[greggf]

Koss ESP950 is the warmest electrostatic.

Beyerdynamic DT770 is the warmest otherwise.

(Sennheiser HD650 is pretty warm, too, but not the warmest.)

But, this is just based upon my opinion of what I've heard........

 

[troymadison]

hd650, anything warmer would probably be too warm.

 

[dizzyorange]

For ultimate warmth, try adding an SET amp to the Darth Beyers or Senn HD650s.

 

[Dept_of_Alchemy]

Bose Triport OE...

Just kidding, HD650.

 

[ZARIM]

Super-Fi 5Pro, 5EB, Shure E4c...........

 

[Mrvile]

Super-Fi 5 Pro is one of the warmest IEMs..the E4C is pretty warm too but not overbearingly so.

 

[b7nguyen]

I thought the e4c is too warm. Whats out there thats warmer?

 

[steviebee]

Out of my little stable, Bass Freqzzzzzzzzzzzzzz.....

So warm I could fall asleep!

 

[carlosgp]

Oh, yes, the darths. In a first reading I understood a portable one, do not know why...

 

[SonicDawg]

the unmodded K340s are very warm...

 

[ChevymanZL1]

The Hifiman HE-500 

 

[davidgotsa]

The HD650 is warmer than the HE-500 in my opinion. 
Quote:

The Hifiman HE-500 

 

[wje]

Quote:

The HD650 is warmer than the HE-500 in my opinion. 

 
I also thought my HD-580s (Predecessor to the HD-600 / 650) was a warmer sounding headphone than my HE-500s.

 

[feigeibomber]

I reckon my LCD-2's are quite warm

 

[K_19]