The disappearance of the traditional amplifier

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...

I haven't heard the Audiokinesis loudspeakers, but I have spent a little time with Dr. Geddes' "Summa" loudspeaker, on which (as I understand it) the Audiokinesis designs are based. The Summa's horn/waveguide is a true constant-directivity design, and this is immediately evident in their excellent imaging, and very consistent tonal balance. I actually feel that Dr. Geddes' research in this area is some of the most interesting, competent, and relevant work in loudspeaker design in recent years.

But the "waveguide" designs in the Genelec monitors bear very little resemblence to a true constant-directivity spherical or bi-radial "waveguide" horn, in both the theory and the way they behave. This is mainly because they don't use compression drivers - and the waveguides are so short that the directivity characteristics of the driver itself dominate the polar response of the loudspeaker. Genelec's "waveguides" do seem to clean up the directivity performance of their drivers at the more extreme realms of their off-axis response, but they are NOT constant-directivity.

I'm really not trying to slam Genelec in general, and when used in the vertical configuration, their directivity characteristics similar to many well-behaved direct-radiating monitors. I just feel that some of their recommended setup configurations give lackluster performance, and their marketing material seems to imply that they are truly constant-directivity (even though they don't actually make that claim).

I don't know if it's accurate to say Duke's designs are "based" on Geddes' work, but he certainly pays tribute to the man. (I mean he pays vocal respect and acknowledgment, not that he pays tribute in the Cosa Nostra sense.)

Yes, Dr. Geddes obviously understands acoustics very well and it is enlightening to read his material.

But the "waveguide" designs in the Genelec monitors bear very little resemblence to a true constant-directivity spherical or bi-radial "waveguide" horn, in both the theory and the way they behave.

Good Discussion. Yes but....horns are different in that they use a compression chamber. For horns the exact mathematics and expansion design become critical, however, for a normal non-compression driver a simple conical expansion often has teh best performance and is enough to control dispersion such that a smooth power response is achieved.

See this

and see K&H O500C - click on the "measurements" link in thr right hand corner for directivity plot. This is an example of an impressive response that is extremely smooth and wide both on and off axis and illustrates the use of the "waveguide".