Are Wide Bands Optimal?

A wideband is more like a narrowband compared to multi-way designs. It is a minimum phase system, but one with a very narrow quasi-linear frequency response. And it is also - at least on rough inspection - a point source, but one with often very uneven radiation characteristics. A full-range driver, however, is free of the usual phase and impulse problems that otherwise occur in the transition regions of drivers. There are limitations: the maximum sound pressure level in the high frequency range (cut-off frequency / fine resolution) in the bass range (cut-off frequency / / excursion / distortion) in the impulse response (the radiation resistance curve causes weak first half waves in the fundamental and especially in the bass range). Full range drivers have great difficulties especially at the ends of the frequency range. They are not really powerful bass speakers. The limited linear excursion and the relatively small diaphragm area seldom allow a significant extension of the bass response at low frequencies, especially if you exceed room volume. In terms of measurement, the relationship to other "time-directed" concepts is in the time-synchronous way of playing. Within the transmission range everything plays together to the point. The result is a feeling of naturalness when listening. The highest sensitivity of our hearing organ lies in the middle of the hearing spectrum and with the transients and can therefore be served very well with a full range driver. The usable frequency range often ends at considerably less than 10 kHz. The amplitude values in the higher frequency range are then only a superposition of membrane resonances on the low pass of the chassis, which cannot be corrected by filters. Occasionally full range drivers are combined with another tweeter to improve the high frequency reproduction. However, this is not possible in principle, because the chaotic amplitude and phase behaviour in the upper transmission range of a full range driver means that the addition and subtraction of the sound waves is also random and not in accordance with the music signal. So-called "super tweeters" or coupled basses destroy the characteristic of the point source, unless it is already limited by partial oscillations. Wild Thing

Full-range drivers usually have not only a powerful drive, but also very light diaphragms. This results in the stated very high efficiency at a given frequency. Considered over the entire bandwidth, however, the efficiency is already significantly lower! High efficiency due to often short voice coils and light paper diaphragms also leads to non-linear excursion with strong distortions and, due to the diaphragm, to an early uneven drop of the dynamic phase.
Lightweight diaphragms are also not very stiff, resulting in so-called partial oscillations. These are the result of partial diaphragm vibrations, in which the diaphragm breaks down into many small partial areas, each of which vibrates separately. They each have their own acoustic centre. It is therefore not a pure point source. Due to these acoustic centers distributed on the membrane, which also vary in time, time-shifted, chaotic sound additions and subtractions are generated, which as interferences lead to unevenness in the frequency response.
Flat diaphragm loudspeakers as in the Myro Spirit IV are still the most suitable for a broadband application. The resonance phenomena are in the upper high frequency range and are often perceived by the listeners "only" as lively highs. On the other hand, the advantages of a much deeper coupling to the mid-woofers than with the usual tweeters outweigh the disadvantages, which ensures a more benign vertical dispersion behaviour of the overall system.

ESS PS-61

The transient A full-range driver combines the characteristics of tweeters and woofers. Its transient response is thus determined by a high-pass and a low-pass at the lower and upper cut-off frequencies. The transient distortions are thus just as present as with separate tweeters and woofers. A time aligned loudspeaker should have a fast transient tweeter, which can already reproduce the first half wave correctly. This requires a high resonant frequency. So far the Accuton diamond tweeters offer the best characteristics. But the full range driver behaves the other way round. If one looks at its frequency response, one sees besides a quite smooth course in the midrange to increasing ripple in the high frequency range. These are resonances, which produce the high frequency level. As with all resonances, this is unmodulated sound that contains no musical information. Wide-range drivers therefore hardly reproduce any music in the high-frequency range, but a chaotically generated mixture of frequencies. The useful bandwidth available for music is therefore much smaller than the frequency response indicates! Accordingly, one has the impression that there is no lack of high frequency level, but there is a lack of resolution. It has to be noted that the frequency response shown in the data sheet is often smoothed, so the ripple is even more pronounced in real measurements. Due to the inertia of the diaphragm and the development of high frequency resonances, a very poor reproduction of the first wavefront is to be expected in the high frequencies. For the low frequencies, on the other hand, there is a lack of the necessary diaphragm area. In the transient response the full range driver becomes a driver that only delivers a correct reproduction in a narrow band range. Radiation under angle For time-correct listening in a room not only the direct sound but also the reflections at the side walls are relevant. This is because reflections are also of varying authenticity and contribute their part to the sound experience. However, full range drivers are usually extremely non-linear off-axis and therefore there are no time-corrected reflections in the room. Filters should only be used to correct non-linearities that do not occur only at certain angles. There are many resonances which, for example, lead to extreme overshoots on axis, but form a dip at an angle, e.g. 30 degrees, because the partial oscillations cancel each other out at this angle. Especially with drivers that are operated openly in their upper transmission range, i.e. with full-range drivers, these problems show up clearly. And they are not covered by the sound component of a tweeter. If diaphragm resonances make up the frequency response at higher frequencies and these mainly consist of partial oscillations, then the time correctness under angle does not work.

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