04-04-14: Bob_reynolds
Here's my guess...
Put one driver on a baffle and you should have the same dispersion horizontally and vertically. Place a second driver vertically adjacent to the first driver and vertical dispersion will suffer.
Yes, and doubly so when the tweeter has mid/woofers above and below the tweeter as in a D'Appolito or MTM array. tHe larger waves of the midrange drivers keep the shorter tweeter waves from having much of a vertical dispersion at all. MTMs have a famously narrow vertical dispersion. An example is the Atlantic Technology AT-1, near fullrange MTM tower. Its
measurements showed a vertical dispersion of 5 deg. above the tweeter axis and 10 deg. below. The commentary also mentions that crossover design can influence dispersion, especially suckouts.
A pistonic driver's dispersion depends on its employed frequency range relative to the piston's diameter. For example, suppose we have a 2-way monitor with a 6-1/2" woofer and 1" dome tweeter, a pretty common configuration. A 6.5" dia. diaphragm starts beaming at about 2100 Hz, whose wavelength is 6.457. Let's suppose the speaker designer chooses a crossover point of 2.5Khz to improve power handling. That pretty much guarantees that the dispersion will narrow significantly at and near the crossover point.
