Questions about Ohms

[BaconComputing]

Hello! Recently I have been interested in what the different ohm values mean. Here are some questions I have.

1) How many ohms can you use until you need an external amplifier?

2) Is an amp really necessary for high ohm headphones? (Such as Beyerdynamic dt770 pro, 250 ohm)

3) How many ohms can an everyday computer or iPod drive?

Thanks in advance,

-Bacon

[helping]

1) depends on the source and how loud you listen, typically <100 ohms for most mobile devices. Many motherboards can handle up to 300 ohms perfectly fine, and up to 600 ohms in certain cases. 

2) depends on source, and depends on if it's not loud enough for you. In general, you buy the headphones first and then amp later if you need it louder (assuming you don't have an amp already). Everything that makes noise for audio already has an amp in it, the issue is if it's enough. 

3) answered above

[Goldilock]

Please you need to know that manufacturer only state impendence (ohm) in certain frequency range,other frequency range could spike and require much more load. Armature IEM may only state 10 ohm but in practice it could spike up to 90 ohm in certain frequency.

 

Yes, you can make 250 ohm loud enough from onboard, but because there are spikes of impendence it will make certain frequency less audible, in other word you lose detail.