Hi Bryon, Another of your fascinating and thought-provoking threads, which expectably has stimulated some excellent responses. The one thing that occurs to me that has not yet been mentioned, and which I think factors into "warmth" significantly, is hall ambience, or the lack thereof. It seems to me that proper reproduction of hall ambience is a key factor underlying Learsfool's astute comment that Assembling a system that sounds "real" is automatically also going to be a system that sounds "warm." I suspect this is true for the great majority of audiophiles out there, especially those whose reference is live, unamplified acoustic music in a good performing venue. And it strikes me as a key factor in achieving the "richness" that several other posters referred to. Hall ambience, of course, was discussed at great length in your excellent "They are here" vs. "You are there" thread. Obviously its proper reproduction is highly dependent on the recording. I would offer the hypothesis that recordings that are lacking in "warmth," or "richness," or which tend not to sound "real," commonly have not adequately captured hall ambience. If so, the obvious question is what to do about it. One approach, which iirc you offered in the other thread, is to try to adjust room acoustics such that they draw a reasonable compromise between adding some semblance of concert-hall acoustics to enhance the presentation of ambience in the case of mediocre or poor recordings, while not overshadowing the ambience that is captured on good recordings. Obviously there will usually be practical limitations to how effectively that can be done. Another approach would be to try to adjust frequency response. But while emphasizing upper bass and lower mid-range frequencies, for instance, may to some rough approximation replicate the frequency response effects of hall ambience, that approach will be unsatisfactory IMO because it does not address the timing relationships between direct and reflected sound. What does strike me as likely to be, in general, the most promising way of enhancing warmth and ambience on mediocre and poor recordings, without significantly compromising the reproduction of well done recordings, is the introduction of tubes into the system, as others have suggested above. The added dimensionality that is commonly attributed to tubes (that attribution being correct in my experience, although from a technical standpoint I have no idea why that would be so), and perhaps the relative emphasis that they may give to lower order even harmonics, seem to me to be the best way of achieving that balance. Concerning where to put the tubes in the system, as you’ve no doubt seen there have been many debates on that question in prior threads here, with opinions sharply divided. FWIW, I am in the tube power amp camp. However in this case I certainly do not think that replacing your XA-30.5 with a tube amp would be the right approach. I say that partly because of the Pass amp’s outstanding reputation, but also because, assuming that the impedance characteristics of your 1027be’s are similar to those of the 1037be, the higher output impedance of a tube amp would result in increased treble emphasis and de-emphasized lower mids and bass, counter to what you are trying to achieve. So I have no bottom line answer to suggest, beyond some of the suggestions that have already been made, but those are some thoughts. Best regards, -- Al |
The output impedance of an amp has to do with the damping factor. True. Damping factor is usually defined as output impedance divided into 8 ohms. It has no relation to treble response. Not true, in the case where speaker impedance is significantly different in the treble region than at lower frequencies. If you look at the impedance curve that I linked to for the Focal Electra 1037Be, which I am assuming is similar to the impedance curve for Bryon's 1027Be, you will see that it is around 5 ohms in the bass and lower mid-range, and generally upwards of 10 ohms in the upper mid-range and treble region. That kind of impedance characteristic is not uncommon, btw. For a given input voltage, an amp having negligibly small output impedance, such as most solid state amps, will maintain an essentially constant output voltage into that impedance as a function of frequency. Based on Ohm's Law, that will result in twice the amount of current and power being supplied into 5 ohms compared to what would be supplied into 10 ohms. A tube amp, having relatively high output impedance, will not behave that way. The voltage that it "tries" to output will divide up between the speaker impedance and its own output impedance, in proportion to the ratio of those impedances. Therefore for a given input voltage to the amplifier, the amount of power that is delivered to the speaker at low frequencies will be smaller in relation to the amount that is delivered at high frequencies, compared to what a solid state amp would deliver. That will result in an over-emphasized treble. If I recall correctly you have electrostatic speakers, which would interact with amplifier output impedance in exactly the opposite manner. The impedance of electrostatics decreases at high frequencies, so a tube amp would provide a treble response that is under-emphasized relative to what the response would be with a solid state amp. Best regards, -- Al |
Mrtennis 02-07-11: So, you are saying that a tube amp would have a different frequency response than a ss amp, when driving an electrostatic speaker. Yes. The ss amp will produce a brighter and more extended top end than the tube amp with an electrostatic (which may or may not be preferable, depending on the particular components, the room, the listener, etc). The same ss amp will produce a weaker and less extended top end than the same tube amp, when used with dynamic speakers having an impedance curve similar to Bryon's Focals. In other words, one amp can be either more bright or less bright than another amp, depending on the speaker that is being used! Would you expect the difference to be as much as 5 db difference at frequencies exceeding 3 db, or what difference in spl would you expect and at what frequencies It depends on the damping factor/output impedance of the tube amp, and the impedance curve of the speaker. I did a quick calculation based on the impedance characteristic of the original Quad ESL, and based on a 2 ohm output impedance (damping factor 4) for the tube amp, and a 0 ohm output impedance for the ss amp. The ss amp in that case would be about 6db stronger in the 15 to 20kHz area than the tube amp. The 6db number would be smaller if the damping factor of the tube amp were higher. How might the frequency response change if the amp was a hybrid (tube input stage), such as the aria amp, designed by mike elliot? I have quad esls and am considering the aria wt 100. It has a tube front end and bipolar transistors. With respect to the effect we are discussing, that amp would behave the same as a purely ss amp. What counts is the type of output stage, which is ss in this case. Consistent with that, the amp has a damping factor of 44 according to the specs shown in this review. An important consideration with many electrostatics, also, is that the amp not be weak in terms of its current capability, because current requirements will be increased as a result of the capacitive nature of the speaker's impedance. The WT100 certainly appears to meet that requirement, based on the specs and description shown in the review linked to above. Learsfool -- just saw your comments. Thanks! Your perspectives on these kinds of questions are always particularly valuable. Best regards, -- Al |
A slight clarification to my previous post:
In referring to ambience, my intent was to refer to the totality of hall effects, rather than to the sense of "air" with which that term is commonly associated, "air" primarily involving high frequency effects (as was stated earlier by others).
In fact I should probably have used the term "hall effects" instead of "ambience." I'm referring to the totality of the complex interplay that occurs in a hall between directly heard sound, and reflected sound that has been both frequency contoured and delayed by multiple increments of time. All of that, as I have perceived it in my concert-going experience, is a key factor in perceived sonic "richness," which I (and others earlier in this thread) correlate with "warmth."
Best regards,
-- Al |
Hi Learsfool and Newbee, ALL natural harmonics are always present in the natural timbre, so you can't introduce a new overtone that wasn't there before. Let's say that a note includes a frequency component at 1kHz. In response to that 1kHz frequency component, the system may create distortion products at 2kHz, 3kHz, 4kHz, and any and all other multiples of 1kHz that are within the bandwidth of the system. Let's take the 8th harmonic (8kHz) as an example. Whether the 8kHz distortion component that is created by the system, in response to the 1kHz frequency component of the note, constitutes an INTRODUCTION of a harmonic, or an ENHANCEMENT of a harmonic, depends on whether or not an 8kHz harmonic is already part of the sound that the instrument created. If you are saying that any note produced by any instrument will naturally and invariably contain frequency components of non-zero amplitude at ALL harmonic multiples of the fundamental (lowest) frequency component of the note (and I don't know whether or not that is true), then yes, that would mean in a literal sense that the system cannot INTRODUCE a harmonic that isn't already there. However, the system can certainly, as I see it, CREATE a harmonic, as a distortion product of the fundamental frequency of the note, irrespective of the existence of that harmonic in the original signal. If a harmonic already exists in the note at the same frequency as that newly created distortion product, then the natural harmonic and the artificial one would combine in some manner, depending on their phase relationship. In your violin examples, yes, those overtones are of course part of what make differences in timbre. However, each individual one is indeed indistinguishable from the others to the ears of at least 99.9% of humans. It is not possible to tell which of those overtones are the ones that are different, in your example of two different playings of the same note on the same instrument. If I played the same note twice, at the same volume, on my horn, you would not be able to tell me which individual overtones were affected and how, and this is doing you the credit that you would be able to hear the difference in the timbre between the two at all - a great many audiophiles would not, especially if I tried to the best of my ability to make them exactly the same. And in the same case, it would have to be a VERY bad recording/system indeed that would distort them so much so that most people could hear it. These sorts of differences are MUCH more audible live and at very close range than they are on a recording. Yes, certainly I would not be able to identify and describe the specific differences in harmonic structure that correspond to the differences in timbre that I may hear, at least without the aid of sophisticated instrumentation. But my point is this: For a note with a given volume, a given fundamental frequency, and what I'll refer to as a given "envelope" (duration, rise, decay, etc.), audible differences in timbre, tone, and even the basic character of the note (e.g., violin vs. flute) are the result of differences in harmonic structure (i.e., the relative amplitudes of each of the harmonics). To the extent that differences in timbre, tone, and the basic character of the note are perceivable, differences in harmonic structure are perceivable. I don't see how that can be incorrect, because (for a given volume, fundamental frequency, and envelope) I can't envision anything other than differences in harmonic structure that could account for differences in timbre, tone, or the basic character of the note. Best regards, -- Al |
... For a given volume, fundamental frequency, and envelope I can't envision anything other than differences in harmonic structure that could account for differences in timbre, tone, or the basic character of the note. Just to be sure it's clear, I should add with respect to this statement that I am referring to the directly heard sound produced by the instrument, apart from hall effects and apart from artifacts of the recording and playback processes. Best regards, -- Al |
This thread has certainly evolved, as might be expected considering the parties who are participating, into a really excellent dialog.
FWIW I must very respectfully say that at this point I agree with Hifibri and I disagree with Learsfool. I see it as follows: Yes, the FREQUENCIES of all of the harmonics are determined unalterably by the fundamental frequency (i.e., the lowest frequency component) of the note that the musician chooses to play. However, wouldn't the individual AMPLITUDES of each of those harmonics, relative to the amplitudes of the other harmonics and to the amplitude of the fundamental, vary depending on the waveform changes you agree can occur?
If not, what would a spectrum analysis of the waveforms indicate is changing? I doubt that extraneous or spurious frequencies are being introduced, that are not harmonically related to the fundamental. What could be changing, that would account for the waveform changes, other than the relative amplitudes of the harmonics and the fundamental?
And if the waveform changes are in fact in the form of alterations of that harmonic structure/balance, then doesn't it stand to reason that there is a relation between "warmth" and harmonic structure/balance?
I do think it is very much an oversimplification, and a common audiophile misconception, to speak of warmth as just being a frequency response that is non-flat in some way. A mid-bass peak, or some similar frequency response emphasis, might contribute to a subjective perception of warmth. But realistic reproduction of timbre, which as I see it correlates with accurate reproduction of the RELATIVE amplitudes of the harmonics and the fundamental of each note, as well as proper time domain performance and ambience reproduction, I envision as being the keys to the PROPER reproduction of warmth.
Best regards,
-- Al |
RE: Time domain behavior. Earlier on the thread, Newbee said something similar - that warmth is partly a matter of a system's ability to portray the decay of notes. I suspect you mean something similar. Do you think that tubes are inherently better at this? I would not go so far as to say that tubes are inherently better with respect to time domain performance. Their main advantages, as I see it, relate to harmonic balance, and also to increased dimensionality and better imaging (although as I indicated earlier, I can't explain technically why that would be so). However, tube designs lend themselves more readily to minimal use of feedback. As Atmasphere has frequently pointed out, feedback, at least if not done judiciously, can create or enhance objectionable distortion components. It can also affect the quality with which the leading edge of rapidly changing transients are reproduced. Our hearing mechanisms give particular emphasis to those leading edges, as a result of the Haas Effect and the Precedence Effect. Although as was stated in Newbee's excellent post, that is most applicable to instruments whose notes have fast risetimes. His comments about decay times I also think are very true. It seems plausible that the indirect sound from a recording space might contribute to the perception of warmth.... But that also seems to imply that, under some circumstances, flawed recording spaces might diminish the perception of warmth. In other words, some hall effects might sound warm, while other hall effects might sound cool. Do you think that's true? I would doubt it, at least assuming the hall is at least semi-decent. I can't remember ever being in a hall in which the instruments sounded "cool," in the way that they can on some recordings. In a hall, I just about invariably sense a sort of "aura" surrounding each note (more so or less so depending on the instrument and the music, of course), that contributes to a sense of richness/body/warmth, and which I believe is a result of the summing together of delayed sound and directly heard sound. ... Hence there might be ways to increase the warmth of a system through acoustical treatments in the listening room, which is an interesting idea to me. Room acoustics and treatments are not one of my areas of expertise, but my instinct, with respect to situations where physical and aesthetic considerations are not too limiting, would be that it should often be possible to find a compromise that would enable "cold" recordings to be warmed up somewhat, without significantly degrading reproduction of good recordings. But only to a limited extent, given the disparities in delay times between listening rooms and halls. Best regards, -- Al |
Learsfool, The basic difference in timbre between a flute and a violin, to use your example, is that one is made of metal and one is made of wood, not to mention the fact that their sounds are created in a completely different manner as well. This is obviously the largest factor in the difference in timbre. Without going into the science of it, waves produced by a string behave very differently from waves produced by a tube. A tube with one end closed behaves differently than one open at both ends, and conical and cylindrical tubes behave differently as well. Side holes in the tubes have their effects as well, of course. Not to mention different types of wood or metal alloys used in the instrument's construction, which have very great effect on the timbre. I think that in order for our understandings to converge, what is needed is a description of the differences in spectra that RESULT from the differences you are describing. Although I'm not sure that any of us can provide that without further research. I may try to do some research on that if I get a chance tonight or tomorrow. If a violin and a flute were to play notes having the same fundamental frequency, the same volume, and the same duration, and if their respective notes as captured by a microphone were fed into a spectrum analyzer (a device which shows the frequency components of a signal, and the amplitudes of each of those components), what would the differences be between the two spectra, that account for their very different sounds? That is the key question, as I see it. Electronic distortion cannot introduce or create new harmonics, it can only distort those already present. Although it may not have been your intention, this statement would seem to imply that a distortion component at a given frequency would not be added by the system were it not for the presence in the original sound of a harmonic at that same frequency. Which is not the case, as I and Kijanki (whose post I am in full agreement with) indicated. Although some of these various timbres are more acoustically complex than others, the overtone series for all of them is always the same - it doesn't matter what instrument is creating it. Their frequencies are always the same, for a given fundamental frequency. But the amplitudes of each overtone in the series will be very different for different instruments. The flute happens to be one of the purest instrumental timbres. Yes, which I think corresponds to its notes having less harmonic content than in the case of most other instruments. I.e., its notes come closer to being a pure sine wave than those produced by other instruments (although of course they are still considerably different than a pure sine wave). Which I think is a basic reason that a flute, when not well recorded and reproduced, can often tend to be "hard" sounding. Another word on the audibility of these harmonics.... To clarify, I certainly do not assert that individual harmonics are readily perceivable. What I believe is that differences in harmonic structure (the amplitudes of the harmonics, relative to the amplitudes of other harmonics and to the amplitude of the fundamental) are the primary determinant of timbre and tone. Therefore when we perceive differences in timbre and tone, we are perceiving the EFFECTS of differing harmonic structures. Best regards, -- Al |
Hi Bryon, ... The issue of whether instrument timbre is reducible to harmonic content. I am completely out of my depth here, so will remain agnostic. Let me make sure it's clear that implicit in my previous post (the one with the lengthy quotes from the "What Is A Sound Spectrum?" writeup) is that I now recognize that timbre is only partially reducible to harmonic content, and other factors also affect timbre significantly. An example of those other factors is the low level broadband component of the flute spectrum that the article discussed. I still suspect, though, that for most instruments harmonic content is typically the most significant determinant of timbre. IF instrument timbre is EVEN PARTIALLY reducible to harmonic content, then it reveals a flaw in the “additive approach” to playback.... What is ADDED during playback will not be identical to what was SUBTRACTED during the recording process. The reason is because, while the harmonic contents of live events are almost infinitely VARIABLE, the harmonic “additions” of playback equipment are largely CONSTANT, being persistent artifacts of a circuit's more or less fixed parameters.
I'm not sure that the variable/constant distinction is particularly meaningful, even within the limited context of harmonic distortion. The harmonic components resulting from distortion in the electronics will continuously vary as a function of the varying spectral components of the music, and to some extent with the overall signal level. Harmonic distortion introduced by the speakers will vary with signal level as well as with frequency, and will often overshadow the distortion components introduced by the electronics. Throw in intermodulation distortion, transient intermodulation distortion, the complexity of the music, the complexity of the sounds of the instruments themselves, hall and room effects, the vagaries of the recording process, etc., etc., and the “approximation” you spoke of would seem to be all that can be hoped for, regardless of the approach that is chosen. The upshot of all this is that, in light of my desire for additional warmth, maybe I chose the wrong amp. On the other hand, as was said earlier, with your speakers an amp having a high output impedance (such as the Prima Luna and probably most other tube amps) will de-emphasize lower frequencies relative to upper mid and high frequencies. Obviously, that would be in the wrong direction with respect to adding warmth. So I'm not sure where that leaves us, but those are some thoughts. Best regards, -- Al |
... When I think of “warmth,” I tend to think of a sound that is “intimate” or “immediate.” In other words, I think of a high ratio of direct to indirect sound, which would typically correspond to listening to a live event from a relatively close position. But that may be an idiosyncratic association on my part. Like you, Hifibri seems to have the OPPOSITE association.... This makes me wonder whether you, or Hifibri, would say that studio recordings (i.e. those with few or no ambient cues) can’t sound warm? Others can undoubtedly speak to that more knowledgeably than I can, in part because most of my listening is to classical music that has been recorded in halls. But I would say that depending on the instrument, and on what is being played and how it is being played, warmth can in many cases certainly be captured and reproduced via up close miking in a studio. While at the same time it can often be better captured in a hall via more distant miking. The key to that apparent paradox, it seems to me, is that warmth is a multi-faceted concept, as this thread makes clear. “Woodiness,” “body,” etc. are for example certainly important aspects of warmth, and their successful reproduction involves capturing the fine detail and harmonic balance of the instrument. That in turn can be expected to be compromised as distance increases. On the other hand, massed strings, to cite another example, can sound overly bright at close distances. As was noted above, high frequencies will be attenuated more rapidly as a function of increasing distance than low and mid frequencies. Also, reflected energy will be subject to frequency response contouring as a result of both the greater distance it travels before reaching the listener or the mic’s, and the acoustic properties of the reflecting surface. Finally, and perhaps most significantly, summation of reflected energy with directly captured sound will result in comb filtering effects. So it would seem that optimal reproduction of recordings that are produced in a concert hall, at least, would involve drawing a balance between preservation of detail and harmonic balance on the one hand, and either reproducing hall ambience and distance effects correctly, if present in the recording, or enhancing them, if they are not present but should be. There would seem to be no easy answers .... Best regards, -- Al |
Learsfool, as I see it an audio system can introduce harmonics, enhance harmonics, or even reduce harmonics that may be present in the source material. Harmonics can, and to some degree inevitably will, be introduced by the system in the form of distortion products. They can be enhanced either by virtue of a frequency response emphasis that happens to occur at a frequency corresponding to some harmonic (multiple) of the fundamental frequency of a note, or by virtue of a frequency response dip that happens to occur at the fundamental frequency, or by virtue of distortion of the fundamental frequency of a note, the distortion products therefore occurring at the same frequencies as harmonics that may be present in the note. They can be reduced by the converse of those frequency response effects, or by introduction of a distortion product that is out of phase with a harmonic that may be present in the note at the same frequency. I'm just saying that there is a whole lot more to do with that than amplitudes of individual harmonics within the overall timbre - again, these harmonics are inaudible to far more than 99.9% of us. I respectfully disagree. My understanding is that timbre and the relative amplitudes of individual harmonics are one and the same. As I understand it, to cite an example, a violin playing a note whose fundamental frequency is say 1 kHz will produce very audible harmonics at 2 kHz, 3 kHz, and other higher multiples of 1 kHz. A flute playing a note whose fundamental frequency is also 1 kHz will produce very audible harmonics at those same multiples of 1 kHz. The reason that the note produced by the flute will sound different than the note produced by the violin is that the relative amplitudes of those harmonics will be in different proportions. And, similarly, differences in timbre and tone between two different playings of the same note on the same instrument will be the result of differences in the relative amplitudes of those harmonics, as I understand it. Best regards, -- Al |
Following up on my previous post, I found this excellent writeup: http://www.phys.unsw.edu.au/jw/sound.spectrum.htmlIt appears that I was partly right, but not seeing the whole picture. Some excerpts from the writeup: If you change a sound without changing its loudness or its pitch then you are, by definition, changing its timbre. (Timbre has a negative definition - it is the sum of all the qualities that are different in two different sounds which have the same pitch and the same loudness.) One of the things that determines the timbre is the relative size of the different spectral components.... Let's look between the harmonics. In both of the examples shown above, the spectrum is a continuous, non-zero line, so there is acoustic power at virtually all frequencies. In the case of the flute, this is the breathy or windy sound that is an important part of the characteristic sound of the instrument. In these examples, this broad band component in the spectrum is much weaker than the harmonic components. We shall concentrate below on the harmonic components, but the broad band components are important, too.... Introductory physics text books sometimes give the impression that the spectrum is the dominant contribution to the timbre of an instrument, and that certain spectra are characteristic of particular instruments. With the exception of the closed pipes mentioned above, this is very misleading. Some very general or vague comments can be made about the spectra of different instruments, but it is not possible to look at a harmonic spectrum and say what instrument it comes from. Further, it is quite possible for similar spectra to be produced by instruments that don't sound very similar. For instance, if one were to take a note played by a violin and filter it so that its spectrum were identical to a given spectrum for a trumpet playing the same note, the filtered violin note would still sound like a violin, not like a trumpet.
Here are some general statements about spectra:
* bowed strings and winds have harmonic spectra
* plucked strings have almost harmonic spectra
* tuned percusion have approximately harmonic spectra
* untuned percusion have nonharmonic spectra
* the low register of the clarinet has mainly odd harmonics
* bowed strings have harmonics that decrease relatively slowly with frequency
* brass instruments often have spectra whose harmonics have amplitudes that increase with frequency and then decrease.
To say anything that is much more specific than that is misleading. The rest of the writeup is quite interesting as well, and even provides a good deal of additional specific discussion concerning the flute. Best regards, -- Al |
