Full range with tweeter

Although full range speakers can measure almost flat on axis, they often beam of axis. They generally benefit from adding the tweeter. Ideally concentrically. Here are some examples.

Tang Band W5-1611SAF is 5" PP full range which according to the manufacturer has almost flat response from 100Hz to 20kHz. However, I find the driver to sound quite boring, lacking some detail and spark. How is this possible?

We do not only listen on axis. First arriving signal may be from the on axis flat response, but sound projected of axis bounces in the room and eventually reaches the listener few tens of milliseconds later. If this later arriving signal is significantly different, our brain does not like it.

This is how W5-1611SAF measured on its own. Please notice significant beaming.

I was not happy with the sound, so I added the tweeter. This is how it measures now. I like the sound and use the speakers in the bedroom system, together with the sub. Great sound. Pleasant, natural, non fatiguing.

Here is the whole system.

Another small system with betsy and tweeter