[JMIJohn]

Title says it all. Looking at offerings from Grado (RS1/1i, 325is, PS500) but would also consider Korg, Sennheiser, and especially Hifiman headphones or other planar magnetic phones. Or anything you guys suggest! I generally like a warmer sound, and the 990's response can seem a little too smiley-faced at times. But I love their bass.
 
I currently use an Aune T1 amp which has a tube DAC stage and a solid state amp. Thanks!

 

[manbear]

HE-400 has killer bass, but the signature is generally similar to the dt990 (slightly recessed mids and aggressive treble). However, they just do everything better. Soundstage, detail, speed, you name it, the HE-400 does it better.

 

[JMIJohn]

BUMP

 

[rubinstein]

HE-400 has killer bass, but the signature is generally similar to the dt990 (slightly recessed mids and aggressive treble). However, they just do everything better. Soundstage, detail, speed, you name it, the HE-400 does it better.

+1 for HE 400

 

[JMIJohn]

I would be willing to spend up to the price of an HE-500. And is that upgrade worth it?

 

[rubinstein]

in that price range, you could also consider Alpha dogs.
 
regarding your question, you may be able find an answer somewhere in this thread, http://www.head-fi.org/t/646812/hifiman-he500-he400-jergpad-mod-v2-5-new-measurements-posted-modulor-orders-updated

 

[manbear]

Aune T1 might not have enough juice for the HE-500. 1w into 32 ohms is borderline.

 

[JMIJohn]

Hmm...the HE-6 is 50 ohms, about 50% more...would that work?
 
Pretty tempting heh.

 

[jackwess]

  Hmm...the HE-6 is 50 ohms, about 50% more...would that work?
 
Pretty tempting heh.

 
The HE-6 are harder to drive. They require crazy loads of power. 

 

[manbear]

  Hmm...the HE-6 is 50 ohms, about 50% more...would that work?
 
Pretty tempting heh.

 The Aune has less power into 50 ohms than into 32 ohms. I'm not sure if you understand how impedance works. In any case, you should absolutely not get the HE-6. Hifiman recommends 6-8 Watts for them. The only inexpensive way to drive them is with a speaker amp. 

 

[jackwess]

   The Aune has less power into 50 ohms than into 32 ohms. I'm not sure if you understand how impedance works. In any case, you should absolutely not get the HE-6. Hifiman recommends 6-8 Watts for them. The only inexpensive way to drive them is with a speaker amp. 

 
To the Op, this is taken from one of the Articles found on Head-fi. Pretty easy to understand. 
 
High impedance headphone:  requires more voltage but less current
Low impedance headphone:   requires less voltage but more current
Amplfier output impedance: the lower the better for any impedance headphone
higher efficiency (for example:  102 dB/1 mW) less power required
​lower efficiency: (for example: 91 dB/mW) more power required
How they effect sound is dependent on the magnetic field generated and diaphragm construction (physical response of diaphragm).

 

[manbear]

It's also important to note that impedance itself isn't everything. Efficiency also matters. The HE-6 has extremely low efficiency, so it needs a serious, serious amp. Most headphone amps won't cut it. A 600 ohm Beyerdynamic headphone, for example, would be easier to drive than the HE-6 because of increased sensitivity, in spite of having 12x the impedance. Impedance by itself doesn't tell you all you need to know. 

Most amps will have less power as headphone impedance increases (with the exception of OTL tube amps). The Aune T1 has a solid state output stage, so its power decreases as headphone impedance increases. Thus, 1W into 32 ohms means that you are getting less than 1W into 50 ohms. 

1-2 W is recommended for the HE-500, so the Aune doesn't quite have enough juice. However, this doesn't mean it won't work. You will get sound, and you will probably like what you're hearing too, but you won't be hearing the HE-500 at its best. For the HE-6, you will get sound, but it probably won't be good at all. For the HE-400, you will be good to go. I'm currently using a ~300 Mw amp with my HE-400. 

 

[rubinstein]

you can find further explanation about the difficulty of driving low sensitivity headphones in this thread
 
http://www.head-fi.org/t/680240/would-a-fiio-e17-be-good-enough-for-a-he-4

 

[adrianjones]

I ve owned dt990 600 since 2007 and have found them to be an incredibly exciting listen but not to the extent of being tiresome. I always find myself spending hours listening and thoroughly enjoy music. They require a great front end and amp to drive them. I bought a valve head amp and have re built it in stages with high end components. Each upgrade was easily detected. This speaks volumes for the dt990 quality.
I recently bought a pair of AKG 701. At first listen they weremore detailed and brighter. I ran them in with little change to their presentation. Eventually even though they are more detailed I found them a flat and boring listen. Kept finding myself swapping back to the beyers. Also the AKGs have a strangly hollow colouration in the mid band. The AKG worked well from standard line level outputs but the Beyers need quality and power to drive them properly.