All systems play wav files. All systems sound equal when firing a cannon, engine, idling, starting or stopping. These are just single wav files that are just simply played.

I could take an $18 sound card from 123 electronics and play engine start and stop files that rival anyone's. What makes convincing sound is how the software manipulates the wav files to represent an engine coming off idle and going into motion and then back to stop. This is the single thing that separates the best from the rest, and currently yes it doesn't come cheap. It seemed at one time Clark was going to go down this round, but appears as if he may have pulled back. He did showcase a video recently that leads me to believe he is back in the game. However don't expect this to be cheap either at some point the quality your ear requires for sound to be beleivable will cost you.

A $500 sound system in a $12,000 tank is normal. So when you start talking larger scales the quality of sound hardware is generally better. However most people buying Heng Longs are not in the market for a $500 sound system.

I don't know how the Benedini manages the wav files so well, but it does. The only other system I know that seems to be able to produce the seemless engine transitions is a Company called Model Solutions based in Canada. Again not cheap. I have no experience with them other then the examples they showcoase on their site, which are very good examples fully showing the tank moving off of idle and ramping out to full speed with amazing transitions. Minimum voltage requirement is 10 volts which kind of moves it out of the 1/16 scale market.

Your question about who makes these systems for reasonable amounts is a tough one to answer. IF you think a $139 Benedini is expensive you best not get into anything larger then 1/16 scasle tanks. Because $139 is just the tip of that iceberg.