That said, it looks to me that about 50 people are driving the conversation and a whole bunch are just along for the ride. As a non-pay site, as long as the conversation is flowing, I'm not sure our membership number really matters.
I'm at another small public forum for left handed bass players and the total membership is about 1300. Out of that, the number of actively participating in posts has gotta be even lower, like maybe less than 30.
50 actively posting out of about 500 members, that's about 10% if my math is right. I think that's actually above average. At that rate out of every 10 new members, you can expect maybe one of them that will actively post. I think that's probably about as good as you can expect.