I am going to show you the comparison AKG K52 vs K240, where the first device is closed-back and the second one — semi-open. Both pairs of headphones are wired and have an over-ear wearing style.
I found out that the mentioned devices have pretty similar sensitivity, as the model K240 has 104 dB and K52 has 110 dB. The distinction in frequency response is more remarkable since in the case with AKG K52, it is 18 Hz - 20 kHz and AKG K240 works in a range of 15 Hz - 25 kHz. When it comes to impedance, K52 has 32 Ohm, meanwhile, K240 has 55 Ohm.
Let's talk about the sound of AKG K52. The bass here lacks the thump, the mids and highs are pretty clear, one can hear the separation of the instruments well. These headphones are so evenly balanced that you can listen to them for hours without getting tired. There are no bright edges or booming bass lines.
The vocals which you get with K240 are clear and direct. Also, there is a very pleasant airiness to the overall presentation, and the tonal balance is very even.
These headphones are not heavy as the weight of AKG K240 is 240 g and AKG K52 has even less — 200 g. It is not a good idea to take them on the trip as the devices do not fold. The height of the headband of both appliances is adjustable, so wearing these headphones is convenient.
The model K240 has an advantage as its audio cable is detachable. The length of the wire is 300 cm. Meanwhile, AKG K52 has a 250 cm long cable. None of the appliances have a microphone or any control buttons.
The AKG K240 STUDIO is better headphones in this comparison. Check AKG K240 STUDIO price