Question

I use Sennheiser hd 650 headphones which are known to need a good amp for them to drive/perform at their best.  The headphones have an input impedance of 300 ohms, 103dB sensitivity, and a max power rating of 500mW. If I'll use a Presonus Studio 68 which has headphone outputs that have an Impedance Working Range of 32Ω to 300Ω and Maximum Power - 150 mW/channel (56Ω load).  Is it enough to drive the Sennheiser hd 650’s without buying a headphone amp? Will they give out correct and flat sound in all frequencies without deviations and distotions?

Answer 1

Your Sennheiser hd650 headphones have a Nominal impedance of 300 Ω.

http://en-ie.sennheiser.com/high-quality-headphones-around-ear-audio-surround-hd-650

The headphone output on the Studio Series interfaces have an Impedance Working Range of 32Ω to 300Ω.

https://www.presonus.com/products/Studio-26/tech-specs

As such your headphones should work fine with either interface.