New Technologies

The Centro Force Redesign:

For years we have been waiting for new Sennheiser innovation, since it's first iteration of the HD800 in 2009..

Imagine in 2009 the HD800 was simply an engineering marvel, so way ahead of its time that even with the 2015-2016 800S release, it still looked space age.

The point is that it took a genius engineer, Axel Grell, who was able to think “outside the box” to create such an engineering marvel.

So with the loss of this engineer, it took this same “outside the box” thinking, in order to achieve what has never been thought possible with the HD800S. A "restoration" to the design, not simply an addition, as it will “restore” hidden potential beyond what was conceptually intended. Transparency & Realism was the goal and accomplishment with this “Centro Force” design.. Not just any change in “signature” sound.

10yrs later and amazing coincidence (or destiny) for me (Charles) and Vince (whitigir) to get together and combine our “outside the box” engineering ideas, which synergistically transformed and evolved the HD800 original design into a new, never before explored mod, neither by Sennheiser nor ANY other modder, continuing in an evolution to what we believe Axel Grell's design would have intended.

With this redesign, we will finally see the fruition and goal of the full potential that the HD800s design was truly capable of.

Greater Potential in Frequency Response, phase, and linearity for all HD800 variants.

The Theory Behind The New Centro-Force "Technical Upgrade" :

The New “Centro-Force” design implementation basically introduces two new aspects (two-fold):

1- First, the Ground breaking new implementation The internal “Trinity core”. Plural magnetic elements, combining triple magnetic field structures into “unified core” of varied intensity, according to the driver’s excursion.

With this new manipulation, we can control dynamics, soundstage, and every other measurable aspect of driver performance. The "trinity core" is an advanced core, designed to last indefinitely the lifetime of the headphone, without any change or loss in efficiency and exacting performance.

This is the frontal redesign:

2- Second, A New rear design :

An “Acoustic reinforcement waveguide cavity” design, for uniformly reshaping the whole spectrum, elevating the Frequency Response “preference boundaries”, while carefully correcting Frequency Response, Phase, Peaks, and dips(!). All while uniquely preserving the soundstage openness (holography) that all previous mods have reduced or destroyed.

Important to note is that No "material tunning" is used...

All improvements are of technical design origin.

This is not a "tuning mod".

No stifling signature changes from front or rear materials, or even felt “resonators”, but instead the focus was on actual design improvements. So no strange add-on materials are employed, as all past versions from other sources had.

Technical Specifications:

Initial HD800 (non 800S) Measured Results below:

Specific choice was made to use visual data on the popular REW program, for familiarity. We will be updating also with the measuremwents with 800S model soon, and performance improvements are just as impressive.

This advanced 3D rear design, incredibly increases BASS spectrum substantially (up 9db), down to a “perceivable” 10hz(!), as we can see it is elevated to the 1khz reference level (noticable level).

We are increasing over 72% of the overall bass spectrum…Never heard before on any hd800 variant(!).

With this “Centro Force” mod, even the sensitivity is increased..

The Production unit has a 2db sensitivity improvement across the whole spectrum:

This 26% increase in sensitivity also corresponds to higher dynamic range. An increase of sensitivity to 104db, so less output power needed from your amp. So the “Centro-Force mod” will allow the headphones to perform at a higher potential with even just a DAP, and no longer be "amp dependent”, or bound to home desktop” setups.

** Improved Frequency Response:

The yellow line is a stock version, and the blue line is the new “Centro Force” Frequency Response. Each line is 1db, for easy counting.

First take notice that the whole mid-range region is exactly preserved, and only the “Target Curves” were adjusted. This was intended.

We see how the whole bass region is not only elevated, but more linear and higher than the trebles.

Subbass is now perceivable, as it is all above the white line (1khz reference level).

Frequency extension is an aspect few headphone companies will focus on, yet allows for pristine clarity and dynamics in the trebles, without the traditional harshness associated in this region.

Harshness is commonly associated from phase response changes. Especially at the most critical parts of the frequency 5-8khz range (sibilance). This is due to an inability for the average headphones to replicate these areas cleanly with the higher speed and dynamics necessary for "live event" levels. The Centro-Force solves this with higher speed and dynamics.

So, Phase shift is the main culprit. An important factor in the Frequency Response. Changes in phase are often linked to peaks and dips in the Frequency response graph, and sharp phase changes often occur where this response has wiggles or dips.

Here we see how Centro Force Phase line (red) is way more linear (flat) in the critical areas of sibilance, while the stock headphones (green line) has a phase shift line that's wiggling and moving away, at both the bass & treble extremes.

Phase variance in the 5-8khz "Sibilance" area, (which is already problematic by issues coming from your source gear), can easily result in increased sibilance, if your headphones has phase shifts in this region.

This is the main reason why manufacturers don't want to deal with this, and simply cut off the whole "sibilance" area with a dip in frequency response, so you end up with MISSING information. This is where Centro-Forcce design departs from the rest, by tackling this issue head on, resulting in notably superior performance in the "Sibilance" area, giving a clarity not seen before on these and most other headphones.

Next is the Frequency Response “Target Curves”

Take note that the midrange region was unaltered(!) and preserved, so that only the bass & trebles “preference regions” were expanded.

The bass and treble elevations fall within the latest proposed equalization standards and target curves for upper treble, according to the AES E-Library, and also with more recent “preference boundaries”, set by others in online headphone communities.

AES E-Library Target:

Next, the CSD/Waterfall plots:

The standard measurement goes down 35db for easier viewing of differences. Here we are, @ 35db down:

Here we see before and after. All the spurious decays above 2.5khz are gone with the Centro Force Mod. Also a ridculously clean area after 1.5 milliseconds.

Also the green area has also been improved lower and way more uniform. . This all shows how much cleaner and controlled this headphone has become.

Lastly, lets look at the impulse response:

Centro-Force version showing noticeably faster impulse (blue):

Notice how much narrower the blue response is. A fast (faster impulse time) and ridiculously well controlled decay… This shows that the driver speed has increased, which leads to better resolution.

Also notice the “decay”, how much less vulnerable the driver is to “parasitics” like the basket wave, acoustic impedance, and all other variables influencing the driver. That is from the increased driver control.

Speed, linearity, low phase, and custom driver control. That is what allows Centro-Force to perform at "live event" level performances.

According to the Different measurement setups online, they will look different in appearance overall, but the resulting increase of improvement will still be the same.

The Sennheiser HD800 variants were true to the legacy of being one of the best headphones in the world, and now with the Centro Force Mod, it will be proven yet again to definitely be one of the best in the world. We can't thank Sennheiser enough for giving us this diamond we have just made brilliant.

We also see the stock treble peaks & dips (causes of phase shifts) are eliminated, while the response range (beyond the 6-8khz sibilance area) has been leveled and extended. The focus was on accurate frequency range extension, well into the “air” region. The (now restored) audibility of the “air” region, is the missing aspect of most headphones today.

So the Trebles "control" is more linear, and rise only after 10k, according to how our hearing diminishes. This illustration below, shows why a "Harman Curve" or similar "V" shape curve is preferred, in order to offset our loss of auditory sensitivity. So as to hear everything without efforts.