[MDR30]

I observed that the K3 driver and the XXL driver were similar in size, around 26-27 mm (i e smaller than the DKK32 driver). Different diaphragms though, as you point out.
 
Pics of XXL drivers courtesy akgfan, different diaphragm pattern and closed back (except the "bass holes"):

 

 
Same XXL driver in the K242 HD:

 
And here are some pics of the 1984 K3 and driver, basically open back except for the ubiquitous white paper filter:

 

 

 

 

 
 
 

 

[Neighbour]

AKG entered the market as a Microphone manufacturer only.
All the capsules had a small diameter design. I think, it was a strategic movement to name the bigger capsules in headphones XXL Driver for better product placement..

 

[Adda]

 

[Punnisher]

I wanted to bump this thread because I have performed a simple modification to my new K240 Studio and it seems like a great success. After hearing about mods to the K240 Monitor that turn it into a K240 DF, I wanted to try this with mine.
 
Look at the XXL driver in post #31. On the back of the driver you can see a small "arc" shaped hole that goes through to the inside of the driver. Note that the newest driver as of now looks slightly different with the arc being shorter but wider. I took a piece of adhesive-backed felt and covered this port in each driver. I think this would be equivalent to covering it completely with tape, sticky tack, etc.
 
The result was actually much better than expected. Drastically reduced midbass which is what most people complain about with this headphone. There seems to be no midbass hump at all. Deep notes still have impact but it's much cleaner. Mids and treble are cleaned up significantly, probably due to the driver being less burdened with excessive midbass. Better imaging and separation, not unlike the k702. Overall it's a step closer to the analytical side but still warmer and more comfortable to listen to than the K702. If you want a more linear sound out of your K240 Studio it's a no-brainer.

 

[mrrDUDE1]

Look at the XXL driver in post #31. On the back of the driver you can see a small "arc" shaped hole that goes through to the inside of the driver. Note that the newest driver as of now looks slightly different with the arc being shorter but wider

Ive lurked around here before but decided to join because I'm interested in modding the 240 S
Could you download the picture and circle the arc shaped hole you are talking about with Microsoft Paint or something?

 

[Punnisher]

I just wanted to give an update. I'm still listening to these and enjoying them immensely.
 
My theory is that AKG made their XXL driver highly accurate and full-range even when closed. By using various tuning port sizes AKG can tailor the sound to whatever headphone they want. Obviously they were going for a fuller, bassier sound with the K240 Studio. Though once you close the port the mids and treble are opened up considerably. Still there's no lack of low-end. I don't feel there's bass "missing" but rather it's under strict control which does great things for the rest of the spectrum.
 
 
Here is the picture with an arrow pointing towards the arc. It is very similar on my new K240 Studio.
 
The exact material I used is a small felt disc with adhesive back. Used for placing on furniture feet to protect wood floors. This is the exact pack I took them out of:
http://www.amazon.com/Piece-Self-Stick-Home-Protection/dp/B007XIDEVY
I used the smallest size which is about 3/8".

 

[mrrDUDE1]

Wow it was right in front of my face the whole time :I
I stared at that picture for like 10 minutes
Anyways when my 240S comes in I'll be sure to try this little mid and report back
There's not a chance that the felt pad could deteriorate a bit and gunk up some of the driver's innards is there?

 

[Punnisher]

I don't think it will cause any problems. It's adhesive backed so the felt is contained. Also the hole is very small which makes it hard for anything to get inside.

I don't think this headphone would trump the k702 but I hear a lot of good similarities. Not bad for 80 dollars.

 

[MDR30]

This is similar to the wax mod someone did ages ago, closing a side vent with wax (it was even mentioned in one of the AKG service manuals).

 

[Punnisher]

Mr Dude,

Any updates on this mod? I'm curious to hear what others have to say.

 

[mrrDUDE1]

Sorry man I went through a brief period of wanting a q701 but then decided against it
Currently looking for a good deal on eBay for a 240
If I can't find any I'm just gonna go for a new one on amazon
It's only 88 bucks so what the hell I might as well
I'll burn it in and report back
Could tape also work to cover the hole? Or blu tack? As long as the hole is covered anything works right?

 

[Punnisher]

I think it would all be the same. Though I would lean towards the felt to be sure. The felt may be more flexible than tape so it offers better fit. It may also seal slightly less than blu tack, which could be an advantage for sound signature.

 

[mrrDUDE1]

Ordered them!
They will come in this week!
2 final questions… I'm so eager to see how this will turn out…
1: Are the drivers easy to take out? These are my first pair of actual headphones :I
2: Should I burn them in BEFORE or AFTER I cover the hole?

 

[Punnisher]

You don't actually need to take the drivers out. You only need to take the cups apart.

1. Remove the stickers on the outside of the cups. The "akg" and U shaped ones.

2. Remove the screws under the stickers.

3. Remove the small black caps, exposing the wiring.

4. De-solder the wires going to each driver. They should be red and white. Don't de-solder the wires on the actual driver, but where they terminate inside the small black caps. Remember where each wire goes.

5. Remove the large screw. The cups can now be disassembled. Be sure to remember the orientation of each piece.

6. Using a needle-nose pliers, apply the felt piece to the back of the driver. Press firmly to ensure a proper seal.

7. Reassemble the headphone.

It may be possible to do the mod without de-soldering but you'd need a small and long needle nose pliers similar to one you'd see at a dentist's office. Detaching the cups fully will make it easier to work on.

As for burn-in, I dont know for sure. The diaphragm will move more when stock, so it could be advantageous to do it before for a few days. Use the time to research dissasembley of the headphones and get any tools you may need.

 

[RamblinE]

This thread is making me really want to try out the K240 Studios!