[Coug]

You're lucky. I haven't found a set of older AKGs
(22 so far) that didn't need refresh on the soft parts. For the 240s and 141s a lot of soft parts are available because they continued production into the last decade as the studio and mkII versions. Some day soon those parts might not be available either.

Don't give up on those ovations, I have a set of their closed back brothers (HD 250), and was able to find close, but not exact, products to replace the pads and foam. Not the same, but still enjoyable. Search around on here for what others are using.

 

[Precaud]

I'm allowed to post pics now, here are pics of these DF's.

 

[Precaud]

I'm set up to measure impedance right now, so I thought I'd show the early vs late version of the DF's.

Resonant frequency on both versions is about 125Hz. The tunings are unusually broad, extending well into the midrange.

The voice coil windings on the later version are different, about 15 Ohms higher across the board. It's resonant peak is a bit higher and narrower, suggesting the later version would have more mid-bass output. But overall the two versions sound more alike than different.

The broad impedance tuning also says that any mods to ports, vents, etc. will impact a wide frequency range. That has certainly been my experience with them.

With the entire impedance curve above 650 Ohms, these things are piece of cake to drive. An NE5532 or LM4562 would have no problem.

 

[Steve Karl]

Although it has been some years since I've compared K240DF with my K240M, my memory suggests that there is a bigger difference than just the character of the midbass response. From what I recall, in addition to flatter bass response, the DF was also more open and extended in the highs. My suspicion is that a change in driver porting would not be sufficient to explain such a difference. I remember wishing to replace my K240M with a DF.

On a side note, there's simply no comparison in detail between my K702 and K240M, nor do I think that the DF would come close to the same resolution of the new model.

Sorry for necro-posting but I have more (subjective ... yes it's just my point of view but it might help someone) information to add here.
I have 2 sets of k240DF and 2 sets of K702.

I was just doing a preliminary mix on a piece of music the other night, late at night.
I started with the K702 then switched to the K240DF.
Yes. the k702 has a more open sound stage and sound more spacious and are vastly more comfortable
BUT
The K240DF is more detailed, in my opinion, in that the show everything in a very 'clinical' way. I'd call it more sterile - or more flat.
I then switched back to the K702 after a while to find a subtle yet startling peak in the mids - I'd guess around between 1,200 to 1,300,
and also more pronounced bass in what I'd call the "sweet" bass range - 70 to 80.
The difference is very subtle and only takes a short time for my subjective perception to re-align and get back to work, but there are differences
that I'm glad that I can now be aware of.
For overall clinical accuracy and hearing what is really *there* - in the sound - I'm always going to go back to the K240DF - - -
even though I absolutely love the K702.

I totally agree that the K240M doesn't have the clarity, detail and accuracy of the K240DF.

I "suspect" that the actual drivers in the K240DF and the K240M are a different design but I'm glad I found this thread since I have a set of K240M that are
partially torn down getting cleaned up and new cushions, and I think I'll try blocking those holes and then do a compare to the DF and also my other set of K240M that are in great shape with relatively new 6 month old cushions.
It might be a while before I get to it but I'll probably come back when it's done to share my experience.

 

[Steve Karl]

I cleaned up my second set of DF the other day and took some macro photos.
In my 2 pairs of DF, there are 2 different drivers. One is marked 18R5 and the other 18S0. (S as in Sam)

A long time ago I ordered a set of 2 new drivers from AKG when they were available and I'm not thinking it was about being a matched set as much as it was being a different specific Left and Right side.
I replaced one driver in this DF (not sure which side) because it was sounding "fuzzy" so I still have a new (old stock) never used driver and the "fuzzy" sounding one
so I was able to take photos of the drivers that were not installed in the phones.

Also, my drivers have less holes that some one else mentioned and you can clearly see how the white blob is used to cover something.
3 smaller images attached here to this thread.
and
More high res. images here:
https://photos.app.goo.gl/zLnkDf9XHPnkBa1d8

When I open up my K240M I'll post photos of the drivers. Not sure when I'll get to it.

 

[Precaud]

This is not worth starting a new thread for, there aren't many K240DF-related threads, so I'm piggybacking on this one.

Back when the K240DF's were designed and made, there was a DIN spec/standard (can't recall the number) that most if not all European headphone makers adhered to. It defined a uniform set of procedures and conditions for testing headphones. A part of that standard states that headphones are to be driven from a 330 Ohm source (or was it 300?). This was typically accomplished by tapping off the amp's speaker outputs with 330 Ohm resistors. If this is true, it occurred to me that I have never listened to my K240DF's under these conditions. So I put together an adapter using some 315 Ohm Dale CMF70.

The sound of the DF's makes much more sense this way, and I definitely prefer it. Much better tonal balance across the spectrum. Look at the impedance curve I posted earlier in this thread, and you can see why. A 300+ Ohm resistor divided by that impedance curve creates subtle EQ shaped exactly like the impedance curve. I highly recommend trying it.

 

[Steve Karl]

Although it has been some years since I've compared K240DF with my K240M, my memory suggests that there is a bigger difference than just the character of the midbass response. From what I recall, in addition to flatter bass response, the DF was also more open and extended in the highs. My suspicion is that a change in driver porting would not be sufficient to explain such a difference. I remember wishing to replace my K240M with a DF.

On a side note, there's simply no comparison in detail between my K702 and K240M, nor do I think that the DF would come close to the same resolution of the new model.

Sorry for necro-posting here. I know this thread is really old but I've been doing some listening comparisons.
*** K240 M - K240 DF and K702.
I just, this afternoon, re-cabled my second set of M (stock AKG cable) and wanted to compare to my first set of M to make sure everything was good. Yes - both the same.
Then - - -
I also have 2 sets of DF so I got to doing a compare (again) between the M and the DF.
Of course this is just my 'subjective' take on everything, including estimates of Hz.
My amp is a vintage Marantz 1060 and I have an attenuating box / knob on the headphone out so I can ramp up the power an not fry my ears.

My audio compare files are 2 short sections of 2 Star Wars sound tracks (Return of the Jedi and The Rise of Skywalker)
that I have loaded in Sound Forge and the 2 compare 'Regions' are looped so I can swap phones quickly while the loop is playing.

The DF as the most neutral - linear - flat - of the 3 models I mention above. ***
If we want to see sound as colour I'd call the DF grey.

The M are slightly richer / thicker in the upper bass - lower and middle mids. - the 'solid' mids -
before we get to around 2,300 / 2,500 / 3,000 Hz - where things can get a bit edgy and harsh.
If I was to draw hump on a straight line that I see as the DF - - -
I'd start at about 125 Hz and end at about 1,200 Hz. Just a gentle mound in shape.
Areas that are more obvious to me, probably because I'm familiar with the colours I associate with the frequencies, are
125 Hz, 200 Hz, 320 Hz, 400 Hz, 640 Hz, 1,280 Hz, 1,620 Hz.
This is probably my ingrained memory from using Graphic Equalizers for so many years in the past.

So, the M are slightly 'warmer' in the upper bass, (the pop and messy 'ooofff' of a snare drum or higher tom tom)
- have slightly more detail, to me, in the 'woody' tones. Imagine a marimba or an acoustic guitar.
- have slightly more 'snarl' - like the woody growl of a blues guitar.
- they might be very slightly harsher from 2,000 Hz to 4,000 Hz but It's hard to tell because of the hump below that.

As far as I can hear, the highs - from 5,000 all the way up are so close to the DF that I'd not care,
'just maybe' the DF are slightly more open in the highs,
but then again, that warm hump does distract enough that it's really hard for me to tell.

Now - onto the K702 - yea - more detail in every range compared to the M and the DF.
But I still don't know if I trust them the way I trust the DF.
The 702 sound very close to my Mackie HR 824 monitors. The sub bass on the 702 is really there.

So, that's all for now, just wanted to share in case it might help in some way.

 

[RuslanG]

The K240DF is more detailed, in my opinion, in that the show everything in a very 'clinical' way. I'd call it more sterile - or more flat.

I didnt have k240DF, but I have the same experience with K271mk2. At low volumes K271 is more precise mid-range monitor than K612, k701,k712. Compared with k240 (studio, MK2) by my opinion k271 is a better monitor because it doesnt have mound on upper bass/lower mids

 

[Steve Karl]

I didnt have k240DF, but I have the same experience with K271mk2. At low volumes K271 is more precise mid-range monitor than K612, k701,k712. Compared with k240 (studio, MK2) by my opinion k271 is a better monitor because it doesnt have mound on upper bass/lower mids

That's for the info on the K271mk2.

Are you using the leatherette or velvet earpads?

 

[RuslanG]

That's for the info on the K271mk2.

Are you using the leatherette or velvet earpads?

velvet pads