Difference between revisions of "Resonances"

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== Allgemeines ==
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== General ==
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Resonanzen sind eine Ursache für Verzerrungen, das heißt von Abweichungen bei der Schallerzeugung gegenüber dem Eingangssignal. Es sind Energiespeichereffekte, die bei bestimmten Frequenzen in Membranen und Lautsprechergehäusen auftreten und Fehler in der Musikreproduktion erzeugen. Frequenzfilter und Gehäuse werden daher so entwickelt, dass Resonanzen möglichst gering auftreten. Jede Resonanz bewirkt auch eine zeitliche Verschiebung der zu übertragendem Töne. Resonanzen klingen außerordentlich aggressiv und verschmieren das Klangbild, die Transparenz geht verloren. Gleiches gilt für die Verständlichkeit.<br />
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Resonances are a cause of distortion, i.e. of deviations in sound generation compared to the input signal. They are energy storage effects that occur at certain frequencies in diaphragms and loudspeaker cabinets and create errors in music reproduction. Frequency filters and enclosures are therefore designed to minimize resonance. Every resonance also causes a temporal shift of the sounds to be transmitted. Resonances sound extremely aggressive and smear the sound image, transparency is lost. The same applies to intelligibility.<br />
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Als Energiespeicher sind Resonanzen zeitlich träge, sie können nicht spontan entstehen oder verschwinden. Sie treten damit nur im eingeschwungenen Zustand vollständig in Erscheinung. Während des Einschwingens eines Impulses hingegen wird die Resonanz noch mit Energie aufgeladen und macht sich erst verzögert bemerkbar. Dadurch wird dem Signal Energie entzogen. <br />
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As energy stores, resonances are temporally inert, they cannot spontaneously arise or disappear. Thus, they only become fully apparent in the steady state. During the transient of an impulse, on the other hand, the resonance is still charged with energy and only becomes noticeable with a delay. This removes energy from the signal. <br />
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Der Resonanzfall des schwingenden Systems Lautsprecher beinhaltet eine Zeitvariable. Somit ist die Hochpassfunktion nicht konstant. Bei der Messung der Impedanz eines Lautsprechers über die Zeit erkennt man, dass die Impedanzkurve bei der Resonanzfrequenz anfangs linear ist und die typische Impedanzüberhöhung sich erst im zeitlichen Verlauf ausbildet.
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The resonance case of the oscillating system loudspeaker contains a time variable. Thus the high pass function is not constant. When measuring the impedance of a loudspeaker over time, it can be seen that the impedance curve is initially linear at the resonance frequency and the typical impedance rise only develops over time.
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Bei der Messung mit Sinusperioden unterschiedlicher Frequenzen (Dynamic Measurement) erkennt man, dass das Verhältnis von erster zu zweiter Halbwelle ebenfalls nicht konstant ist, sondern dass sich bei der ersten Halbwelle ein hauptsächlich strahlungswiderstandsabhängiger Verlauf zeigt, während der Verlauf der zweiten Halbwelle schon durch den Einfluss der Resonanz des Systems mitbestimmt wird. Beim Abklingen des Impulses entlädt sich die Energie der Resonanz wieder, sodass sich das Abklingen verzögert und das Signal zeitlich gedehnt wird.
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When measuring with sinusoidal periods of different frequencies (dynamic measurement), it can be seen that the ratio of the first to the second half-wave is also not constant, but that the first half-wave shows a mainly radiation resistance-dependent curve, while the curve of the second half-wave is already determined by the influence of the resonance of the system. When the pulse decays, the energy of the resonance is discharged again, so that the decay is delayed and the signal is stretched in time.
  
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''(Ein anschauliches Beispiel für Resonanzen als Energiespeicher ist auch der Mikrowellengrill. Dabei wird das Essen mit der Resonanzfrequenz des Wassers bestrahlt, welches damit in Resonanz gerät, die Energie aufnimmt und sich erhitzt. Da Wasser der größte Bestandteil jeder Nahrung ist, wird das Essen damit insgesamt erhitzt.)''
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''(An illustrative example of resonances as energy storage is also the microwave grill. Here, food is irradiated with the resonant frequency of water, which resonates with it, absorbs the energy and heats up. Since water is the largest component of any food, this heats the food as a whole)''
 
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[[Datei:29332421.jpg]]<br />
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[[File:Concert Monitor.jpg]]<br />
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''[[Myro Elypticon]]''
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''[[Myro Elypticon]]'''
 
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{| class="wikitable" border="1"
 
{| class="wikitable" border="1"
 
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| [[Datei:Wild Thing 2.jpg]]<br />
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| [[File:Concert Monitor.jpg]]<br />
 
''[[Myro Wild Thing II]]''
 
''[[Myro Wild Thing II]]''
 
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== Membranresonanzen ==
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== Membrane resonances ==
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Die Membranen sind akustische Schwachstellen des Gehäuses: Sie sind dünn, schalldurchlässig und resonieren. Da Membranen nicht ideal steif sind, schwingen außenliegende Membranteilflächen anders als innenliegende und dies auch noch vagabundierend chaotisch. Zudem breiten sich innerhalb jedes Membranmaterials Körperschallschwingungen aus, die eine andere Schallgeschwindigkeit haben als der Schall in der Luft. Dies führt an gewissen Orten der Membran oder auch der Randaufhängung zu einer komplexen Interaktion.  
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The diaphragms are acoustic weak points of the cabinet: they are thin, permeable to sound, and resonate. Since diaphragms are not ideally stiff, outer diaphragm sub-surfaces resonate differently than inner ones, and do so vaguely chaotically. In addition, structure-borne sound vibrations propagate within each membrane material, which have a different sound velocity than the sound in the air. This leads to a complex interaction at certain locations of the membrane or even the edge suspension.  
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Jedes Material, das in Schwingung versetzt wird, schwingt auf seiner(n) Eigenresonanz(en) aus, d.h. es reagiert auf eine Anregung durch ein Spektrum von Eigenschwingungen. Dieses Spektrum gibt den Lautsprechermembranen ihren Eigenklang. Die Anregung kann durch eine mechanische Kraftübertragung oder durch akustische Energie von außen (Schallwellen) erfolgen. Resonanzen können bereits durch geringe Energie angeregt werden. Der Resonanzfall, gleich welcher Art, ist unbedingt zu vermeiden!<br />
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Any material that is vibrated will resonate at its natural resonance(s), that is, it will respond to excitation by a spectrum of natural vibrations. This spectrum gives the loudspeaker diaphragms their inherent sound. The excitation can be caused by a mechanical force transmission or by acoustic energy from outside (sound waves). Resonances can already be excited by low energy. The resonance case, no matter what kind, must be avoided at all costs!<br />
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Die generellen Anforderungen an eine Lautsprechermembran lauten: Sie soll im Wesentlichen leicht, steif und mit hoher innerer Dämpfung versehen sein. Da sich diese Forderungen konstruktiv gegenseitig widersprechen, sind Membranmaterialien stets kompromissbehaftet. Jede Lautsprechermembran erzeugt Membranresonanzen. Deren Anzahl und die Ausprägung sind bei unterschiedlichen Chassis-Typen und Membrandurchmessern sehr unterschiedlich.  
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The general requirements for a loudspeaker diaphragm are: it should essentially be light, stiff and have a high internal damping. Since these requirements contradict each other constructively, diaphragm materials are always subject to compromise. Every loudspeaker diaphragm generates diaphragm resonances. The number of resonances and their characteristics vary greatly between different types of drivers and diaphragm diameters.  
  
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* Bei harten Membranen liegen die Resonanzen in einem höheren Frequenzbereich als bei weicheren Membranen. Sie weisen eine geringere innere Dämpfung auf, schwingen dafür aber im eigentlichen Nutzbereich kolbenförmig, ohne Resonanzerscheinungen. Partialschwingungen gibt es bei Hartmembranen in der Regel erst oberhalb des Haupteinsatzbereiches. Sie können sehr stark ausgeprägt und sehr komplex sein. In jedem Fall ist es hilfreich, diese Chassis nicht bis zum Allerletzten auszureizen und die Trennfrequenzen lieber mit einer oder mehreren Oktaven Abstand zu legen. Bei einem extrem steifen Schwingspulenträger (z.B. Titan), einem günstigen Ansatzbereich an der Membran, einer extrem steifen Membran (Keramik, Diamant, Beryllium) und einer hohen Magnetfeldsättigung im Luftspalt ist die direkte Koppelung der Antriebsenergie an die Luft mit Konuschassis hervorragend möglich.
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* With hard diaphragms the resonances are in a higher frequency range than with softer diaphragms. They have a lower internal damping, but vibrate piston-like in the actual useful range, without resonance phenomena. Partial vibrations of hard diaphragms usually only occur above the main operating range. They can be very pronounced and very complex. In any case, it is helpful not to push these drivers to the limit and rather space the crossover frequencies one or more octaves apart. With an extremely stiff voice coil former (e.g. titanium), a favourable starting range at the diaphragm, an extremely stiff diaphragm (ceramic, diamond, beryllium) and a high magnetic field saturation in the air gap the direct coupling of the drive energy to the air is excellently possible with cone drivers.
  
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* Weichmembranen weisen eine hohe innere Dämpfung auf, neigen dafür aber im eigentlichen Nutzbereich zu Partialschwingungen mit ihren komplexen Resonanzerscheinungen. Membranen mit einer hohen inneren Dämpfung schwingen weniger stark auf ihren Eigenresonanzen als Chassis mit geringer innerer Dämpfung. Allerdings liegen die Membranresonanzen in der Regel in einem tieferen Frequenzbereich, im eigentlichen Nutzbereich der Chassis.
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Soft membranes have a high internal damping, but tend to produce partial oscillations with their complex resonance phenomena in the actual useful range. Diaphragms with a high internal damping oscillate less strongly on their own resonances than drivers with low internal damping. However, the diaphragm resonances are usually in a lower frequency range, in the actual useful range of the chassis.
  
  
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Bei der Auswahl von Chassis gilt die Aufmerksamkeit diesbezüglich:<br />
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When selecting drivers, attention should be paid to:<br />
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1. dem schwingenden System aus Masse, Aufhängung und elektromagnetischem Antrieb sowie<br />
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1. the oscillating system of mass, suspension and electromagnetic drive as well as<br />
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2. der Verformung der Membran (ebenso von Sicke und Spider) und<br />
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2. the deformation of the membrane (as well as the surround and spider) and<br />
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3. den Membranresonanzen.<br />
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3. the diaphragm resonances.<br />
 
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Membranresonanzen sind ein komplexes Phänomen. Sie erzeugen im wesentlichen den für ein Membranmaterial typischen Eigenklang und können zeitvariant oder zeitinvariant sein. Nur in dem letztgenannten Fall können die Myro-typischen Frequenzfilter zur Korrektur eingesetzt werden. <br />
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Membrane resonances are a complex phenomenon. They essentially produce the inherent sound typical for a membrane material and can be time-variant or time-invariant. Only in the latter case can the Myro-typical frequency filters be used for correction. <br />
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Will man den Membraneigenklang eliminieren, werden mehr oder weniger aufwändige Filter notwendig. Eine störende Membranresonanz zu eliminieren, klingt immer besser als es nicht zu tun. Wenn ein Chassis eine restlos bedämpfte Eigenresonanz hätte, dann entspräche sein Übertragungsverlauf dem Wirkanteil der Strahlungsimpedanz. Die Filterschaltungen dafür sind kein Problem, kritische Lautsprecherchassis dagegen schon. In einigen Fällen kann es dabei zu Impedanzminima unter 4 Ohm kommen. Diese sind in der Regel aber schmalbandig und in Frequenzbereichen, in denen seitens des Verstärkers wenig Leistung abverlangt wird. Die Membranresonanzen sind aber nicht unter allen Abstrahlwinkeln gleich bzw. wirken sich überhaupt aus. Korrigiert man sie unter einem bestimmten Abstrahlwinkel, also in Bezug auf einen bestimmten Punkt, so schlägt diese Korrektur unter anderen Winkeln durchaus ins Gegenteil um.<br />
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If you want to eliminate the inherent membrane sound, more or less complex filters are necessary. Eliminating a disturbing diaphragm resonance always sounds better than not doing it. If a chassis had a completely damped natural resonance, then its transmission curve would correspond to the effective part of the radiation impedance. The filter circuits for this are not a problem, but critical loudspeaker drivers are. In some cases impedance minima below 4 Ohm can occur. However, these are usually narrow-banded and in frequency ranges where little power is demanded from the amplifier. The diaphragm resonances are not the same at all dispersion angles or have any effect at all. If they are corrected at a certain dispersion angle, i.e. in relation to a certain point, this correction may well turn into the opposite at other angles.<br />
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Das Ergebnis ist ein Lautsprecher praktisch ohne verfälschenden Eigenklang. ''(Lässt sich der Eigenklang der Membranen nicht vollständig eliminieren, so fügen sich gleich- (eigen-)klingende Typen oft besser zusammen. Die Teilbereiche des Übertragungsspektrums klingen dann ähnlich verfärbt und das ergibt einen Eindruck von Stimmigkeit, von Harmonie.)'' Das ist die Vorausetzung dafür, dass es tonal keine störenden Verfärbungen gibt und der Lautsprecher damit als Eigenschallquelle nicht mehr wahrnehmbar ist. Bei richtiger Schallsummenbildung, zusammen mit dem Hochtöner und eentuell eingesetztem Bass, gilt das für den gesamten Lautsprecher, natürlich vorausgesetzt, dass keine anderen Eigengeräusche wie Gehäuseresonanzen (Innenraumreflexionen und -resonanzen / Gehäusematerialresonanzen) oder sonstige Schnarr- und Klappergeräusche auffällig werden.
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The result is a loudspeaker with practically no distorting inherent sound. ''(If the inherent sound of the diaphragms cannot be completely eliminated, types with the same (inherent) sound often blend together better. The partial ranges of the transmission spectrum then sound similarly coloured and this gives an impression of coherence, of harmony.)'' This is the prerequisite for there being no tonally disturbing colourations and the loudspeaker thus no longer being perceptible as an intrinsic sound source. If the sound sum is correct, together with the tweeter and eentually used bass, this applies to the entire loudspeaker, provided of course that no other inherent noises such as cabinet resonances (interior reflections and resonances / cabinet material resonances) or other buzzing and rattling noises become noticeable.
  
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Bei Membranmaterialien, die langzeitstabil sind, bleiben auch die Membranresonanzen in Frequenz und Güte recht stabil. Membranen jedoch, die temperatur- und vor allem feuchtigkeitsempfindlich sind oder zur Korrosion neigen, sind die Verhältnisse weniger stabil. Solche Membranen zeigen oftmals ein Resonanzverhalten, das zeitvariant und somit schlecht oder gar nicht korrigierbar ist. Mit zeitvariant ist hier gemeint, dass eine Membranresonanz zuerst einschwingt, dann durch gegenphasige Schwingungen in sich zusammenbricht und anschließend wieder auflebt, wobei sich in der Regel in diesem Vorgang keine stabile Resonanzfrequenz einstellt. Dies alles geht innerhalb weniger Millisekunden vor sich. Solch einen Vorgang kann ein Filter nicht korrigieren. <br />
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With diaphragm materials that are stable over a long period of time, the diaphragm resonances also remain quite stable in frequency and quality. Diaphragms, however, that are sensitive to temperature and especially humidity or that tend to corrode, the conditions are less stable. Such membranes often exhibit resonance behavior that is time-variant and thus difficult or impossible to correct. By time-variant is meant here that a diaphragm resonance first settles, then collapses due to counter-phase oscillations and then revives, whereby as a rule no stable resonance frequency is established in this process. All this happens within a few milliseconds. Such a process cannot be corrected by a filter. <br />
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Breitbänder bilden unter den Chassis einen Sonderfall und enthalten über einen weiten Bereich im Hochton ausschließlich Resonanzen als Teil des Konzeptes, wo sie zwar einen Pegel, aber keine Musikinformation liefern.
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[[Are full-range drivers optimal?|Broad-range drivers]] are a special case among drivers and contain exclusively resonances over a wide range in the high frequency range as part of the concept, where they provide a level but no musical information.
  
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[[Datei:Mundorf AMT 26 myro-V2 1.jpg]]<br />
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[[File:Concert Monitor.jpg]]<br />
 
''[[Mundorf AMT26-Myro-V2]]''
 
''[[Mundorf AMT26-Myro-V2]]''
  
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=== Harte Membranen ===
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=== Hard membranes ===
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Harte Membranen verschieben die Resonanzen an das obere Ende ihres Übertragungsbereichs oder darüber hinaus, allerdings sind sie dort ausgeprägter mit extrem hoher Güte auf und erfordern entsprechende Korrekturfilter. Der Frequenzgang fällt in der Regel vorher ab, entspricht somit nahezu der idealtypischen Übertragungsfunktion eines Chassis dieser Größe. Es gilt vereinfacht: Je härter das Material, desto höherfrequent die Membranresonanzen. Selten findet man dabei eindeutige Bezüge von Grundwelle zu Oberwellen und zu Subharmonischen. Bei Diamant-, Beryllium- und Keramikmembranen sind diese Beziehungen jedoch erkennbar. Die Partialschwingungen einer Membran, also die Eigenschwingungen von Teilflächen der Membran, sind aber zeitvariant und mit einfachen Modellen nicht beschreibbar.<br />
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The use of hard diaphragms provides better power transfer to the air and thus improves impulse response. However, if one uses the usual standard filters in the crossover, such as non-matching 1st order filters (6 dB/oct) or even 2nd (12 dB/oct) or 3rd order impulse destroyers (18 dB/oct), then the advantage of hard diaphragms is nullified. The result is harshness of a special kind. The impulse distortion of these filters and delay errors within the construction, as well as the combination of drivers that do not match each other, produce distortions that sound hard. But these can also be produced with softer diaphragms.<br>
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Bei steifen Materialien schwingen die Resonanzen über die Zeit gleichmäßig aus. Im Wasserfalldiagramm ist dabei ein gleichmäßiger, frequenzstabiler "Gebirgszug" zu erkennen. Die Sprungantwort zeigt dementsprechend eine gleichmäßige Welligkeit des Graphen. Ein Notchfilter beseitigt diese Welligkeit restlos, wobei zu beachten ist, dass die Anregung durch ein extrem breitbandiges Signal erfolgt, in dem alle Frequenzen der Übertragungsbandbreite des Chassis enthalten sind. Außerdem ist auf Serienstreuungen zu achten.
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Hard diaphragms shift the resonances to the upper end of their transmission range or beyond, but there they are more pronounced with extremely high Q and require appropriate correction filters. The frequency response usually drops off before this point, thus almost corresponding to the ideal typical transfer function of a driver of this size.
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A closer look at the result, however, shows that even with higher order filters, the diaphragm resonances will cut through and produce the typical long after resonance. These are also harshness, a sharp buzz that is added to the sound with each excitation. Hardening is therefore usually a result of errors! If, on the other hand, the advantages of stiff diaphragms are used and their resonances are damped, the speakers sound neutral. Simplified: the harder the material, the higher the diaphragm resonances. It is rare to find a clear relationship between the fundamental wave and harmonics and subharmonics. In the case of diamond, beryllium and ceramic diaphragms, however, these relationships are recognizable. The partial oscillations of a membrane, i.e. the natural oscillations of partial surfaces of the membrane, are time-variant and cannot be described with simple models.<br />
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In the case of stiff materials, the resonances oscillate evenly over time. In the waterfall diagram, a uniform, frequency-stable "mountain range" can be seen. The step response accordingly shows a uniform ripple of the graph. A notch filter eliminates this ripple completely, whereby it is to be noted that the excitation takes place by an extremely broadband signal, in which all frequencies of the transmission bandwidth of the chassis are contained. In addition, attention must be paid to series scattering.
  
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=== Weiche Membranen ===
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=== Soft diaphragms ===
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Weiche Membranen mit hoher innerer Dämpfung zeigen ebenfalls eine Vielzahl von Eigenresonanzen. Sie sind aber auch stärker bedämpft, daher mit geringerer Güte und in der Regel auch in niedrigeren Frequenzbereichen zu finden als bei harten Membranen. Sie liegen darum im Übertragungsbereich und erwecken mitunter sogar den Eindruck, der nutzbare Übertragungsbereich wäre zu hohen Frequenzen hin ausgedehnter. Weiche Membranen reagieren zudem kritischer auf die Sicken-Resonanz (Resonanz der Randaufhängung) als harte Membranen.<br />
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Soft diaphragms with high internal damping also exhibit a variety of natural resonances. They are however also more strongly damped, therefore with smaller quality and usually also in lower frequency ranges to find than with hard diaphragms. They are therefore in the transmission range and sometimes even give the impression that the usable transmission range is more extended towards high frequencies. Soft diaphragms also react more critically to bead resonance (resonance of the edge suspension) than hard diaphragms.<br />
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Die Partialschwingungen sind extrem komplex und aufgrund ihrer Zeitvarianz eingangsseitig durch Filter nicht eindeutig nachbildbar und verminderbar. Zudem gibt es Partialschwingungen, die zusammen mit den Membranresonanzen auftreten. So ergibt sich ein zeitvarianter Mix mit einem über die Zeit auf- und abschwellenden Verlauf. Partialschwingungen treten minimal verzögert ein und wirken nicht direkt auf das Einschwingen. In deren Entstehungsprozess nimmt die Spannung der "Federn" der einzelnen Membransegmente Energie aus der Vorwärtsbewegung. Dies ist vor allem ein Problem weicher und wenig steifer Membranen im Allgemeinen. Die Schwingspule taucht bei nachgiebigen Membranen, insbesondere bei schnellen, impulsartigen Vorgängen, in die Membran ein und verformt diese. Dadurch geht Energie verloren, die Impulse werden verzögert und die eingetragene Energie wird in Wärme oder nachfolgende Restschallwellen gewandelt, die mit dem Direktschall interferieren.<br />
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The partial oscillations are extremely complex and, due to their time variance, cannot be clearly reproduced and reduced by filters on the input side. In addition, there are partial oscillations that occur together with the diaphragm resonances. This results in a time-variant mix with an upward and downward swelling over time. Partial oscillations occur with a minimal delay and do not directly affect the transient response. In their generation process, the tension of the "springs" of the individual membrane segments takes energy from the forward motion. This is mainly a problem of soft and not very stiff diaphragms in general. The voice coil dips into and deforms the diaphragm in compliant diaphragms, especially in fast, impulsive processes. As a result, energy is lost, the impulses are delayed and the energy introduced is converted into heat or subsequent residual sound waves that interfere with the direct sound.<br />
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Ein weit verbreitetes Phänomen bei weichen Membranen ist die sogenannte Midrange-(Edge)-Resonanz.
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A common phenomenon with soft membranes is the so-called midrange (edge) resonance.
  
  
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'''Die Plüschmembran'''<br />
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'''The plush diaphragm'''<br />
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... gibt es aus guten Gründen zwar nicht, sie hätte aber durchaus einen Vorteil. Denn Koaxiallautsprecher werden gern als Annäherung an die Punktschallquelle verwendet und haben dahingehend unbestreitbare Vorteile. Sie enthalten aber auch das Dilemma zwischen den Vor- und Nachteilen der harten und weichen Membranen, denn sie haben stets ein Problem: Der Hochtöner gibt mitten im Zentrum mit vollem Pegel Impulse und Frequenzen auf die Mitteltieftonmembran, so dass diese wie eine Klangschale angeschlagen wird und resoniert. Entsprechende Nichtlinearitäten sind die Folge. Je härter das Material, desto ausgeprägter der Effekt. Und leider liegen diese Membranresonanzen der Mitteltieftonmembranen genau im Übertragungsbereich des Hochtöners. Für Koaxialkonzepte sind also mehr oder weniger weiche Membranen erforderlich, um den Effekt zu begrenzen. Da harte Membranen aber eigentlich akustisch im Vorteil sind, lässt sich dieser Zielkonflikt nicht auflösen. Eine Plüschmembran wäre, allein unter diesem Aspekt betrachtet, also vorteilhaft. <br />
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... does not exist for good reasons, but it would have an advantage. After all, coaxial speakers are popularly used as an approximation of the point source and have undeniable advantages in that regard. But they also contain the dilemma between the advantages and disadvantages of hard and soft diaphragms, because they always have one problem: the tweeter gives impulses and frequencies to the midrange / bass diaphragm in the centre at full level, so that the diaphragm is struck like a sound bowl. It excites the diaphragm resonances of the midrange / bass diaphragm and these movements build up to resonances. This causes the diaphragm, as the sound source, to radiate sound waves that add or subtract, depending on the time correlation to the high frequency sound. We can see this in the diagrams.
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Die Anregungen durch den Hochton-Schalldruck lassen sich auf der Frequenzskala mit jenen vergleichen, die der Konus bei Anregung via eigener Schwingspule zeigt. Denn wenn man den Hochtöner allein misst, dann regt er die Membranresonanzen der Mitteltieftonmembran an. Dadurch gerät die Membran in Bewegung und diese Bewegungen schaukeln sich zu Resonanzen auf.
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Dadurch strahlt die Membran als Schallquelle Schallwellen ab, die sich, je nach zeitlicher Korrelation zum Hochtonschall, addieren oder subtrahieren. Dieser Effekt lässt sich messtechnisch zeigen.<br />
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The harder the material, the more pronounced the effect. And unfortunately these diaphragm resonances of the mid-woofer diaphragms lie exactly in the transmission range of the tweeter. So coaxial designs require more or less soft diaphragms to limit the effect. But since hard diaphragms are actually acoustically advantageous, this conflict of objectives cannot be resolved. A plush diaphragm would therefore be advantageous, considered from this aspect alone. <br />
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Die Problematik wird immer auch dann bemerkbar sein, wenn Chassis nah beieinander platziert sind, von denen mindestens eines in den Resonanzbereichen des anderen arbeitet. Der Schalldruck der Anregung ist jedoch um viele Dezibel geringer als bei einem Koaxialchassis.<br />
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The excitations by the tweeter sound pressure can be compared on the frequency scale with those shown by the cone when excited via its own voice coil. This is because when the tweeter is measured on its own, it excites the diaphragm resonances of the mid-woofer cone. This causes the diaphragm to move and these movements build up to resonances.
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Die folgenden Bilder zeigen die Messungen von Seas Koaxialchassis, wie sie in verschiedenen Modellen, z.B. dem [[Myro Coax Monitor]], zum Einsatz kamen. Hier ist eindeutig die Korrelation der Mittelton-Membranresonanzen mit den Nichtlinearitäten des Hochton-Frequenzgangs zu sehen. Überall dort, wo die Mitteltonmembran eine Resonanz ausbildet, gibt es eine Interaktion mit dem vom Hochtöner abgestrahlten Schall.
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As a result, the diaphragm, as the sound source, emits sound waves that add or subtract, depending on their temporal correlation to the high-frequency sound. This effect can be demonstrated by measurement.<br />
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The problem will always be noticeable when drivers are placed close together, at least one of which operates in the resonance ranges of the other. However, the sound pressure of the excitation is many decibels lower than with a coaxial chassis.<br />  
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{| class="wikitable" border="1"
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<gallery>
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F Seas Excel loudspeaker coaxial E0051 C16N001 F--2.jpg|Magnesium membrane
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</gallery>
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<gallery>
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F Seas Prestige loudspeaker coaxial H1602 L12RE XFC--2.jpg|Aluminium diaphragm
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</gallery>
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F Seas Excel loudspeaker coaxial E0051 C16N001 F--2.jpg|Magnesium Membran
 
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F Seas Prestige loudspeaker coaxial H1602 L12RE XFC--2.jpg|Aluminium Membran
 
 
F-Seas-Prestige-loudspeaker-coaxial-H1699-MR18REX-XF 450x274 22265fac69b71c4500846059914f50f3.jpg|Reed-Paper-Membran
 
F-Seas-Prestige-loudspeaker-coaxial-H1699-MR18REX-XF 450x274 22265fac69b71c4500846059914f50f3.jpg|Reed-Paper-Membran
 
</gallery>
 
</gallery>
−
''Quelle: Fa. Seas, www.seas.no''
+
|
 +
The pictures on the left show measurements of Seas coaxial drivers as used in various models, e.g. the [[Myro Coax Monitor]]. Here you can clearly see the correlation of the midrange diaphragm resonances with the non-linearities of the high frequency response. Wherever the midrange diaphragm forms a resonance, there is an interaction with the sound radiated by the tweeter. The resonance points each have a specific amplitude phase response and are related to the amplitude phase response of the tweeter.
 +
The effects are very complex.<br />
 +
<br />
 +
Example: <br />
 +
Where there is a peak (resonance) of the midrange diaphragm (black) in the reed-paper diaphragm, there is an interaction with the tweeter sound and in the frequency response of the tweeter we see exactly (almost mirror image) in the ripples of the midrange diaphragm corresponding ripples in the tweeter frequency response. These are the interactions of the resonating midrange diaphragm with the tweeter sound.
  
 +
|}
 +
''Source: Seas Company, www.seas.no''<br />
  
−
'''Manger-Wandler'''<br />
+
'''Manger transducer''''<br />
−
Eine spezielle Art der weichen Membranen ist der Manger-Wandler. Hier gehört die sich verformende Membran zum Konzept, indem sie Biegewellen ausbildet. Dabei wird ein Teil der Bewegungsenergie in der Membran gespeichert bzw. dort in Wärme gewandelt. Selbstverständlich hat auch die Membran eines Manger-Wandlers Resonanzen, ebenso wie das gesamte schwingende System eine oder mehrere Eigenresonanz(en) besitzt. Es gibt einige Phänomene zwischen dem inneren Membran-Teil (innerhalb der großen Schwingspule) und dem Bereich außerhalb. Und auf diesen Resonanzen schwingt das System nach Anregung aus - und genau so klingt es auch. Rückstellkräfte gibt es dort ebenso, die Membran nimmt letztendlich ihre Urspungsform wieder an.
+
A special type of soft diaphragm is the Manger transducer. Here, the deforming diaphragm is part of the concept by forming bending waves. Thereby a part of the kinetic energy is stored in the membrane or converted into heat there. Of course, the diaphragm of a Manger transducer also has resonances, just as the entire vibrating system has one or more self-resonances. There are some phenomena between the inner membrane part (inside the big voice coil) and the area outside. And it is on these resonances that the system oscillates after excitation - and that is exactly how it sounds. There are also restoring forces there, and the diaphragm eventually returns to its original shape.
  
−
=== Zusammenfassung ===
+
=== Summary ===
−
Gut entwickelte Hartmembranchassis sind in ihrem Einsatzbereich Weichmembranchassis in der Regel in allen Punkten überlegen und haben nur einen Nachteil: die schwach bedämpften Membranresonanzen am oberen Ende des Übertragungsbereichs.
+
Well developed hard diaphragm drivers are usually superior to soft diaphragm drivers in all points in their range of application and have only one disadvantage: the weakly damped diaphragm resonances at the upper end of the transmission range.
−
Lässt man diese unbedämpft, klingen diese Lautsprecher wie viele es kennen: hart, harsch und bimmeln und rasseln wie eine Fahrradklingel. Darin finden viele Vorurteile ihren Nährboden. Setzt man nun einen Hochtöner in deren Mitte (koaxial), dann wird dieses Resonieren extrem stark vom Hochtöner, von außen, angeregt und spiegelt sich sogar extrem im Frequenzverlauf des Hochtöners wieder.<br />
+
If these are left undamped, these drivers sound like many know them: hard, harsh and ringing and rattling like a bicycle bell. This is the breeding ground for many prejudices. If a tweeter is placed in the centre (coaxial), this resonance is extremely strongly stimulated by the tweeter, from the outside, and is even extremely reflected in the frequency response of the tweeter.<br />
−
Unbedämpfte Membranresonanzen zu bedämpfen, ist mechanisch (aufbringen dämpfender Masse = schwere Membran) oder elektrisch durch äquivalente Filter möglich, aber sehr aufwändig und in der Produktionsserie einzumessen (Serienstreuung des Chassis). Die Erhöhung des Membrangewichts ist gleichzusetzen mit einem elektrischen Tiefpass, wirkt also wie Bauteile im Signalweg. Die Partialschwingungen einer Membran werden durch das Aufbringen einer dämpfenden Masse zu tieferen Frequenzen hin verschoben und in ihrer Wirkung abgeschwächt. Der Übertragungsverlauf des Chassis sieht entsprechend aus. Der Abfall zu höheren Frequenzen wird dadurch stärker und die Phase nacheilender. Die Linearität nimmt zu, wenn es insgesamt richtig gemacht wird.<br />
+
To damp undamped diaphragm resonances is possible mechanically (applying damping mass = heavy diaphragm) or electrically by equivalent filters, but very complex and to be measured in the production series (series dispersion of the chassis). The increase of the diaphragm weight is equivalent to an electrical low pass, thus it acts like components in the signal path. The partial oscillations of a diaphragm are shifted towards lower frequencies by the application of a damping mass and their effect is weakened. The transmission path of the chassis looks accordingly. The drop to higher frequencies becomes stronger and the phase more lagging. The linearity increases if it is done correctly overall.<br />
−
Man sollte aber aufpassen, dass die Membranaufhängung und die gesamte Auslegung des Antriebs eine höhere bewegte Masse vertragen können, denn ursprünglich waren sie auf eine geringere bewegte Masse ausgelegt. Andererseits wäre auch eine Zunahme der Verzerrungen zu erwarten, insbesondere wenn die Membranmasse bei größeren Hüben in die nichtlinearen Bereiche der Randaufhängung und des Spiders eintaucht.
+
One should be careful, however, that the diaphragm suspension and the overall design of the drive can tolerate a higher moving mass, because originally they were designed for a lower moving mass. On the other hand, an increase in distortion would also be expected, especially if the diaphragm mass dips into the nonlinear regions of the rim suspension and spider at larger strokes.
  
−
==== Kann eine Sensorregelung helfen? ====
+
==== Can sensor control help? ====
−
Einige Aktivlautsprecher verwenden eine Sensorregelung, um Nichtlinearitäten der Chassis zu verringern. Für die Korrektur einiger Phänomene können sensorische Regelungen hinzugezogen werden. Sie sollten nur möglichst in "Echtzeit" wirken. Allerdings werden durch Sensoren nur bestimmte Eigenschaften am Ort des Sensors erfasst. Was in mehreren Metern Entfernung als Interaktion aller Systeme passiert, z.B. Laufzeitdifferenzen am Hörplatz, lässt sich damit nicht erfassen. Selbst wenn sich jede einzelne Membran völlig korrekt, gleich dem Eingangssignal, verhalten würde, wäre dies kein Indiz für die richtige Schallsumme der Systeme. <br />
+
Some powered speakers use sensor control to reduce driver nonlinearities. Sensory controls can be added to correct some phenomena. They should only act in "real time" if possible. However, sensors only detect certain characteristics at the location of the sensor. What happens at a distance of several meters as an interaction of all systems, e.g. delay differences at the listening position, cannot be captured by this. Even if every single membrane would behave completely correct, equal to the input signal, this would not be an indication for the correct sound sum of the systems. <br />
−
Gleiches gilt für die Auswirkungen (Summe / Differenz im Zeitverlauf) von Partialschwingungen der Membranen in Hörentfernung, die Strahlungsimpedanz der Chassis im Gehäuse, die Sekundärschallwellen durch Schallbeugung usw. Sie sind prinzipiell nicht korrigierbar. Eine Sensorregelung kann nur regeln, was sie am Ort der Regelung erfasst. Wenn der Sensor ein Mikrofon an der Membran ist, kann dieses nur den Schalldruckverlauf an dieser Stelle aufnehmen und als Information in die Regelung einspeisen. Da Membranen aber nicht ideal steif sind, schwingen außenliegende Membranteilflächen anders als innenliegende. Zudem breiten sich innerhalb jedes Membranmaterials Körperschallschwingungen aus, die eine andere Schallgeschwindigkeit haben als der Schall in der Luft. Dies führt an gewissen Orten der Membran oder auch der Randaufhängung zu einer komplexen Interaktion. Davon bekommt der Sensor nicht viel mit. Von Schallanteilen, die durch Beugung an den Chassis- oder Gehäusekanten zu Sekundärschallwellen werden, bemerkt der Sensor ebenfalls nichts. Hier ist eine Regelung darum unwirksam.<br />
+
The same applies to the effects (sum / difference over time) of partial vibrations of the membranes at listening distance, the radiation impedance of the drivers in the cabinet, the secondary sound waves due to sound diffraction etc.. In principle, they cannot be corrected. A sensor control can only control what it senses at the point of control. If the sensor is a microphone at the diaphragm, it can only record the sound pressure curve at this point and feed it as information into the control. However, since diaphragms are not ideally stiff, outer diaphragm parts vibrate differently than inner diaphragm parts. In addition, structure-borne sound vibrations propagate within each diaphragm material, which have a different sound velocity than the sound in the air. This leads to a complex interaction at certain locations of the membrane or even the edge suspension. The sensor does not notice much of this. The sensor also does not notice sound components that become secondary sound waves due to diffraction at the chassis or cabinet edges. Therefore, a control is ineffective here.<br />
−
Außerdem sollte man dynamische Zeitfehler durch die Frequenzfilter vermeiden. Sonst nützt die ganze Regelung nichts.
+
Furthermore, dynamic time errors caused by the frequency filters should be avoided. Otherwise the whole control is useless.
  
 
{| class="wikitable" border="1"
 
{| class="wikitable" border="1"
 
|-
 
|-
 
|  
 
|  
−
[[Datei:Concert Monitor.jpg]]<br />
+
[[File:Concert Monitor.jpg]]<br />
 
''[[Myro Concert Monitor]]''
 
''[[Myro Concert Monitor]]''
 
|
 
|
  
−
== Gehäuseresonanzen ==
+
== Cabinet resonances ==
−
Im Gegensatz zu Membranen sind Resonanzen im Gehäuse meist, aber nicht immer unerwünscht. Die untere Grenzfrequenz kann im offenen, geschlossenen oder in einem Gehäuse mit einem Resonanzprinzip (Bassreflex / Transmissionline etc.) erreicht werden. Das oft genutzte Bassreflexprinzip regt gezielt eine Resonanzfrequenz an, um den Schalldruck im Tiefton zu verstärken. Anhand der Wirkweise des Bassreflexprinzips zeigt sich, dass ein solches Resonanzsystem eine gewisse Zeit braucht, um einzuschwingen.
+
Unlike diaphragms, cabinet resonances are usually, but not always, undesirable. The lower cut-off frequency can be achieved in an open, closed or in an enclosure with a resonance principle (bass reflex / transmission line etc.). The often used bass reflex principle specifically excites a resonance frequency in order to amplify the sound pressure in the low frequency range. The way the bass reflex principle works shows that such a resonance system needs a certain amount of time to settle in.
−
Bei der Impulswiedergabe steht die Schallenergie des Resonanzsystems noch nicht zur Verfügung!<br />
+
During impulse reproduction, the sound energy of the resonance system is not yet available!<br />
−
Auch Transmissionline und Backloaded Horn nutzen Resonanzen zur Schallverstärkung. Für alle Resonanzen aber gilt: Sie erzeugen ''unmodulierten'' Schall. Sie erzeugen damit zwar Schalldruck, enthalten aber keine Musikinformation, weil der Schall unkontrolliert erzeugt wird und nicht dem Musiksignal folgt. Resonanzen erweitern den Übertragungsbereich für Musik daher nicht. Dies ist ausschließlich mit größerer Membranfläche zu erreichen. <br />
+
Transmissionline and Backloaded Horn also use resonances for sound amplification. However, the following applies to all resonances: They generate ''unmodulated'' sound. They generate sound pressure, but do not contain any musical information, because the sound is generated uncontrolled and does not follow the music signal. Resonances therefore do not extend the transmission range for music. This can only be achieved with a larger diaphragm area. <br />
−
Zudem bestimmen weitere Aspekte [[Die Formgebung des Gehäuses]], u.a. zur Vermeidung unerwünschter Resonanzen im Gehäuse.
+
In addition, other aspects determine [[The design of the cabinet]], among other things to avoid unwanted resonances in the cabinet.
  
−
== Gehörresonanzen ==
+
== Aural resonances ==
−
Resonanzen prägen ''alle'' Hörerlebnisse, auch bei natürlichen Schallereignissen, denn sie sind nicht nur Bestandteil technischer Wiedergabesysteme, sondern auch des menschlichen Gehörs. Sie sind damit Bestandteil jedes natürlichen Höreindrucks.
+
Resonances characterize ''all'' listening experiences, including natural sound events, because they are not only part of technical reproduction systems, but also of the human auditory system. They are thus a component of every natural auditory impression.
−
Resonanzen bilden sich aufgrund der Länge des äußeren Hörkanals aus und führen zu erhöhter Empfindlichkeit in bestimmten Frequenzbereichen. Im Bereich des menschlichen Hörspektrums existieren drei Resonanzstellen, die das Hörempfinden prägen. Sie führen dazu, dass die aufgrund mechanischer Trägheit abnehmende Empfindlichkeit des Gehörs zu hohen Frequenzen kompensiert wird und bei 4 kHz sogar ansteigt. Die Fachliteratur bietet dazu weitergehende Beschreibungen, auf welche die Konstruktion von Lautsprechern keinen Einfluss hat.   
+
Resonances form due to the length of the outer auditory canal and lead to increased sensitivity in certain frequency ranges. In the range of the human auditory spectrum, there are three resonance points that shape the auditory sensation. They lead to the fact that the sensitivity of the auditory system, which decreases due to mechanical inertia, is compensated for at high frequencies and even increases at 4 kHz. The technical literature offers further descriptions of this, on which the construction of loudspeakers has no influence.   
  
−
== Raumresonanzen ==
+
== Room resonances ==
−
Resonanzen sind Bestandteil fast jeden Raumes bedingt durch parallele Wände, Boden und Decke. Sie erschweren damit ebenfalls [[Zeitrichtiges Hören im Raum]] und verändern wie jede andere Resonanz die im Schall enthaltene Information.
+
Resonances are part of almost every room due to parallel walls, floor and ceiling. They also make [[time-correct hearing in the room]] difficult and change the information contained in the sound like any other resonance.
 
|}
 
|}
  

Latest revision as of 10:51, 22 January 2019

General[edit]

Resonances are a cause of distortion, i.e. of deviations in sound generation compared to the input signal. They are energy storage effects that occur at certain frequencies in diaphragms and loudspeaker cabinets and create errors in music reproduction. Frequency filters and enclosures are therefore designed to minimize resonance. Every resonance also causes a temporal shift of the sounds to be transmitted. Resonances sound extremely aggressive and smear the sound image, transparency is lost. The same applies to intelligibility.
As energy stores, resonances are temporally inert, they cannot spontaneously arise or disappear. Thus, they only become fully apparent in the steady state. During the transient of an impulse, on the other hand, the resonance is still charged with energy and only becomes noticeable with a delay. This removes energy from the signal.
The resonance case of the oscillating system loudspeaker contains a time variable. Thus the high pass function is not constant. When measuring the impedance of a loudspeaker over time, it can be seen that the impedance curve is initially linear at the resonance frequency and the typical impedance rise only develops over time. When measuring with sinusoidal periods of different frequencies (dynamic measurement), it can be seen that the ratio of the first to the second half-wave is also not constant, but that the first half-wave shows a mainly radiation resistance-dependent curve, while the curve of the second half-wave is already determined by the influence of the resonance of the system. When the pulse decays, the energy of the resonance is discharged again, so that the decay is delayed and the signal is stretched in time.

(An illustrative example of resonances as energy storage is also the microwave grill. Here, food is irradiated with the resonant frequency of water, which resonates with it, absorbs the energy and heats up. Since water is the largest component of any food, this heats the food as a whole)

Concert Monitor.jpg
Myro Elypticon'

Concert Monitor.jpg

Myro Wild Thing II

Membrane resonances[edit]

The diaphragms are acoustic weak points of the cabinet: they are thin, permeable to sound, and resonate. Since diaphragms are not ideally stiff, outer diaphragm sub-surfaces resonate differently than inner ones, and do so vaguely chaotically. In addition, structure-borne sound vibrations propagate within each membrane material, which have a different sound velocity than the sound in the air. This leads to a complex interaction at certain locations of the membrane or even the edge suspension. Any material that is vibrated will resonate at its natural resonance(s), that is, it will respond to excitation by a spectrum of natural vibrations. This spectrum gives the loudspeaker diaphragms their inherent sound. The excitation can be caused by a mechanical force transmission or by acoustic energy from outside (sound waves). Resonances can already be excited by low energy. The resonance case, no matter what kind, must be avoided at all costs!
The general requirements for a loudspeaker diaphragm are: it should essentially be light, stiff and have a high internal damping. Since these requirements contradict each other constructively, diaphragm materials are always subject to compromise. Every loudspeaker diaphragm generates diaphragm resonances. The number of resonances and their characteristics vary greatly between different types of drivers and diaphragm diameters.

  • With hard diaphragms the resonances are in a higher frequency range than with softer diaphragms. They have a lower internal damping, but vibrate piston-like in the actual useful range, without resonance phenomena. Partial vibrations of hard diaphragms usually only occur above the main operating range. They can be very pronounced and very complex. In any case, it is helpful not to push these drivers to the limit and rather space the crossover frequencies one or more octaves apart. With an extremely stiff voice coil former (e.g. titanium), a favourable starting range at the diaphragm, an extremely stiff diaphragm (ceramic, diamond, beryllium) and a high magnetic field saturation in the air gap the direct coupling of the drive energy to the air is excellently possible with cone drivers.

Soft membranes have a high internal damping, but tend to produce partial oscillations with their complex resonance phenomena in the actual useful range. Diaphragms with a high internal damping oscillate less strongly on their own resonances than drivers with low internal damping. However, the diaphragm resonances are usually in a lower frequency range, in the actual useful range of the chassis.


When selecting drivers, attention should be paid to:
1. the oscillating system of mass, suspension and electromagnetic drive as well as
2. the deformation of the membrane (as well as the surround and spider) and
3. the diaphragm resonances.


Membrane resonances are a complex phenomenon. They essentially produce the inherent sound typical for a membrane material and can be time-variant or time-invariant. Only in the latter case can the Myro-typical frequency filters be used for correction.
If you want to eliminate the inherent membrane sound, more or less complex filters are necessary. Eliminating a disturbing diaphragm resonance always sounds better than not doing it. If a chassis had a completely damped natural resonance, then its transmission curve would correspond to the effective part of the radiation impedance. The filter circuits for this are not a problem, but critical loudspeaker drivers are. In some cases impedance minima below 4 Ohm can occur. However, these are usually narrow-banded and in frequency ranges where little power is demanded from the amplifier. The diaphragm resonances are not the same at all dispersion angles or have any effect at all. If they are corrected at a certain dispersion angle, i.e. in relation to a certain point, this correction may well turn into the opposite at other angles.
The result is a loudspeaker with practically no distorting inherent sound. (If the inherent sound of the diaphragms cannot be completely eliminated, types with the same (inherent) sound often blend together better. The partial ranges of the transmission spectrum then sound similarly coloured and this gives an impression of coherence, of harmony.) This is the prerequisite for there being no tonally disturbing colourations and the loudspeaker thus no longer being perceptible as an intrinsic sound source. If the sound sum is correct, together with the tweeter and eentually used bass, this applies to the entire loudspeaker, provided of course that no other inherent noises such as cabinet resonances (interior reflections and resonances / cabinet material resonances) or other buzzing and rattling noises become noticeable.

With diaphragm materials that are stable over a long period of time, the diaphragm resonances also remain quite stable in frequency and quality. Diaphragms, however, that are sensitive to temperature and especially humidity or that tend to corrode, the conditions are less stable. Such membranes often exhibit resonance behavior that is time-variant and thus difficult or impossible to correct. By time-variant is meant here that a diaphragm resonance first settles, then collapses due to counter-phase oscillations and then revives, whereby as a rule no stable resonance frequency is established in this process. All this happens within a few milliseconds. Such a process cannot be corrected by a filter.
Broad-range drivers are a special case among drivers and contain exclusively resonances over a wide range in the high frequency range as part of the concept, where they provide a level but no musical information.

Concert Monitor.jpg
Mundorf AMT26-Myro-V2

Hard membranes[edit]

The use of hard diaphragms provides better power transfer to the air and thus improves impulse response. However, if one uses the usual standard filters in the crossover, such as non-matching 1st order filters (6 dB/oct) or even 2nd (12 dB/oct) or 3rd order impulse destroyers (18 dB/oct), then the advantage of hard diaphragms is nullified. The result is harshness of a special kind. The impulse distortion of these filters and delay errors within the construction, as well as the combination of drivers that do not match each other, produce distortions that sound hard. But these can also be produced with softer diaphragms.
Hard diaphragms shift the resonances to the upper end of their transmission range or beyond, but there they are more pronounced with extremely high Q and require appropriate correction filters. The frequency response usually drops off before this point, thus almost corresponding to the ideal typical transfer function of a driver of this size. A closer look at the result, however, shows that even with higher order filters, the diaphragm resonances will cut through and produce the typical long after resonance. These are also harshness, a sharp buzz that is added to the sound with each excitation. Hardening is therefore usually a result of errors! If, on the other hand, the advantages of stiff diaphragms are used and their resonances are damped, the speakers sound neutral. Simplified: the harder the material, the higher the diaphragm resonances. It is rare to find a clear relationship between the fundamental wave and harmonics and subharmonics. In the case of diamond, beryllium and ceramic diaphragms, however, these relationships are recognizable. The partial oscillations of a membrane, i.e. the natural oscillations of partial surfaces of the membrane, are time-variant and cannot be described with simple models.
In the case of stiff materials, the resonances oscillate evenly over time. In the waterfall diagram, a uniform, frequency-stable "mountain range" can be seen. The step response accordingly shows a uniform ripple of the graph. A notch filter eliminates this ripple completely, whereby it is to be noted that the excitation takes place by an extremely broadband signal, in which all frequencies of the transmission bandwidth of the chassis are contained. In addition, attention must be paid to series scattering.

Soft diaphragms[edit]

Soft diaphragms with high internal damping also exhibit a variety of natural resonances. They are however also more strongly damped, therefore with smaller quality and usually also in lower frequency ranges to find than with hard diaphragms. They are therefore in the transmission range and sometimes even give the impression that the usable transmission range is more extended towards high frequencies. Soft diaphragms also react more critically to bead resonance (resonance of the edge suspension) than hard diaphragms.
The partial oscillations are extremely complex and, due to their time variance, cannot be clearly reproduced and reduced by filters on the input side. In addition, there are partial oscillations that occur together with the diaphragm resonances. This results in a time-variant mix with an upward and downward swelling over time. Partial oscillations occur with a minimal delay and do not directly affect the transient response. In their generation process, the tension of the "springs" of the individual membrane segments takes energy from the forward motion. This is mainly a problem of soft and not very stiff diaphragms in general. The voice coil dips into and deforms the diaphragm in compliant diaphragms, especially in fast, impulsive processes. As a result, energy is lost, the impulses are delayed and the energy introduced is converted into heat or subsequent residual sound waves that interfere with the direct sound.
A common phenomenon with soft membranes is the so-called midrange (edge) resonance.


The plush diaphragm
... does not exist for good reasons, but it would have an advantage. After all, coaxial speakers are popularly used as an approximation of the point source and have undeniable advantages in that regard. But they also contain the dilemma between the advantages and disadvantages of hard and soft diaphragms, because they always have one problem: the tweeter gives impulses and frequencies to the midrange / bass diaphragm in the centre at full level, so that the diaphragm is struck like a sound bowl. It excites the diaphragm resonances of the midrange / bass diaphragm and these movements build up to resonances. This causes the diaphragm, as the sound source, to radiate sound waves that add or subtract, depending on the time correlation to the high frequency sound. We can see this in the diagrams.

The harder the material, the more pronounced the effect. And unfortunately these diaphragm resonances of the mid-woofer diaphragms lie exactly in the transmission range of the tweeter. So coaxial designs require more or less soft diaphragms to limit the effect. But since hard diaphragms are actually acoustically advantageous, this conflict of objectives cannot be resolved. A plush diaphragm would therefore be advantageous, considered from this aspect alone.
The excitations by the tweeter sound pressure can be compared on the frequency scale with those shown by the cone when excited via its own voice coil. This is because when the tweeter is measured on its own, it excites the diaphragm resonances of the mid-woofer cone. This causes the diaphragm to move and these movements build up to resonances. As a result, the diaphragm, as the sound source, emits sound waves that add or subtract, depending on their temporal correlation to the high-frequency sound. This effect can be demonstrated by measurement.
The problem will always be noticeable when drivers are placed close together, at least one of which operates in the resonance ranges of the other. However, the sound pressure of the excitation is many decibels lower than with a coaxial chassis.

  • Magnesium membrane

  • Aluminium diaphragm

  • Reed-Paper-Membran

The pictures on the left show measurements of Seas coaxial drivers as used in various models, e.g. the Myro Coax Monitor. Here you can clearly see the correlation of the midrange diaphragm resonances with the non-linearities of the high frequency response. Wherever the midrange diaphragm forms a resonance, there is an interaction with the sound radiated by the tweeter. The resonance points each have a specific amplitude phase response and are related to the amplitude phase response of the tweeter. The effects are very complex.

Example:
Where there is a peak (resonance) of the midrange diaphragm (black) in the reed-paper diaphragm, there is an interaction with the tweeter sound and in the frequency response of the tweeter we see exactly (almost mirror image) in the ripples of the midrange diaphragm corresponding ripples in the tweeter frequency response. These are the interactions of the resonating midrange diaphragm with the tweeter sound.

Source: Seas Company, www.seas.no

Manger transducer'
A special type of soft diaphragm is the Manger transducer. Here, the deforming diaphragm is part of the concept by forming bending waves. Thereby a part of the kinetic energy is stored in the membrane or converted into heat there. Of course, the diaphragm of a Manger transducer also has resonances, just as the entire vibrating system has one or more self-resonances. There are some phenomena between the inner membrane part (inside the big voice coil) and the area outside. And it is on these resonances that the system oscillates after excitation - and that is exactly how it sounds. There are also restoring forces there, and the diaphragm eventually returns to its original shape.

Summary[edit]

Well developed hard diaphragm drivers are usually superior to soft diaphragm drivers in all points in their range of application and have only one disadvantage: the weakly damped diaphragm resonances at the upper end of the transmission range. If these are left undamped, these drivers sound like many know them: hard, harsh and ringing and rattling like a bicycle bell. This is the breeding ground for many prejudices. If a tweeter is placed in the centre (coaxial), this resonance is extremely strongly stimulated by the tweeter, from the outside, and is even extremely reflected in the frequency response of the tweeter.
To damp undamped diaphragm resonances is possible mechanically (applying damping mass = heavy diaphragm) or electrically by equivalent filters, but very complex and to be measured in the production series (series dispersion of the chassis). The increase of the diaphragm weight is equivalent to an electrical low pass, thus it acts like components in the signal path. The partial oscillations of a diaphragm are shifted towards lower frequencies by the application of a damping mass and their effect is weakened. The transmission path of the chassis looks accordingly. The drop to higher frequencies becomes stronger and the phase more lagging. The linearity increases if it is done correctly overall.
One should be careful, however, that the diaphragm suspension and the overall design of the drive can tolerate a higher moving mass, because originally they were designed for a lower moving mass. On the other hand, an increase in distortion would also be expected, especially if the diaphragm mass dips into the nonlinear regions of the rim suspension and spider at larger strokes.

Can sensor control help?[edit]

Some powered speakers use sensor control to reduce driver nonlinearities. Sensory controls can be added to correct some phenomena. They should only act in "real time" if possible. However, sensors only detect certain characteristics at the location of the sensor. What happens at a distance of several meters as an interaction of all systems, e.g. delay differences at the listening position, cannot be captured by this. Even if every single membrane would behave completely correct, equal to the input signal, this would not be an indication for the correct sound sum of the systems.
The same applies to the effects (sum / difference over time) of partial vibrations of the membranes at listening distance, the radiation impedance of the drivers in the cabinet, the secondary sound waves due to sound diffraction etc.. In principle, they cannot be corrected. A sensor control can only control what it senses at the point of control. If the sensor is a microphone at the diaphragm, it can only record the sound pressure curve at this point and feed it as information into the control. However, since diaphragms are not ideally stiff, outer diaphragm parts vibrate differently than inner diaphragm parts. In addition, structure-borne sound vibrations propagate within each diaphragm material, which have a different sound velocity than the sound in the air. This leads to a complex interaction at certain locations of the membrane or even the edge suspension. The sensor does not notice much of this. The sensor also does not notice sound components that become secondary sound waves due to diffraction at the chassis or cabinet edges. Therefore, a control is ineffective here.
Furthermore, dynamic time errors caused by the frequency filters should be avoided. Otherwise the whole control is useless.

Concert Monitor.jpg
Myro Concert Monitor

Cabinet resonances[edit]

Unlike diaphragms, cabinet resonances are usually, but not always, undesirable. The lower cut-off frequency can be achieved in an open, closed or in an enclosure with a resonance principle (bass reflex / transmission line etc.). The often used bass reflex principle specifically excites a resonance frequency in order to amplify the sound pressure in the low frequency range. The way the bass reflex principle works shows that such a resonance system needs a certain amount of time to settle in. During impulse reproduction, the sound energy of the resonance system is not yet available!
Transmissionline and Backloaded Horn also use resonances for sound amplification. However, the following applies to all resonances: They generate unmodulated sound. They generate sound pressure, but do not contain any musical information, because the sound is generated uncontrolled and does not follow the music signal. Resonances therefore do not extend the transmission range for music. This can only be achieved with a larger diaphragm area.
In addition, other aspects determine The design of the cabinet, among other things to avoid unwanted resonances in the cabinet.

Aural resonances[edit]

Resonances characterize all listening experiences, including natural sound events, because they are not only part of technical reproduction systems, but also of the human auditory system. They are thus a component of every natural auditory impression. Resonances form due to the length of the outer auditory canal and lead to increased sensitivity in certain frequency ranges. In the range of the human auditory spectrum, there are three resonance points that shape the auditory sensation. They lead to the fact that the sensitivity of the auditory system, which decreases due to mechanical inertia, is compensated for at high frequencies and even increases at 4 kHz. The technical literature offers further descriptions of this, on which the construction of loudspeakers has no influence.

Room resonances[edit]

Resonances are part of almost every room due to parallel walls, floor and ceiling. They also make time-correct hearing in the room difficult and change the information contained in the sound like any other resonance.


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