What Are Time Correct Speakers?
ContentsBasic characteristics[edit]Dynamically time-aligned means that the loudspeaker with all drivers is in time or phase-aligned and radiates the transients (i.e. the reproduction and shaping of impulses) in their characteristics largely true to the original in the direction of the listener. Technically, this is referred to as a constant group delay of all frequencies over the entire transmission bandwidth, which - in the ideal case - also shows itself in a precise square wave reproduction.
The in-phase polarity is the second basic requirement! In the context of analogue concepts, the following basic requirements must therefore be met for correct reproduction:
Filter circuits exert their time-shifting, energy-delaying effect on the signal conversion from the starting point of the signal. This is amplified by the similar inherent behaviour of the loudspeaker chassis. Only if all conditions are fulfilled, a signal can be converted correctly. Within a sound event, time correctness is not a property that is decoupled from sound pressure. It is fundamentally about the correct conversion of vibrations. Sound oscillations are density changes of air over time (with a temporal progression). So it's always about the right sound pressure at the right time - correct in time. If the speaker is making mistakes, then it is not delivering the right pressure at the right time. So any discussion about whether you can do without time correctness to a greater or lesser extent makes no sense in principle. If you play a piece of music backwards, it has the same energy content and the same frequency response as if you played it the right way round - just in the wrong time sequence! And it sounds correspondingly wrong.
The basic prerequisite for the correct conversion of a loudspeaker is the exactly simultaneous arrival of the sound components of the individual loudspeaker chassis and their correct summation. Only when the sound components of all loudspeaker systems reach the listener's ear at the same time, with the same polarity, with the correct energy content and dynamically in phase, is the reproduction of the stored "musical original" successful. |
When loudspeakers excel in individual disciplines such as high-frequency resolution, stage imaging, or impulsivity, they usually lack the time-correct summation that produces the proper interplay, the proper fusion of the sound components of the individual drivers. Instead, the signals are broken down into artificial sound waves and individual components of them stand out. Particularly spiky distortion products suggest impulsiveness and high frequency resolution and time delays suggest a depth of space, which however can be debunked when listening closely, as the spatial action is not plausible. Such speakers usually sound spiky and hissy.
Loudspeakers with timing errors / distortions, whose artificial sound products are rather compressed-rounded, on the other hand, suggest homogeneity, which, however, is also not plausible on closer listening. Here, above all, less attention is demanded of the listener, which can create a relaxed feeling in some. Other listeners become restless because their high attention demands more intelligibility, more details, more real impulse dynamics. For these listeners it even becomes exhausting!
A synchronous bass response sounds different from that of the usual speakers. Due to the synchronous attack the bass does not stand out as a separate, trailing sound event from the music. Rather, it is one with the rhythm and dynamics of the music as a whole. For listeners with decades of experience this is at first strange, simply unfamiliar. The bass, although fully present, cannot be heard separately as usual and is therefore less noticeable (or prominent).
A synchronous mid-treble also sounds different than usual. Since the energy (amplitude) of the transients is not cancelled out by counter-phasing in the transient, the full natural impulse dynamics are delivered here. As a result, it sounds much fresher and more concise, but at the same time much smoother. And it's exactly this combination that contradicts the listening experiences made with false walking speakers. The faulty up and down, the multiple spiky pre-swing at faulty transient sound rather aggressive, rough, hissy, deaf.
|
Loudspeakers that are only optimized for a flat frequency response show one or more of the following faults:
Non-constant group delay due to steep filter edges: The individual frequencies of a signal are transported to the listener at individual speeds. Impulses are thereby temporally ground and distorted in their amplitude.
Loudspeakers with completely asynchronous, antiphase sound summation do not produce a correct step response at any distance or angle. For more technical descriptions, see the following document.
Development sequences[edit]The development of time-correct loudspeakers is divided into four stages: In the first stage of development, simulations, amplitude and phase-frequency response measurements are used to obtain crossover circuits that move towards phase-linear transitions. In the second stage of development, a look at the step response reveals the first correlations and the circuit concept in its final form emerges. In the third stage of development, the step response becomes the ultimate measurement. This is about the linearization of the step response, which automatically leads to the linearization of amplitude and phase / group delay frequency responses etc. and this in an accuracy, which can hardly be achieved by other measurements. In the fourth stage the ear comes into play. With pink noise, the developer can hear and evaluate differences that are no longer apparent, visually recognizable, or interpretable based on measurements. With music the impressions can be deepened. |
|
The fruit tree[edit]The subject of readings and their correct interpretation is not easy to understand. As an aid, the nature of the readings and what they mean can be illustrated using a fruit tree.
This information is also of vital importance, for: If one also wants to know how the fruit tastes, one should bite into it. It follows: Frequency response:
|
Time correctness - a question of definition[edit]The term "time-correct speakers" is actually a pure buzzword. It is not easily definable in its claim to designate the time behaviour as correct. The reason for this is that the time relations in the transient process differ considerably from the time relations in the steady state. 1. the ideal case is the 1:1 transducing electroacoustic transducer. Its bandwidth would be theoretically unlimited and the step response would be a clean square wave. 2. in practice there are only normal cases whose bandwidths are limited. If the theoretical ideal case were taken as a basis, no real product would be time-correct, phase-linear, group delay-linear, frequency response-linear, signal-correct, etc. The terms would not be applicable. It follows: The definition of the terms must be based on real circumstances. Here again there are two possibilities: First: One orients oneself to the auditory bandwidth of the human ear. The basis for this can only be the healthy, young hearing. According to conservative measurement methods (continuous tone intensity), its bandwidth is 20 - 20,000 Hz or 16 - 24,000 Hz, depending on the source. Measurements of dynamic processes result in values of up to 100,000 Hz. Secondly: Loudspeakers are offered in a variety of practical sizes, the transmission bandwidths of which vary due to physics. Consequently, one possibility is to accept the bandwidth limitation as a fact in principle and to put the main focus on the area between the transmission ends. This is where the transition areas between the drivers, which are decisive for the reproduction quality, are located in the case of multi-way loudspeakers, and in the case of a one-way loudspeaker the resonances of the diaphragm are the main problem. This area is also the area of highest perceptual sensitivity. Time correctness (group delay, phase frequency response), like amplitude frequency response, is not an audible event. They are isolated theoretical parameters. One cannot hear time correctness, only waveforms. Therefore, time correctness alone should not be defined, but more meaningfully signal correctness. Only the sound vibrations, i.e. the sound pressure curve over time, are audible. Our sense of hearing distinguishes between sound events on the basis of the forms of oscillation (signal forms). This is already possible with an extremely short oscillation, such as a sine half-wave. Some sound events, such as hand claps, consist in part of only one or two oscillations. They can be distinguished from each other. They do not have a steady state in their signal structure.
The recommendation on the subject of time correctness is therefore: Time correctness should not be considered in isolation, since it is not an audible event. The term signal correctness should be used.
|
Why don't all right walking speakers sound the same?[edit]
First of all, by "properly transducing" is meant the ability to maintain signals in their form as much as possible. Unlike loudspeakers with basically distorted transient response, signal / time correct loudspeakers in principle produce signal responses that are similar in shape to the input signal. Of course, this is only possible within the physically limited bandwidth of the transmission range. This is where the first difference between loudspeakers that convert correctly in principle can be found, as well as in the characteristics of the high and low pass of the respective loudspeaker.
In the border areas of the transmission range there are deviations of the signal form produced by the loudspeaker from the input signal. In addition, the loudspeakers differ in the slew rate, in the decay and in slight deformations or superpositions of the signals, e.g. by non-linearities in the amplitude course, the linearity of the movement of the membranes and by their partial oscillations and resonances. The radiation behaviour and the maximum sound pressure are also distinguishing features.
The limits of correct low frequency reproduction[edit]
The problem of correct low frequency reproduction basically lies in the physical limits. Low frequencies are slow oscillations. A woofer has to generate pressure with a sound wave moving away with approx. 340 m/s. The diaphragm is in relation to the wave. Thereby the membrane is small in relation to the wavelength. This requires an extremely wide excursion to faithfully reproduce the first half-wave, such as the beat of a bass drum. Even the excursion of long excursion drivers is completely insufficient for this. To bring a bass closer to the ideal by using more excursion has several disadvantages:
- Doppler distortion / acoustic centers jumping back and forth.
- Distortions due to non-linearities of the system
- Electrical stress / heating of the voice coils
- thereby high impedance and loss of dynamics
On the other hand, an increase of the membrane area together with the corresponding enclosures is a measure in the sense of the cause, but the possibilities and the acceptance of the users are the measure of all things here. The "right conversion" should therefore always be related to the transmission bandwidth of a certain loudspeaker size. There is no other way, because each loudspeaker represents a size limitation.
Subwoofer[edit]
Subwoofers are usually limited with higher order filters, which causes a timing error. The basic idea of limiting subwoofers low and steeply sloping, because low tones are difficult to locate, is counteracted by the timing errors that occur. A subwoofer that is coupled with the correct impulse needs flat filters like all other loudspeakers and thus plays into the midrange.
Another reason for bad timing is due to different travel times from the subwoofer and the main speakers to the listening position(s), which can only be compensated to a limited extent by electronic time delays. Bass impulses are locatable. And if they do not resonate at the same time and in phase with the overall signal, subwoofers are locatable. Rhythm errors regularly occur when subwoofers are used. Therefore, the recommendation is to do without them if possible.
Conclusion[edit]
The concept behind a loudspeaker design ultimately determines the result. There is a multitude of applications and user requirements that have to be taken into account when planning a model. In particular, there are aspects that enter into a design as specifications / restrictions on the part of potential buyers, such as the size, shape, price range, design, sound preferences, etc.. The insight from decades of loudspeaker development is that a loudspeaker designed according to all rules of the art would be almost unsaleable. Price, brand and design are the primary decision criteria of the "normal" customer. For mass manufacturers, many technical solutions are therefore out of the question, as they are simply not accepted. A manufacture like Myro, on the other hand, which also produces individual pieces, can respond to individual wishes that are excluded in mass production.
Terms for describing sound[edit]The sonic nature of signal / time accurate sound transducers can be summarized under the term reality impression. Differentiated the following aspects are to be emphasized:
The vocabulary for sound descriptions is largely exhausted in the field of conventional loudspeaker descriptions.
Thus, an attempt is made to describe the aspects in more detail by analogies and examples. Impulse Dynamics This does not refer to how loud it pops when the drummer hits his drums. Rather, you hear the impulse dynamics in the clarity of the attack, in the lightning-like intensity. The attack doesn't stutter, doesn't get muddled. Impulse timbre With old pianos, you often have the problem of worn action. A worn hammer felt, for example, will make the attack of otherwise intact piano strings sound out of tune. Very similar to this, piano string strokes sound distorted in speakers with distorted transient reproduction. Spatiality With speakers that are not signal / time correct, the impression of space is like looking through a more or less large, differently shaped window, with more or less clear window glass. With a signal / time correct loudspeaker it seems as if everything, including oneself, is outside in the open air. This impression can be affected by phase / time errors within the recording and within the rest of the playback chain, or by very strong early reflections. The loudspeaker itself does not create the impression of spatial boundedness. Time relations of fundamental to harmonics If a bartender mixes us a cocktail and combines all the aromas and flavors into a delicious whole, but we turn to this cocktail only after an hour-long bar conversation, then the different components have partially separated again, settled. We taste then for example at the first sip a sour note, followed by some bitterness and a sticky sweet sediment. Atmosphere As an example, the processing of a recording in a church, 16 bit / 44.1 kHz output format. There was a basic noise level to be discerned, the cause of which was not clearly definable, somehow disturbing, and it pushed itself between the tones. Overall, there was a mixture of sharpness and jamminess in the sound. The consequence was the use of a noise filter and the recording was smooth and free of noise. The cause, however, was a lack of resolution of the subtle sound components, a lack of fine dynamics, disturbed time relationships. |
<zurück: Myroklopädie>
<zurück: Myro>