I ran my horn without a rear chamber too. It sounds great that way, but when you install the horn in corners, the backwave is loaded by the corner apex and that brings it up to compete with the front wave. So the rear chamber is particularly important when used near corners.You're right about size. Having a horn in the corners does a lot, since the corner itself is essentially a very large conical horn. But putting that aside, you really need size to get the response down low. That's why I like the π cornerhorn. It uses the corner as the complete horn, and it's simple and effective.