The disappearance of the traditional amplifier

I kindly disagree with some of the comments concerning Genelec waveguides. In non-anechoic conditions we always listen both direct and reverberant field, most often the reverberant field is dominating. The reverberant field balance depends on speaker system's power response, i.e. total radiated power in all directions, not only on axis. Systems without any directivity control exhibit uneven power response having dips around crossover frequency(-ies) due to the simple fact, that lower frequency driver is more directive at its high end cutoff, than next smaller driver at its low end. The waveguide limits the directivity of the higher frequency driver (MF or HF) to the same as that of the lower frequency driver, and makes the total directivity uniform. This happens with the Genelec waveguides and for example with the JBL Bi-radial horn used in 4430/35. The frequency range depends on the size of the waveguide. The other important consequence is reduction of diffraction from the cabinet edges, and this is obvious in stereo imaging. A trivial mono signal reveals the truth easily.
If the power response is not uniform, the perceived balance depends heavily on the room and listening distance, and these simple facts are source of endless discussions.

As for field coil drivers, they still suffer from the very basic source of nonlinearity, iron. Regardless of that, field coil drivers would be easiest to use with active speakers, as power supply is inherently available. The drawback is naturally heat dissipation.

IMO active speakers can definitely be better performers than passive - there are many inherent technical reasons for that - but in addition to skills in electroacoustic design it requires a second skill set for proper amplifier design.

K_ilpo_p, I once heard a two way-speaker that used a waveguide on the tweeter the same size as the woofer, to even the power response as you say (and get the other benefits of horn-loading such as the increased dynamics and higher sensitivity). It was one of Duke's (Audiokinesis) creations and it was one of the best speakers I've ever heard in virtually every way. I probably would have bought a pair then & there (RMAF) had I not already had something like 5 pairs at home.

It seems to me that the best-sounding speakers are the ones that pay give proper attention to power response, which is indeed rare. The AN/E is another example.

Duke's speakers are indeed special. I own the Jazz Modules and in addition to the waveguide design and power response (summed omnidirectional response), another factor that contributes to the sound of these speakers is the fact they have negligible power compression. Duke uses pro sound drivers with the woofer being a TAD model with a alnico magnet and the tweeter using a neodymium magnet. The result according to Duke is that sound pressure levels up to 112 dB are reproduced with less than 1 dB of power compression.

When it came down to me choosing new speakers to replace my Spendor 1/2e, both Duke's and the Audio Note AN/E were on my shortlist.

It seems to me that the best-sounding speakers are the ones that pay give proper attention to power response, which is indeed rare.

Dr. Floyd Toole devotes quite a lot of time to this important aspect in his new book: Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms. ATC have been preaching about even power response for about 30 years. Careful attention to driver size and use of waveguides can create a smooth continuous off axis response which means the speaker will sound consistent in almost any room and from any position in the room. Ignoring the off axis response or power response can create an exciting and impressive speaker due to the nasty discontinuities like this huge hole or "scoop" in the mid range - this can make the speakers seem artificially "revealing" or amazing but will make it very difficult to setup as the user will really struggle to find a good placement which creates a balanced sound from primary and reflected energy as well as a good stereo image.

The result according to Duke is that sound pressure levels up to 112 dB are reproduced with less than 1 dB of power compression.

Although this thread seem to be digressing there have been many excellent comments.

Duke's claims are extrodinarily good. Most people would be surprised how effortless undistorted and uncompressed sound can be - even at what would seem to be very high SPL's (provided a good recording of course).

Sadly most speakers do not come with anything like high quality pro type drivers but at least they usually come with nice cabinets and great veneers...