If the rear wave is not isolated from the front wave, they will tend to cancel below a certain frequency,
which is related to the path length that the rear wave has to travel to reach the front wave.
which is related to the path length that the rear wave has to travel to reach the front wave.
Metaxas emperor electrostats are supposedly covering all the frequencies. For that you need to be big.
http://www.metaxas.com/pages/products/emperor.html
http://www.metaxas.com/pages/products/emperor.html
With AMTs, I think the folding is also an issue at low frequencies. You only have so much excursion capability before things run into each other. Seems like I've read they can get buzzy/rattly if driven too low also, but I could be misremembering. The smaller ones tend to have resonances up where a tweeter would, so that's going to be a significant limit. The diaphragm free span tends to be small, which pushes up resonance frequency, even when tension is light.
Dipoles generate velocity waves, boxed speakers generate pressure waves. The rolloff of a dipole is 6dB/octave, that of a closed box is 12dB/octave. With dipoles, you are sitting in the path of the front-to-rear waves, whereas with boxed woofers the room modes have more influence on LF perception. So a dipole woofer is able to generate low frequencies, just differently. Perhaps is doesn't have the same punch as a boxed woofer.
There are figure-of-eight (dipole) condenser microphones capable of picking up low frequencies. There is no theoretical reason for dipole loudspeakers not being able to do so.
There are figure-of-eight (dipole) condenser microphones capable of picking up low frequencies. There is no theoretical reason for dipole loudspeakers not being able to do so.
Audible sounds span a 1000:1 range of wavelengths. 1 KHz is approximately one foot wavelength. The behavior depends on the wavelength relative to the size of the speaker.
Ed
Ed