but a bunch of conversations among people they don't know, with nothing obvious that they can engage with on some level, then they will walk right out of here as quickly as they came in.