The Conn pipe speakers were constructed with either two or four 6 X 9 inch oval speakers in the pipe chest which fired up through the bottom of the pipes.
The sound from the speakers, which were all wired the same, excited the column of air in the pipes which were made to resonate at appropriate pitches.
This enhanced and enriched the harmonic structure of the sound, much the same as lifting the dampers from all the strings of the piano.
Conn had a demonstration of this where a small microphone could be dropped inside any given pipe.
This microphone was hooked to a regular guitar amp.
They also had a set of 145 pipes with the pipes labeled as to their tuned pitch.
While holding down middle "C" on the organ, the microphone would be lowered into ANY "C" pipe, and you heard a "C" coming from the guitar amp.
Then, while still holding the middle "C", the microphone would be lowered into an "E" pipe, and you would hear an "E" coming from the amp, and likewise with a "G" pipe, a "G" would be heard coming from the amp.
In addition, the sound became non-directional, thusly eliminating the direct sound blast so common to electronic organs.
There was also a very slight bit of sustain, or reverb, to the sound after the key was released as the sound within the pipes dissipated.
These units worked the same way with any electronic organ whether it was vacuum tube oscillator, transistor oscillator, analog, digital, or a virtual pipe organ (VPO).
They're not good for reproducing pedal tones however; a large powered subwoofer would still be needed for that.
Also, while they're made to resonate at appropriate frequencies, the pipes themselves are not tuneable.
The Conn organ division manufactured a great line of products, these units were an example, a ton of them were sold back in the 1960's and 70's, and those individuals who happen to have them connected to their own electronic instrument today seem to love them.
This information will help get the truth out about these units and maybe even put to rest some of the needless controversy relative to their effect on the sound.
Pricing these days seems to be all over the place; a lot depends upon condition, as it seems they're easily damaged and not very amenable to shipping given their shape and spindliness.
Whether one likes them is, of course, a matter of personal taste, but many people appreciate having them, and not just for their effect on the sound, but for the "look."