What does "Warm" mean?

Warm may be a coloration, as lewm suggests.  I generally associate warm with sounds produced by tubes, less sharp edged and slight 80-160 Hz boost.  SS based systems can sometimes sound brittle or unnaturally metallic to me.  I expect this could be distortion or variation form flat response - a coloration..

@elliottbnewcombjr, I’ve not seen that chart before and no that was not Fulton’s chart.  From your link that was furnished by Nexdrum in 2026, about four decades after I was aware of Fulton’s concept.  As I remember his chart there was a detailed color assignment to each common instrument as mentioned.  But your other AI information was interesting and matched my memory. 

I'm familiar with both drummers Bill mentioned but have not noticed the tonal differences he described.  I suspect that is a variation from individual perceptions.  And I admit I'm not a musician.

It's a coloration by definition in that as soon as you use terms like warm, you are inferring that the sound quality deviates from reality.  Even though live music can occasionally be described as warm, because live music is all things at once, and then some when it comes to dynamics.

Lewm, please read my post to Raul above.  I used examples of actual instruments that differ in ways that I describe using the term warm as a differential descriptor.  I can think of another excellent example that you probably can listen to from your own record collection.  Find a Baroque ensemble playing on period correct instruments and another ensemble playing the same music on modern instruments.  String instruments using cat gut will invariably sound softer, I use the term warmer, than instruments using modern steel strings.  Please note that warm or soft, louder or sharper these sounds are all real.  Your inference of deviation from reality is misplaced within the context of what Raul and I were trying to convey to each other.  He bases his judgement of what is correct in relationship to what he hears at live musical performance sitting at or near the front row.  This is his frame of reference.  Mine comes from sitting at a drum kit, which is quite different.  BTW, musicians generally make lousy audiophiles.  ;-)  I still have a drum kit and a piano in my listening room in Florida to this day.  

Dear @billstevenson   : I can hear those differences ( minute ) using same tonearm but that " warm/coloration " in your Denon comes probably from its tonearm that it's not so well damped as the Technics magnesium build material.

R.

It’s nice to listen together, after a while we describe what we hear, and know what we agree on, mine/yours/his systems, various cartridges, ...

To me, there is a difference between ’Presence’ (midrange slightly elevated) and ’Warm’ a characteristic rather than a frequency variation. 

My and many vintage speakers have Level Controls to adjust the speakers in whatever space they find themselves and for the users preferences.

Mine are called ’Presence’ and ’Brilliance’. In a hard reverberant space, you might cut the highs to avoid too bright, shrill, brittle, edgy: find the right word. The presence has not been frequency boosted, but the listener is more relaxed and the sound is more enjoyable, the presence more apparent. I would not call that warm either, just tamed.

I went for extended bass when younger, but I came to think that was not so important, and in fact, I think what I and other people like most about my speakers is related to ’not too much bass’. (they are 15" huge magnets, weigh 37 lbs each,16 ohm highly efficient, bass is not lacking, just not further extended).

As I have said many times, Bass can be directional, i.e. Stereo Bass, always consider the overtones, and when there is less low room filling mono bass, and all the omni-directional reflections of that, everyone remarks on how the imaging of Jazz bass players and the sounds of bass decay are wonderful. Can less bass produce ’warmer’ bass? Not frequency emphasized, but a purposeful lack of extension, again, more apparent, not frequency emphasized.

Certainly well executed extended low bass is amazing, but mostly large spaces, larger than mine.