Hi David,
I had a similar problem as I often saw new features that were shown publicly and introduced on my product designs that would appear from the competition before we actually started delivering because of of a slow initial manufacturing process. The solution to this was to NOT release any photos or drawings of pending products. I would privately show photos or drawings of pending products to dealers but not let them handle or take away any of these images. But I would give text descriptions, omitting sometimes a key element that made the product different, as I always needed to keep the market interested and aware that new product was in the works.
Based upon your concerns, I would suggest not posting photos or drawing until you are ready to take it to production (which hopefully will not to too far off ;-). I think that the most useful information to those planning to purchase this product would be approximate size and the expected low frequency response.
The most important thought though is that you take the time you need to get this product right, no mather how much customers like me keep looking for progress and a delivery target...
Chuck A