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

Following up on my previous post...

02-06-11: Almarg
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.

I had the same thoughts, Al. If my speakers were a little more friendly to tube amps, then I would seriously consider replacing the Pass amp (even though I like it quite a bit). So, if I want to add a tube amp to the system, then I would need to consider replacing my speakers as well. I don't have any great objection to changing my speakers either, except for the cost associated with it. Like all crazy audiophiles, the only other speakers I think about are considerably more expensive than what I currently own. :-(

If possible, I would like to explore ways of adding warmth to the system that don't involve such large (and expensive) changes.

Bryon

the output impedance of an amp has to do with the damping factor. it has no relation to treble response.

i own a tube amp and there is no peak in the treble or dip in the midbass or lower midrange.

consider the cj mv 125. that amp would hardly be considered bright or lean. yet when compared with ss amps its damping factor is much lower.

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

... 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

02-06-11: Almarg
“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.

This is a good point, Al, and it makes perfect sense of the idea that, in at least some cases, warmth increases as the distance of the listener to the live event increases. That would explain the correlation you observed between recordings with ambient cues and those with warmth. On the other hand, it also seems to suggest that, for smaller scale performances, warmth might DECREASE as the distance of the listener to the live event increases. So maybe there is reason to believe that a common characteristic of warm recordings is that the distance of the microphone to the live event is “proportional” to the scale of the event being recorded. That idea makes a lot of sense to me.

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.

The first of these points is more or less what I meant in the OP by item #5, which I called “room resonance,” but would probably more accurately be called simply “room acoustics.” Having said that, it never occurred to me that comb filtering might be a detriment to a system’s warmth. That strikes me as a plausible idea, since the destructive interference of comb filtering effects could conceivably result in a kind of "harmonic thinning,” which might very well be experienced as a lack of warmth. An insightful observation, Al.

Bryon