What is Warmth?

Hi Raul, it is difficult to define such a subjective term. I agree with you about the location of recording microphone and actual listening position in a concert hall and all that. On the other hand, I am not sure about the difference between warm sounding stero equipment and instrument/hall. Let see if I get this right. Most people tends to imply that roll off high frequency and the bump in mid upper bass seems to give rise to what we hear as warmth in stereo equipment. Now, acoustically dry concert hall, as I understand it is a hall the have very small reverberation time, say 2-3 ms where as the acoustically more pleasing tone hall, those that seems to be richer, denser tonal color, usually has longer reverberation time, around 4-6 ms (I read about this somewhere a long time ago, not sure if I remember the number correctly). However, richer, denser tone does not neccessarily means warmer sound. Depending on where you sit in the audience, there is definitely going to be some roll off of high frequency in comparison to close mike position. Sitting at 10-30-50m away from the stage, one would expect certain decline or roll off of high frequency, more so than low frequency by various instruments to exist. I think that's why real symphonic concert seems to sound less bright and duller than what I hear on recording and that's why orchestra nowaday tries to compensate for that by raising the frequency on the note to give that extra brightness. Whether the roll off characteristic of each hall give rise to warmer sound in some concert halls over the other, I am not sure.

When talking about different made of the same instruments, warmth is definitely a term that I often hear people using to describe the different in sound, French vs German tone, brands of pianos, various wood used in instruments. However, I have not heard anyone specifically say that it is the characterisitic high frequency roll off of mid/upper bass bump that give rise to the warmth quality in each instrument or not. Personally I play piano and own a Grotrian grand piano. I have also played quite a bit on Steinway, Fazioli, Yamaha, Ibach, vintage Erard and Pleyel and I what perceived as warmth tone when compare each instrument is definitely quite valid.

PS when talking about roll off high and mid/upper bass bump, I tend to think of some ported speakers or some tube equipments. However, a warm sounding class A solid state amplifier generally tends to measure pretty flat from 20Hz to 20,000Hz, does it not? May be I am missing something here.

Well designed solid state gear can indeed have "warmth", and often more accuracy...If something is on a recording I don't want it masked by euphonic distortion or anything else. I've heard amazing low powered "SE" tube amps that sound amazingly accurate (to a wattage limited point) and solid stuff that is lifeless...so It's up to the designer how things are voiced and the listener to how it all tastes, so to speak. Warmth for me is lack of harshness. Period.

Suteetat and Raul are both correct.

Instruments and halls can have warmth of their own. This is natural.

HiFi systems can have warmth too. This is not natural- it is a coloration caused not so much by frequency response errors (as is the common myth) but instead by distortion.

The 2nd order harmonic is the most to blame, and is why SETs are so well-known for a warm sound.

It happens that the ear hears distortion as tonality. In the case of music, where most of the energy is in the bass, you get the upper bass emphasis simply because of the harmonics (in addition to the 2nd, the 3rd and 4th also contribute, although to a much lessor degree).

This is why you can measure the frequency response of two amplifiers on the bench, and while they may measure the same, one will sound warm and the other will not. Its because of distortion, not frequency response variation.

Single-ended circuits in general contribute to the 2nd harmonic. Tubes are often blamed for making more 2nd harmonic, but in reality it has more to do with the topography of the electronics than it does the type of amplifying device. It *is* true however that due to the greater linearity of tubes that you can build single-ended circuits with them and get away with it- this has gone on for many decades and so has contributed to the idea that tubes have more 2nd harmonic. But if that were true, how does that square with tubes being more linear??

Now a system can also sound 'cold' which is caused by distortions that are of a higher ordered nature (and especially the odd harmonics). Any harmonic above the 4th is considered a higher-order harmonic. In addition, the ear uses the 5th, 7th and 9th harmonics to determine how loud a sound is. If these harmonics are messed with by the electronics, the system will sound louder than it really is and it will sound brighter (harsher) as well.

Again this is because the ear interprets distortion as tonality.

This issue is tricky for designers! By picking a certain type of topology you will get a certain distortion signature; that can be modified somewhat by the addition of loop negative feedback. Note that I say modified; 'reduced' is not necessarily correct in all cases.

As an example, if one choses a fully differential topology in which there are no single-ended circuits, the primary distortion component will be found to the 3rd harmonic. If you add feedback to reduce it, other higher harmonics will appear.

Finally one should keep in mind that as much as we are wanting to get to the actual musical experience, the fact is that the closest we can get is to correct reproduction of the recording itself. That recording contains distortions of its own!

Hence the great degree of discussion and debate on this topic...

Dear Suteetat: ++++++ " it is difficult to define such a subjective term. " +++++

yes, this is the main issue on that word. Now, I think that people is using the warm term/word to define an instrument/audio system or the like about its intrinsecal " tone ".
Now, you are an experienced/pro piano player: which other word came to you other than warmth when you compare the Grotrian grand piano against a Steinway or other one? which other word could give you/us a better definition of each piano overall tone color?

I have some difficult about because here in México we don't use the warmth meaning to compare different tone colors in music instrumentation or audio systems.

That's why maybe what Wolf posted: +++ Warmth for me is lack of harshness " +++ makes no precise means to me.

Regards and enjoy the music,
Raul.