What is “warmth” and how do you get it?

Hi guys - I wrote a very long post last night, only to discover that I could not post it, for some reason. The discussion has meanwhile left me far behind, but it has been a very good one. Obviously, the main problem here is terminology. As Newbee politely pointed out, some of you seem to have a misconception of what "harmonics" or "overtones" are, and my attempts to define it were obviously unsuccessful. I refer you to any book on acoustics. Hifibri in particular has misconstrued what I have been saying about them, and I give up - there is a reason why I am a musician, and not a writer, LOL (Hifibri, if you want to email me through the audiogon system, I can try to explain to you why your guitar example is not quite correct). I am in agreement with what Al and Newbee have said about harmonics in general.

What I will say is that I think I do finally have a handle on why you all think that frequency response is a major part of warmth. The terminology was holding me back - partly some people's incorrect usage of it, but also and mainly the differences between the meaning of certain words when used in the context of a musician's performance as opposed to the attributes of an audio system's "performance." The only quibble I still have with this discussion is with the importance many of you are placing on minute changes of amplitude in overtones within a musician's timbre as being the major factor in a perception of "warmth." (I am NOT denying that this is a factor) Overtones are inaudible to 99.9% of us. Changes in their amplitude, therefore, would not be heard independently from changes in amplitude to the main frequency actually being sounded. Harmonics do of course have to do with the "warmth" of the timbre, but the musician has no control whatsoever over specific harmonics within the overall timbre. Nothing the player does can isolate a specific harmonic and change it's amplitude - all harmonics will be affected by anything happening to the main frequency being sounded. Let me give a couple of examples.

If I sound the same tone with the same amplitude on two different horns in the same room, the differing "warmth" of the instruments will have everything to do with the alloy of the metal used in constructing the instruments, as well as the difference in the way the horn is designed (not to mention the differences in execution of the same design). Assuming that a strobe tuner is present so we can be sure that the two tones are of exactly the same frequency, the harmonics will be exactly the same. And if the frequency is off by say a cent or two, the harmonics will be proportionally off as well, and this extremely slight difference would not be perceived by 99.9% of us, anyway. You would perceive perhaps a great difference in the "warmth" of the two horns, but it is not because of harmonics. Same if I play the exact same frequency and amplitude in two different rooms on the same horn. They WILL sound perceptibly different to everyone, but it is because of the acoustics of the room, not because of overtones. One more example - two different recordings made of one note in the same room (with a different mike placement for each, or very possibly with the same mike placement) will also sound different. One may sound "warmer" than another, but again not because of harmonics.

Bryon, you are definitely on the right track here: "some acoustical environments, whether a recording space or a listening space, can CONTRIBUTE to the perception of warmth, while other acoustical environments can DIMINISH the perception of warmth. The fact that most concert halls - being highly acoustically designed environments - contribute to the perception of warmth is something I do not take issue with. I was merely trying to point out that LESS WELL DESIGNED acoustical environments might diminish the perception of warmth. Two things seem to follow from that observation. First, for recordings that lack warmth, the acoustics of the recording space might be a factor. Second, for systems that lack warmth, the acoustics of the listening space might be a factor." Change the first word from "some" to "all," and change each use of the words "can" and "might" to "will". Despite all the best acousticians know, it is impossible to predict exactly what the hall is going to do to the overall sound. These factors and others mentioned in other posts (the audio equipment itself, in particular) have a great deal more to do with "warmth," IMO.

02-17-11: Learsfool
The only quibble I still have with this discussion is with the importance many of you are placing on minute changes of amplitude in overtones within a musician's timbre as being the major factor in a perception of "warmth." (I am not denying that this is a factor)...Harmonics do of course have to do with the "warmth" of the timbre, but the MUSICIAN has no control whatsoever over specific harmonics within the overall timbre. [emphasis added]

Hi Learsfool - I may be wrong, but I think the importance many folks have given to harmonics in the perception of warmth has less to do with how harmonics are produced by a MUSICIAN and more to do with how they are reproduced by the PLAYBACK SYSTEM. In other words...

Some systems merely PRESERVE whatever warmth exists on the recording. Other systems seem to ADD warmth, whether it exists on the recording or not. For these systems, a common belief is that the added warmth is often a consequence of added HARMONICS.

Do you not think that added harmonics, as you might get with a tube amp, are a significant contributor to the perception of warmth during playback?

Bryon

Hi Bryon - perhaps Al can weigh in on this and correct me if I am wrong, but I'm pretty sure harmonics couldn't truly be "added," (they are of course all already present in the timbre) though digital reverb would be an example of an "addition" that would certainly affect the perception of warmth. Overtones can be and are sometimes removed by digital processing.

Perhaps a better word to describe what you are speaking of would be "emphasizing." Atmasphere has posted quite informatively about these types of issues, talking of even or odd order harmonics being emphasized by the design in different types of amps, and whether or not the designer is thereby following the "rules" of human hearing. This is very similar to the way the acoustical environment affects the timbre, except the designer of a piece of audio equipment I suspect has alot more control over his end result than an acoustician does.

And yes, I would say that tube designs are certainly "warmer," speaking very generally, than solid state designs, therefore sounding more lifelike. 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.

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

Hi Al - thanks for weighing in on this. However, I think you are incorrect when you say "Harmonics can, and to some degree inevitably will, be INTRODUCED by the system in the form of distortion products." (My emphasis) Your own examples that follow are all examples of what I was speaking of in my previous post - what you call enhancing certain harmonics via distortions (and they are good examples). However, ALL natural harmonics are always present in the natural timbre, so you can't introduce a new overtone that wasn't there before, though you can distort (or even remove) it. This is what I was trying to say in my previous post. If this statement is indeed incorrect, please explain.

One other point - 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.