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

Hi Bryon and Al - Al, you interpreted my comments exactly right, and clarified/elaborated them nicely with your discussion of hall ambience. Bryon, I am not so sure, though, that it has as much to do with distance from the performers in the hall, other than to state that to be too close is not ideal, as the sound will definitely be brighter. And sound does generally travel up and back in a good hall, so that the "nosebleed" seats in many halls are actually the best ones. However, the latter is not always true, often mezzanine seats, or seats in the middle to the back of the floor are best (as long as they are not under an overhang, then they are definitely the worst).

As to the question of whether or not something recorded in a studio can be "warm," that is a much more interesting issue. The studio itself is of course a very cold, dead space. I would say that the vast majority of the time, studio recordings that sound "warm" have been altered with digital reverb, etc. - studios are the playgrounds of the engineer, for sure. And while Al may be right that close miking can result in some good studio recordings of certain instruments, this is IME not usually the case - normally close-miked recordings of acoustic instruments do not sound very good, if by good we mean "real." This, to me, is sort of equivalent of sitting too close in a concert hall. I guarantee you that whenever an engineer puts a mike too close to an instrument, the player tries to move it as far away as he can get away with.

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

02-05-11: Tmsorosk
Warmth is an added artifact of electronically produced music. A properly tuned acoustical instrument should not have the added warmth that you hear on many systems.

02-07-11: Frogman
Music that approaches the sound of a live performance is, by definition, warm.

It’s interesting that some folks experience live acoustical music as "warm," while others do not. Maybe that’s a consequence of how people hear differently. On the other hand...

I suspect that it’s a consequence of how people understand the conceptual metaphor of 'warmth.' Many metaphors have a systematic structure and consistent rules of use. But this thread seems to highlight that, for the metaphor of 'warmth' in audio, there doesn’t seem to be a systematic structure or consistent rules of use. It's no wonder, then, that consensus on the issue of warmth is difficult to achieve, since there is reason to believe that, much of the time, people aren't even talking about the same characteristic.

Bryon

Get a heating pad!!

Bryon, exactly. It’s like using the word ‘blue’ to describe a color. It only gets you in the ball park unless you describe the hue, intensity (value), contrast, gradation etc. in known terms. In my experiences warmth is relative and is dependent on context. To complicate things, as system accuracy improves and smaller differences become larger, not everyone describes these differences in the same absolute terms. A neutral system compared to a sterile system will sound warm(er) and can be described that way as more natural, neutral etc. A system can be neutral but as a requirement must have warmth. Because accurate tone can be difficult to describe, the word warmth is helpful in describing the accuracy of that tone. "The sax was warm and round sounding, as if it were in the room." could be an acceptable statment. Of course the term can also be used to describe a system that is too warm.

Ambient information, or ‘air’, which is key in recreating the recording space is not necessarily the same as warmth. A sterile system can and frequently does have lots of ambient information, but lacks body or warmth.

Recording studios can and usually are 'warm', dead maybe, designed to lack reverberations to control the sound, but not usually characterized as cold. Great pains are taken to control studio acoustics.

All instruments, some more than others have a degree of directionality, so your listening position in relationship to them (distance and direction) will affect the sound perceived. The same is true for microphones. Close miked sources can have more high frequency energy than you would hear from a normal listening position. In addition, the proximity effect of microphones increases bass response of the signal the closer you place a mike to a source like a guitar or vocalist. A lot of singers like this effect as it adds richness to their voices. When you hear a studio singer, you are usually hearing it from the perspective of the singers mouth on your nose (where the mike would be), being played through speakers in front of you. Hardly a 'natural' situation. Instruments, room acoustics, microphone and equipment selection and placement, multi tracking, all manner of tweaking and manipulating the sound after it is captured, and lots more must be accounted for in the recording process to create a recording to give what they hope you consider a natural sounding perspective. In general, its unrealistic to think a recording would ever be heard exactly that way live. Although it’s amazing it works as well as it does...well, sometimes anyway.