If I was going to put a coax on a Unity horn, it might look like this.

The depth is 3.5". The depth is largely dictated by where we want the midrange taps to be. (See the beginning of this post.)

Here's where your coax would go. The tweeter fires through the throat of the horn, and the output of the midrange fires through that ring shape.

Okay, this diagram is super important.

It is *critical* that the area of the midrange tap is expanding.

Here's a few reasons why we want that midrange tap to expand:

1) this is still a horn. If the area of the midrange tap is constant, we're going to get a resonance. In the original Unity horns, from 20 years ago, the area of the tap was constant. The reason that it worked was because

**the taps were short.** For instance, if your midrange taps are only one inch deep, it's ok if they're straight. But if your midrange taps are three inches long, or six inches long, or TWELVE inches long, you want the area to expand. If not, you're going to get a big ol' resonant peak and that's going to ruin your speaker. Long story short: you want those midrange taps to be expanding. If you're a complete madman, you can mass load the ends of those taps. That's a story for another day.

2) If the area of the midrange taps are expanding, the horn behaves a lot more like a horn. If the area of the midrange taps are NOT expanding, you're going to maximize diffraction off of the slots, and you'll probably get some reflections off of the transition from the midrange taps to the rest of the horn. Also known as "higher order modes."

If it's not clear from this post, the reason that the AREA of the midrange taps is growing, is because the diameter of the midrange taps at the throat and at the exit of the taps is higher.

For instance, at the entrance of the midrange taps, the diameter of the midrange taps is 2". At the exit, the diameter is something like 4". This means that the *area* at the exit of the midrange taps is 4X higher.

Here's a cutaway giving a better idea of how the area of the midrange taps is constantly expanding.