I should elaborate further. There is nothing inherently wrong with a 2.5 way design. I have designed quite a few. In fact my center is a 2.5 way and my surrounds are 2.5 ways. What I don't do with 2.5 way is use as MTM layout that is horizontal. To work it would have to be vertical. So if you want to salvage that center, then it needs to be turned vertical and not horizontal. Doing what they have done does nothing to solve the lobing issues of horizontal MTM centers, but off centers the acoustic axis, which in undesirable.
Now my 2.5 way center is not only vertical, but uses a coaxial driver.
The more I think about this, the more I think the BBC is correct. Because of the difficulty using properly designed centers under domestic conditions the center channel should be abandoned. In BBC mutichannel broadcasts there is no center channel.
Now in the townhome we are closing on next week, I used a single full range driver that was very satisfactory, like my coaxial.
For one of the systems in my new home I have designed the usual design to help overcome the lobing issue of MTM horizontal centers. That is the vertical mid and tweeter with woofer either side.
Crossover points are 400 Hz and 4000 Hz.
Whilst the results are fairly satisfactory, results are not ideal. The lobing issue is not entirely solved as there is a change in bass balance moving across the sound field.
So I now have come to the conclusion that a center speaker needs to use a coaxial driver or a full range driver if not to be a vertical array, which is seldom practical.
So the answer to the center conundrum is essentially no center, a coaxial or full ranger. Anything else is less than optimal.