Class-D amplifiers are digital systems in the sense, that they have for one thing fixed band-width, say are sampling, and for another thing fixed Switching Range, say a least bit, belo which level they start to stay quieter than they should. In this paper I am only interested in the band-width issue, also for one may design a new digital recording system from scratch.

First to mention, in order to not obtain too much ringing and aliasing, sample rate must be at least 2*Pi*band-width. With band-width set to 16 KHz, I set sampling rate to 100 KHz. Most Class-D amplifiers have modulation frequency (resembling sampling rate) of 200 KHz or higher. Since raising sampling rate swells data or reduces Switching Range, I keep sampling rate as lo as sonically pleasingly possible, and that is 100 KHz.

The filter must put out at most -8 Bel-full-scale at 50 KHz, because I presume, that the following system will have only 10 Bel dynamic range or will not mind a few bits...

Recently it has been archieved to capture, store, propagate and play back audio with the full human hearing frequency range (16 to 16000 Hz) and contrast (7 Bel). Still, if a big sound source or several sound sources at once are the matter of content, such play-back sounds artificial, because all is emitted from one acoustic source. In order to hear, what is going on, we use both ears simultaniously, turn our head in different directions and will detect the electro-acoustic device.

While an indetectable electro-acoustic reproduction incorporated six microphones, storage and transmission channels and a house-sized sphere covered by loudspeakers on the inside and containing the listener, we can help imagination at least a little bit by introducing sonic differences between left and rite. We also want this stereo, after Greek stereos shape, to integrate thoroly and easily with already existing mono electro-acoustics. We may double transmission and storage channels, for example...

This is about spectra-pathing ("multi-way") loud-speakers made of several monopoles, in explanation omni-directional sound sources, but I really mean direct radiators as opposed to horns, which are more uni-directional. I think about home, rehersal and club loud-speakers, not stadium ones. While spectra-pathing enables large power at wide band-width, seams between paths are usually audible, altho that could have been avoided rite from the start, at least technically. But instead of fixing problems at source, one has relentlessly used power to paint over them.

The natural solution is a symmetrical arrangement of lo-pass monopoles embracing a hi-pass one, combined with a cross-over of first order.

When Germans started to loose ground in World War II, wide-range drivers playing from Large E to 10 KHz were state of the art. Mister Eckmiller developed a co-axial two-spectra-paths driver consisting of hi-pass encircled by lo-pass piston. But for mass...