Sennheiser HD 800 S: Tweaked and Delightful...and a French DIY Response

Sennheiser HD 800 (left) and newly evolved HD 800 S (right).

Sennheiser HD 800 S ($1699)
When introduced in 2009, the Sennheiser HD 800 rapidly became recognized as one of the world's best headphones, having unbelievably good transient response and detail retrieval, spectacular imaging, and being competitive with the best electrostatics and planar magnetics—having some trade-offs here and there.

But the HD 800 is also quite problematic. It has a sharp sounding peak at around 6kHz that will, at times and with problematic recordings, drill a bleeding hole in your eardrums. Adding to this problem is an overall cool response, lacking the bass extension that, say, an Audeze LCD planar magnetic can has.

I'm not going to do a traditional InnerFidelity headphone review here; the new HD 800 S is very much like its predecessor only changing a few small acoustic tweaks, and being dressed in a black livery—a look I like very much. So, if you want to read about styling, comfort, and build quality—all of which are terrific—you can look at my previous HD 800 review here and just imagine it in black. Oh, and with two cables: one with standard 1/4" plug; and the other with a 4-pin XLR for balanced use.

In this article, I'm going to bring out exactly what I've found as the acoustic differences between the HD 800 and HD 800 S. And! I'm going to tell you about a very cool modification you can do to an old HD 800 to get some of the benefits found in the new HD 800 S. Grab a cuppa, sit back, and enjoy, I promise this will be an interesting read.

Acoustic Changes to the HD 800 S
Sennheiser, from what I can tell, has done two things to the HD 800 S to improve its sound quality: Damped the spike in response at 6kHz, and warmed up the headphone a bit. We'll take them one at a time.

Killing the 6kHz Spike
Right after I published my HD 800 review, I also published what was termed at the time "The Anaxilus Mod", which intended to damp the 6kHz spike by putting felt in certain positions in the earcup of the HD 800 to reduce its ability to resonate. This mod has evolved over time and it seems lives on in this SBAF thread.

The problem with adding a bunch of damping material in the ear cup is that it's not particularly selective about what frequencies get attenuated. If the problem at 6kHz is narrow-band, well, using a solution that's narrow-band makes more sense than wide-bandwidth absorbing material.


Current SuperBAF mod using a specific rug liner material to damp the earcup.

I need to note here that the materials now being recommended by HD 800 modders at this point are not simply wide-band absorbing felt. Many, many materials have been tried and measured. The current material of choice is somewhat elastic and has regularly repeating holes (see photo above)—both of these characteristic may give the material a degree of selectivity in what frequencies are attenuated, and may also be a source of spurious secondary emission of sound.

Sennheiser, being the smarty-pants engineers they are—and I say that with a great deal of affection—took the alternate route of engineering what, it seems to me, is a narrow-band Helmhotz resonator into the opening at the center of the driver. Essentially a surgical attack, providing a tightly tuned anti-resonance at 6kHz.

Helmhotz resonators have been around since 1850 when Hermann von Helmholtz exhaled a sharp sigh of relief after finishing a bottle of poor brew and heard the bottle emit a tone...Ha! No, sorry, I have no idea how he figured it out.


He invented these cool looking resonators, and observed that if you stuck the bottle neck and hole into your ears, the resonator would amplify the frequencies near the resonators natural resonance and damp other frequencies. He went on to make a variety of sizes of the resonators and, when presented with a sound, each bottle would resonate with certain ranges of the sound presented. Measuring the amount of sound resonating in each bottle would permit a crude method for measuring the spectral frequency content of the sound. Amazingly, this was one of the first audio frequency response measurement system. Here's the Wiki for Helmhotz Resonance.

I was fascinated to learn that one of the most common modern uses of Helmholtz resonators are in engine exhaust systems. Resonators are built into the muffler and tune the "exhaust note" of the system. Want to bring out the growl of a V8? Tune it with a resonator. But it's also important to know that you can use these resonators to tune out a frequency. Want your Benz to whoosh silently down the road? Tune out the noise with resonators.

Basically, if you use the right resonator in the right place it can be anti-resonant with the tone of interest. Imagine the sine wave of an audio signal of a particular frequency of interest passing by the opening of the resonator. At the top of the sine wave, high pressure enters the bottle, which then bounces of the inside of the bottle at the resonant frequency, and the high pressure returns to the opening of the bottle one half wavelength later. Well, the original sound is now one half wavelength from its previous maximum and is now at the low point of the sine wave. So, you now have the low point of the sine wave meeting the high point of the wave as it exits the bottle delayed by a half wavelength, and the two cancel. In other words: Helmholtz resonators can be used either to amplify or cancel particular frequencies.

The new HD 800 S has, as far as I can tell, a Helmholtz resonator—or something very much like it; there are variations on this theme like 1/4 and 1/2 wave resonators—built right into the center opening of the driver on the inside of the headphones. And this resonator, from what I can tell through measurements, is anti-resonant to the 6kHz spike generated by the acoustics of the earcup enclosure. Measurements show that the HD 800 S does precisely damp the problem.


In the photo above, I'm shining a flashlight in through the back of an HD 800 S. There's a fine screen mesh over the entire front of the driver up to the screwed down metal ring. This mesh has a small donut of air impermeable material partially closing the space behind it in the central hole. You can equate this to the neck and opening of the resonator. In the bottom of the well there's a mesh screen that looks identical to the HD 800 from the outside, but as I closely inspected it, it does seem that there's an additional layer of screen at the bottom of the hole on the inside. I think this screen may act as the bottom of the closed bottle, but does allow some air to pass slightly diminishing the amplitude of resonance for a given input. I think controlling the permeability of this layer at the bottom is used by the engineers at Sennheiser to adjust the damping to the right level. Caution: A lot of guesswork going on here.

The important thing to note is that the enclosed chamber of this resonator is completely empty...just like the beer bottle you can blow across. If you put damping material—like the batting inside speakers—into the bottle, it would become much harder to get a clear tone out of the bottle. The damping material would "spoil the Q" (damping the ringing bell-like quality) of the resonator. So, a surgical strike on the peak at 6kHz by the Sennheiser engineers. Well done!

Warming the HD 800 S
No onto a bit tougher problem: Making the HD 800 S a little warmer and more inviting—even with the fix to the 6kHz spike the headphone remains a bit cool. This is really tough to fix for an open acoustic design. With sealed headphones you can use the sealed chamber of the ear cup to contain the pressure of the long low-note wavelengths and boost the bass some. With open headphones, the driver usually has a primary resonance between 60 and 150Hz (it's about 110Hz on the HD 800), below the primary driver resonance, driver efficiency will evermore reduce as frequency lowers. The result is loss of low frequency extension. Bottom line: there's not much Sennheiser can do to increase bass response of the HD 800.

But! There's a little trick you can do to increase perceived bass response in low frequency limited devices: Add second harmonic distortion to the low notes to "bloom" them up a bit. This is often done in the Bluetooth portable speakers, which, due to their small drivers and overall small size, have problems reaching way down into the bass. By selectively adding 2nd harmonic overtones to the low notes, overall bass energy is increased—albeit at a higher frequency than the original tone—and your perception will be a euphonic warming of the bass. It's euphonic because the second harmonic is exactly an octave above the primary tone, so it remains in harmony with the original music. On the other hand, it is a distortion, and those with well trained ears will hear the bass as slightly less precise and authoritative.


The plot above shows the spectra content of an HD 800 S and HD 800 reproducing a 40Hz sine wave. As you can see, the second harmonic at 80Hz has 20dB more amplitude than the 2nd harmonic of the HD 800. The third harmonic at 120Hz is about the same; the fourth harmonic at 160Hz is about 3dB louder on the HD 800 S.

Editor's Note: When I first saw an increase in distortion of the HD 800 S over the HD 800, I wanted to make sure it wasn't just a problem with the one HD 800 S I had at hand. Neither Todd the Vinyl Junkie nor HeadRoom had any left, the U.S. PR rep had none either. I immediately went over to and asked for some help. Members TMoney and Dr. Higgs volunteered their new HD 800 S headphones, which I arranged to have shipped overnight. Upon receipt I did repeat my measurements and found these headphones to perform essentially identically to the pair I initially tested. My experience is that Sennheiser has great quality control with unit to unit variation being very low...but I did triple check, and my measurements for all three were very similar.

The first observation I'd like to make here is that there's a thought in audio that the best sounding gear should have a nice, asymptotically reducing level of the harmonic series. In other words: The level of the harmonics should reduce smoothly with each subsequent harmonic being lower than its predecessor. You can see in the plot above that the level of the second and third harmonics are are roughly the same on the HD 800, which, according to this rule, would not be optimal. With the HD 800 S the second, third, and fourth harmonics are ever smaller. This might indeed be a preferable tuning. I do have to note that the fifth harmonic at 200Hz is higher than the fourth in both headphones; this may not be desirable, but it also may be one of those things that Sennheiser engineers likely can't adress without screwing up something more audible. It's 60dB down from the fundamental tone, so it's likely not an audible problem.

And now, the big question...

HD 800 S Sound Quality
For me, the HD 800 S delivers a markedly more pleasant listening experience than the HD 800. The piercing treble problem has been reduced to insignificance and replaced by a marvelously articulate and responsive presentation of the treble. And the overall tonality of the HD 800 S is indeed noticeably warmer and more inviting; the bass is more present in the mix.

But, I do hear the bass as a little less precise in the HD 800 S, having a bit more pleasant bloom, but also being just a tad growly and congested, calling attention to itself. Please understand that I use "just a tad" very specifically here; these headphones don't have noticeably distorted bass; it's just noticeably warm and inviting, but less clear and pure than the HD 800. On the other hand, the HD 800 bass level is a bit too low, and the headphones are cooler sounding than I would prefer.

So, did Sennheiser make a good decision trading off a little added distortion for better tonality? Yes, you bet, I'd much prefer to listen to the new HD 800 S over the stock HD 800. Much. This is where small objective differences can make disproportionately large subjective improvements. I find the new HD 800 S much easier on the ears....musical even, but with clarity taking a front seat over euphony, which seems unusual and very cool to me.

My last note on HD 800 S sound quality is something that has persisted in both the new and original model. The upper-mid-range is a bit withdrawn causing voices to loose some of their natural overtones making them seem a bit more distant. Though I need less bass and treble adjustments when I EQ the HD 800 S, I find I still need a bit of boost centered around 1kHz.

Speaking of EQ, when I listen to the two headphones EQed, I think I tend to prefer the old HD 800, but it's close. With the HD 800 S I find myself being somewhat cautious about my bass level setting—bringing it up to where I like it does make the distortion a bit more obvious. On the other hand, I can tweak out a notch at 6kHz to try to tame the spike in the old HD 800, but the resonance is still there in the headphones, and if a signal gets hot around 6kHz then you can hear it zinging. Niether are perfect, but I think I prefer having to fiddle with the 6kHz notch a bit based on the music playing rather than not being able to dial the bass up to where I want it without lows becoming a bit too congested. However, if I wasn't using EQ, I'd easily prefer the HD 800 S.


My EQ settings for the HD 800.


My EQ settings for the HD 800S.

There are other options though, if you're willing to take the risk. Let's flip the page and see what the DIYers are doing.

Sennheiser USA
1 Enterprise Dr.
Old Lyme, CT 06371
(860) 434-9190

Chiumeister's picture

Thanks Tyll for the report. Which amp type works best with the 800S in your findings. Was there a particular amp that you enjoyed the most the updated Sennheiser?

gevorg's picture

Very informative review with multiple measurements, EQ settings, and DIY/mod options. Thank you!

I would choose HD800 over HD800S only if I was mostly listening to well recorded classical music, but since my music collection has all kinds of genres, the HD800S is more enjoyable (relatively to HD800, the HD800S can still be overwhelming with some albums/mastering quality).

Something I found with HD800 vs HD800S is that there is some difference in imaging/soundstage between the two. The HD800S is not as wide and expansive as the original HD800, nothing major, but noticeable when you have two side-by-side and can quickly switch. Is this a side-effect of taming the 6K spike by the resonator? Or maybe I heard this difference due to the more worn pads on my older HD800.

Jazz Casual's picture

Thanks for the thorough and forensic investigation Tyll. So Sennheiser has traded some of the HD800's precision for musicality and an increase in distortion is the by-product. It is interesting that the HD800S, which seemingly editorialises more than the HD800, has also succeeded in knocking it off the wall of fame. I don't have a problem with that - I like Grados after all, but it should ignite heated arguments over whether the modified HD800S is as worthy of being described as a high fidelity headphone as its predecessor. Kudos to Sennheiser for recognising that audiophiles really "can't handle the truth" and offering a more palatable alternative. ;)

Tyll Hertsens's picture
Where's the "like" button around here?
zobel's picture

I don't want you using it though Tyll!

Beagle's picture

Remember when you were a kid, those little puzzle games, where there was an empty space and you had to slide the plastic number pieces around to put them in order? Us headphone fanatics are looking for what goes in the empty space.

tiger's picture

I have been waiting for this review for so long Tyll! Was wondering why it took so long :)

The Boss's picture

Tyll, thanks for your review on the HD800S. I also picked up an HD800S recently and whoelheartedly agree with your findings. What I'm curious about is, what can you tell me about HD800S + SuperBAF Mod in comparison to stock HD800S, both in terms of objective measurement and subjective impressions?

In your article you first mentioned the SuperBAF mod and how it tames the sound of a stock HD800. Then you moved on to discussions on resonators and compared the HD800S with HD800SDR(HD800 + SuperDupont resonator). This is great and all, but I've read in SBAF that HD800 should be modded with both SuperDupont resonator and SuperBAF absorber for the best effect. In that vein, since HD800S is in a way a variation of the HD800SDR (or should it be the other way around), wouldn't it make sense to apply the SuperBAF mod to HD800S as well to further tame the sound?

What do you think? Does applying the SuperBAF mod to HD800S helps further and makes the sound more enjoyable overall, or is it somewhat overkill with HD800S (and HD800SDR for that matter) and results in an overdampened, perhaps relatively congested sound?

On a side note, I would like to know whether it is more preferable SQ-wise to leave the dust cover on or off when using the SuperBAF aborober mod.

Tyll Hertsens's picture
....this is exactly the kind of stuff that has to be hashed out in the forums. I can only intermittently interrupt with a cogent comment.
zobel's picture

Some bed rest and plenty of fluids should help clear that up.

inventionlws's picture

Hi, Tyll, thanks for a very helpful review. One thing I noticed that might be a typo: the upple-treble being withdrawn that causes the human voice to be distant...I think you meant upper-midrange.

Tyll Hertsens's picture
Excellent catch and exactly right. Fixed and thanks again.
zobel's picture

That was a fun read! I play a djembe and an udu, so I knew about Helmholtz resonators, but that was an ingenious use of one to tame that peak! Very nice review, thanks.

johnjen's picture

Excellent work there Tyll!
Its good to get a direct comparison between these 2 not so different HP's.

And being another one of them tweakers myself, I use a different method to gain access to the innerds of the 800.

I found that the spring was tedious, so I use the method of pulling off the ear cushion and then unscrewing the 2) 8mm torx screws that hold the earcup assembly to the attachment arm.

WAY less fiddly and also opens up the earcup cavity for greater access.
Just a small change in a to way fuss with these remarkable headphones.

Good job and the humor was a great source of laughter for both of us.

JJ :thumb

zobel's picture

AKG was able to increase the bass in the open K7XX by 3dB without increasing the harmonic distortion? Does anyone who has tried both think the HD800S is worth 8X the price of the AKG K7XX? If so why? They measure very similarly.

It looks like the HD800S will fit around even large ears? Are they comfortable?

Torq's picture

The longer I'm involved in this hobby the more I see that measurements don't tell the whole story.

As to whether the HD800S are worth 8x the price of the K7XX ... that's always going to be a personal call. For me it's simply down to enjoying the music more with the HD800S - every aspect of it is improved - sometimes a little, sometimes a lot, but I can't think of anything that's better on the K7XX.

I keep things like the K7XX, Q701 and HD650 around mostly for use with my alternate systems (e.g. my much simpler, smaller, lower powered bed-side rig), and for comparisons.

Are the HD800S "8x better"? No ... but that's the law of diminishing returns for you.

I suspect the bass increase in the K7XX was accomplished by making the pads thinner than those on the Q701/K702.

The HD800/HD800S are the most comfortable headphones I've ever worn. Can barely tell they're there. Very little in the way of clamping pressure and they're pretty light.

zobel's picture

That what I was looking for, a testimonial on the value of the HD800S, and a comparison to something I have. I wasn't serious about 8X better because I realize the actual value is subjective, and relative to ones willingness to invest in incrementally smaller improvements in overall quality. It sounds (no pun) like these HD800S compete very well with costlier cans, Sounds like (again - no pun) I have myself convinced to save up for a pair. I guess after new furniture and floors, these will first on the list. Yep, married. I had heard that pad modification might have improved the bass of the K7XX, and it makes sense that it would without changing the THD in those cans. I also have read that the HD800S are uber comfortable. I lust for them, much more than furniture or flooring. If you are still available, what amp do you like with the Senns?
Thanks again, zobel

Torq's picture

My primary headphone amplifier currently is a Schiit Ragnarok. That wouldn't be my choice for a stock HD800, but with the HD800S it pairs up very nicely.

I also use a Woo WA6, which drives the HD800S fine and sounds very musical, but isn't the last word in authority with those particular cans. Now and again my Chord Mojo has driven the Senns, and that fits quite well also - this is one that I use with the HD800S in some scenarios because I have the Mojo for portable use with other headphones - I wouldn't buy one just to drive the Sennheisers.

I've heard the Decware Taboo Mk III with the HD800 and think that would be a fantastic pairing with the HD800S also.

I have a WA5LE on order ... I'm excited to see how that pairs with the new HD800S.

It's worth noting that I'm a multiple-headphone kind of person. I have the Abyss for some types of listening, the HD800S for others and I nearly bought an HE-1000 a week or so ago (though that's more likely to be an Edition X now).

I could be very happy with any of those headphones as my ONLY pair if I had to be. My choice to have multiple is about genre optimization and even then the differences are signature and stylistic preferences more than good/bad matches.

zobel's picture

Let us know what you think of the WA5LE pushing those HD800DS when you have had a chance to check it out here, please. The only amp of any quality I own is the O2. It pairs well I think with the HD600s, and has plenty of guts to drive my AKG K7XX, but I'm not sure it does those any favors, since they both seem pretty analytical at times (a little on the dry side on top). Straight from any player w/o amp, I like the sealed Sennheiser HD380 Pro, and the Noontec Zoro HD II for on the go. In still get some mileage out of the Senn PX 100 II - with some parametric EQ from my PCDP. (Sony D-NE300). Don't laugh... I can lower the upper bass 4dB, the lower mids 2dB, and bring up the mid treble 2dB, and get good sound from them. Whatever works right? The HD 380 Pro doesn't need or benefit at all from any EQ, IMO.
I'm sure I'm not the only one here who appreciates your reports on the gear you are up with!

Franc's picture

"By selectively adding 2nd harmonic overtones to the low notes, overall bass energy is increased—albeit at a higher frequency than the original tone—and your perception will be a euphonic warming of the bass. "

This is very interesting but I have no clue how to do this. Say you have a sound system that lacks deep bass how do I lift lower frequencies? Do I use some sort of device or software?

Torq's picture

The easiest way to do what you're asking is with an Equalizer. That can be a hardware device, or if you're using a computer as your source (or many Digital Audio Players) it can be done in software. Many software players have Equalization (usually abbreviated to "EQ") capabilities built-in.

Basic hardware EQ is often of the "Graphic Equalizer" variety. You put the box between your source (DAC) and your amplifier, and then move little sliders (potentiometers - variable resistors) up and down to provide a "graphic" (visual) representation of the boost or cut (increase or decrease) for each of the represented frequencies bands. 5-band EQ is common and you can often find more.

Parametric EQ is more powerful and a bit more involved on the hardware side. Software Parametric EQ is incredibly powerful and that's what you'll see in the articles that Tyll and Bob Katz post (they're using DMG's Equilibrium, which works with various audio-player applications). Things like J-River Media Center have parametric EQ capabilities built-in.

Franc's picture

Awesome, thank you for replying. I will have to do some digging to find a standalone equalizer that works on Windows. VST's I do have.

Sorrodje's picture


First of all, let me tell you that I'm super proud to be mentionned on Innerfidely. Actually, even for french community, you're the Godfather of personal audio so such a mention for my work is the best reward i can think of.

Actually the story you related is almost 100% true and I had a good laugh when I saw the way you related it. I worked on the mod during a month and my measurements rig was made before the whole adventure though ;)

Happy to see that you share basically the same opinion I wrote about the HD800S I wrote on Head-fi and To be honest, I didn't hear that much difference in the bass and I definitely think the tamed 6khz is the more noticeable (and welcome) effect. IMO, less 6 khz means we hear more of the whole other frenquencies bass included. Super Interesting thoughts about distorsion though. Very well put.

To be honest, the fact I liked the HD800S so much was the starting point of the "SuperDupont Resonator" and I'm glad you appreciated the result I reached. I let go my HD800S now and I'm perfectly Happy with My HD800SD.

Please just notice that SD Resonator specs are 7mm thick from top to bottom. The felt ring is 5mm thick. Such a...ahum...Big 14mm Resonator wouldn't fit in the 7mm "Hole of Glory".. ahum.... lol.

jussy1254's picture

I own the HD800 and cannot stand the shrill metallic sound. I've actually given up listening to headphones because of this and cannot be bothered to fork out more money for a different pair as I also invested in a hideously expensive 5m cable to go with the HD800. Can anyone please offer me some advice on improving the sound? This is not something I would want to attempt myself so would adore any info/recommendations on a company offering a modding/tuning service. Many thanks

Humbi2's picture

After this article about the HD800S I thought: "Wow. This guy has really trained ears. I could never hear distortion in headphones this good."
So what do you think about the K702. What are its strenghts and weaknesses. Do they have much distortion and a annoying peak in any frequencies. And aren't they way to good for 180€

Dadracer's picture

Hi Tyll
Comprehensive, informative, humorous and insightful. Thank you.
I just wondered if I missed which amp you did your listening tests with please and did you use the headphones balanced?

tony's picture

I loved these 800s the first time I heard them, still do. I wondered what the Germans could do to refine them as I feel them to be the finest Audio transducers (dynamic) in existence.
Sennheiser have never offered up-grade "kits" for any of their products. Leave it up to "our" Tyll to pull back the curtains for us, thank you, who else dared even try?
The HD800 sells for $800 to $1,000 on Ebay, about 10 per month. None of the 800S models have been sold, yet.
Nice video quality : the first one came in a 1080P while the Standard Review version remained at 720P. Color seems very good, frames per second looks higher with depth of field significantly improved, nice work, you're turing into a "Pro".

Tony in MIchigan

evanft's picture

I used your EQ with my lightly modified HD800 (foam ring and trapezoid) and it had a very pleasing effect.

echoplex's picture

Hello Kyle,

Many thanks for your continued work/exploration of headphones, their tweaks, and the recent series of articles on the Harmon Target Response curve. Those of use who work in pro-audio/mastering know Bob Katz's work well, and it was interesting to read about his take/tweaks. With regard to the HD800S, would you mind posting a full screen shot of your EQ settings with DMG Equilibrium? I have/use that plugin, and I would like to compare your DMG EQ settings to the curve of the Sonarworks plugin settings for the HD800. While sonarworks has gotten good reviews, (see, my experience is that for the HD800, the Sonarworks HD800 setting only seems to sound acceptable with a wet/dry mix of approximately 50%. Users in other forums have posted similar remarks. You might also want to check out the new Waves virtual room plugin, (a free demo for 14 days is available),
This tries to simulate various rooms in software, and some people think that the combination of an EQ'd headphone curve - together with a room simulation - could give you a better out of head experience with headphones, i.e., like listening in a well calibrated monitoring suite/studio. Keep in mind that Sonarworks does nothing (thus far) with HRTF's - it just does frequency response. And convesely, Waves NX does psychoacoustics together with HRTF (you need to enter your head dimensions for it to work), but nothing with frequency response. Thus in combination, they may complement each other. This begs the question - is a good sounding room the reference (including the listeners HRTF), or simply a more abstract listening environment "in the head" headphones. Happy experimenting.

echoplex's picture

Sorry - I meant to ask you to post a full screen shot of the DMG Equilibrium settings for the HD800 (the HD800s is all there I believe).