How about comparing two open back headphones? AKG K712 PRO vs Sennheiser HD 660 S has an extraordinary design. But what makes them similar is an over-ear wearing style and an audio cable that comes with both of them.
The sensitivity of these headphones is almost identical since Sennheiser HD 660 S has 104 dB and the other device`s rate is 105 dB. When it comes to sound detail, frequency response matters most. In the case with AKG K712 PRO it is 10 Hz - 40 kHz and Sennheiser HD 660 S works in a range from 9 Hz to 41.5 kHz. There is also a dramatic difference between their impedance. The appliance made by Sennheiser has 150 Ohm, while AKG K712 PRO has 62 Ohm.
The sound of Sennheiser HD 660 S can best be described as balanced and resolving. Its bass is not ear-rumbling but really good. The voices and instruments are clearly contoured and naturally reproduced. Due to the lack of noise-canceling, you will hear all the sounds that surround you and people in public places will hear your music as well.
AKG K712 PRO has an accurate treble and tight bass. Its soundstage is super wide. The mids sound incredibly natural, they are full-bodied and not tinny at all.
Let's talk about the weight first. Probably, holding these devices in hand you will not feel any difference, as AKG K712 PRO and Sennheiser HD 660 S weigh 235 g and 260 g respectively.
Both of them have an adjustable headband and an audio cable with 300cm length. Only AKG K712 PRO comes with a premium carry case. Its “hammock” headband is made out of leather and should not wear out too fast. Consider, that the earpads are plush and exert little pressure on the ears.
The Sennheiser HD 660 S is better headphones in this comparison. Check Sennheiser HD 660 S price