Passive, active, single

No, it’s not the title of the latest Richard Curtis rom-com. Passive, active and single refer to the three primary ways of designing hi-fi and studio loudspeakers.

Most loudspeakers feature multiple drive units, each of which has a restricted bandwidth. For instance, in a typical two-way design the bass/mid unit may cover 50Hz to 3000Hz and the smaller tweeter will take over from there to around 18000Hz. How the two units are connected defines whether the speaker is a passive or active design. A single, full-range speaker is one drive unit which endeavours to cover the whole frequency range, from 50Hz to 18000Hz.

All three have advantages and disadvantages – the art of successful speaker design is knowing which compromises are acceptable and designing accordingly.

PASSIVE LOUDSPEAKER

These dominate the hi-fi market. They use passive (non-powered) crossovers featuring components designed to operate at tens of volts and high current. This makes the components large and expensive, particularly if close-tolerance parts are used. Even at relatively low powers, the components can exhibit significant harmonic distortion which would be deemed unacceptable in an amplifier or other electronic hi-fi component. Furthermore, at higher powers, the components may heat up, their values alter and the crossover point – carefully calculated and designed for, often with computer modelling – may move, leading to more distortion.

Finally, the crossover appears after the power amplifier,and effectively decouples the drive units from the amplifier, allowing no electrical damping and control over the movement of the cone or dome.

ACTIVE LOUDSPEAKER

Technically, these are a huge improvement over passive loudspeakers. The crossover is powered, like a preamplifier, and uses small voltage components, making them cheaper, closer tolerance and cooler running. An active crossover can be designed and manufactured much more accurately than a passive crossover. The amplifiers come after the crossover and are connected directly to the drive units, allowing much greater control and damping. Distortion is a magnitude less than with a passive system, something one would think all hi-fi enthusiasts would strive for.

The main disadvantage over a passive speaker is the requirement for a second power amp. However, the power amps themselves can be smaller – they are precisely matched to the drive unit with no requirement to drive high-current loads. Many systems – for example, Linn, Meridian, AVI, Bang & Olufsen and Genelec – fit the power amplifiers within the loudspeaker cabinet, leading to a further cost saving in expensive metalwork for the amplifier.

Despite these advantages, the active speaker shares with its passive counterpart a number of significant problems.The sound is still generated by two or more separate sound sources, leading to a lack of focus. The units themselves may be wildly dissimilar in both design (cones and domes or ribbons) and materials. The units may have different transient responses, as you might expect when trying to match a lightweight dome to a heavy plastic or paper cone.

Would you be happy to listen to a piano solo split between a church organ and a harpsichord?

SINGLE-DRIVER LOUDSPEAKER

Despite their apparent simplicity, these can be amongst the most sophisticated loudspeakers available. The sound is generated by one drive unit, usually from one point in space and manufactured using one material. The sound is more focused, coherent and natural than the best active or passive speakers. There is none of the distortion and poor damping of the passive speaker and they avoid the complexity of the active.

But a high-end, full-range speaker is not the easiest or cheapest thing to design and manufacture. The Jordan Eikona 2 is the culmination of decades of research and development. The proprietary materials used are expensive and specialist in nature, many of them hand-tooled.

So the single, full-range driver has many advantages over the active and the higher cost of the drive units is offset by the need for only one power amplifier, the choice of which is entirely left to the end user.

The results are worth it. Listen to the Jordan Eikona 2 and instead of a loudspeaker, you are listening to music.

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