The Amplifier – Speaker Relationship

In the previous issue it was suggested that the amplifier is the most important component in the audio playback system, and this point was defended on the basis of tolerable versus intolerable distortion.  Specifically, the amplifier is prone to producing distortion products that are egregious to the listening experience, more so than are the forms of distortion produced by speakers.  

In this issue we set out to explore the relationship between the amplifier and the speaker.  Particularly, we are concerned with the speaker’s resolution.  Resolution is a characteristic that is seldom measured and almost never specified.  It refers to the ability of the speaker to follow details of the musical signal that are extremely low amplitude and/or extremely short lived; hereafter referred to as micro-details or just details.  To grasp this better, consider a speaker that rings, that continues to generate sound after the incoming signal stops, as a bell continues to sound long after being struck.  This rather common error masks the micro-details in music because those details are often found in the decay of sound, that is to say, the content that occurs after the initial attack.  Consider a snare drum that is struck once.  After the initial attack, the drum resonates briefly and decays in a way that gives the drum its distinctive sound, what the drum shell is made of, how it is tuned, etc.  Further, the room in which this occurs also exhibits a complex series of sonic reflections or echoes that also decay quickly.  This information is what allows the listener to perceive where the drum is, how large the room is, where he is in the room, etc.  Though one may be unable to produce very specific information about the drum or about the distances in the room, he has a palpable sense of location and realness that contributes to a convincing musical rendition.  If the speaker has enough resolution, that is to say, it starts and stops in good keeping with the incoming signal, the listener will receive this information intact and will have a believable and enjoyable experience.  If, however, the speaker is reluctant to stop in response to the incoming signal, i.e., it rings, it will mask this detail and rob the listener of an experience he otherwise would have enjoyed immensely.  Notably, one isn’t always aware of a problem with the speaker, he simply doesn’t find the playback to be as involving and authentic as he otherwise would.

Let us now consider two common flaws in the power amplifier.  The first is the generation of complex or high order nonlinearity distortion.  Similar to total harmonic distortion, or THD, this form of distortion can produce a floor of additional tones or sound energy that undergirds the music, what is referred to in the industry as a non-linearity noise floor.  If this noise comes from only simple non-linearities and is sufficiently low in amplitude, it may be entirely inaudible to the listener.  This might be the case with the very finest amplifiers available.  However, many amplifiers produce distortion from more complex non-linearities, resulting in noise that is destructive to the harmonic content perception of the listener.  In these cases, there exists subtleties that lesson the beauty of the music, obscure its precious micro-acoustical content, and contribute to listener fatigue.  One may not be specifically aware of this distortion, even when it occurs at levels sufficient to degrade the listening experience.  When he is aware of it, the listener often attributes the problem to the recording, or to other possible sources.  

What does this have to do with the amplifier – speaker relationship?  It is the case that a highly resolving speaker will tend to reveal the distortion produced by the amplifier, while the less expensive and lower resolving speaker more graciously covers up the amplifier’s flaws.  Now, it is a common goal of all audiophiles to extract as much sonic “information” as possible from the music file or record groove, because in that information are the details that make the sound convincingly real.  Thus, we find that, with regards to detail, we want the most highly resolving speaker possible, but with regards to tolerating the flaws of the amplifier, we want a lower resolving speaker.  What emerges from all of this is a very useful principle that will serve the audiophile over a lifetime of excellence pursuit: “The better the speaker one has, the better the amplifier one must drive it with.”   A corollary principle is: “A bad speaker will hide a bad amplifier, whereas a good speaker will not.”  Of course, neither bad speakers nor bad amplifiers will get the audiophile where he is trying to go.  So, if you are ready to buy a really good set of speakers, be sure to put aside enough money to buy a really good amplifier as well.

Mike Vice

President

Bella Sound

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On a lifelong pursuit of audio excellence.

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