I thought that the idea was to have the tweeter above the woofer to get it closer to ear level? I see a number of two ways designed with the tweeter on the bottom now. Are these designs mainly for movie/TV setups?
The Zu line of Hi end speakers have the tweeter under the woofer. I can’t speak to the science behind it but I know I really like the sound. $12,500
For a typical speaker layout, you often have lobing in the vertical response, and the primary lobe may be offset from normal (90°). Inverting the layout sometimes puts the desirable lobe at the speaker height and above, which is the typical window most people are interested in. The crossover topology and Z offset between the drivers both influence this as well.
When I designed a time-aligned, linear phase speaker, my measurements showed the vertical response would benefit from rearranging the drivers. I calculated the listening height and distance, and placed the tweeter below the midwoofer to direct the lobe null towards the floor. This way, when a listener stands up there isn’t a dip in the response at the crossover frequency.
Some manufacturers may do the same, and that might be why you see it done in some designs.
Some manufacturers may do the same, and that might be why you see it done in some designs.