12-22-09: Kijanki writes
> Bipolar speakers don't make nodes in the room.
Bipolar speakers most definitely stimulate room modes - I measured over 10dB peak around 70Hz in one room with a pair of Definitive BP8s.
In the modal region conventional speakers are omnidirectional (a 100Hz wave is 11' long and wraps around any speaker you can fit in your living room like it wasn't there). Apart from the force cancellation you get which reduces structure borne vibrations having the drivers on opposite sides instead of one surface doesn't make a difference you can't get by moving a box with drivers on one side.
Dipoles with the front and back waves 180 degrees out of phase do interact differently, producing measurably weaker height and width modes although you need to equalize at 6dB/octave and use multiples to get sufficient head room (with 15" separating the drivers, at 40Hz it takes 4 drivers to play as loud as a single driver in a closed box).
> Bipolar speakers don't make nodes in the room.
Bipolar speakers most definitely stimulate room modes - I measured over 10dB peak around 70Hz in one room with a pair of Definitive BP8s.
In the modal region conventional speakers are omnidirectional (a 100Hz wave is 11' long and wraps around any speaker you can fit in your living room like it wasn't there). Apart from the force cancellation you get which reduces structure borne vibrations having the drivers on opposite sides instead of one surface doesn't make a difference you can't get by moving a box with drivers on one side.
Dipoles with the front and back waves 180 degrees out of phase do interact differently, producing measurably weaker height and width modes although you need to equalize at 6dB/octave and use multiples to get sufficient head room (with 15" separating the drivers, at 40Hz it takes 4 drivers to play as loud as a single driver in a closed box).