Is it supposed to do that?

[cdahdude]

Hey folks,
 
I've had my HD 650's for a while now and I've paired them with a Modi DAC and Qinpu A-3 amplifier. I've read lots of posts about recommendations for amps for high impedance headphones and am confused about how loud these headphones should sound with and without an amp. In terms of clarity, there is a significant improvement in sound quality when I switch from just plugging in my phones directly to my MBP to my current setup, but both systems are loud enough for listening even when not at maximum volume. I even plugged them into my smartphone and the volume can be still raised loud enough to hurt my ears. Why doesn't it sound too soft or quiet like I would anticipate from reading other forums even without proper audio setup? 
 
Thanks!

 

[144004]

You're asking if it's normal for your HD-650 to sound plenty loud out of a phone and laptop? 
Yes.
 
As you noticed, you like the way it sounds with the amp, not that it necessarily sounds louder with the amp.
Amps are basically about loudness, but a good amp should be about "good" sound too.
 
Don't be too surprised that some folks find stuff too soft. I once had a guy try my HE-400 (a fairly efficient headphone) out of his phone at max volume, and he told me it still wasn't loud enough. I totally didn't understand.

 

[weirdfishes]

Loudness is usually determined by impedance (higher needs voltage, lower needs current), sensitivity, and gain, assuming things like isolation and hearing are the same.

 

[blueangel2323]

For a 300 ohm headphone, the HD600 and HD650 are quite sensitive, so it's not hard to get sufficient volume out of them. There are other headphones that need a lot of power to reach a decent volume. But for the HD650 the main point of an external amp (and DAC) would be to improve the sound quality over the headphone out on your laptop, mainly in soundstage, imaging and separation.

 

[Thujone]

The sound quality goes up due to the higher voltage that the high impedance headphones are calling for. Sure, they can be loud enough out of just about anything, but you aren't necessarily supplying them with enough voltage to do them justice (especially for their price tag). On the other hand, as mentioned above, the HE-400 is  a fairly efficient headphone (one of the most efficient planar magnetic headphones) but they seem to require a lot of power in order to bring out the clarity and detail that they're known for. I wouldn't necessarily say that they can't get "loud" enough out of an iPhone but I would definitely say that they need much more juice than an iPhone can produce (whether that be voltage for the HD650 case or power for the HE-400 case). Either way, the reason the HE-400 is worth bringing up is because it has an impedance of 35 ohm and my poor tube amp needs to be cranked up nearly twice as much as it does for my HD580's/HD600's.