Does hi-fi end here?

Reports are coming in that hi-fi may, after a century of development, have actually reached its logical conclusion. It is beginning to look as though the Kii Three may be the technology beyond which it simply wouldn’t be worth going, for the vast majority of people. If so, this is quite a significant moment.

Everything up to this point has been a flawed, intermediate step.

It all started in the 19^th century with the stunningly simple observation that sound is nothing more than variations of air pressure and that these can be picked up by a diaphragm and reproduced by another diaphragm. The hi-fi story has been one of how best to store the information encoded within the vibrations, and how to get the vibrations back out into the world at some time later.

First, we had purely mechanical systems which had to contend with the imbalance between the tiny amount of energy that can be picked up when making a recording versus the large amount of energy that is needed to play the recording back.

Then, with the introduction of electronics into the equation, the path towards the truly linear system was opened up. We had recording on magnetic tape, distributed to the listeners via vinyl LPs. Amplification with valves, then transistors, Class A, AB and now Class D. Horn speakers, multi-way speakers, direct radiators, acoustic suspension, and detours into panel speakers, electrostatics and even plasma. Interestingly, active crossovers are not new: they were used in cinemas in the 1930s, and there was at least one well-heeled enthusiast using them in a domestic system in the 1950s.

A major disruption occurred with the development of digital audio in the 1980s which, at a stroke, propelled performance in terms of noise, distortion and linearity to the point of practical perfection and slashed the size, weight and price of audio storage and playback equipment.

(At this point, ‘high end’ audio as a hobby left the rails and, for many, became an exercise in masochism, superstition and nostalgia).

The next part of the puzzle was solved when computing power became available. Using a computer it is possible to perform digital signal processing (DSP), allowing precise tailoring of crossovers and EQ, and for the characteristics of mechanical transducers (the speaker drivers in their boxes) to be modified.

The linear system

Now, all the pieces were in place to build a linear reproduction system using the following building blocks:

• Digital storage of stereo or multichannel recording
• DSP to process the signal for crossover, time alignment between drivers, driver amplitude and phase correction, EQ, woofer distortion correction using voice coil current or motion feedback
• One DAC per driver
• One solid state amplifier per driver
• Loudspeaker comprising several dynamic drivers each allocated to a narrow frequency range, including sealed woofer whose bass can, if necessary, be extended using DSP EQ.

This is all perfectly realisable at low cost using physically small electronics. The advent of Class D amplification makes it even smaller and cheaper. Such a system is virtually noiseless, has extremely low levels of distortion and covers the entire human hearing frequency range.

The final part of the puzzle

There has been a lag in the acceptance of such systems even though they are spectacularly good. The recent development of a system to tackle directly the issue of the speaker’s interaction with the room at bass frequencies may be the final part of the puzzle that means these systems take off. I think the Kii Three is the first speaker to do this using DSP, followed closely behind by the huge and expensive Beolab 90.

There is some confusion over why DSP-based ‘room correction’ is needed, and what it is capable of. Although the room appears to mangle the signal terribly in terms of frequency response and phase when measured, the listener hears the direct sound from the speaker first, and an average room just adds agreeable ‘ambience’ that blends the immediate surroundings with the recording and helps to cement a convincing illusion of ‘being there’. Trying to ‘correct’ the effects of the room will make the system sound worse.

The one area where genuine problems may occur, however, is in the bass, and people attempt to solve this with DSP (not very successfully), and with room treatments (not particularly effective for the bass). The Kii Three and Beolab 90 both take the approach of using extra drivers driven by DSP to make the speaker more directional at low frequencies by cancelling out some of the almost omnidirectional bass that comes from the main driver, at the sides and rear. This effectively provides the same directionality as a huge baffle, but from a compact speaker.

Intuitively, it seems obvious that in a highly reflective, echoey room, this technique would improve the clarity of what was heard. It would also tackle problems of speaker placement near walls and corners. The amount of bass bouncing around the room is being reduced at source, rather than trying to catch it afterwards with bass traps etc. The result, apparently, is spectacularly good.

By all accounts, the Kii Three is a compact, good looking speaker with a moderate (OK, not outrageous) price, that simply disappears acoustically, leaving the music as a solid 3D image. It is loud enough and goes deep enough to satisfy the vast majority of people. No other equipment is needed other than a digital source, which could be a PC, streamer or network.

The search is, apparently, over. While it would be possible to build a bigger system, with bigger drivers, higher powered amps and so on, this would just be scaling the same fundamental design. This has already been done in the form of the Beolab 90. The system could be further scaled to provide more channels than just stereo, and more precise control of dispersion in the vertical as well as the horizontal – if anyone thought it necessary.

Conclusion

In the end, it turned out that the ‘objectivists’ were basically right: you really do just need perfect linearity to build the perfect hi-fi system (but you also have to have accuracy in the time domain, which most audio objectivists ignore).

According to reviews, and based on my own experience of not completely dissimilar DIY systems, the Kii Three is the only hi-fi system anyone will ever need. Valves, vinyl and passive crossovers seem positively quaint in comparison; ‘high tech’ passive speaker systems seem almost perverse. No doubt the Kii Three will be copied, and cheaper versions will appear, but there is no need to fundamentally change the design from now on. It should be game over for other forms of hi-fi. (It won’t be, of course!)