[daltonlanny]

Below is a copy of a post I made in one of the Sennheiser HD660S threads that is relevant to the Sennheiser HD800 and HD800S discussion. It is about the longstanding rumor that 2nd order harmonic overtones/distortion was added to the Sennheiser HD800S (versus the HD800):

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I decided to examine this further here, with the one HD800 and the one HD800S we have. Here's what I did:

---

• First I did a quick FFT plot of the HD800 (16,000 points, no averages), playing a 40 Hz sine wave. I ended up with a plot that looked somewhat like this:
  
  
  
  As you can see, that's not particularly detailed, so I took advantage of our audio analyzer's ability to do extremely detailed FFT's, opting for 1.2 million points, and doing three averages. Setting it to 1.2 million points provides a much more detailed plot, and the averages help remove random noise (better revealing the actual noise floor, too). Without having moved the HD800 from the above plot, here's the FFT re-run with 1.2 million points with three averages:
  
  
  
  And here are the two overlaid:
  
  
  
  NOTE: The examples above are actual measures of the Sennheiser HD800, but these were just quick preliminary measurements done without turning off the building's heating / ventilation systems. Even though we do employ a lab-grade acoustic and vibration isolation enclosure, the measurement gear is obviously very sensitive, so we still turn off the HVAC systems when we're doing audio measurements to lower the noise floor. As a result, the example measurements above may have a higher noise floor than the measurements that follow (which were done with the building's HVAC systems turned off).

• Again, the above measurements were just done as examples of two different FFT resolutions. Now let's get to the actual comparisons. Following are FFT spectrum measurements from the first seatings of the Sennheiser HD800 and Sennheiser HD800S, set to 1.2 million points and three averages, and playing a 40 Hz sine wave. I made the plot lines a bit thicker (and different colors) to try to make the two plots easier to distinguish from one another:
  
  
  
  Here (below) is the same plot with cursor lines showing the difference at 80 Hz (80 Hz being the second harmonic of the 40 Hz sine wave fundamental tone, since we're examining the theory that the Sennheiser HD800S's richer sound is due to (as quoted above) deliberately added 2nd harmonic overtones/distortion):
  
  
  
  The difference between the Sennheiser HD800 and Sennheiser HD800S at 80 Hz (H2) is only 2.783 dBSPL. Keep in mind that the center of this 2.783 dBSPL difference is occurring around 45 dBSPL lower than the fundamental tone. While the Sennheiser HD800S unit we have here does (to my ears) sound like other HD800S's I've heard (richer than the Sennheiser HD800), I do not believe this measured difference at 80 Hz suggests deliberately added 2nd harmonic overtones/distortion (to the HD800S versus the HD800).
  
  
• I decided to do a second seating of both headphones, also increasing the size of the headband for both headphones by one click on each side. Here (below) are the FFT spectrum plots from the second seating:
  
  
  
  Again, this time (below) with cursor lines showing the difference between the two in this seating at 80 Hz (the second harmonic of the 40 Hz fundamental test tone):
  
  
  
  The difference in this plot at 80 Hz is lower than the previous one, measuring only 1.673 dBSPL. As above, the center of this difference is about 45 dBSPL below the 40 Hz fundamental tone.

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Again, keep in mind we only have one Sennheiser HD800 and one Sennheiser HD800S here at this time. I may measure more.

Based on discussions with Sennheiser and the above measurements of the Sennheiser HD800 and HD800S we have on hand, it does not appear there was any deliberate addition of 2nd order harmonic overtones/distortion to the HD800S as has been the common theory for the past couple of years.

If you have any other suggested tests you'd like to see performed on these two units here that you think might generate different results, let me know. That said, based on the THD measurements I posted in this thread earlier, and other measurements we've performed on these two headphones (also on the GRAS 45BB-12), I'm not surprised by the above results.

The measurements in this post were made using:

• GRAS 45CA Headphone Test Fixture with:
  • GRAS RA0401 High Resolution Ear Simulators
  • GRAS KB5010/KB5011 Anthropometric Pinnae for 45CA
• Audio Precision APx555 Audio Analyzer
• Audio Precision APx1701 Transducer Test Interface
• Herzan custom acoustic enclosure

Hi Jude. Very interesting indeed.
Not trying to disagree with your findings or anything, and definitely not defend Tyll Hertsens or anyone else, for that matter, but several other people, as well as other publications, (besides Innerfidelity), have measured significantly higher harmonic distortion in the bass below 80 hz on the HD800S compared to the HD800.
And this is with both headphones available to measure back to back.
Why would this be?
I personally find the HD800S to sound just a slight touch muddier and less distinct in the bass compared to my regular HD800, especially when listening to bass heavy music, plus my regular HD800 takes equalizing (boosting) the bass, better than the HD800S, which becomes even more muddy with low bass boost, compared to regular HD800...
Just sayin.

 

[Arniesb]

Great post Jude!

 

[Arniesb]

I probably don't know what I'm sayin, but what if You Eq HD800S to have exactly same fr as HD800 and then test it?
I always think that eq highs dow make bass: bloomier, less fast, less crisp less layered and so on and so forth...

 

[csglinux]

Based on discussions with Sennheiser...

That should nail the argument more convincingly than any measurement, no?

Two things that puzzle me about this. 1) How would one modify a passive driver to selectively add 2nd harmonic distortion? 2) Existing measurements (Innerfidelity) of THD+N from frequency sweeps show error increasing as frequency drops. Are the measurements of the error themselves in error, or is there another explanation for this?

 

[SilverEars]

I think the idea of distortion added to the low end started out of innerfidelity. Tyll's rig points out 20dB difference in the 80hz overtone whereas Jude's rig shows 2.78dB.

Here's the article

https://www.innerfidelity.com/conte...tweaked-and-delightfuland-french-diy-response

 

[daltonlanny]

But there are other people, besides Hertsens, who have actually also measured higher distortion in the bass on the HD800S compared to the HD800.
Maybe it's inconsistencies in manufacturing, or maybe it's a fluke?
It doesn't matter either way to me.
I still love the HD800S, and enjoy listening to them quite often.
I actually prefer them over the Focal Utopia, so I am not bashing them, nor Jude at all.
I am only pointing out something that is sort of a mystery concerning bass distortion measurements on the HD800S compared to the normal HD800.

 

[jude]

Hi Jude. Very interesting indeed.
Not trying to disagree with your findings or anything, and definitely not defend Tyll Hertsens or anyone else, for that matter, but several other people, as well as other publications, (besides Innerfidelity), have measured significantly higher harmonic distortion in the bass below 80 hz on the HD800S compared to the HD800.
And this is with both headphones available to measure back to back.
Why would this be?
I personally find the HD800S to sound just a slight touch muddier and less distinct in the bass compared to my regular HD800, especially when listening to bass heavy music, plus my regular HD800 takes equalizing (boosting) the bass, better than the HD800S, which becomes even more muddy with low bass boost, compared to regular HD800...
Just sayin.

But there are other people, besides Hertsens, who have actually also measured higher distortion in the bass on the HD800S compared to the HD800.
Maybe it's inconsistencies in manufacturing, or maybe it's a fluke?
It doesn't matter either way to me.
I still love the HD800S, and enjoy listening to them quite often.
I actually prefer them over the Focal Utopia, so I am not bashing them, nor Jude at all.
I am only pointing out something that is sort of a mystery concerning bass distortion measurements on the HD800S compared to the normal HD800.

Different results from different measurement setups do not surprise me. Here are some links where I discussed this recently:

Headphone measurements: different measurement setups, different results (1)

Headphone measurements: different measurement setups, different results (2)

As for manufacturing inconsistency: That's always a possibility, but, in my experience, nobody is better at unit-to-unit consistency than Sennheiser. (Focal is also impressive in this regard.) That said, I may test other units.

That should nail the argument more convincingly than any measurement, no?...

It certainly is an interesting aspect to this discussion, and it seemed like something worth asking them about (so I did, after my first set of measurements on the GRAS 45BB-12, which yielded similar results).

...Two things that puzzle me about this. 1) How would one modify a passive driver to selectively add 2nd harmonic distortion?...

This is a very interesting question, and I'm curious about how one might be able to so specifically add only H2 and nothing else to a passive headphone. Perhaps an acoustical engineer reading this thread can answer this question for us? Maybe there's a simple answer, maybe there's not -- either way, I'm curious about the way(s) this can be accomplished.

...2) Existing measurements (Innerfidelity) of THD+N from frequency sweeps show error increasing as frequency drops. Are the measurements of the error themselves in error, or is there another explanation for this?

I'm not sure, and won't venture an answer here.

 

[jude]

Hi Jude. Very interesting indeed.
Not trying to disagree with your findings or anything, and definitely not defend Tyll Hertsens or anyone else, for that matter, but several other people, as well as other publications, (besides Innerfidelity), have measured significantly higher harmonic distortion in the bass below 80 hz on the HD800S compared to the HD800.
And this is with both headphones available to measure back to back.
Why would this be?
I personally find the HD800S to sound just a slight touch muddier and less distinct in the bass compared to my regular HD800, especially when listening to bass heavy music, plus my regular HD800 takes equalizing (boosting) the bass, better than the HD800S, which becomes even more muddy with low bass boost, compared to regular HD800...
Just sayin.

I decided to look into this further, and looked again at the InnerFidelity FFT from which it seems the conclusion was reached that perhaps Sennheiser was adding 2nd order harmonic distortion to the HD800S (vis-à-vis the HD800).

At InnerFidelity the following was posted:

...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.

Here's the InnerFidelity FFT, enlarged (click to see full size):

(Above graph from InnerFidelity.com)


From that measurement, the InnerFidelity observation was made that...

...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...

I noticed on the graph that the HD800 is labeled "HD 800 DP Mod Left" and "HD 800 DP Mod Right". Is it possible that the HD800 represented in the graph was a modified one? To be clear, I am not saying it was, I am only wondering, as the HD800S is simply labeled in that same graph as "HD 800S Left" and "HD 800S Right".

It seems to me that the InnerFidelity HD800S FFT is showing bass region harmonic distortion characteristics that are more similar (versus the HD800) to what we're seeing here with the HD800S, with the highest being the 2nd harmonic, and the 3rd being lower. (That said, relative to the fundamental, InnerFidelity's HD800S 2nd order harmonic distortion does still appear to be higher than ours.)

Also, the InnerFidelity HD800 FFT shows higher 3rd order harmonic distortion than 2nd (the 2nd and 4th looking blunted relative to our HD800 FFT's), which results in InnerFidelity's HD800 FFT plot looking very different than ours.

Knowing I was going to be taking time away from the office the other day, I decided to leave the HD800 on the GRAS 45CA enclosed in the isolation enclosure, and the measurement rig powered up -- I did this so that I could access it remotely on my "vacation."

Running the rig remotely from my home the other night, I wanted to run some quick measurements (keeping in mind the heating system was probably on at the office, as the outside temperature was (at the time of the measurement) -2° F (around -19° C)). For these measures I used 1.2M-point FFT (with no averaging to keep it quick). I wanted to measure the delta between H2 and H3 with a 40 Hz sine wave played at 90 dBSPL (the level of all the measurements in my previous post), the output voltage being 166.2 mVrms. The difference at 40 Hz at 90 dBSPL was 10.31 dBSPL (H2 minus H3).

I decided to increase the output to 1000 mVrms (1.00 Vrms) with a 40 Hz sine wave, which exceeds 105 dBSPL -- this is far higher (at least I hope it's far higher) than normal listening levels. That reduced the difference, but H2 was still 7.523 dBSPL higher than H3. I like the HD800, so I'm not going to drive it much harder than this, and I think exceeding 105 dBSPL at 40 Hz is high enough to establish that with this unit, I'm not likely to see H3 exceed H2 with this configuration within any reasonable drive level.

In short, the differences between our FFT measurements and InnerFidelity's FFT measurements of same seem to be a combination of a couple of key things:

• The HD800S 2nd order harmonic distortion measured at InnerFidelity is higher than what we measured here.
  
  
• More dramatically, though, the InnerFidelity HD800 FFT measurement shows higher 3rd order bass harmonic distortion than 2nd order. This is something I was not able to reproduce here (at least within the reasonably high drive limits I'm willing to venture to). Again, here's a re-post of one of the measurements from my previous post showing an HD800 FFT spectrum graph two different ways (16,000 points, with a 1.2M-point FFT overlaid):

Also, today my business partner brought back his HD800 so we could measure it. Here are those measurements (two different seatings), these measurements taken with the office's HVAC systems turned off:

Sennheiser HD800, unit 2, seating 1:

Sennheiser HD800, unit 2, seating 2:

In both seatings, this second HD800 also shows substantially lower H3 than H2, consistent with the first HD800 we measured earlier.

Again, with the above InnerFidelity measurement label showing "HD 800 DP Mod Left" and "HD 800 DP Mod Right", I'm wondering if there is any chance at all that was a modified HD800. If so, perhaps this helps explain some of the differences. If not (or perhaps even if so), then we'll just have to go with different measurement rigs, different results (and different units, different results).

In summary, so far our FFT analysis of two different HD800's and one HD800S does not support the nearly two-year running line of thought that the Sennheiser HD800S was engineered with added 2nd harmonic distortion to achieve the perception of fuller bass. Our measurements are also consistent with feedback from engineering discussions with Sennheiser on this topic. I may measure more units of both models in the future.

See our initial posts and measurements on this topic.

Our measurements in this post were made using:

• GRAS 45CA Headphone Test Fixture with:
  • GRAS RA0401 High Resolution Ear Simulators
  • GRAS KB5010/KB5011 Anthropometric Pinnae for 45CA
• Audio Precision APx555 Audio Analyzer
• Audio Precision APx1701 Transducer Test Interface
• Herzan custom acoustic and vibration isolation enclosure

 

[exdmd]

Thanks for disproving an urban myth about the HD800S bass. People tend to believe what they want to believe though.

 

[wldcohso]

WOW... Judes post just makes me feel really happy about head-fi community and research. Just look at the detail and his explanation of things.. All I can do is listen to the music and go off what I like but to actually read his technical details just blows me away. I've been contemplating getting HD800S after selling them but I sure do miss them, even after purchasing Focal Utopia. I thought about getting Focal Clear but since i already have the Utopia I'm not going to waste my time on them.

 

[exdmd]

WOW... Judes post just makes me feel really happy about head-fi community and research. Just look at the detail and his explanation of things.. All I can do is listen to the music and go off what I like but to actually read his technical details just blows me away. I've been contemplating getting HD800S after selling them but I sure do miss them, even after purchasing Focal Utopia. I thought about getting Focal Clear but since i already have the Utopia I'm not going to waste my time on them.

Don't you miss the sound stage of the HD800S compared to the Utopias?

 

[wldcohso]

Don't you miss the sound stage of the HD800S compared to the Utopias?

Not sure if it’s just the soundstage but it’s everything about them that I miss. It’s just a totally different experience, feel, fit, look and sound wise for me.

 

[MacedonianHero]

Don't you miss the sound stage of the HD800S compared to the Utopias?

The solution is simple...keep both!

 

[kzii]

The solution is simple...keep both!

I had both Focal Utopia for and Chord Dave. I bought this combo because of curiosity. However, I still like Sennheiser HD800S more because it has better soundstage and overall sound signature. I don't want to say that Utopia is worser than HD800S. In my opinion, Utopia is awesome piece of engineering like HD800S. Just choose whatever serves your ears better. For me HD800S is a masterpiece. It's packed with top sound and build quality. Soundwise is on par with Utopia.

Now, I enjoy HD800S with Hugo 2 (endgame). Utopia and Dave went to my brother, mainly because I have found that Hugo 2 serves me better because I love to listen to music around my home/garden. H2 is not much behind Dave which is more revealing. I ordered silver usb cable to H2 to replace the stock cable to improve the sound even more. Reading the reviews about silver usb cables I think that thanks to that H2 will get even better.

PRO TIP:
I have found that other factors than sound quality should be evaluated to fully choose headphones/amp/dac. For instance, Utopia was not comfortable for me so I ended up prefering HD800S. Dave has better sound quality but I cannot move it around and travel with it (I do it often) so I prefer H2 more. I think that sometimes we just forget that other factors are also as important as sound quality. In my case, if something regarding mobility or comfort bothers me, I just can't fully enjoy the sound quality.

PS: I saw some posts stating that Utopia has better build quality because of material used (carbon fibre vs plastic). I am engineer and I think that it's a nonsense. HD800S may use plastic but tolerances and quality of the materials are top notch. In engineering world, it is well known that the materials should be chosen according to the intended use of the product. I think that Focal used carbon fibre to reduce weight of the headphones. Does HD800S need this? The answer is no, and because of that they can also keep the price lower.

 

[MacedonianHero]

I had both Focal Utopia for and Chord Dave. I bought this combo because of curiosity. However, I still like Sennheiser HD800S more because it has better soundstage and overall sound signature. I don't want to say that Utopia is worser than HD800S. In my opinion, Utopia is awesome piece of engineering like HD800S. Just choose whatever serves your ears better. For me HD800S is a masterpiece. It's packed with top sound and build quality. Soundwise is on par with Utopia.

Now, I enjoy HD800S with Hugo 2 (endgame). Utopia and Dave went to my brother, mainly because I have found that Hugo 2 serves me better because I love to listen to music around my home/garden. H2 is not much behind Dave which is more revealing. I ordered silver usb cable to H2 to replace the stock cable to improve the sound even more. Reading the reviews about silver usb cables I think that thanks to that H2 will get even better.

PRO TIP:
I have found that other factors than sound quality should be evaluated to fully choose headphones/amp/dac. For instance, Utopia was not comfortable for me so I ended up prefering HD800S. Dave has better sound quality but I cannot move it around and travel with it (I do it often) so I prefer H2 more. I think that sometimes we just forget that other factors are also as important as sound quality. In my case, if something regarding mobility or comfort bothers me, I just can't fully enjoy the sound quality.

PS: I saw some posts stating that Utopia has better build quality because of material used (carbon fibre vs plastic). I am engineer and I think that it's a nonsense. HD800S may use plastic but tolerances and quality of the materials are top notch. In engineering world, it is well known that the materials should be chosen according to the intended use of the product. I think that Focal used carbon fibre to reduce weight of the headphones. Does HD800S need this? The answer is no, and because of that they can also keep the price lower.

The sound staging on the HD800S can be a blessing and curse. For small studio recordings, it still colours what I'm hearing to make it sound too expansive. The stock cable on the Utopia is fairly poor and I'd suggest you look at upgrading that. The Utopias are simply the best dynamic driver headphones I've heard and comparing them to the HD800S/HD800 isn't totally fair due to the price differences. The dynamics, tonal balance, detail retrieval and transparency are all better on the Utopias.