AKG K551 free download

File name AKG K551 modifications.pdf

AKG K551 modifications The AKG K551 is a headphone intended for use with portable equipment and for Apple products specifically. In the very thin cord it also has a microphone and (volume) control buttons when connected to certain Apple products (have not used nor tested it). It is a closed headphone with a pretty good isolation. The drivers are 50mm in diameter which is quite large meaning that when you move it around on your head the sound doesn't alter too much. The ear-pads are quite big, much bigger than most headphones and are very comfortable and soft. Downside is the ears get warm quite soon. Getting a proper seal is PARAMOUNT to getting a good sound. People with bony faces or small heads might not be able to get a good seal. My head is average sized and anything but bony, so little seal problems for me. Without a good seal the K551 sounds 'cuppy' and has no body or bass to it. Clamping force is very low so when moving your head it is quite easy to momentarily break seal which is annoying (bass disappears on one or both sides). Working, or walking outside, (for which it seems to be intended) isn't very do-able for me. It works well when you remain pretty stationary. The cable is short and very thin but totally not microphonic. Yes, it has a microphone in it, but that's not what is meant with microphonic. It means when you touch the cable that sound isn't mechanically transferred to the cups and heard. For me this is an important asset (not the microphone/remote as I don't own Apple products). Looks are appealing to me and the build/feel seems very durable. Adjusting the cups isn't very easy to do and even have to forcefully 'bend' it in position to get a good seal. No squeaking sounds though, or earcups 'falling' in unintended positions when trying to put it on. Inside the cups (that can be swivelled 90 degrees so they can lie flat on a surface / transported) are VERY big letters 'L' and 'R' indicating both channels. This is much better than small print on the inside or outside of the cups or headband. The headband padding is soft and comfortable. The plastic covers on the inside of the headband 'slide' open pretty quick when attempting to adjust the height. Very annoying and a little screw or other mounting method could have prevented that. Technical: The K551 is a low impedance (35 nominal) headphone and doesn't react much to sources with different output resistances between 0 and 100. The output resistance of most portable equipment varies between (close to) 0 and 10 in general. Nominal power rating is 200mW (0.2W) which is a pretty standard rating for portable headphones. The efficiency is pretty good. With 1V applied it produces 114dB. 1V 30mW, this means at the specified 200mW an SPL is reached of 122dB... that's painfully LOUD ! As the 200mW is nominal it is quite safe to have peak signals in music that are much higher. Don't know if your hearing likes that though. To pr