The AKG K240 Monitor was a variant of the famous K240 introduced in the 1970s by AKG, the Sextett. It was intended for monitoring and studio use. Apparently, sound of the vintage K240s is a bit different than current K240 Studio models.
The K240M is very light and comfortable, but the vinyl pads can quickly get sweaty. With 600 Ohm impedance and 92-95 dB/mW sensitivity, it is quite difficult to power and thus limits more its use.
The K240 Monitor (and Sextett) are one of the most common vintage headphones, easily found on Ebay and various marketplaces for $50-100. The K240 DF is a bit harder to get.
○ Release : 1984
○ Current status : Discontinued
○ Type : Over-ear / Open-back
○ Measured weight : 252g
○ Impedance : 600 Ohms
○ Sensitivity : ~92-95 dB/mW
○ Average used price : $40-80
The K240 Monitor is a well balanced headphone and is very close to the Diffuse Field target.
The bass has a light lift around 80-100hz, but the extension is lacking below 70hz. The midrange is very uncolored ; no overwhelming lower-mids presence and the upper-midrange is not forward or recessed. The treble is, again, nicely calibrated and presents a peak around 9-10 khz that gives a correct amount of energy and prevents the K240M from sounding dead. However, upper-treble (above 10khz) is pretty much non-existent, it lacks “air”.
Technicalities are not very strong and poor compared to modern midfi headphones. Staging is a bit closed-in and lacks width and depth. Dynamics are rather compressed and decay is a bit slow. Sense of openness is not great but I’ve heard worse open-back headphones in that regard.
As this blog is about personal listening pleasure, I don’t really recommend this headphone, even if the frequency response is good enough (though lacking in extension in both ends). High power requirements and poor technicalities dont do justice to the K240M.
It is easy to find used for cheap, but most of the time it will come with worn out pads so you’ll need to buy replacement parts.
Measurements & Resources
The 3.7 khz peak wasnt really audible when listening to my pair. Other than that, the measurements by Tyll are close to what I heard. Quite balanced from 100hz to 10 khz, with no annoying treble peaks and rolled-off bass. Slightly warm midrange tilt.