Recently i was looking for info about HD 800 ring radiator transducer.I found this blog: http://rinchoi.blogspot.fi/2013/01/sennheiser-hd800-part3-in-depth.html Then i wondered if hole in the diaphgram would work in PortaPro.First i cutted off some of that plastic grill.Then i pressed the middledome against the magnet with finger and cutted off the dome.This operation needed steady hands,patience and tweezer.
The results? Simply magnificent!! Overall sound performance has improved significantly.Gone is that loose bass,somewhat veiled sound,lack of details and fuzzy imaging.
Here are my observations:
BASS:
What i noticed first after this mod was how tight and very well controlled bass became.I haven´t compared these with HE-500,but i think the bass tightness is propably on par with it.Bass is also quite textured aswell.
MIDS:
I have to admit that i´m not that good reviewing midrange.All i can say is that it sounds more detailed and thus,more realistic.
TREBLE:
At first i didn´t notice any difference in treble.After a while,improvements in resolution and speed started to get more noticeable.Treble is now much more refined and smoother.Not smooth like planar magnetics can be but not rough either.This modded PP is now more detailed than SRH 940 and HE-500 were ever,at least for me.I suggest to raise treble for about 2 db´s.
IMAGING:
Biggest surprise was the super precise imaging.First time ever i was able to locate individual instruments and hear previously unheard ambience information.Imaging was also quite out of your head (depending of recording) which is something i´m missing with HE-500.Instrument separation also became unbelievably good.
SOUNDSTAGE:
Soundstage grew noticeably.It is also airier than ever before.
TRANSIENTS:
Crisper,weightier and faster.For now i cant say much more.Need to listen more.
Did this mod make PP sound analytical like HD 800? No,absolutely not.That PP signature is retained.So you get fun and accuracy in same package.I have not detected any peaks on 5-6 khz region described in the link i posted above.So far this modification makes PP technically better than all the other above mentioned headphones.
I hope you will try this mod and share your observations.This mod surely works with all dynamic headphones.