AKG K340 Electrostatic-Dynamic Headphones

The original top model from AKG unfortunately weakens on many levels. A pair of headphones can be as great as you like, but if they don't fit properly to the head due to a lack of hinges for horizontal adjustment, or the ear pads are too thin and the ears touch the inner plastic grille, or the suspension headband is too weak, the sound can still be as good as you like - the headphones are put away after 10 minutes. This is exactly what is present with the K340. I have made some modifications to improve the wearing comfort, but I demand that from a manufacturer itself - in 1979 the heads were not different than today (in terms of shape).

I own the model with gray drivers, so it is a "bass heavy" version, while the others (red and black) are also often described as that, or at least as "neutral". The green version is referred as "bass light". My test combination can be seen in my signature.

And yes, the bass is good in quality and quantity, reaching below 40 Hz and producing a pressure that electrostatic drivers could never do on their own. And yes, the electrostatic drivers reproduce a great amount of detail, including fine detail. They are never intrusive, bright or metallic, instead the high frequencies are very pleasant to listen to. Combined together in the AKG K340's cabinet, it sounds like this: As if you actually put good speakers in a laundry room with tiles on the walls. Unlike other models from the time (explicit the K240 Sextett), the K340 are not brightly tuned, also the soundstage is extremly wide and large. However, this combination makes everything sound hollow, synthetic and washed out, as if there was a big veil over everything. Everything sounds wrong, out of phase, not homogeneous in itself, every driver playing separately for itself. After half an hour I had a headache because of this, the brain tries to permanently compensate the obviously audible delay between the electrostatic and dynamic driver.

So the K340 had to be modified. Rewired the entire headphone, the dynamic driver is thus directly connected, a cable from the dynamic driver then leads to the PCB, instead of first to the PCB and then to the dynamic driver. This solved the "out of phase" problems, the sound image is much more homogeneous. Other ear pads also immediately help the headphones in terms of sound as well as comfort. I also removed the inner grille, this made a big difference. For more details feel free to look at my posts.

Connected to a rather darkly tuned OTL tube amp, the slightly modded K340 suddenly becomes great fun. I admit, I was initially very disappointed with the headphones and didn't understand what they did better than a K240. But now I understand what people mean that these headphones can easily compete with today's models. I won't say it's better than the 500€ price range, but it attacks them with its very interesting unique presentation.

When I first began my career, I was looking for some inexpensive but good quality headphones for my personal reference. The K340`s were less expensive than the cream of the crop at that time, the Staxx system with the discrete amp, etc. Over the years I have had no problems with the jack shorting, cord fraying, plastic breaking, etc. They have always been reliable and within the factory specs.  At the time the k340 came about, most of the less expensive headphones had the standard 3 strand wire design that was not well shielded and little separation of the left-right-gnd wires inside the mono outer casement. My K340`s have the molded 4 wire flat cable that provides about .080" separation between the conductors. I have never had problems with crosstalk or noise from the headphone wiring that I can remember. They have held up very well over the years. I have used them as reference head monitors for a number of recording projects from Margo O'Donnell, Dolly Parton, Five Bucks, to the smokey mountain travelers. They remind me of a headphone version of some JBL 4310`s or some good NS-10s. For live, the ear  foam ring does do an ok job with high spl situations during a loud show. They have survived many road shows over the years. I still pack them in the original Styrofoam vendor packaging. They are well used and loved and they have never let me  down. I am surprised that AKG stopped making them years ago, but has continued making the k240 which is the baby. I feel as though I made a decent investment those many years ago. And, if I ever need to, I can send them to Austria for a tune-up. thanks all 

I bought the AKG K340 Electrostat-Dynamic System twice. The first pair was very worn out and sounded weird so I sold them after a while. I bought the second pair from Ebay, and this one sounded very different. I used the first pair with the Beta 22 amp which really struggled to drive it properly. The second pair I'm using with Headroom Ultra Micro Amp with Astrodyne PSU, and surprisingly it drives this pair with no problem, I hardly pass 10 o'clock of volume!
 
I suspect that the second pair is the bass heavy version. There is a lot of bass here with deep impact, although not very detailed but not loose bass like that of D2000/D5000. It's well integrated into the spectrum of sound and adds a lot of warmth to the sound character. 
 
The Mids and Highs are the best quality of this pair. They are very clear, very detailed and very smooth. This is attributed to the double driver system of the K340 (electrostat and dynamic), which eventually results in a very layered sounstage of 3D holographic nature, while on the K702 it feels 2D in comparison.
 
Compared to my beloved K702, the violins and flutes sound very smooth and extended, while on K702 they seem very bright in comparison with slight harshness. If I don't compare the K340 to K702 and keep listening to the K702 I don't feel there is any problem with the highs, they look absolutely OK, but when I put the K340 on, the K702 pales in comparison and sounds gray while the K340 is all black and white. The only area where K702 excels is a wider soundstage (which lacks in depth) and the bass is more detailed but without the impact and warmth of the K340.
 
On listening to DG's marvellous CD "Fiesta" or Boulez excellent recording of Varese's Arcana on Sony, I feel like a real Orchestra is playing on the stage, giving the instruments a great weight and impact that I never felt with the K702. Playing Beethoven's Cello Sonata No.1 by Schiff and Perenyi  I was overwhelmed by the Cello's deep and dark sound, it was a great emotional experience that brought tears to my eyes!
 
On listening to the K340 I only think about the music and the composer who created it, while on listening to the K702 I only think about the good sound quality! 
 
Considering their price range of 150 to 200 those cans are a steal, they can beat HD650, HD600, K702 and even my recabled K400 in performance. They are not perfect but considering the price and value they are a real treasure!