Standing waves are a common issue, especially in small and mid-sized apartments. Rooms with large parallel surfaces made of dense materials (such as concrete, stone, or brick) easily generate strong standing waves, which emphasize certain low frequencies, causing them to dominate the sound.
The only effective way to minimize this effect is to use a dipole bass (which radiates in only one dimension, forwards and backwards in opposite phase). Gradient had already employed this system in the SW-63 subwoofer designed for the Quad ESL 63 electrostatic.
The bass section of the Gradient Revolution speaker used two long-throw woofers, providing a ruler-flat response down to the lower threshold of human hearing in real rooms. As seen in Stereophile (March 1997), the in-room measurement of the Gradient Revolution was an impressive 32 Hz - 10 kHz +/- 1.3 dB (see fig. 5: Stereophile Review).
Thanks to the triangular shape of the cabinet, the bass section could be oriented in three different directions, allowing low frequencies to be directed accordingly. This flexibility helped to tame annoying standing waves and fine-tune the bass response to the listener’s preference. (In the current lineup, the speakers utilizing a dipole bass are Gradient R-5 and Gradient R-5A.)
