The AKG K400 is a classic headphone that is produced back when the K500 was produced. They were launched at the same time, and both were prior the K401, K501. For more background information, you should search in these forums or google.
Its bass is not deep by any definitions. Very tight and lean is how I would describe it. I do think it is similar to the K701 but maybe I need to loan a pair to confirm such. The roll off is very early but I find its mid-ish bass satisfying enough for a bass light experience, at least it is not non-existent.
The treble of the K400 is very smooth. It also does not offer the highest highs in other flagship / treble head headphones. However it is not as sibilant as others e.g. the DT880. In fact, one can listen to these for very long sessions and the sound is very pleasing, because of...
THE K400 MIDS IS MAGICAL. The clearest mids in my collection, the most natural ones. Not as upfront as the Alessandro MSPro, but it is really a high-fidelity experience. Again not the most detailed headphone (even the HD580 is more detailed to my ears); but there is no mid bass hump, no sharp treble. Every bit of research AKG has done to the K400 has went down to its mids. Absolutely neutral, flat FR in that middle range and rolls off both end. It avoids being too dark, nor too clinical sounding; which is why I have chosen it instead of the K701. To me it far surpasses the K701 in terms of musicality. Not everyone could enjoy a K701 - clinical, cold, 'plasticky', 'unreal soundstage' etc., EVERY audiophile would enjoy the K400 mids.
- Not the quickest headphone. Very quick music will sound congested e.g. metal like 'Dragonforce'; Visual Kei band 'Versallites'
- Not the biggest soundstage. It is bigger than the HD580 due to having less midbass (I find warm sounding headphones having a close and intimate soundstage that is not the widest nor the closest); but smaller than the K500 (close). From sonic memory it is smaller than the well regarded ones namely the HD800, K701 and the Sony SA5000.
- Detail - it will not give you that magnifying lens you had with the K701 or SA5000. What you get is a lovely picture of the music as a whole.
Conclusion / Other notes:
I'll give an anology as a conclusion. The K400 portraits a very real natural scenic picture. It does not have too vivid colours, it does not offer a gazillion pixels. However its positioning is very appealing, and white balance, exposure is spot on. The clarity and detail might be confusing, so in my definitions (at least in here) clarity is the lens, and they are sharp; detail is the pixels and no it is just enough for a standard monitor wallpaper; and the high/low end roll offs sort of create a lovely depth of field that makes the focus point so appealing.
Any music that does not require super low bass or high treble would yield good results with the K400, if you enjoy purity/clarity in your music. Maybe try something that appeals in a natural way, e.g. instrumental, orchestral depending on what you focus on, accoustic, OPERA might be good etc. you get the flow. You are either very special or stupid if you purchased these to listen to dubstep or crazy metal riffs in my opinion.
K500 deserves a mention!
A side note to the K400. I at one time had a K500 but ultimately decided to sell the K500. While the biggest deciding factor was demand and price (ashamed); I was glad the buyers made that decision for me. K500 had better treble, better clarity, sounded more airy etc, but that is due to the treble's strong performance. The K500 nailed the connection between mids and highs, it is done very smoothly, it is its strongest suit. K400 however trumps at its narrow mid frequency range. I put on the K500 and get amazed, goes back to the K400 to listen to my music, to feel the singer's emotions. Lovely headphone.
Both the K400 and K500 requires MONSTEROUS CURRENT to sound good. Good thing is their impedance is high so an OTL tube amp would work; or a mid/higher end solid state. They will produce decent volume out of a normally designed amp, but you only get that smoothness and bass and everything on a very solid performing amp.
I used an AUDIO-GD NFB5.2 on HIGH GAIN as my DAC feeding into my DARKVOICE 336 OTL tube amp.
Edited by mrAdrian - 1/21/13 at 6:07am