Casters are attached under most of the larger system prototypes so they could be moved around the lab easily. We found that there was too much high frequency output to the sides of the system. This could be a problem if the system is located against one wall in a corner. Also, the angle between tweeters causes uneven response. By rearranging the tweeters into a semi-ellipse, more output can be maintained at the front and less to the extreme sides.
Vertical response is inherently very good.
Felt strips are placed above and below the tweeters to prevent edge reflections from above and below. The curved array is an alternate solution to providing good dispersion with a short horizontal column. It also worked very nicely on the top of an XRT20 cabinet and so the final shape was established. Although only 12 tweeters are used in the XR19, the power handling is still comparatively high at 150 watts of program material from 1.5kHz to 20kHz. Later, with the design of the XRT18, another solution was found to overcome the directionality of a short column.