New Technologies

The Centro Force Redesign Origin:

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 of Plural magnetic elements. What we named as the “Trinity core”. It combines 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, longer than the lifetime of the headphone, without any change or loss in efficiency and exacting performance. Upcoming kits (for technically inclined) will show the multi-element design complexity.

This is the frontal redesign:

2- Second, A New rear design :

A new rear “Acoustic reinforcement waveguide cavity” and baffle design, for uniformly reshaping the whole spectrum, elevating the Frequency Response “preference boundaries”. This new part consists of specific design angling, size, and "micro groove dispersion" to carefully control Frequency Response, Phase, Peaks, and dips(!). Uniquely preserving the soundstage openness (holography) that many previous mods and remakes have reduced or destroyed.

Important to note is that No "material tunning" is used in this design change...

The focus was on actual design improvements, so All improvements are of technical design origin.

This is not a "tuning mod", so this departs from traditional methods and thinking.

So there is no stifling or destructive signature changes from using strange added on sticky materials, “resonators”, or covering pieces, which are all basically post-design ideology that past attemps from other sources had.

Technical Specifications:

HD800 & 800S CF Measured Results below:

For greater familiarity to consumers, we chose to display our results on the popular REW program, that many are more familiar with..

Along with the overall increase of the low range, we also restored more liveliness in the 5-6khz area, along with a welcomed gentle dip in the usual sensitive 8-9khz area. Then we have an leveled off extension above 10khz for proper "air" (explained in bottom "ideologies" section). The gradual lowest dip at 3.5k simulates the HD800 level, to preserve the soundstage depth, because of the increase in "pin-point focus" & clarity. This is due to the clean up of mid-level ringing distortions (explained in waterfall measurements). So here we have what we feel is the perfect signature created by true design performance.

**HD800S-CF Improved Frequency Response:

For the HD800CF, we see how the whole bass region elevated and more linear. Even sub-bass can now be perceivable, as it is all above the white line (1khz reference level).

Next, the CSD/Waterfall plots:

Standard measurements go down 35db for easier viewing of differences.

Here is the Stock HD800S, at about 35db down:

Here we see this Centro-Force version of the HD800 impulse (in blue):

We will now explain what our own testing has revealed, not "common engineering" or the recent "everything is EQ camp" consensus explanations, but key points revealed...

**The peak rise time before the "0" vertical is the actual speed.

**After the "0" is the decay, which reveals multiple aspects.

**The "normalization ability" is the decay time to rest at zero. This involves things like diver control and "air impedance".

** The negative travel of this impulse has an association with image depth & solidity.

**Anything after the completion of initial wave are artifacts like basket reflections.

So in this image we are noticing faster impulse time, and ridiculously well controlled decay… This translates to both driver speed and control has increased, which leads to better clarity and resolution.

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.

For those who prefer the HD800 (not "S") sound, we see the HD800CF version eliminate the stock treble peaks & dips (causes of phase shifts), with the whole treble area leveled and restored well into the “air” region (at the 1khz white reference line),

This trebles extension rise after the 8-9khz area of sibilance sensitivity, according to how our hearing diminishes. Audibility of the “air region" (the missing aspect of most headphones today) is now restored. 

Lastly, lets look at the impulse response:

First off, the Bass:

Here we see (on 800CF) a 9db increase @ 10hz (extreme sub bass). While this isn't evident in actual music (as normal mid-bass frequencies are around 60 HZ), this increase represents the scale of mechanical improvement in its driver's control.

Below we show a "before and after" of the HD800 version, showing similar issue of ringing decays above 2.5khz, which are all gone with the "CF" Mod.

The lack of all ringing (trailing peaks) after 1.5 milliseconds leads to insane level of clarity and pin-point imaging.

For the 800S, a lesser 5db increase @ 10hz is observed, but regardless, but both 800CF & 800S-CF retain a sustained increase of 4-5db across the whole bass & "low mids" region, which adds up to a quite noticeable improvement, and a huge benefit the sound signature's natural bass ability. This presents a realistic native bass level which is very different than artificial EQ boosting. (artificial EQ issues explained at bottom page "Ideologies"). The cumulative amount represents an increase of over 72% of the overall bass spectrum. This increase in sensitivity shows how it is no longer be "amp dependent”, or bound to home desktop” setups.

Notice we marked the peak trails on the waterfall plots (thin red lines), which represent multiple rows of lower-level "ringing" in key multiple frequency areas.

This audibly translates to the diffuse soundstage and artificial spaciousness that plagued these headphones with less focused image placement as a result.

These peak "trails" are about 25-30dB down, which is easily discernible to the human ear (diffuse sound), as the human ear sensitivity typically hears details 60-70db below the peak. This sensitivity is even greater with headphones, and more so with IEMs.

This is where the "Centro-Forcce" mod distinguishes itself from ALL other modifications, with the elimination(!) of these ringing, to produce a clarity of notes in space, that was unachievable before:

HD800S-CF version:

Here we see (thin red lines) no vertical "red mrked" rows of peaks, and a sharp cut off of any trails. The bass is showing gradual downward slope with little ripple, unlike the stock image ripples.

The result is a much clearer/deeper soundstage, with nuances in music fleshed seemingly out of nowhere.

Here is a quick "before & after" comparison.