DIY Modification for the Sennheiser HD 800: "The Anaxilus Mod" Page 2

Experimentation
Not having all the cool software that Arnaud has to predict how the mods might work, I decided to take the empirical approach and simply try a lot of different materials and shapes and then measure them. The materials I tried were:

  • Closed cell polyethylene foam - this is the material sometimes used like bubble-wrap to protect things during shipment. It's a rather springy closed-cell foam. Buddy and Head-Fi member JohnJen built and sent me the 5mm part, which is what really got me going on doing this article and the HD 800 review now. Thanks, JJ.
  • Creatology craft foam - this material is available at craft stores (I went to Michaels). It comes in two thicknesses (2mm and 10m), multiple colors, and has a peal-off adhesive backing.
  • Creatology foam with a polyester felt layer on top - the felt material is also available in small sheets at craft and fabric stores.
The geometric variables were the width and thickness of the ring around the driver. The "wide" rings extended out to touch the stainless steel mesh of the earpiece; the narrow rings were wide enough only to cover the surface of the ring. The thickness varied depending on the material used.

The picture above shows some of the mods I tried. There were more parts tested, but a number of the thinner and more fragile parts were destroyed upon removal from the headphones.

Findings
I first compared the frequency response of the various parts. (The FR graphs are all aligned to be the same level at 200Hz.) I'm just guessing here, but this is what I think I'm seeing. As the part takes up more volumetric space in the headphones (the thick ones, and to a lesser degree, the wide ones) you get an increase in level between 300Hz and 5kHz. As the part gets wider, the tendancy to dip at 3kHz increases. As the part provides a less reflective surface, the peak at 6.5kHz lessens. (Clicking on the frequency response plots below will link you to a .pdf that you can zoom in on the curves for a closer look.)

Sennheiser_HD800mod_graph_CompareLeft Sennheiser_HD800mod_graph_CompareRight

Initially, I thought I was going to hear some reduction in treble energy relative to the lows, but that's not the way I heard things. I did notice as I listened to the various mod's mild colorations that are hard to describe. Sometimes a "heaviness" with the bigger parts; sometimes just a sense that the sound was less transparent; but it was pretty clear to my ears that the Foam Felt Narrow part got in the way least. It seemed the most pleasant and least biting.

Looking at the frequency response comparison of that particular part (it's the heavy red line in the plots), the main differences I can observe are: a clear lessening of the peak at 6.5kHz; a slight level increase between 500Hz and 3kHz; a very slight increase in bass; and possibly slightly smoother and lower in level than average response above 10kHz.

Somehow, that didn't seem to have a lot of meaning relative to what I was hearing, so I decided to have hard look at the square wave response.

300Hz Square Wave Response
Sennheiser_HD800mod_graph_SquareWavesTo the right are all the left channel square wave response plots of the stock and modified headphones. Let's work our way down the list. Comparing the stock headphone with the stock headphone without the liner, you can see that the amount of noise significantly increases without the liner. I think the noise seen is some ringing at 6.5kHz, which I think is the culprit that tends to make the HD 800 sound piercing. The half wavelength of sound at 6.5kHz is about one inch, which is about the distance between the ring around the driver and the side of your head. I suspect the peak we see at 6.5kHz is the primary resonant mode between the driver and ear/side of the head.

The next square wave is the 2mm Creatology Wide part. Here we see a reduction in noise from the stock headphone without the liner, but it's not quite as quiet as the stock headphone with liner. I'm not sure why that is, except to say that the elasticity of the foam might be storing a little energy (wild speculation on my part). Also note the slight tip downward of the top of the square wave. This typically indicates a change in the relationship between mids and highs. Tipped in this direction tends to indicate a thinner sound; tipped the other way tends to indicate a warmer, punchy sound. Don't know if I really heard it that way, except to say that this part did seem a little colored to me relative to the narrower version we'll see next.

The 2mm Creatology Narrow seemed a bit better sounding than the Wide to my ears, and it did seem to clear up the bite of the HD 800 some. I liked this one, but decided that more exploring would still be worthwhile.

I next tried the much thicker 10mm Creatology foam. Because it was so thick I tapered the sides figuring it might make a tube around the driver that would color the sound too much. This part did seem obviously colored to me in that it seemed brighter and more piercing. A hard look at the frequency response comparison will reveal this part showed large increases in energy between 500Hz and 5kHz, and a significantly bigger peak 6.5kHz. The square wave has quite a bit more noise as well.

The 10mm Closed Cell Poly part was similar in shape to the previous part, but sounded even more colored, though not quite in the same way. This material is quite a bit more "springy" than the Creatology foam. I suspect this part was vibrating and adding its own resonances to the mix.

The 5mm Closed Cell Poly part seemed significantly less colored than the 10mm and had a sort of happy and alive sound to it. I did think this might be the best mod so far, but just the fact that it did have some character caused me to believe it was colored somehow and wouldn't stand the test of time, so I pressed on to the felt parts.

These last three parts are made of a layer of 2mm Creatology Foam with a layer of felt on top. The Foam Felt Wide seemed to have similar coloration to the 2mm Creatology Wide but without the piercing sound. It was nice to think I may have made headway in that regard.

The Foam Felt Thick has two layers of felt, and was actually the one I tried last. It was an improvement over the Foam Felt Wide, but it did seem a little thick and muffled compared with the Foam Felt Narrow I finally settled on.

The Foam Felt Narrow seemed to change the HD 800's characteristic transparency little, if any. You can see in the square wave plot it had the lowest amount of noise of any of the square waves observed. It bears a fairly strong resemblance to the stock square wave otherwise. Frequency response comparison against the stock headphone shows it within a couple dB of the stock headphone, though slightly flatter to 10kHz, and slightly lower in level above that. To my ears, this mod makes a remarkable difference. For me it does change the HD 800 from a headphone that's brutally honest, to one that's simply honest. I think it really is a worthwhile modification.

I need to add a disclaimer here: a lot of these changes were very subtle and having measurements available to me as I do the tests almost certainly has my head thinking of all sorts of things. There certainly could be a whole lot of confirmation bias going on as I do these types of articles. In other words, I can easily be fooling myself here, and all should be taken with a grain of salt. I am trying my level best to be unbiased and open as I do my listening, though.

Summary
If you're 98% of the way there (which the HD 800 is), and you make a 1% improvement, you've solved half the problem you'd been left with. The HD 800 is already the world's best dynamic headphone in my opinion. It images like no other. But in its stock form, it has a tendency to be a bit steely sounding ... or something like that. Hobbyists have struggled mightily with finding the right amps and cables to settle them down for a more enjoyable listening experience.

I think this mod suppresses the potential for ringing due to the hard surfaces in the HD 800 ear piece, and does a very good job of taking the edge off the HD 800 without otherwise changing its world class performance. While I'm glad to have had the chance to add my own two cents here, the design team at Sennheiser deserve most of the applause. And much of the credit for the mod goes to the guys mentioned earlier in the article, so I'm going to continue to keep referring to it by its current name: The Anaxilus Mod. I'm very glad the headphone hobbyist community continues to explore DIY headphone modification and improve its abilities along those lines, and I'm very happy to be a part of that.

Well ... the next step is yours.

Directions for the "Anaxilus Mod" to the Sennheiser HD 800

sennheiser_HD800mod_Photo_finalmod

The finished mod installed in my HD 800 headphones.

Performing this mod is fairly easy. You simply construct the Foam Felt layered material by adhering it together; then staple the template to the material; cut out the parts with an exacto knife; then peel off the adhesive backing and stick it in your headphones. Rather than write a lot of confusing words, I made an instructional video that should be quite clear.

You'll need:

  • Printed .pdf template for the Anaxilus mod. You may need to turn off all scaling on your printer. (Print at 100%, no fit to page.)
  • A ruler
  • An Exacto knife with fresh blade
  • Tweezers
  • A stapler with about 16 staples.
  • One roughly 9"x12" sheet of 2mm adhesive backed craft foam (Creatology "Adhesive Foam Sheet," but any similar from a craft store should work.)
  • One sheet of craft felt (polyester, but I may experiment with other types of felt)
  • One pack of Aleene's "Tacky Double Stick Tape" or equivalent
  • The courage to to really take ownership of your headphones and start "cutting shit up."

Resources
The trainwreck that was iPodPJ's first HD 800 mod thread.
JaZZ's HD 800 mod thread where he slowly evolves from one solution to a better one.
Arnaud's first post on a Melamine foam mod, and his subsequent thread on the mod.
Purrin's "Anaxilus" foam mod thread.
What Hi-Fi article on how the HD 800 is made.
Head-Fi HD 800 appreciation thread and Skylab review.
Sennheiser HD 800 product page and brochure pdf.

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COMMENTS
thune's picture

Great work Tyll. A complete report like this is worth 10,000 forum postings about mods. This consolidation of previous work and exploration of materials was very engaging.

My question would be: can one get good results with a notch filter? (Either in EQ or with a passive network.) Can you get closer to what you want from the HD800 with signal contouring or with acoustical modifications?

Tyll Hertsens's picture
It's important to understand that it's not the driver putting out the excess between 6-8kHz, but rather that there is an acoustic "ringing" in the space within the earcup. Sort of like when you blow across the top of a bottle and it toots. Of course it's much less dramatic than that.

So, you can reduce the signal between 6-8kHz with an EQ filter so that the ring doesn't get excited, but of course then you're throwing away some portion of the music. Much better to damp the chamber with the mod, and keep the music properly balanced.

That said, for general use I don't see anything wrong with using EQ to to get the sound balance more to your liking, as long as the EQ filter (analog or digital) is of good quality. For audiophile and pro use, I find the phase shifts associated with EQing does damage coherence and imaging.

johnjen's picture

Well presented investigation and description of your findings, musings, and suppositions. :thumb

All of which help to make up the text for the circles and arrows on the back of the 44 full color glossy photographs, graphs and charts for all of us tweakers to ponder and mull over.

And truth be told Tyll pointed me at the many threads on Head-Fi where I 'got the bug' (thanks to Anaxilus, Purrin, arnaud, iPodPJ, JaZZ and the entire supporting cast of thousands ;-). And as we all know once smitten, there is no known cure.

And speaking of being smitten I think I see another variant that might just prove to be yet another tweak of a tweak. And because curiosity is such a marvelous motivation, I simply must explore it.

AND I have yet another level of exploration I'm pursuing as well, one that, so far anyway, is providing results as copacetic as this mod as well.

JJ :thumb

mward's picture

What a great writeup. I appreciate that both you and many of the hard-working Head-Fi-ers put some science into this. I'll take that any day over a few people claiming that something "just sounds better".

arnaud's picture

Hey Tyll, the least we can say is that, when you take interest in something, you don't just scratch the surface but really push as far as you possibly can. Another impressive write up, it's both thorough and consize at the same time, you got a talent for this!
Since you're always thinking outside the box as well, I am just eager to see all the other stuff you'll get your head around to this year ;).
Many thanks for referencing me and all those before and after who contributed, much appreciated :).

Jazz Casual's picture

I find these analogies unconvincing for the same reason that I don't accept the "surgical instrument" description for this TOTL headphone from Sennheiser. The HD800 is a state of the art dynamic headphone presumably designed to reproduce recorded music with a hitherto unknown level of fidelity.

It seems to me that "brutally honest" could be replaced with "hot treble", as the HD800's well documented treble peak has been too hot to handle by owners and "tyre kickers" alike. Many have found it so bothersome that they've resorted to all manner of methods to remedy it. Whether it be "The Anaxilus Mod", tube amps or after market cables, these are all measures that are being taken by HD800 owners to redress a perceived flaw in the way this headphone reproduces treble, and to beef up its bass presentation.

Fans of the HD800 say that it is extremely revealing of shortcomings in upstream components. Some of them advocate that the HD800 benefits from tube amplification because it relaxes this highly strung thoroughbred. Is this a situation where we can't handle the truth or is the truth as the HD800 presents it not entirely accurate and consequently, slightly unpalatable? Is it just possible that the problem lies with the headphone itself rather than everything that is attached to it, including us?

Does the Stax SR-009 require similar modifications to temper its rendition of "brutally honest" audio reproduction?

Tyll Hertsens's picture
Man, do you have problems with the world not being perfect?

In my view, the HD800 is an incredibly good headphone with one small flaw. Yes, a pebble in your shoe can make a walk in the park miserable ... especially if you obsess over it. Most headphones are a cluster of problems that may or may not sound good, and no simple mod is going to fix them. I place the T1 in that category; it sounds pretty good for the number of flaws.

I don't think the 009 images as well as the HD 800, and that's after spending more than double the money. Can't fix that.

I think you just like being negative.

Jazz Casual's picture

Let's not confuse how I deal with an imperfect world, with my response to the use of flawed analogies and pretzel logic in the discussion of expensive flagship headphones. And shoes don't come with the pebbles already added by the way.

With regard to the HD800, I take the view that if many of its owners are resorting to DIY modifications to temper the sound signature of a $1500 headphone, then it is far from perfect. Am I the only person who finds it rather absurd that those who are claiming the HD800 is the "best" dynamic headphone currently in production, are also the same people fiddling with foam mods, and throwing even more money at expensive tube amps and after market cables in the hope of making it more listenable?

mward's picture

I think you make some great points.

Philosophically, I believe in purely neutral audio components. Do people not like the HD800's treble because it's accurate and makes their bad recordings sound bad, or because they're used to artificially smooth headphones, or because its presentation is just that flawed?

Tough to say (especially since I haven't spent much time with this model). But I'm glad that someone ias asking these questions. i think the HD800 is probably a spectacularly good headphone, but there's no reason to take that as given just because it's one of the most expensive.

frenchbat's picture

Hi Tyll, great piece as usual. Please keep them coming !

Funny how felt appears to be one of the very best material when it comes to sound reproduction. I also ended up using some felt to mod my K702, and so far it's the best result.

Can I ask what is the thickness of the foam + felt material ? I'm using 2mm felt and I was wondering if doubling the thickness by sticking 2 pieces together would give me good results too. By the way: yes it's a PITA to cut this thing properly !

Tyll Hertsens's picture
Both the foam and felt were about 2mm thick. I felt doubling the thickness of the felt colored the sound a bit too much. YMMV.
frenchbat's picture

Ok, so if I understand correctly, you have 4mm total (foam + felt). I reckon that doubling it might simply be too much. Besides, the HD800 and the K702 are two different beasts altogether. The first one appears to only be needing some correction for a ringing, while the later could do with a slightly different presentation.

I ended up trying 4mm thick felt yesterday night. So far the details and the soundstage don't seem to have suffered much, and the treble peaks were attenuated a bit further than with 2mm of felt.

I also looked into melanin foam after reading your article, but this thing is really difficult to cut properly, and I understand why you left it out. The sponge form factor in particular is really hard to cut straight. I tried a 2mm layer, but it didn't work the way I was intending on the K702, and I doubt that adding some thickness would actually change anything.

Anyway, lots of fun playing with this. Thanks a lot for the article.

TheWuss's picture

here's a quick question / tip ...
must the felt ring and the trapezoidal area be connected?
why can't they be two separate pieces.
it seems the most tedious part of the procedure is tucking the trapezoidal area into the headphone.
if it was its own piece, that would be a cinch.

thanks,
The Wuss

Tyll Hertsens's picture
You certainly could do it in two pieces, if you like. No problems.
jherbert's picture

Just curious: Arnauld chose melamin foam for its acoustical properties I guess - it is an open cell material known to be very effective in damping.

Is there a reason you did not try that stuff? In Germany you can buy small blocks of that stuff in every supermarket - it is used to remove dirt and stains.

Tyll Hertsens's picture
I was looking for a mod that was easy to do, and reliably consistent when people do it. Cutting the foam is a bit more difficult, and would vary a bit from person to person. None the less, I just may try it one day. I think I'll also try natural wool felt. If/when I do, I'll post results in a monthly update.
donunus's picture

Props to all the guys that contributed in the creation of this mod and to Tyll for compiling it into one article. Everyone with an hd800 needs to read this at least once.

Tyll Hertsens's picture
It's pretty easy to do, and I've fallen in love with my HD 800s. Use to be they were the best tool in the box, now they're my favorite listen.
Nuwanda's picture

Twenty minutes working time and the rest of my life to enjoy my new HD800. Now they're really easy on the ear! Can listen to music for hours with no fatigue at all.
Millions of thanks for making it soooooo easy for us, Tyll.

Skyth2nd's picture

I liked you walk through it was trough and seems like a good mod if you own the HD800. Your method seems like it works just fine so I may be splitting hairs here but I have never liked those adhesive sheets So you might try using a spray adhesive. and if you do that you could put the templet on the backside with it as well so you do not need staples. then pull it all off with the paper. Agin I know I'm splitting hairs here but the templet appeared to be rather deformed for the staples.

Tyll Hertsens's picture
DIY is one of those things where splitting hairs makes a difference sometimes. Maybe someone has a different idea, but the adhesive sheet wouldn't work. Your comment might give them an idea.

Thanks!

MacedonianHero's picture

So I got around to trying this mod and colour (sorry for the Canadian/British spelling) me impressed. It's smoothed out the treble to the point where its taken the HD800s from the perfect window into the recording to the perfect window into the recording's soul.

I wish I came across this mod before dropping a lot of $ on my Cardas GOLD cable, but such is life. Put the two together and these headphones are right up there with my LCD-3s as the best cans I've heard/owned to date.

Thanks Tyll for such a great write up and article. I love this place. :)

Tyll Hertsens's picture
Thankss,mate. I hope other do too. Be silly to bother with stuff like this if it wasn't worth doing.

Any body else out there give this a shot? Whaddaya think?

Windsor's picture

Just got my HD 800 today. :)

I've heard the HD 800 on a few occasions before, so I'm aware of its pointy treble, and after that very feature revealed itself as I played a few tracks earlier tonight, I decided it was time for the Anaxilus mod, so modded my HD 800 became. FYI: the foam I used was ~2mm thick and the felt was ~1mm thick.

I decided to clear my head after the mod was made, so I did, and with a clear head I now listen and am really, really impressed by the result!

There's no overbearingly harsh treble sound any more, just a healthy natural sparkle in the upper end. I've noticed it does get a little bit uncomfortably bright at times, such as at the end of Jimi Hendrix's "Still Raining, Still Dreaming" when the cymbal roll is happening. I'm not too keen on that as I don't want pain from my headphones, but I'll see how it plays out with different recordings.

I've not been A/B'ing the modded/non-modded sound, but from memory the bass seems a little bit muddier than without the mod, but the bass is still very clear with subtly powerful air-shifting heft.

Compared to my LCD-2 rev.2, which I've recently been using EQ'd to make more neutral-sounding, which has resulted in less bass bloom and veil (though at the slight expense of the LCD-2 timbre) and made the top end clearer (a definite improvement in clarity than the standard non-EQ'd LCD-2 IMO), the Anaxilus modded HD 800 takes the clarity to a level beyond that. The Anaxilus HD800's frequency balance is very close to neutral though ever-so-slightly treble happy, and to me music is very enjoyable through it so far.

I still love the warm tone of the LCD-2, which is like a wearing a warm pair of slippers by the fireplace, compared to the HD 800, which seems a bit like wearing a T-shirt on a breezy day that can get uncomfortably chilly at times. As far as my preference goes between the two headphones, I can hear that they're obviously different in character, and I'd like to listen more before drawing conclusions.

Tyll, one small question re. the anaxilus mod: the way I've installed one of the felt mod parts, it overlaps the circular metal piece surrounding the HD800 driver and covers the diaphragm very slightly, by ~1mm or so. Have you noticed if variations on the felt position around the metal ring affect the overall sound of the modded HD 800 in any way?

Thanks again.

Tyll Hertsens's picture
Glad you're enjoying the mod!

The overlap shouldn't be too much of a problem if it's small. I'd also caution you that you have some headphones that are extremely revealing of the gear driving it. It may be time to look at your DAC and amp for further improvements.

Windsor's picture

I'm currently using a Lavry DA10 as my DAC/Amp - any suggestions?

MacedonianHero's picture

EDIT, for the few weeks I had this mod in place I've come to the conclusion that in the end it took away too much from the brillance that is the HD800s. I found myself sacrificing clarity and detail too much. I have since looked back to my rig and changed/upgraded components over the past year that I feel this mod is no longer required.

Nebby's picture

Thanks for putting together all the information and providing the template that made implementing the mod a piece of cake! Picked up the materials today and just finished the mod. I'm listening now and I really like how it changed the HD800's.

Tyll Hertsens's picture
Nice! Glad to hear it!
mrog's picture

Does anyone know if Sennheiser themselves are doing something about the issue, i.e. ammending the design of the chamber on the same lines? I'm considering the hd800s so an upgrade like this in some near future might be worth waiting for.
Great to know there is a diy solution in the meanime, big thanks.

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