[Mad Max]

I got a chance to compare these in sound to PX360, indeed the same headphone, though bass sounded a little better on the PX.  Then again, its little string of a cable is much shorter, which is probably the cause, in my opinion, if the driver quality in my HD360 isn't slightly lower by chance or slightly below average if the PX360 I auditioned is average or what have you there, hahaha!
So, same headphone for sure, it seems.

 

[ThomasHK]

   
Quite a unique baffle design to me here.  There's a cup structure with three notches close to the center.

 

 
I'm surprised no-one else has picked up on this, but the proof of all the ongoing discussion in this thread is in this picture. Of course it's a unique baffle ... because it's from a noise cancelling model. I believe the MM 550-X. Those three notches mentioned are grooves in the microphone holder. You can see the slit which would normally hold the microphone cable and which leads to the back housing, where the electronics normally reside.
 
It seems Sennheiser has just been doing some clever modular headphone building, using the same tooling for several different models. This HD360 PRO uses the same baffle as the MM 550-X, maybe even the headband is using identical parts, I don't have those details.
 
Just a note: using the same baffle or cup doesn't mean that two headphones will sound the same. A simple felt paper change can completely modify the characteristics of a headphone. 

 

[Mad Max]

I tried adding much more Dynamat Xtreme to HD360 than before, and isolation has improved significantly.  Midrange/treble balance became much better than before, to my surprise.  What blew me away was how much the soundstaging improved as well, very holographic and precise now, bested only by K701 and T90 in my collection.
Something really nice that Sennheiser did with this headphone was to keep cup reverb to a minimum, something kind of rare in closed headphones these days.  My HD360 is an even better portable mixing monitor than before now, too bad it is discontinued.
 

 
And that piece of acoustic foam is unnecessary, I forgot to remove it.
I did sacrifice some of the bass boost by going this far, but it remains extended and very noticeably rumbly when the music calls for it.

 

[vb17]

Hello,

I recently overstretched my cable and now my beloved PX360 (regular, not HD) are dead-silent .

So far I have tried to remove the baffle cover but am really struggling to succeed with it. Since I am scared to break something I would just really like to ask those users who have carried out a re-cabling to give me some hints as to how to get it off. A picture of you @Mad Max was posted previously where you mention it is snapped in place with double adhesive tape...

I even X-ray'ed them to see whether there are any hidden screws or such

So yeah... any help in getting the baffle cover off would be greatly appreciated.

Many thanks,
Valentin

 

[vb17]

Hello,

I recently overstretched my cable and now my beloved PX360 (regular, not HD) are dead-silent .

So far I have tried to remove the baffle cover but am really struggling to succeed with it. Since I am scared to break something I would just really like to ask those users who have carried out a re-cabling to give me some hints as to how to get it off. A picture of you @Mad Max was posted previously where you mention it is snapped in place with double adhesive tape...

I even X-ray'ed them to see whether there are any hidden screws or such

So yeah... any help in getting the baffle cover off would be greatly appreciated.

Many thanks,
Valentin

Never mind, I got it if ever anyone happens to struggle with this: it is really only the baffle cover that needs to come off to reveal the screws. Its a thermoformed plastic sheet with a thickness of around 0.5 mm with the veil directly bonded to it. Best is to use a knife to get underneath it.

Cheers anyways

regards,
Valentin