Difference between revisions of "Why Is There No Impulse Right Speaker With High Efficiency?"
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==== Was sagt der Wirkungsgrad aus? ====
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=== What does the efficiency rate say? ===
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Ein nominal hoher Wirkungsgrad bei Kleinsignalanregung besitzt keine Aussage. Oftmals wird ein besonders hoher Wirkungsgrad bei einer besonders günstigen Frequenz angegeben. Der Kennschalldruck definiert den mittleren Schalldruck jedoch im Mitteltonbereich. Ein Lautsprecher mit hohem Kennschalldruck kann also durchaus einen niedrigen ("Kenn-")Schalldruck im Bassbereich oder im Hochtonbereich haben. Die Angabe gilt demnach nicht für die gesamte Bandbreite, insbesondere nicht für den Tiefton, ist irreführend und ermöglicht keinen Vergleich von Lautsprechern ohne die Berücksichtigung weiterer Parameter. Chassis mit hohem Wirkungsgrad haben diesen zum Beispiel oftmals durch Verwendung einer kurzen Schwingspule und leichter Papiermembranen. Der maximal erzielbare Schalldruck leidet darunter. Zudem spielt die Linearität des Magnetfeldes (B-Feld) eine entscheidende Rolle und auch die Linearität der bewegten Teile. Dies führt zu nichtlinearem Hub mit starken Verzerrungen und membranbedingt zu frühzeitig ungleichmäßigem Abfall der dynamischen Phase.<br />
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A nominal high efficiency at small signal excitation has no statement. Often a particularly high efficiency is indicated at a particularly favorable frequency. However, the characteristic sound pressure defines the average sound pressure in the midrange. A loudspeaker with a high characteristic sound pressure can therefore have a low ("characteristic") sound pressure in the bass range or in the high frequency range. The specification is therefore not valid for the entire bandwidth, especially not for the low frequency range, is misleading and does not allow a comparison of loudspeakers without taking other parameters into account. Drivers with high efficiency often have this, for example, by using a short voice coil and light paper cones. The maximum achievable sound pressure suffers from this. In addition, the linearity of the magnetic field (B-field) plays a decisive role, as does the linearity of the moving parts. This leads to non-linear excursion with strong distortions and, due to the diaphragm, to an early uneven drop of the dynamic phase.<br />
  
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Zeitrichtige Lautsprecher sind wegen der hohen Impulsamplituden lauter als andere vergleichbare Lautsprecher. Musik ist ein dynamisches Ereignis. Für das Lautstärkeempfinden sind die Transienten (Einschwingvorgänge) von besonderer Bedeutung. Die Nervenaktivität des Hörsinns ist bezogen auf die Transienten stark erhöht und der Hörsinn hat dabei seine höchste Empfindlichkeit. Lautsprechermessungen sollten dies berücksichtigen, erfolgen aber in der Regel im eingeschwungenen Zustand.
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Time-directed loudspeakers are louder than other comparable loudspeakers because of the high impulse amplitudes. Music is a dynamic event. The transients (transient processes) are of particular importance for the perception of loudness. The nerve activity of the auditory sense is strongly increased in relation to the transients and the auditory sense has its highest sensitivity. Loudspeaker measurements should take this into account, but are usually carried out in the steady state.
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Das begründet, warum zwei unterschiedliche Lautsprechermodelle mit zum Beispiel gleichem Kennschalldruck, mit Musik angeregt, durchaus unterschiedlich laut wiedergeben können. '''Eine zeitrichtige Summenbildung klingt aufgrund der höheren Impulsamplituden lauter als eine nicht zeitrichtige bei ansonsten gleichem Wirkungsgrad im eingeschwungenen Zustand.'''  
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This justifies why two different loudspeaker models with, for example, the same characteristic sound pressure, excited with music, can certainly reproduce differently loudly. '''A time-corrected summation sounds louder than a non-time-corrected one with otherwise the same efficiency in steady state due to the higher impulse amplitudes.'''  
  
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Einen Hinweis darauf liefert die Sprungantwort beider Modelle.
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The step response of both models provides an indication of this.
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Wenn die Konstruktion dabei nicht zeitrichtig funktioniert, verschenkt man Energie in den Impulsspitzen, den Transienten. Das Modell mit der korrekten Sprungantwort bietet mehr Energie pro Zeit, summiert richtig, erzeugt deutlich höhere Amplituden im Einschwingvorgang, ist somit lauter und effizienter.  
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If the design is not correct in time, energy is wasted in the impulse peaks, the transients. The model with the correct step response provides more energy per time, sums correctly, produces significantly higher amplitudes in the transient, and is therefore louder and more efficient.  
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Modelle mit fehlerhaften Sprungantworten strecken den Energiegehalt über die Zeit und schaffen dabei nicht mehr die möglichen Maximalamplituden im Einschwingvorgang. Der "impulsdynamische Wirkungsgrad" sinkt damit. Die Impulse / Transienten sind aber die lautesten Ereignisse in der Musik!
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Models with incorrect step responses stretch the energy content over time and in the process no longer create the possible maximum amplitudes in the transient. The "impulse dynamic efficiency" decreases with it. But the impulses / transients are the loudest events in music!
  
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Die Angabe des Kennschalldrucks gibt also keine verlässliche Auskunft über die Effizienz eines Lautsprechers. Erst im Zusammenhang mit dynamischen Messungen kommt man der Wahrheit näher. <br />
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The indication of the sound pressure level does not give any reliable information about the efficiency of a loudspeaker. Only in connection with dynamic measurements one comes closer to the truth. <br />
  
 
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''[[Myro Amur C]]''
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''[[Myro Amur C]]'''
 
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==== Der Hochton ====
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=== The tweeter ===
  
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Im Hochtonbereich (Grenzfrequenz 20 kHz) wird man ohne eine parasitäre Membranresonanz kaum über 90 dB/Wm kommen. Wenn die Membranresonanz zum Beispiel bei 20 kHz liegt und wenig bedämpft ist, dann surrt der Hochtöner oben stark und schafft im Bereich der Resonanzspitze vielleicht 95 dB/Wm. Aber welcher audiophile Hörer möchte sich eine solche Konstruktion anhören? Darf darum schon bei 15 kHz Schluss sein? Zudem steht der durch Resonanz abgedeckte Frequenzbereich für die Impulswiedergabe nicht zur Verfügung.<br />
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In the high frequency range (cut-off frequency 20 kHz) one will hardly get above 90 dB/Wm without a parasitic membrane resonance. However, a resonance is not a (sensible) usable sound pressure, it is the worst possible area (slow decay, phase rotation, high distortion). For example, if the diaphragm resonance is at 20 kHz and is not very damped, the tweeter will hum strongly at the top and might achieve 95 dB/Wm at the resonance peak. But which audiophile listener wants to listen to such a design? Should this be the end of the line at 15 kHz? Furthermore, the frequency range covered by resonance is not available for impulse reproduction.<br />
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Abhilfe schafft mitunter - auch im Mitteltonbereich - der Einsatz von Hornlautsprechern. Dies führt jedoch zu starken Phasendrehungen an den Übertragungsenden.  
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Sometimes the use of horn loudspeakers - also in the midrange - can be a remedy. However, this leads to strong phase rotations at the transmission ends.  
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==== Mittel- und oberer Tiefton ====
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=== Midrange and upper bass ===
  
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Wenn man einen Lautsprecher so konstruiert, dass er ein Bandpass mit weniger Bandbreite ist, dann erhöht man sozusagen die Güte und bekommt einen Mittenbuckel. Das heißt, der Schalldruckpegel in den Mitten steigt, an den Übertragungsenden sinkt er.
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If you design a speaker to be a bandpass with less bandwidth, you sort of increase the Q and get a midrange hump. That is, the sound pressure level in the mids goes up, and at the transmission ends it goes down.
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So kann man im mittleren Übertragungsbereich auf weit mehr als 90 dB/1Wm kommen. Das gilt im Prinzip für jedes einzelne Chassis. Durch eine Mehrwegekonstruktion mit schmalbandigen Einzelchassis kann man den Kennschalldruck in den von den Chassis abgedeckten Übertragungsbereichen erhöhen. Die Problematik der Grenzbereiche bleibt jedoch.
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So you can get well over 90 dB/1Wm in the midrange. In principle, this applies to every single driver. By using a multi-way design with narrow-band individual drivers, it is possible to increase the sound pressure level in the transmission ranges covered by the drivers. However, the problem of the limiting ranges remains.
 
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''[[Myro La Musica 2005]]''
 
''[[Myro La Musica 2005]]''
 
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==== Der Tiefton ====
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=== The low frequency ===
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Oftmals verzichten Konzepte mit hohem Wirkungsgrad auf Bandbreite. Damit kommt es zu frühen, steilen Phasendrehungen.  
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Often, high efficiency concepts forgo bandwidth. This results in early, steep phase shifts.  
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Wenn sie nicht auf Bandbreite verzichten und mehr als den Tiefgang einer kleinen Regalbox erreichen sollen, dann benötigen sie zwingend einen großdimensionierten Bass, denn die abgestrahlte Schalleistung hängt mit dem Strahlungswiderstand zusammen und dieser ist abhängig von der Membranfläche. (Die Strahlungsimpedanz ist in der Sprungantwort zu sehen.) Die akustische Leistung ist außerdem abhängig von der Membrangeschwindigkeit, also abhängig von der Frequenz und von der Güte der Resonanz des schwingenden Systems. Der Wirkungsgrad korreliert aber nicht ausschließlich mit der Membrangröße, denn Voraussetzung für einen hohen Wirkungsgrad sind bei sinnvoller Auslegung der Chassisparameter eine große Membranfläche ''und'' geringe bewegte Masse. Große Membranen mit geringer Masse sind tendenziell aber instabil und weisen Übertragungseigenschaften auf, die das Erreichen der anderen gesteckten Ziele erschweren oder unmöglich machen, z.B. die Auslegung der impulsrichtigen [[Filter]]. Zudem erfordert der Tiefbass bei deutlich über 90 dB/Wm ein Resonanzsystem (Bassreflex oder anderes). Macht man die Membran leicht (dünn und z.B. aus Pappe), dann schwingt sie nicht wirksam mit ihrer ganzen Größe, sondern bricht in Partialschwingungen auf. Eine leichte Membran stabil hinzubekommen, ist praktisch unmöglich. Die Folge sind völlig unkontrollierte Membranschwingungen, deren Interferenzen gegenphasige Schallwellen erzeugen und im Zusammenspiel mit anderen Chassis interagieren, bis hin zu Auslöschungen. Das widerspricht zudem einem hohen Wirkungsgrad. Es ist nicht die Zielstellung, ein beliebiges Schallgemisch zu erzeugen, bestehend aus Resonanzen, um möglichst viel Pegel zu erzeugen. Dies widerspricht zudem der Forderung nach einer präzisen Wiedergabe. <br />
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If they do not forgo bandwidth and are to achieve more than the low end of a small bookshelf speaker, then they necessarily need a large-dimension bass, because the radiated sound power is related to the radiation impedance and this depends on the diaphragm area. (The radiation impedance is also to be seen in the step response among many other properties). Acoustic power also depends on diaphragm velocity, so it depends on frequency and on the quality of resonance of the oscillating system. However, the efficiency does not correlate exclusively with the diaphragm size, because a prerequisite for a high efficiency is a large diaphragm area ''and'' low moving mass if the chassis parameters are sensibly designed. A strong drive essentially increases the efficiency in the midrange.
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Ein kleinerer, aber stabiler Bass kann dann unter Umständen einen Bass lauter wiedergeben. Tiefbass und Wirkungsgrad zusammen erreichen zu wollen, ist noch viel schwieriger. Daher werden die Lautsprecher mit "hohem Wirkungsgrad" im Bass hoch abgestimmt (Bassreflex / Hochpassfilter). Hilfreich dabei ist, dass der Schallanteil unter 50 Hz in der Musik bei verschwindend geringen Prozentsätzen liegt. Wenn ein Lautsprecher daher z.B. 95% des Geschehens erstklassig wandelt, dann ist schon viel erreicht.  
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A large diaphragm and low moving mass results in a large equivalent volume (VAS) and thus large enclosure volumes. However, large diaphragms with low mass tend to be unstable and exhibit transmission characteristics that make it difficult or impossible to achieve the other goals set, such as designing the [[filters]] to be in the correct impulse response. In addition, low bass at well above 90 dB/Wm requires a resonant system (bass reflex or otherwise). If you make the diaphragm light (thin and e.g. made of cardboard), it will not resonate effectively with its whole size, but will break up into partial oscillations. It is practically impossible to make a light membrane stable. The result is completely uncontrolled diaphragm oscillations, whose interferences generate sound waves in phase opposition and interact with other drivers, even to the point of cancelling them out. This also contradicts high efficiency. It is not the objective to produce an arbitrary sound mixture, consisting of resonances, in order to generate as much level as possible. This also contradicts the demand for precise reproduction. <br />
 +
A smaller but stable bass can then reproduce a bass louder under certain circumstances. To try to achieve low bass and efficiency together is even more difficult. That's why speakers with "high efficiency" are tuned high in the bass (bass reflex / high pass filter). But a relatively high tuned bass reflex has an unfavourable group delay and a correspondingly strong phase rotation in the high pass. This means: the signals are shifted more on the time plane. It's helpful to know that the sound portion below 50 Hz in music is at vanishingly small percentages. Therefore, if a loudspeaker converts e.g. 95% of what happens in a first-class way, then a lot has already been achieved.  
 
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Vorteil: Große Membranflächen sind in Bezug auf die Strahlungsimpedanz günstiger. Das bewirkt eine bessere Bassattacke (besseres Einschwingen). Die erste Halbwelle einer großen Membran ist in Relation zu den nachfolgenden Halbwellen in der Regel deutlich lauter und entspricht eher der Anregungsfrequenz als bei kleinen Membranen. Demzufolge verläuft der Graph der Sprungantwort ab der Startflanke flacher! Die Schnelligkeit ist dabei der günstigeren Strahlungsimpedanz geschuldet, aber nicht dem hohen Wirkungsgrad. Einen hohen Wirkungsgrad im Bassbereich mit gleichzeitig hoher Qualität kann man aus physikalischen Gründen nur mit einem großen Aufwand hinbekommen. Dazu braucht man vor allem eine große wirksame Membranfläche und ein entsprechend großes resonanzarmes Volumen mit stabilen Wandungen (wir sind hier im Bereich des Waschmaschinen-Formats) oder ein gigantisches Basshorn. Aber nicht jeder große Bass hat eine große wirksame Membranfläche!
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Advantage: Large diaphragm areas are more favourable in terms of radiation impedance. This results in a better bass attack (better transient response). The first half wave of a large diaphragm is usually much louder in relation to the following half waves and corresponds more to the excitation frequency than with small diaphragms. Consequently, the graph of the step response is flatter from the starting edge! The speed is due to the more favourable radiation impedance, but not to the high efficiency. A high efficiency in the bass range with high quality at the same time can only be achieved with a great effort for physical reasons. To achieve this you need a large effective diaphragm area and a correspondingly large low-resonance volume with stable walls (we're talking washing machine size here) or a gigantic bass horn. But not every big bass has a large effective diaphragm area!
  
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Bei "Hochwirkungsgrad-Lautsprechern" nimmt man also gezwungenermaßen unzählige, typische Fehler in Kauf. Hohe Belastbarkeit wird zudem durch steilflankige Filter ermöglicht. Diese vernichten jedoch die hohen Impulsamplituden und verzerren die Signalstrukturen.
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So with "high efficiency loudspeakers" one is forced to accept innumerable typical faults. High power handling is also made possible by filters with steep flanks. These, however, destroy the high impulse amplitudes and distort the signal structures.
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Daraus resultiert insgesamt der typische PA-Sound, der von derart gewöhnten Menschen mit "Live-Sound" assoziiert wird. Einen PA-Sound ohne diese Fehler gibt es praktisch nicht - denn dann wäre es kein PA-Sound mehr!
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All in all, this results in the typical PA sound that is associated with "live sound" by people who are used to it. A PA sound without these errors practically does not exist - because then it would no longer be a PA sound!
  
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Vereinfacht kann man folgendes Fazit ziehen (linearer Frequenzverlauf vorausgesetzt):
+
Simplified, one can draw the following conclusion (assuming a linear frequency response):
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*Eine große Übertragungsbandbreite, also hoher Wirkungsgrad im Tiefbass und im oberen Hochtonbereich, verlangt einen angepassten, relativ niedrigen Pegel im Mitteltonbereich.
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*A wide transmission bandwidth, i.e. high efficiency in the low bass and upper high frequency range, requires an adjusted, relatively low level in the midrange.
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*Eine geringe Übertragungsbandbreite ermöglicht einen höheren Kennschalldruck im Mitteltonbereich.
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A small transmission bandwidth allows a higher characteristic sound pressure in the midrange.
  
  

Latest revision as of 13:17, 31 October 2020

Template:Delete candidate

What does the efficiency rate say?[edit]

A nominal high efficiency at small signal excitation has no statement. Often a particularly high efficiency is indicated at a particularly favorable frequency. However, the characteristic sound pressure defines the average sound pressure in the midrange. A loudspeaker with a high characteristic sound pressure can therefore have a low ("characteristic") sound pressure in the bass range or in the high frequency range. The specification is therefore not valid for the entire bandwidth, especially not for the low frequency range, is misleading and does not allow a comparison of loudspeakers without taking other parameters into account. Drivers with high efficiency often have this, for example, by using a short voice coil and light paper cones. The maximum achievable sound pressure suffers from this. In addition, the linearity of the magnetic field (B-field) plays a decisive role, as does the linearity of the moving parts. This leads to non-linear excursion with strong distortions and, due to the diaphragm, to an early uneven drop of the dynamic phase.

Time-directed loudspeakers are louder than other comparable loudspeakers because of the high impulse amplitudes. Music is a dynamic event. The transients (transient processes) are of particular importance for the perception of loudness. The nerve activity of the auditory sense is strongly increased in relation to the transients and the auditory sense has its highest sensitivity. Loudspeaker measurements should take this into account, but are usually carried out in the steady state. This justifies why two different loudspeaker models with, for example, the same characteristic sound pressure, excited with music, can certainly reproduce differently loudly. A time-corrected summation sounds louder than a non-time-corrected one with otherwise the same efficiency in steady state due to the higher impulse amplitudes.

The step response of both models provides an indication of this. If the design is not correct in time, energy is wasted in the impulse peaks, the transients. The model with the correct step response provides more energy per time, sums correctly, produces significantly higher amplitudes in the transient, and is therefore louder and more efficient. Models with incorrect step responses stretch the energy content over time and in the process no longer create the possible maximum amplitudes in the transient. The "impulse dynamic efficiency" decreases with it. But the impulses / transients are the loudest events in music!

The indication of the sound pressure level does not give any reliable information about the efficiency of a loudspeaker. Only in connection with dynamic measurements one comes closer to the truth.

2341319742 g.jpg
Myro Amur C'

The tweeter[edit]

In the high frequency range (cut-off frequency 20 kHz) one will hardly get above 90 dB/Wm without a parasitic membrane resonance. However, a resonance is not a (sensible) usable sound pressure, it is the worst possible area (slow decay, phase rotation, high distortion). For example, if the diaphragm resonance is at 20 kHz and is not very damped, the tweeter will hum strongly at the top and might achieve 95 dB/Wm at the resonance peak. But which audiophile listener wants to listen to such a design? Should this be the end of the line at 15 kHz? Furthermore, the frequency range covered by resonance is not available for impulse reproduction.
Sometimes the use of horn loudspeakers - also in the midrange - can be a remedy. However, this leads to strong phase rotations at the transmission ends.

Midrange and upper bass[edit]

If you design a speaker to be a bandpass with less bandwidth, you sort of increase the Q and get a midrange hump. That is, the sound pressure level in the mids goes up, and at the transmission ends it goes down. So you can get well over 90 dB/1Wm in the midrange. In principle, this applies to every single driver. By using a multi-way design with narrow-band individual drivers, it is possible to increase the sound pressure level in the transmission ranges covered by the drivers. However, the problem of the limiting ranges remains.

P 100106.jpg
Myro La Musica 2005

The low frequency[edit]

Often, high efficiency concepts forgo bandwidth. This results in early, steep phase shifts. If they do not forgo bandwidth and are to achieve more than the low end of a small bookshelf speaker, then they necessarily need a large-dimension bass, because the radiated sound power is related to the radiation impedance and this depends on the diaphragm area. (The radiation impedance is also to be seen in the step response among many other properties). Acoustic power also depends on diaphragm velocity, so it depends on frequency and on the quality of resonance of the oscillating system. However, the efficiency does not correlate exclusively with the diaphragm size, because a prerequisite for a high efficiency is a large diaphragm area and low moving mass if the chassis parameters are sensibly designed. A strong drive essentially increases the efficiency in the midrange. A large diaphragm and low moving mass results in a large equivalent volume (VAS) and thus large enclosure volumes. However, large diaphragms with low mass tend to be unstable and exhibit transmission characteristics that make it difficult or impossible to achieve the other goals set, such as designing the filters to be in the correct impulse response. In addition, low bass at well above 90 dB/Wm requires a resonant system (bass reflex or otherwise). If you make the diaphragm light (thin and e.g. made of cardboard), it will not resonate effectively with its whole size, but will break up into partial oscillations. It is practically impossible to make a light membrane stable. The result is completely uncontrolled diaphragm oscillations, whose interferences generate sound waves in phase opposition and interact with other drivers, even to the point of cancelling them out. This also contradicts high efficiency. It is not the objective to produce an arbitrary sound mixture, consisting of resonances, in order to generate as much level as possible. This also contradicts the demand for precise reproduction.
A smaller but stable bass can then reproduce a bass louder under certain circumstances. To try to achieve low bass and efficiency together is even more difficult. That's why speakers with "high efficiency" are tuned high in the bass (bass reflex / high pass filter). But a relatively high tuned bass reflex has an unfavourable group delay and a correspondingly strong phase rotation in the high pass. This means: the signals are shifted more on the time plane. It's helpful to know that the sound portion below 50 Hz in music is at vanishingly small percentages. Therefore, if a loudspeaker converts e.g. 95% of what happens in a first-class way, then a lot has already been achieved.

Advantage: Large diaphragm areas are more favourable in terms of radiation impedance. This results in a better bass attack (better transient response). The first half wave of a large diaphragm is usually much louder in relation to the following half waves and corresponds more to the excitation frequency than with small diaphragms. Consequently, the graph of the step response is flatter from the starting edge! The speed is due to the more favourable radiation impedance, but not to the high efficiency. A high efficiency in the bass range with high quality at the same time can only be achieved with a great effort for physical reasons. To achieve this you need a large effective diaphragm area and a correspondingly large low-resonance volume with stable walls (we're talking washing machine size here) or a gigantic bass horn. But not every big bass has a large effective diaphragm area!

So with "high efficiency loudspeakers" one is forced to accept innumerable typical faults. High power handling is also made possible by filters with steep flanks. These, however, destroy the high impulse amplitudes and distort the signal structures. All in all, this results in the typical PA sound that is associated with "live sound" by people who are used to it. A PA sound without these errors practically does not exist - because then it would no longer be a PA sound!

Simplified, one can draw the following conclusion (assuming a linear frequency response):

  • A wide transmission bandwidth, i.e. high efficiency in the low bass and upper high frequency range, requires an adjusted, relatively low level in the midrange.

A small transmission bandwidth allows a higher characteristic sound pressure in the midrange.



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