Solo off-axis Response
When listening to a loudspeaker in a room, you are in fact listening to the sum of the direct sound and the sound that is reflected by the walls, ceiling and floor. Therefore it is important to control how a loudspeaker radiates the music into a room. Physics tells us that the larger a loudspeaker driver is compared to the wavelength, the more forward-only the sound will travel. And vice versa. For example, at the cross-over between a large mid-range driver and a tweeter, the mid-range radiates mainly forward and the tweeter radiates in all directions (the tweeter is smaller than the mid-range at the cross-over wavelength.) But this discontinuity in the off-axis response means that the reflected sound is not linear. Which in turn means that the sound you hear is not linear. It is distorted.
The graphs above shows the off-axis response for the Solo, from 0 degrees (forward) to 90 degrees (sideward), relative to the forward response curve. The Solo cabinet, drivers, membrane material and cross over together deliver a very smooth off-axis response for the Solo. This means the response in the room will be linear and music will sound as intended. On www.stereophile.com, many of the same loudspeaker measurements have been published for comparison (note, some only go to 45 or 60 degrees).