My Tempests do not have a control for the tweeter. They are the 3e models. I think that meant economy. If memory serves there was a regular 3 with a pot. I'm pretty sure mine has a fixed attenuator for the tweets, but it has been a while since I've opened them.
They don't have a huge amount of bass but I bought them over the 10" model because I figured the smaller woofers would disperse better in the mid range, and I was planning a sub-woofer.
The sub is an Electrovoice 30W. I crossed the Tempests at 80 Hz to the 30W which worked well. That was in my old house. Now they are crossed to a pair of 12" ceiling mounted subs also at 80 Hz. I think the 12" subs are more seamless with the Tempests at 80 Hz. 80 Hz is a bit high for a 30W with a first order crossover.
The 30W now resides in my upstairs stereo room ceiling where it will be mated to the AMT1s.
I will cross it at ~ 50 Hz to the 12" woofers in the AMT1s. The 12" woofers will cross to a 6" mid/woofer @ 200 Hz. The mid will cross to the big Heil at 1 KHz. The 6" will be in a sealed box on top of the existing cabinet and the Heil will go in top of it. The original cabinet is a truncated pyramid and I really want to stay with the same motif so I will look for someone more skilled than me to make the boxes. I'm pretty sure I can make a decent rectangular box but blending to the OEM cabinet may be beyond my woodworking skill. All the crossovers will be first order passive high level to start, with the Frankenstien AMT1s driven from my Citation 5 amp. I will leave hooks to bi-amp the AMT1s so I'm seeking a 6" with ~ 94 dB/Watt to match the Heil. If I'm on top of the grass long enough a class A triode amp will drive the Hiel & Mid with the Citation 5 driving the 12". The big 30" monster will be driven by a class AB MOSFET which I built for it years ago.
The little Heil tweeters sound pretty good, but I had to dial them back a bit to better match the woofers. Still missing good bass, but a twitch of the tone control helps.
I like cheap.
If you are building a set of 3-way speakers, you might consider separate woofer, midrange, and tweeter enclosures, so that you can move them. Then you can adjust the phase/transient integration at the listening position easily.