The Unthinkable Has Happened: The Sennheiser HD700 is now listenable. The HD750 mod.

//-----------Tak's Stupid HD700 Mods-----------//​

See part one on changstar for disassembly: http://static.changstar.com/www.changstar.com/index.php/topic,2627.msg78989.html#msg78989

//--Part 2: Actually modding the f'ing thing--//​

I spent a lot of time dicking around with this headphone... and I mean a LOT. I've taken it apart almost entirely over and over again, and put dynamat, creatology foam, felt, and blutak in all of its many orificies. Literally all of them. Yes, I have molested this headphones in ways I've never done with any other. This poor little bastard child was my defenseless prison bitch.

And it did nothing. Nothing I did induced any significant sonic changes. Literally jack shit. Turns out this is actually a well designed headphone that was simply tuned awfully. The 6kHz peak and ridge on this Porker had absolutely nothing to do with the baffle plate. Not reflections, not resonance from the driver mount, absolutely nothing of the sort was going on inside this Porker. Well played, Sennheiser.

So I racked my brain for weeks, and after even further experimentation, I finally found the problem.

It was the f'ing EARPADS this entire time.



Take a close look at the rear of the earpad, the headphone side, the one that the driver's frontwave hits directly. That's pleather. Pleather reflects sound waves, which is why it boosts bass response. And its not just any pleather either, its the super cheap chinese shit used on most sub-$20 headphones. And it's right smack dab in the middle of one of the most key acoustic regions of a headphone. Unbelievably stupid.



I discovered this by trying other earpads on the headphone: Pads from my Sony MDR-605, which was a low-end version of the MDR-F1. These pads almost entirely fixed the headphone: killed the midbass hump, AND the 6kHz peak, AND the 2kHz dip. Unfortunately, this headphone is long long discontinued and I had to find another method to fix this headphone.

Well, I figured out something that works. This guide will show you how to do it.

Required tools and materials:

• The headphone
• Needle and thread -- I used Coats Upholstery Thread. Be careful with your thread choice as cheap threads tend to knot while working. Use a small-ish needle.
• Basic sewing skill
• Small scissors or shears
• 3 ish hours of free time
• Filter paper -- This comes from the inside of medical face masks, the non-rigid type. This is the brand I got. The paper is somewhat waxy feeling while still remaining permeable.

WARNING: This is a DESTRUCTIVE mod. If you can't afford to buy another pair of earpads in the event that you f**k up, be prepared to go without a headphone for a while.



Start by taking the earpads off the headphone. Do not remove the mounting rings; they are necessary as they provide a solid part as a reference while you're shaping the earpad.





Alright, here's the destructive part. Start ripping the inner seam of the pads apart. These are pressed earpads so you don't have any stitches to worry about, but you do have to take it slowly and be careful. It becomes easier once you get the rip started.

(I missed a photo here, my apologies. Thank god it was just using scissors.)

Still destroying shit. You'll need to cut out the pleather. MAKE SURE YOU LEAVE ENOUGH ROOM TO STITCH IT BACK TOGETHER! I gave myself a generous 3/16" seam allowance. I would not suggest going lower. Be as precise as possible with this cut so your pad doesn't end up all lumpy looking.



Make sure you pull it tight when you cut it so you don't end up with too much slack. The more of this that's left over, the more will be there for the driver to reflect off of when you're done. Keep that in mind.

Pick a spot and start stitching. This will take a long time, trust me. The easiest way to do this is to start in the top of the pad and do a running stitch.



Pinch the foam together like so and put your needle in the velour from the outer side.



Poke it through the front of the pleather and bring it back through the pad opening. Repeat about 3 or 4 times, keeping it loose, then pull it tight.

Keep going, keeping your stitches tight.



A good start...



Still going...



The light at the end of the tunnel is visible...





And done. I overlapped the first stitches and pulled both ends tight before tying it off.







Compare to the stock pads. The new pad is much thinner and has less over the driver. Ideally, there'd be zero over the driver, but from what I can tell that's impossible.

Now you have to do all of it again. Hey, I never said this was a fun mod.





Done and attached. These pads look fantastic, oh my god. And since I didn't take these pictures in order, you can see the seam allowance I used on the unsewn left pad after all.

Hit the post length limit I guess?? Continued on next post.

 

Ok, now that the pads are done, its on to the damping. To my surprise the headphone actually does not need very much damping, just something to attenuate the highs slightly. I experimented with a lot of stuff and finally found something that works well enough for me. As follows:



You need to cut four circles of the filter paper, two for each driver. I personally did this using a roughly 40mm aluminum coin and a razor blade, but you might be stuck with scissors if you can't find something like that to use as a template.



These are actually three different layers of paper. Keep two of them together...



...and split the other two like so, and take only the center piece.



Place it directly over the driver...



... and layer the blue one over top like so. Then put the dust covers back in and put the pads back on. Wham, you're done.



To me, this is perceptibly cleaner and more natural sounding, if a tad warm for my tastes. The metallic timbre is now gone and these are certainly enjoyable. Sort of like the HD600, with (much) better bass extension, a more cohesive soundstage, and a less erratic/hot sounding upper midrange. Possibly closer to the HD650, but I'm not sure as I haven't heard it. Significantly superior resolving capabilities as well.

(excuse the red paint and cable, this WAS a used pair...)

I may experiment with some backwave stuff at a later date, but for now, I believe this is done. I'll send it to Tyll once RMAF is done and get them sent on the loaner tour ASAP.

Cheers!

 

So it looks like you HD800'd your HD700 pads. HD800 pads are very flat and don't cover the driver much. Instead of using a rounded pad to create distance, HD800 pads are almost like a suspension conforming to your head.

 

Yep. Just like a little baby HD800.

 

I can't express how hyped I am for measurements of this. Hard to believe Sennheiser's fuckup comes down to the pad design on a $1000 headphone.

 

Chinese pleather, of all things Chinese pleather...

Sennheiser owes you a "Vielen Dank."

 

This...wow. Pleather.

Can't wait for the measurements to come out Tak. This is pure diligence and dedication here regardless of how they measure.

 

Excellent work Tak. Looking forward to hearing and doing a comparison to the 650's and 800's...

 

Anyone this crazy warrants lifetime measurement services.

Whenever you're ready, Tak.

 

There may be a way to kill 6KHz peak without putting stuffs in front of the driver, Tak.

Although I'm not sure how much that'll help the HD700 since I'm working on the HD800 and I'm killing pretty much >6KHz whereas you're only trying to kill 6KHz.

Stay tuned for that HD800 mod guide.

 

Man, I remember laughing so hard when you bought a 700 and here you are, delivering. I'm really excited to see what this produces. Sennheiser is way too smart and technically adept to deliver something at this price point that is truly poorly engineered - could be the folks making the driver knew exactly what they were doing after all and a bean counter downstream ruined it.

 

This is amazing. And this actually might explain so much, one stupid late decision, surely a been counter as Azteca has said.

 

One final tweak:

These were sounding kind of muddy-warm to me, so I did the backwave damping now.

Extra materials required:

• Pads from an on-ear foam cheapie: You know what I'm talking about. Those open cell flat pad things. Black will look the best, but I only had gray lying around. Bah.
• A razor blade, and for reasons to be explained later, balls
• Scissors

Refer to the disassembly tutorial, and take off only the charcoal colored ring. Leave the black ring on.



Take your pad and place it on the rear of the driver. Use it as a sort of stencil, and trim the edges to where it fits in the grooves for the gray piece.



Like so. Now, simply reassemble the headphone. Yes, you heard me. Clamp the foam in there. It takes some gusto, but the clips on the gray piece will cut right through the piece and compress it into place.



The result is quite clean looking.



Did you bring your balls? Here's where you need them. Take the razor blade and poke around until you find the inner ring of the driver. In all seriousness, this is mostly safe, since the fragile parts of the driver are on the other side. Still, be careful. Don't cut the metal mesh that's layered with the magnet.

Cut out a circle the size of the driver magnet/housing.



Done.

This tightens the bass very slightly without overdamping. Much nicer sounding to me, to say the very least.



If you want, from there you can disassemble it again, leaving the foam on the ring as you do so to keep the alignment, and put a piece of filter paper under it. This boosts the subbass dramatically at the cost of cleanliness. I prefer leaving it out, but its amazing to hear how much bass that little 40mm driver can push in an implementation like this.

Cheers!

 

Try using some sorbothane to dampen excess vibrations, Tak:
http://www.amazon.com/gp/product/B004LYGH3U/

I've found that that works better than dynamat on the HD800. Dynamat has a tendency to give a bit of an edge to things, which I don't think is desirable in this case. Sorbothane works much better here.

 

Already got some of that on order, bill.

 

Awesome. I'd say... don't put it on the ring. That can kill resolution, soundstage, and a lot of other things. Put it on the trapezoid piece... much like the HD800.

 

This is exactly what is happening with the pad mod. I tried to increase this effect by bending the headband inwards, but it always returns to its original shape. At least it's durable...