[drtturnip]

I have always liked these headphones but felt that they had a little more to offer. My complaints were twofold and common. Lack of bass and a slightly phased blurred upper mid. I have been running them through a modified harmam kardon hk505. I dropped the series 470 ohm limiting resistors with 100 ohm and 10 ohm to ground thus lowering the output impedance from 470 to 10.
 
My theory on the blurred upper mid was that by design Sennheiser uses the baffle and ear cup interaction to widen the sound stage and create a more room like presentation. However this interaction was causing the blurring. Since I was more interested in accuracy (music production) I thought I would try a few things.
 
I removed the pads and then the snap in driver covers. I cut out two sheets of double ply pleated paper towel to fit under the snap in covers with a hole for the driver. This effectively limits the interaction between the ear cup and and ear area by covering the chambers built into the baffle. The results were promising as I was now able to run the bass control much lower and the upper end was clearer. I new I still had interaction because if I held my hands over the ear cups I could hear the mids jump up. I then removed the drivers and placed another two sheets of paper towel inside against the outer ear cup against the perforations along with a thin layer of poly which was cut as to not touch the back of the driver. I also cut a small plug of open cell foam and inserted into the hole on the back of the driver. (If its good enough for the hd650 then why not?). This really cleaned things up and it is easier to hear small details which otherwise would have been hidden. The trade off (there almost always is) is that I think the sound stage has shrunk, but that was not my goal. Now if I only had a multi thousand dollar testing device I would post pretty little graph. I attribute the fuller bass to the simple fact that the reflection of the upper mids into the listen area have been dramatically reduced, thus shifting the frequency response and at the same time reducing smear.

 

[drtturnip]

After listening for a while I found this hd595 mod a little too aggressive. I have since removed the paper towels from under the earcup snap ins and replaced the poly/paper towel inside the earcup with a felt like material ( synthetic chamois ). I left the foam plug in the driver for now. 
 
I made a test tone in audacity that jumps from 20, 200, 2000, 30, 300, 3000 etc. up to 120 1200 12000. Seemed pretty balanced after 30hz although the dip in the 5k 8k range seems a bit much. Probably part of the Sennheiser sound.

 

[drtturnip]

Since I am replying to myself in this thread is probably of not much interest, but maybe someone will find it helpful.
 
I have done some more messing around with the hd595 and found I liked the sound better with the foam plug removed from the back of the driver. While I had them apart I listened to them with the drivers/baffles completely free from the ear-cups. They actually sounded really good though very laid back with scooped upper mids, similar to the paper towel sound.  When installed back into the ear-cups the upper mids really changed and became more pronounced. I have found that playing with the amount of sound reflected off of the ear-cup is an easy and effective way to tweak the sound and am very happy with the results. I find it a better option that cutting out the back of the ear-cup since it is easily reversible.

 

[aloi]

Great mod! I was always interested in HD5xx series.
595/598, they are good, but too much bass reverb.
using paper towel to reduce the bass...
I always just used clear tape or mesh tape to block them. never thought about using paper towel. (is it popular in this forum?)
If you have some photos of your modification procedure, it'll be more helpful to people who are interested in this.

 

[aloi]

in some countries, HD600/650 are way more expensive than 598/595.
that's why modifying HD5xx series could be so interesting, and great topic.
I've also heard that people could make HD558 resemble HD598, by adding some mod.
that is ; your mod could be possibly used also on 555 or 558.
those will make great mid cost open-air cans.

 

[drtturnip]

 
 

Great mod! I was always interested in HD5xx series.
595/598, they are good, but too much bass reverb.
using paper towel to reduce the bass...

 
I was never trying to reduce bass but reduce the upper mid (2k - 3k) frequencies which to my ears are exaggerated and kind of "smeared".
 
I have gone back and forth with mods on these. What I have now is paper towel sections under the ear-pad chambers to limit reflection in the upper frequencies and and a thin sheet of poly-fiber inside the ear-cup. They are still a mid focused headphone because, well, they are a mid focused headphone. It is just not such a strong focus in the 2k - 3k frequencies. For me they are now listenable. Before I simply found them annoying. The large dips above 3k are only remedied with EQ.

 

[aloi]

oops, sorry. i might have misread your article.
still, using paper towel is very interesting method of modding to me.
reducing the upper mid. it'll be also helpful to me when i listen to the pop with female vocals.
excessive upper mid... not good.

 

[DaBomb77766]

Hm, have you tried the "soundstage mod," which involves cutting out the baffles behind the driver?  It seems to me that those baffles are probably what's causing the spike...since the spike gets even worse when you cup your hands around the sides of the headphones.

 

[drtturnip]

Thanks for the heads up, but I have seen that one. I may want to sell these so I only do things easily reversible.