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AKG history - the introduction of the "parabolic" headphones (K 270, K 280).

post #1 of 25
Thread Starter 

Hi everybody...

 

here's a bit of history for the "vintage AKG geeks" around here.

 

 

I like the good old K 270 and K 280 a lot and I was interested in their history, so I asked AKG for some details.

 

 

The kind folks at AKG clarified some things for me and since this may be interesting for some people around here, I translated their response for you:

 

 

The questions I asked were:

 

-What were the design goals of the K 270 and K 280 headphones? Why was the twin capsule arrangement chosen and are there benefits to it apart from lower distortion and higher maximum sound pressure levels?

 

-What kind of mareket was the K 280 meant to appeal to (home users or rather recording studios)? What role did the K 280 play in AKG's lineup of high quality headphones?

 

-When was the K 270 introduced and why did AKG choose to make a closed-back headphone on the basis of the K 280 as opposed to the current K 171/K 172 models which are based on K 141 / K 240 technology?

 

-Some people believe that the "Playback" model of the K 270 sounds better than the "Studio" model which has the auto-mute feature. Is there any reason to believe the two models perform differently, given that they use the very same parts execpt for the micro switch which should not make any difference?

 

-Are the spare parts that are no longer used by current models (e.g. DKK32 capsules) still produced or is there a limited  number of them in stock?

 

 

Here's the response from AKG:

 

The design goal of the K 280 was to develop a headphone that was capable of reproducing high sound pressure levels with a minimum of distortion. To this end, two transducers were arranged in a way so they focused the sound directly on the entrance of the ear canal. The doubled cone area was responsible for a much better sound quality that was free of distortion.

The headphone was popular with recording studios and home users alike.

The K 280 was introduced in 1987 and the K 270 followed a year after that.

The design goal of the K 270 was to create a closed-back headphone with a sound that is as balanced as possible. Based on the K 280, the K 270 used different acoustic tuning of the capsules which was achieved by using different bass resonators and cavities to achieve this aim.

The headphone was equipped with an automatic mute switch that has no effect on the sound quality whatsoever.

All spare parts for the mentioned headphones are still available.

 

 

The original (German) discussion is available here: http://www.akg.com/forum/index.php/topic,3754.0.html

 

Kind regards,

Stephan

post #2 of 25

Gratifying that you got such a detailed response about what's now a vintage phone. I actually ordered a 280 once but got cold feet when I read a negative review of them and cancelled the order (the review said something about a "comb filter effect"). But I thought the idea of two transducers was intriguing and always wondered what they sounded like. Maybe you could describe the sound for us in the light of today's popular models, if you have any experience of those.

post #3 of 25
Thread Starter 

Ok, let's see...

 

 

I've used the 55 Ohms K 240 S (same as MK II) which has a slightly emphasized mid-bass response (probably to compensate for the fact that you don't get a tactile feel of bass with headphones). On an amplifier that has a high output impedance, this can become pretty annoying.

 

When run out of a low impedance (close to 0 Ohms) jack, the K 240 S sounds quite similar to the old 600 Ohms "Monitor" model which seems to have a slight mid-bass hump as well.

 

Closing the bass hole of the K 240 M's capsule seems to turn it into a K 240 DF which has a more neutral (some might say: light) bass response (which I prefer).

 

 

I'd say the K 280's bass response falls somewhere between the K 240 Monitor and DF. There isn't much of a mid-bass emphasis and the overall bass response seems to be slightly louder than the K 240 DF. I'd say it's quite honest.

 

The K 280 seems to have slightly less treble which to me actually seems to be a little more neutral than the K 240 models. With some recordings, the K 240s seem to be slightly sibilant to me which doesn't happen as much with the K 280. The K 280's  treble response is actually similar to the K 141 M (K 240 M capsule but different diffusor in front of it), but the K 141 doesn't reproduce the lowest octave too well.

 

The midrange seems to be similarly neutral and uncoloured on all of these models.

 

I also have a K 171 S which uses the same capsule as the K 240 S, but in a closed-back, supra-aural configuration. I'd say, this one is quite neutral as well, with a very honest bass response that is quite similar to the K 280. The midrange and treble seem to be pretty similar to the K 240 S, which is probably to be expected since its the same transducer with the same "diffusor" in front of it. Thus, critical recordings can be a little sibilant as well.

 

Of course, the perceived sound depends a *lot* on your personal HRTF (which the reviews with all the fancy "audiophile" terms rarely tell you). I'd expect the "sibilance" thing to be highly dependent on the listener. The bass and lower midrange response may also vary with the shape of your head and the resulting "fit" of the earpads.

 

The K 270 seems to prove this point rather well. The sound quality seems to vary noticeably with the fit of the earpads. When the earpads form a good seal with my head, the K 270 sounds quite similar to the K 280. With worn earpads, though, there seems to be something lacking in the lower midrange which makes voices and some instrument sound "hollow". For me, results seem to be best with the velours earpads.

 

With the K 141, K 240 and K 280, all being semi-open rather than closed, the influence of the earpads seems to be a lot smaller.

 

 

The dual drivers of the K 270 and K 280 do seem to help the headphones eproduce high volume levels, especially in the bass range. With a powerful amp, they are able to deliver ear-splitting levels without distorting. The K 171 is comparable in this regard because of its tiny and closed earcups. I haven't compared them to Sennheiser HD25's or other "super-loud" phones, though. Maybe the bass heads or volume freaks would disagree :-)

 

 

As far as comfort is concerned, I also prefer the K 280. The supra-aural models tend to feel uncomfortable after a while (especially the K 141). The K 240's baffle also tends to touch my outer ear a bit after a while (especially with worn earpads). The K 280 and K 270 offer more room for my ears due to their different baffle, but the K 270, being closed, makes me sweat a bit on warmer days.

 

 

Maybe my description of the relative differences gives you a rough idea.

 

 

As for the "comb filter" thing... As far as I know, two sound sources that reproduce the same frequency will create a pattern of peaks and dips known as a "comb filter". All of the AKG headphones I know have have a disk with several holes in front of the driver which probably tunes the treble response and also acts as a diffusor. Shouldn't there be comb filter effects caused by the adjacent holes anyway? Would a second capsule really make much difference in this regard?

 

Actually I'm not quite sure if the two capsules can really "focus" sound into the ear canal. Maybe they just act like one large driver with a diffusor in front of it (not quite sure how to describe it).

post #4 of 25

Thanks for that, KptKlotz; appreciate you taking the trouble. Unfortunately I'm not hugely enlightened as I'm not familiar with those AKG phones but never mind, it's interesting to hear about older designs and especially how they compare with newer ones. We're always being told that each new model bests the last...they've been assuring us for years in the hi-fi mags that each new amp is better than the last, but when you take a 20-year-old amp and compare it to the latest model it's hard to pick a difference. Of course amps are only there to amplify and shouldn't be changing anything anyway, whereas headphones do have the scope for huge improvements.

 

Hope to see you contribute more impressions, or anyone else with older model phones for that matter.    

post #5 of 25

awesome!

i had a k270 long ago before i really understood what i had. since i had no amp, i was underwhelmed and sold it off. time to start looking again

post #6 of 25

Ooh, I've wanted a K270 Playback for a while, along with the K290 Surround (which is supposedly a better K280)

post #7 of 25

I was never all that impressed with the K280 that I had.

post #8 of 25
Thread Starter 

@pp312:

 

Actually I think the revolutions in audio are few and far between. The products that some companies managed to produce decades ago, without all the computer simulations, modern manufacturing techniques and resources of today can be unbelievably and awe-inspringly good, even by today's standards.

 

I think the constant and radical improvements that some people believe in are mostly a result of marketing and audio magazines that are actually sales brochures that you are expected to pay for.

 

This is not to say that there can't be improvements - all electro-acoustic transducer designs are full of compromises and improving one parameter often means that another will suffer. But "different" doesn't always mean "better".

 

With headphones you also have the problem of indivual HRTFs to worry about, but the audio press rarely seems to point this out. It's a difficult and confusing concept that's hard to explain to the consumer while throwing around some audiophile buzzwords is easy and more entertaining to read (not for me, though).

 

I hope I'm not sounding as cynical as I actually am :-)

 

@ishcabible:

 

The K 290 Surround was my first "real" headphone. I bought it in 1999 and happily used it for 8 years or so. When the cable broke, I contacted the German  AKG distributor and it was then that I found out that there is a full service documentation and spare part supply for AKG's high quality headphones. That's what really sparked my curiosity :-)

 

Anyway, the K 290 is basically the K 280 with the ear cups rotated by 90 degrees so there's one capsule in front of the ear and one behind. Actually, I think this is a pretty dumb idea and I'm not sure you can actually hear surround sound this way because there's no crosstalk between your ears the way it would be with speakers. I have used it with a surround decoder and found it pretty disappointing, to be honest.

 

As a stereo headphone the K 290 is quite good, though. It has more bass than the K 280 since the "bass holes" of both capsules per side are open whereas one bass hole is closed in the K 280. I prefer the more neutral reproduction of the K 280, but you can probably turn one into the other by blocking or opening the bass hole. If you look at the service docs, you will see that the parts are identical, except for the fact that the K 290 has a longer cable, is wired for surround and has a K 141 outer headband and an inner headband that is made of leather.

 

I never noticed much of a difference in the mid range due to the rotated ear pieces (and you could change that as well).

 

If you are *really* interested in this matter, I can try to do a more thorough comparison of the K 280 and K 290, but I'm not very good at writing audiophile "poetry" with lots of interesting sounding terms like "PRaT" or "silky highs" :-)

 

 

As for the K 270 "Studio" vs. "Playback" thing... I find it very hard to imagine that they perform differently. With capsules that are 150 ohms and voice coil wires that are thinner than a hair, what difference could a microswitch possibly make? Apart from that, the headphones are the same according to the service manual. So unless AKG has really modified some of the crucial parts (like the capsules or baffle) during the K 270's long production run, I don't see why this would make a difference (and that difference wouldn't really have to do with the "P" or "S" designation anyway).

 

The state of the earpads probably has much more of an influence (I seem to get the best seal when I use the velours pads on the K 270) and I suspect this may be the reason for some of the perceived differences and bad reviews. Again, this is probably highly dependent on a person's head shape, HRTF and preferences.

post #9 of 25
Quote:
Originally Posted by CptKlotz View Post


 

@ishcabible:

 

The K 290 Surround was my first "real" headphone. I bought it in 1999 and happily used it for 8 years or so. When the cable broke, I contacted the German  AKG distributor and it was then that I found out that there is a full service documentation and spare part supply for AKG's high quality headphones. That's what really sparked my curiosity :-)

 

Anyway, the K 290 is basically the K 280 with the ear cups rotated by 90 degrees so there's one capsule in front of the ear and one behind. Actually, I think this is a pretty dumb idea and I'm not sure you can actually hear surround sound this way because there's no crosstalk between your ears the way it would be with speakers. I have used it with a surround decoder and found it pretty disappointing, to be honest.

 

As a stereo headphone the K 290 is quite good, though. It has more bass than the K 280 since the "bass holes" of both capsules per side are open whereas one bass hole is closed in the K 280. I prefer the more neutral reproduction of the K 280, but you can probably turn one into the other by blocking or opening the bass hole. If you look at the service docs, you will see that the parts are identical, except for the fact that the K 290 has a longer cable, is wired for surround and has a K 141 outer headband and an inner headband that is made of leather.

 

I never noticed much of a difference in the mid range due to the rotated ear pieces (and you could change that as well).

 

If you are *really* interested in this matter, I can try to do a more thorough comparison of the K 280 and K 290, but I'm not very good at writing audiophile "poetry" with lots of interesting sounding terms like "PRaT" or "silky highs" :-)

 

 

As for the K 270 "Studio" vs. "Playback" thing... I find it very hard to imagine that they perform differently. With capsules that are 150 ohms and voice coil wires that are thinner than a hair, what difference could a microswitch possibly make? Apart from that, the headphones are the same according to the service manual. So unless AKG has really modified some of the crucial parts (like the capsules or baffle) during the K 270's long production run, I don't see why this would make a difference (and that difference wouldn't really have to do with the "P" or "S" designation anyway).

 

The state of the earpads probably has much more of an influence (I seem to get the best seal when I use the velours pads on the K 270) and I suspect this may be the reason for some of the perceived differences and bad reviews. Again, this is probably highly dependent on a person's head shape, HRTF and preferences.

 

I'm just going by what Fitz has said, so please, make a comparison if you have the time! And I honestly don't know the deal between the Studio and Playback, but from what I've read, they sound different/more involving, so I'm just taking guesses at this point. I'd like to be wrong though. The Playback version is exceedingly rare.
 

 

post #10 of 25
Thread Starter 

 

Quote:
so please, make a comparison

 

Between the K 280 and K 290? I can't compare the K 270s since I only have a "Playback". I didn't even know they were that rare compared to the "Studio". I got mine on eBay for around € 50 or so some years ago. Unfortunately, I noticed a dent in one of the capsules' diaphragms so I ended up replacing it. I didn't hear any distortion, but the dent annoyed me :-)

post #11 of 25
Yeah between the 280/290. Did the new driver sound any different?
post #12 of 25

I had both a K280 and K290 and they sounded pretty much the same to me.  They both bothered me in the same way so I wound up selling both.  I thought the midrange was a bit hollow sounding, like certain frequencies just weren't there as they should have been, which was really surprising to me since all their other vintage headphones have some of the best midrange ever.  Other then this midrange issue though, they were pretty sublime.  Great balance of bass and treble, and soundstage and imaging were really 3D

post #13 of 25
Thread Starter 
Quote:
I thought the midrange was a bit hollow sounding, like certain frequencies just weren't there as they should have been, which was really surprising to me since all their other vintage headphones have some of the best midrange ever.

Interesting... Actually that's about the impression I get when the K 270 doesn't form a good seal on my head. Some voices and instruments seem to lack some "body" in the lower midrange which makes them sound... well... hollow.

As mentioned above I seem to be getting best results with the velours pads. The pleather pads are ok as long as they're still soft and I make sure the headphone is sitting well on my head.


However, I don't notice this thing with the K 280 or 290 that much, probably because they're half-open anyway. Apart from comfort I don't think the earpads make much of a difference.


Sound-wise, I think the K 290 has significantly more bass. I haven't tried it on an amp with a really low output impedance which might make a difference.


...stay tuned :-)
post #14 of 25

I loved the K280/K290 with music that had no vocals.  As soon as vocals came in, they really bothered me.  Like I said, I didn't really compare the 90 and 80 because they both had the same problem IMO, so I didn't really care what other differences there were.  The K290 I had was even recabled. 

post #15 of 25
Thread Starter 

Ok, I've compared the K 280 and the K 290 and I paid special attention to voices.

 

I'd say that both phones are indeed very similar in the midrange and above. I hardly detect any difference at all. It seems the vertical vs. horizontal orientation of the drivers doesn't make much of a difference, at least on my head.

 

The K 290 has more bass, but I wouldn't say it's really excessive. I do consider the K 280 more neutral and I prefer it that way.

 

@rhythmdevils: I don't really hear the thing you're describing... Maybe my HRTF is better suited to those two phones or it's a matter of preference. One way or the other it's probably safe to say they're not your cup of tea :-)

 

Do you have any of the other phones I have (K 141 M, K 240 M or DF, K 270, K 171), if so, is the "hollow vocals" thing different on those?

 

How do you like the K 340 in comparison (I'd sure like to try one of those)?

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