AKG’s flagship between 1978 and 1982, the K340 is a closed-back headphone with 2 drivers in its housing : a dynamic transducer for frequencies below 4khz, and for the ones above, an electret driver. It was quite expensive at the time, retailing for $300 (around $1100 today). It’s an imposing headphone that requires serious amplification to get loud.
○ Release : 1978
○ Current status : Discontinued
○ Type : Over-ear / Closed-back
○ Measured weight : 402g
○ Impedance : 400 Ohms
○ Sensitivity : ~87-88 dB/mW
○ Average used price : $80-130
I have listened to the K340 (mine is a bass-heavy version, with red drivers) with two different set of pads : stock vinyl pads, worn out, and Brainwavz Pleather XL Round pads.
I honestly couldn’t concentrate on the sound with stock pads for too long, mainly for comfort reasons. My ears were completely smashed into the plastic grill housing covering the drivers. I just thought they sounded quite bright and thin, with a hollow midrange.
With Brainwavz XL Pads, soundstage is way wider and sound a bit more V-shaped. Bass gets bigger and extends a bit, though it doesnt have great sub-bass rumble and texture. Midrange is still weird sounding, and treble a bit annoying. I believe the electrect driver makes the treble sounding way quicker than the bass and mids, and it’s a bit unnatural sounding. Depending on the songs, the K340 could sound warm (warmer than most AKGs I have heard) or hollow with sharp mid-treble. I prefer the K240M linearity though it does not have the speed of the K340 or its soundstage.
The K340 got my interest for some time, but after having bought them and listened for a few months, I was a bit disappointed. I don’t totally understand their popularity among vintage headphones. They might sound okay with a good amp synergy and some pad rolling, but I don’t think anything can remedy their weirdness in the higher frequencies and the bass roll-off, taking naturalness away.
Measurements & Resources
The frequency response (stock pads) shows how the K340 can sound warm or bright. Emphasized upper-bass / low-mids, quite a lot, around 150-400 hz. Midrange is confused with extra energy around 2.5khz (similar to other AKGs). The 1.3khz narrow deep is related to the 4khz cross-over between both transducers. Treble is sharp around 9-10 khz, and (hard to measure), extra treble above 10khz.