Unfortunately I can't tell you why, it's best to ask the manufacturer.... However, these are normally intended for connection to a hi-fi system. Depending on the sound card, this can also work on a PC. However, you have to know the exact model of the sound card or chipset/mainboard for this (although I doubt that it works like this on the latter).

> Can my PC cope with this?
Whether a PC can handle 250Ω depends primarily on the sound chip used. Many higher-quality mainboards also have a headphone preamplifier for the onboard sound, and can therefore also supply listeners with higher impedances with decent levels.

> Why the high impedance (ohm number)?
These are studio headphones that can be used for monitoring or mixing, for example. Studio equipment can (and is allowed to) output much higher voltages than, for example, an iPod. Headphones with high impedance can use smaller, finer coils, so the headphones can react much more finely to impulses, the overall audio reproduction becomes finer. Since mobile devices cannot (and are not allowed to, as they have to be limited to 100db) output such levels, the impedance is lowered accordingly, so that you have decent levels even when you are on the move, and you can also hear the music (otherwise the volume would simply be extremely low). Thanks to the larger coils, this is then again at the expense of accuracy and claim behaviour. If you look on Digitec, you will see that the exact same headphones are available as 32Ω, 60Ω and 250Ω variants. The 250Ω is the studio version, the 32Ω is the mobile version, and the 60Ω is somewhere in between.

I hope I was able to explain this to you in a way you can understand :)

So my relatively normal PC easily manages 250 ohms, even my 13'' MacBook Pro manages a decent volume.