What Is Different About Myro Switches?

The filters are the key elements of the loudspeakers of Myro. While other constructive elements can be found in some other manufacturers, the Myro frequency filters contain unique technologies that make the precise impulse response possible in the first place. Steep filters and a polarity reversal of the drivers against each other are basically ruled out, because the shape of the sound waves is strongly distorted. Simple first order filters (6 dB / octave) do not find the ideal conditions in practice, which would be necessary for a correct sound sum, because each loudspeaker chassis represents a bandpass itself with the corresponding phase shifts. These add up to those of the first order filters. Myro's 6 dB filters, on the other hand, are sometimes part of much more complex circuits that essentially equalize the drivers so that together they form the correct sum signal, over the entire time course. Since the filters are designed individually for each chassis and chassis combination, there is no uniform scheme. Myro frequency filters are not the usual x-order filters. Consequently, no low-pass filter with e.g. 12 or 18 dB / octave or more is generated, which disregards the real transmission curve with its resonance phenomena and time-delays the sound signal. Michael Weidlich developed passive frequency filters which follow the principle of analogue computers and correct the transmission characteristics of the individual drivers in such a way that, in combination, they can convert the electrical input signals into sound with extreme precision. These filters are a prerequisite for time-correct reproduction, as they take into account the actual acoustic phase response of the drivers. In addition, the transmission characteristics of the drivers are correlated in such a way that they are already "in phase" during the transient phase and enable the correct sound sum to be achieved at the first half-wave of a transient. To achieve this, many filters are developed, some of which are very sensitive, and extremely effective filters are only used where the chassis characteristics require them. The crossover circuitry is, so to speak, oriented to the actual requirements. None of the three filter methods mentioned above are used here. With Myro, on the other hand, only the errors of the drivers are consistently corrected or "filtered out". Contrary to usual loudspeaker technology, the impulse peaks of the transient are not distorted and flattened, resulting in a completely different dynamic and significantly more sound energy. Especially in the transition areas of the drivers, usual loudspeakers deliver artificial sound waves with a weak amplitude and a different frequency mixture than in the original. This faulty dynamic behaviour can, as already proven and presented several times, be clearly heard and proven by measurement. Conventional loudspeakers have relatively weak impulse dynamics, especially in the vocal ranges. This is incorrect music reproduction, but shapes listening habits with many years of intensive consumption. When listening through such monitors in recording studios, sound engineers cannot correctly assess impulse energy and dynamic tonality and tend to exaggerate in these areas. Example 1: The following measurement graph shows the frequency response of the mid-bass driver of the Myro Time 2, Accuton C220-6-222, without frequency filter (red curve) and with Myro frequency filter (blue curve). The crossover circuit, which leads to the elimination of diaphragm resonances and to the linearization of the low pass, contains nine resonance filters (blue curve). The effort is worthwhile, the distortion is close to zero. The Accuton C220-6-222 exhibits almost perfectly resonance-free response up to about 700 Hz. The system's self-resonance in the bass range is extremely damped. Above 700 Hz, especially from approx. 2700 Hz, strong diaphragm resonances occur. These are typical for stiff diaphragms. Despite the relatively good internal damping of the Accuton diaphragm, the resonances, especially the main resonance at 3800 Hz, have a high quality. This means that the sound pressure rise at resonance is very pronounced. As can be seen in the frequency curve of the C220-6-222 without filter (red curve), the diaphragm resonates at different frequencies. The Myro frequency filters correct the resonances up to above 20 kHz (blue curve). More than forty components in various circuits ensure the clean frequency response and the correspondingly good-natured phase response. The individual circuits mostly have an extremely subtle, almost homeopathic effect.

Crossover of the Myro Amur D

Example 2: Myro La Musica 2012

Frequency response of the mid/bass driver without filter (blue) and with Myro frequency filter (red). The attenuation is -30 dB at the main resonance of the magnesium diaphragm. Frequency response of tweeter (red), mid-woofer (green), woofer (ochre) and the sum (blue), each with low-resonance slopes.

The Myro crossover circuit allows slopes of less than 6 dB / oct. in areas where this is desirable and achieves slopes of well over 30 dB / oct. where it is necessary to correct for an appropriate error. For deviations from the 6 dB / oct. slopes, "but linear-phase in sum." This is the sufficient criterion for time-correct reproduction. Otherwise the step responses would not look perfect.
In sum, this results in a crossover that is basically minimalist in that it only selectively addresses the errors of each chassis. Because of this, only narrow band corrections can be achieved with the Myro frequency filters. Therefore, for the development of impulse-dynamic phase-linear transducers, the requirements for transmission bandwidth and linearity are enormous. Broadband non-linearities, on the other hand, can only be corrected with the development methods mentioned at the beginning and are therefore not suitable for time-corrected loudspeakers. The same applies to series consistency. And the dynamic reserves of the systems used must be above average. So the use of high quality drivers is obligatory and the careful pre-selection to a loudspeaker concept is an essential part to achieve a successful result. There must be no mistake in the conception, every criterion is also an exclusion criterion! Such requirements cost a lot of money accordingly.

Crossover of the Myro La Musica 2012

The duality of electrical and mechanical quantities In order to achieve the special characteristics of the Myro frequency filters, an old technical principle was reactivated and implemented in a new way. It is well known that mechanical and electronic systems behave physically the same if their dual quantities occur correspondingly the same. For example, the series connection of electrical capacitors behaves exactly the same as the parallel connection of mechanical springs. The formulas for calculating the overall behavior are the same in both cases. For other electrical and mechanical quantities, there are corresponding relationships. Knowledge of this duality was used, for example, in earlier times, before the computer age, to investigate the stability of bridge structures. In order to make the construction of the bridge as insensitive to vibrations as possible, its mechanical parameters were converted into an electrical circuit, which was examined for its stability and tendency to vibrate at low cost and without danger. With these findings and converted back into mechanical quantities, a structure with maximum stability could then be erected. The myro frequency filters use the same concept, in that the mechanical resonances of the loudspeaker are electrically, but inversely, simulated in the filter. The analogue frequency filters of the myro crossovers form the mirror image of the acoustic phenomenon to be corrected, taking into account the impedance or including its correction. They also have the task of providing a high-pass or low-pass filter that is suitable for a time-synchronous, phase-linear transfer to the adjacent transmission range. This notch filter thus counteracts the resonance in its complete characteristics and removes its energy. The precise reproduction of a mechanical resonance sometimes leads to filters of considerable complexity, which, although they interfere only slightly with the signal, require numerous components in complex circuitry.

Are so-called phase-parallel switches correct in time?

Phase parallelism of dissimilar chassis is a fairy tale! Not only do ideal-type drivers not exist in reality, but the different dynamic behavior of dissimilar drivers due to different diaphragm sizes and the resulting different radiation impedances already makes phase parallelism impossible. It is a construct of thinking in steady-state terms and idealized drivers. But phase shifts start at the first half-wave! But to capture that, you have to make appropriate measurements. If one considers how large the sound differences of different crossover component qualities are, which can hardly be made visible by measurement with our coarse methods, then it is clear how large the sound effects of coarse measurable errors are in relation to this!
There is no phase parallelism in the transient response even within the +/-1.5 octaves or better +/-2 octaves around the crossover frequency. You only have to look at the behaviour of the individual drivers during transient response. As already mentioned before, the phase shift starts with the first half wave or especially there! And there the radiation impedance has an effect. The radiation impedance also has an effect over time.
Moreover, phase parallelism within the separation region is isolated and has serious effects on the reproduction of broadband, complex signals. Phase parallelism within 3 - 4 oct. is of little use here. Complex signals are heavily distorted.

Notch filter The function of a notch filter in the signal path to the loudspeaker is that less energy is supplied to the chassis in a defined range. A mechanical resonance (e.g. membrane resonance) can be simulated by a notch filter in frequency, quality and accordingly with the same time constant that the mechanical resonance itself has, so that even the transient in the direction of the resonance is simultaneous. Notch filter and membrane resonance thus behave synchronously in time. This compensates for the membrane-related non-linearities of the chassis, in the frequency response, in the distortion spectrum and over time. Notch filters can be connected as a blocking circuit (RCL parallel circuit) in series to the chassis or as a suction circuit (RCL series circuit) in parallel to the chassis. A suction circuit only works in conjunction with a series resistor (resistor R / coil L / capacitor C) in the signal path (in series) to the chassis, so as not to create a short circuit. Whether there are blocking or suction circuits in a filter circuit has only to do with the characteristics of the transmission behaviour of the chassis. An error must be corrected in mirror image without endangering the interaction with the other chassis. In some combinations this can be achieved with blocking circuits alone, in others it only works in conjunction with absorption circuits. In each case one must judge during the development whether a filter circuit brings more sonic benefit than disadvantages. Unfiltered chassis resonances always sound terrible. A perfectly filtered chassis sounds largely neutral and loses the material-typical inherent sound. The effort is considerable, because it is a very complex matter. The individual frequency filters interact with each other. Each filter determines the function of other filters. The loudspeaker chassis are in themselves already very complex in their behaviour, especially if you consider the behaviour over time. Each resonance point of the membrane has its own time curve. The filters have to be designed accordingly. Each filter has its influence e.g. on the impedance, which in turn determines the operating point of neighbouring filters. If you change something in one filter, others will be affected as well, not to mention nested filters for the correction of overlapping phenomena. Series tolerances of the drivers require a "retrimming" of the filters, in the worst case even a change of the circuit. Therefore, chassis with the smallest possible deviations are required. Errors of the chassis that are time-variant or inconsistent under different dispersion angles are especially difficult. Here, careful choice of chassis is essential and decisions must be made as to which phenomena are correctable in the first place. In addition, the drivers and components must have undergone a minimum amount of running-in so that reliable calibration is possible, all in all an enormous amount of time and effort. So the quality is not only in the material used, but also and especially in the handling of it. Much of this also applies to the development of digital filters. You can't just measure the transfer curve at one point and apply corrections to it.

Myro Rebel

Components

The quality of the crossover components is often underestimated or simply ignored, because the crossovers are hidden and elude the view and usually the expertise of the observer. Nevertheless, they have a decisive influence on the sound quality. To ensure that the crossover components do not add their own distortions to the result, very high quality components must be used. The difference between a crossover with "standard quality" and one with excellent components may well correspond to the difference between average and excellent electronic components in a hi-fi system. If you operate with so-called zero-ohm coils in the bass, you hardly lose any damping. Many a poorly fitted or oxidised connector or a bad solder joint will have a higher internal resistance. Therefore, in the interest of the best sonic result, only very high quality components are used in the Myro frequency filters. The crossover components in Myro loudspeakers are twisted together as directly as possible. The additional soldering essentially serves to fix the components. Thus an optimal contact is guaranteed. Direct wiring reduces the inductive interaction of conductors and components. The components are also calmed by damping measures so that microphonic effects are suppressed.
During the development of the switches, the components are initially connected using crocodile clips. In this way, the connections can be varied quickly and the components have sufficient distance from each other. This is important so that especially the coils do not influence each other. A small but not insignificant detail are the connecting cables with the crocodile clips. The contact points can have sufficiently high contact resistances to manipulate the design of the component values. Therefore, proprietary connections were created to minimize this problem. To be on the safe side, direct soldering of the components is used at the end to check, especially with susceptible filters, whether contact resistances were in play and these must be compensated.

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