When it comes to home-entertainment equipment, plenty of problems have been well and truly nailed. There is now a wide choice of electronic devices, in which actual audio performance is well nigh indistinguishable from perfection. Decent-quality amplifiers, for one.
But there are still plenty of devices, for which perfection remains a far-distant hope. And the main one of those — the loudspeaker.
What it does
The job of a loudspeaker seems simple enough. All it has to do is convert an electrical signal into mechanical energy, in the form of pressure waves in the air (which is what sound is). Simple in concept, but hard in practice.
So hard that — one little-known fact about loudspeakers — the average high-fidelity loudspeaker wastes around 99.5 per cent of your amplifier's power. Rather than turning it into acoustical energy, it turns it into heat.
The problem involves the acoustic coupling of a high-impedance source to a low-impedance medium: the air. That 0.5 per cent efficiency is more commonly expressed as a "sensitivity" measurement: 89 decibels of sound pressure level, measured at 1 metre, for an input signal of 2.83 volts. (Why 2.83 volts? Because this is what produces 1 watt of power in a constant 8-ohm load.)
An increase of 3 decibels in that figure doubles efficiency. So a loudspeaker with 92dB sensitivity is 1 per cent efficient. In the world of high-fidelity loudspeakers, the normal range is between about 85dB (0.2 per cent) and 95dB (2 per cent). One legendary horn-loaded speaker — the Klipshorn — manages 105dB (20 per cent).
Live with it; your loudspeakers will waste a lot of power. But, if you can find a set of speakers with a 3dB higher sensitivity than another set, it will be the equivalent of having twice as much power.
It's about more than volume
It's easy to make more efficient loudspeakers, but that would come at a cost of accuracy. These days, amplifier power is fairly cheap and many techniques for improving efficiency would hurt the sound in other ways.
Perhaps, the most important attribute of high-quality sound is tonal balance. Ideally, a loudspeaker will reproduce a full 10 octaves of sound, from 20 hertz up to 20,000 hertz. In practice, the bottom octave (20 to 40 hertz) is often ignored. This band only rarely contains content of musical significance, so what is important, are the other nine octaves.
Not just that they can be reproduced, but that they can be reproduced in proper proportion to each other. This is expressed in a "frequency response" figure, which indicates the limits of the frequencies the loudspeaker can reproduce and the volume range within that range. For example, 35 to 20,000 hertz at +/-3dB. Unfortunately, two separate systems with that specification can — and most likely will — sound totally different to each other. System A might have the frequency band from 80 to 160 hertz at +3dB, and sound boomy, while System B might have a boost in the octave from 3000 to 6000 hertz, and sound harsh and sibilant on the human voice. Only listening will tell, here.
Spending more often does not yield much in the way of efficiency improvement. But it generally has a large effect on how well a loudspeaker can handle high power inputs, and also tends to provide a smoothing to the frequency response of loudspeakers, leading to a less coloured sound.
Both of which are virtues offered by the speakers we look at, here. They cost from quite large to very large numbers of dollars.
But that is the actual price you pay for trying to master the difficult task of turning electrical energy, accurately, into sound.