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I was visiting the Pure Acourate Sound Project in Germany last month


Active Member
Jul 3, 2020
French side of Europe
Visiting the Pure Acourate Sound Project in Germany - you can do it from Friday, 10th of May @ MHE 2024 -> Hall 3, Box K05

(this is an almost full exerpt (really! ;-) from my blog " Ducktollers Sonic Encounters") - I'll post the photo galleries as extra posts after the two main postings

Disclaimer: I am neither in any way financiaally interested in the PASP project nor related to it's partner - I publish audio related topics since a almost a decade for interested readers and as a time/money consuming hobby, foremost. ;-)

Mid-April I was travelling from France to my home region near Frankfurt/Germany - it was time to celebrate a 54-years friendship with my best friend in our hometown close to Frankfurt, where I had some duties as a DJ for his 60’s anniversary event. I used the fact of having already done the first 500 miles to organize a trip up north, into a region where the formerly excellent German Autobahn network still demands another hour drive on state roads to arrive at a very cold place not far from a ski jumping resort, called ”Winterberg”.

I was accompanied by an old friend who shares an audiophile interest or two. I haven’t seen him lately, it has been approximately 15 years when I had last listened to his Wilson Sabrina powered by Krell monoblocks, thus he recently entered retirement and was open for a new adventure in Hifi. Given that he had neither heard (about) the PuRiFi chassis nor the PuRiFi Class D amplification, our almost 5-hour-long stay in the dedicated listening room @ Rose-Handwerk in Meschede-Freienohl, offered a couple of well perceived surprises for him. He provided for me, too, with some Porsche thrills which can be found at the end of the story.

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Rose Handwerk, Markus Grelka and Joachim Gerhardt & PASP

Rose Handwerk, a family driven enterprise led by Daniela Rose and her hubby Markus Grelka, are designer/ manufacturer of natural woodwork furniture and Markus has proved his woodworking excellence as selected cabinet maker for Joachim Gerhard’s collection line.

Joachim, known amongst audiophiles for his contribution to Audio Physics and Süsskind speaker designs, lives just a couple of villages further east. Having brought together the PASP team, he is likely the spiritus rector of this project, though he usually stays in the shadows, caring about his own projects and customers.

Pure Acourate Sound Project (PASP) main actors are Ralf Höllmann (Digital Loudspeaker), as a director responsible for project coordination and digital presence and Markus, who both have recently teamed up for the project with another audio authority from the region (some 60 miles away in Bielefeld), Dr. Ulrich Brüggemann from AudioVero, provider of the national DRC treasure Acourate / Acourate Convolver.

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Chez Rose Handwerk, Markus has created a purpose build listening room, where we can find one wall with short run creations of his own design and speakers deriving from his collaboration with Joachim Gerhard. The opposite side of the room is restricted to the reference system simply called “Pure Acourate Sound Project”. The room itself is treated with GIK acoustic elements and the center of listening pleasure is measured by AudioVero’s Acourate digital room correction appliance.

Klippel, the German transducer measurement champion with a footprint in the labs of PuRiFi, joined the project, when an additional analysis of the speaker set prototype was run in the Klippel laboratories in Dresden.

The audio hardware is predominantly PuRiFi, with a dip of Viawave (tweeter) plus the Okto Research DAC8 pro, with cabling provided through XLR and SpeakOn connectors from professional audio sources.

The full system will be presented at the MHE 2024, in Hall 3, Box K05, with the team happy to make you smile.

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A special mention for the “East European” Viawave waveguided tweeter.

It is worth to notice that this small company has suffered serious collateral damage from the Russian warfare in Ukraine as the owner’s family has been of both, Russian and Ukrainian origin and decided to leave Russia for understandable reasons. After a stopover in Finland during 2023, they finally established a new production line in Slovakia this year and are happy to fulfill the delivery of postponed orders starting mid-April 2024.

Their tweeter, a model called WRT145-8, is based on the patented SRT (sealed ribbon tweeter) technology and its waveguide allows to work even more effortlessly to crossover into the midrange. The defined frequency range is between 1.8 and 30khz, it provides a characteristic sensitivity of 95db. (Data for the 8 Ohms model).

Danish DIY pope Troels Gravesen remarks fairly positively about the GRT-145 4 Ohms tweeter:
My primary concern with ribbon tweeters is dispersion, but this tweeter has an excellent horizontal dispersion with very little loss even at 30 deg. off-axis. Vertical dispersion is surprisingly good, one of ribbons' usual drawbacks, and good dispersion at 20 deg. off-axis is excellent.” And concludes “Quite impressive although I would prefer a higher impedance and lower sensitivity (…)”.
The PASP uses the GRT145-8 with higher impedance and lower sensitivity.

From the beginning, Viawave had been the 1st replacement alternative for the 2023 announced PuRiFi waveguided cone tweeter, and due to the given insecurity in provision, SEAS has been teamed up as a 2nd option, in case both prime selections would have been doomed solutions. It’s kind of complicated. In future project stages PASP will use the then all new PuRiFi waveguided tweeter.

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PuRiFi – Driver and amplification

The base of this 3-way fully active design are multiple 10”PuRifi Ushindi chassis, with 2 active transducers per speaker, combined with 4x10” aluminum coned passive radiators per unit. (These PR are not yet available at the PuRiFi-Audio website).
The midrange /tweeter arrangement in d’Appolito MTM design consists of the Viawave tweeter WRT145.8 sitting between a pair of aluminum coned 6.5” Ushindi chassis, optimized for midrange use.
Markus runs them with a triplet PuRiFi 1ET400A driven Class D power amplifiers, which he has built by himself. These are DIY designs constructed by Markus and do not comply with the European safety norm called CE by “industrial standards”, thus these are not open for public sale. Perhaps he would do a small run of chassis for DIY customer …

The digital side

The well-known Okto Research DAC 8 pro from Prague /Czech Republic provides the multichannel analog output. This DAC uses the Sabre ESS9028 Pro chipset. I own one for my active 2-way system, and I am very confident that this device performs SOTA – if ASIO is correctly installed.

Software sided, ROON and its convolution engine are used for the FIR correction filters created by Acourate. The music feed is usually online by either Tidal or Qobuz.

The in-room signal was taken and programmed by Dr. Brüggemann himself and perfected to the specified listening position. He has created a fully new x-over configuration idea, crossing the channels at 300hz and 2000hz, with a still undocumented formula that’s reminiscent of a brick wall filter design. According to Markus, it does prevent pre-ringing and ends exactly one octave higher than the filter set.

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The designer, Dr. Brüggemann from Audiovero/Acourate, has a speaker slot about his project involvement at the MHE XPERT stage in the press center at Friday, 10th of May, at 12h sharp (in German), he follows directly after the presentation by Klippel’s Ellis Blackford Strout at 11h sharp (in English).

The listening experience

Spending a full afternoon in a dedicated listening room can be fun - especially when there is one of the wildest storms of the still young year brewing up outside.

It was demanding too, and I have learned a lot about my own abilities of critical listening. It also may lead you to experience your capacitive limits. Resting concentrated, being exposed to pulsating and clear bass registers, crystal clear high ranges and undistorted mids allowed me to reflect on a couple of important questions about my personal approach towards the holy grail of audiophilia
- Will I be content if I can clinically analyze every recording in my library?
- How much precision is adaptable for me ?
- How much bass is necessary allowed to stand a chance of surviving my wife’s wrath?
- Depth of image or soundstage ?
- Are distortion-less midrange and a brilliant top end design goals which connect with my fading hearing? (x-over’ed to the 60ies during this trip)
- Would I want to have different voicings in my set-up to meet my personal taste or stay in line with the purists in the defense of unmolested bit perfect reproduction of the source?

Someow this feels kind of heretic, but in front of a 75k audio system some considerations might certainly be on order. Listening to a reference system like the one of PASP, with such a thundering but controlled and clean bass section, providing a unhinged and relentless clarity and dynamics, excellent imaging with asounding soundstage - if used in such a purposeful prepared environment, made me feel humbled, not only by a tiny bit.

Even as someone deep in this hobby for better part of his life, my level of extended listening to reference systems is far more limited than the number of music servers I have set up in the last decade. I clearly felt that head, body, mind and ears will need to adapt to such an experience. Eventually your bank account too ;-)

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Here is a small subjective run through to the most impressive tracks in the playlist, which you can find at Qobuz: -> https://open.qobuz.com/playlist/21340128 . There are 2 more related playlists to be found here and here .

edit: typos


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Active Member
Jul 3, 2020
French side of Europe
Listening impressions

Here is a small subjective run through to the most impressive tracks in the playlist, which you can find at Qobuz: -> https://open.qobuz.com/playlist/21340128 . There are 2 more related playlists to be found here and here . (duplicate)

Angel by Massive Attack:

A reference track of mine, given the austerulous electronic sub-bass frequency used by the band. With this track I have - even on headphones - the sense of an eardrum massage from it and the experience here had been even more physical. Perhaps it’s correct to feel that it had been just another dimension of physical exposure getting involved into these walls of guitars, the dubby pulse, juxtaposed by Tracey Thorns enchanting singing?
This felt really adventorous …

Five Feet Tall - Lady Blackbird

Everyones favourite soul darling’s voice gave me goosebumps galore. Simply overwhelming and unbelievable gracious - overheard with such brilliance.

Papertrails by Darkiside
A track I have only discovered a year ago, from the NY based duo Darkside.
Quite melancholic, intimate and vulnerable, the production sounds to me like pure craftmanship, all instruments and sound choreographed through an outdoor parcour leading to your personal shady storage room called subconciousness.
Nothing happy at all, but perfect for testing your system.
An ultimate joy to listen to the hypnotic music (predominantly voice, guitars and percussions) and its production, less so to get your mind involved with the presented metaphors.
Thee hypnotic séance left me with goosebumps oncemore.

Erik Truffaz - El tiempo de la revolucion

Thundering marching drums & meandering trompete sounds, this track covers all of our needs for testing system capabilities, I love the context, the Spanish Revolution.
I had once (35 years ago) the pleasure to spend an evening with two survivors of the Francist Regime in Barcelona, people who fought during the Spanish Civil War at the barricades of the Anarchists. This spark in their elderly eyes when they spoke about the happy times before the war will stay with me forever and it gets enlightened everytime I listen to this track.
In Freienohl, vibrant memories were added to the light. I could melt away on the Truffaz’ way of mastering his trumpet.

Battle Royale - Duke Ellington and Count Basie - First Time! The Count Meets the Duke
If I ever want to test speed of sound reproduction, this is the track that leaves me out of breath, wondering how could they do such a recording more than 60 years ago?
Geniuses @work!
For the ones who do not know, in the stereo version each orchester is presented in one separate channel, thus it’s a mono recording in a stereo container.
In fact, on the mono recording you may hear both orchester equally on both speakers (source: Berdon.com)

Finally, we heard the live version of “A fistful of dollars” by the Danish National Symphony Orchestra. Instantly, I felt that I may give up all my future plans for annual subsriptions to the local Symphony Concert Hall if I would own this system.
Just kidding, No Symphony near me and I couldn’t fit the PASP system in my listening space. And nevermind my budget. But this special sensation listening to that live event recording were kind of unreal in quite an interesting way.

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Overall Assessment:

The system’s clarity - from the lowest octave to the highest - was incredible, involving and sometimes otherworldly to me. It provided me with some insights I had to reflect.
I am not used to this overwhelming accuracy, speed, resonance free clarity, deep clean & substantial bass and the sheer sum of details which leaves – if any - only a small margin for sugar coating & overlays of any kind by the source.

“Truthfully to the source” is a design goal which was successfully achieved in my terms, however. Possible owners of this 75k € system should be warned, without the highest quality of source material all deficits of your music library could be quickly exposed to the bone.
I was absolutely baffled from the immediacy and the involvement into the music we heard from our playlist - but forcefully appalled by the miniscule mastering quality of Iggy Pop’s “Free” and New Years Day version of New Orders’s “Bizarre Love Triangle”.

Perhaps, altogether I felt that the listening experience could be a bit too much physical for someone living in cohabitation with an open baffle dipole system.
Given that you can decide on your preferred room curve and the final degree of performance by Acourate settings, fine-tuning your system’s performance to your personal taste seems to be the definite way to go.

Jumping from your 5/10k speakers/system to this rather definite combination could prove a bridge too far for some, this it is quite a serious invest for an end game set up, as always to my ears.

The other side … (subjective ;-)

When we entered the listening area first, after a quick tour through the furniture showroom and the attached work floors, we were asked to sit down, and quickly the light went out.

We were welcomed by Bruce Cockburn’s “Bells of Gethsemane” and immediately sucked into the tune by a paramount soundstage with warmth and clarity. A second tune, Jacintha’s version of “Light my Fire”, followed by the lesser known “Bad Kingdom” by Desiree Mishoe provide us with a wonderful sense of purpose, this is what we want.

Markus did all his little showroom tricks in order to prepare us for the ultimate performance yet to come. He did so with the smallest of his personal designs (6 liters), the 2-way bookshelf speaker called Micro, using Wavecor drivers, the 4,75” WF120BD-08 paper cone mid-bass and a 22mm neodymium dome tweeter called TW22WA09.
Driven by the dual Infineon chipped SABAJ amp, the A20A 2023 in combination with an SMSL SU-1 DAC, using one AKM AK4493S chipset, the chain was in fact well worth 300 Euros, while the hand-manufactured speakers come at a whopping 2.5k Euro.

In relation, this sounds like a lot of money, but the performance was really worth it, every single penny. My friend decided that he will change his active Backes & Müller living room set-up against this wonderful sounding design in the near future. Thus he need to come again with his wife to finalize their decision. By chance, there is more to have chez Rose Handwerk than only pure audio … ;-)

The Porsche experience:

Seeing old friends back home in Germany for 10 days, I had asked this recently retired friend with a shared interest in audiophile excursions if he would like to join me. He agreed, and early in the morning at the time of leaving we decided to have first another coffee but then with an 2nd thought we swapped my reliable Mazda family vehicle, which I had cleaned from every single dog hair mindfully for this precise trip, and vouch for his ride instead.

It was actually my first acquaintance with a Porsche 911 Carrera 4S, precisely sitting in any Porsche more capable than a 924 (1980) model.
His sentence to remember, “..- Google Maps says one hour to the arrival … although we can still bag 10 minutes …”

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I enjoyed this experience, a really physical one – very much comparable to the physical bass performance with PASP - quite thoroughly, especially because on our way back we had one of the worst April storms in a couple of years and when imagining my own dog taxi (+25in height difference) under that conditions would definitely change my usually healthy face color into a pale white flag. The dimension of this storm may be comprehended by the fact that it uprooted one 700 years-old oak tree (Bärenwaldeiche), the oldest tree in the region we were visiting.

On our trip back home, we exchanged our impressions from this extensive listening and my friend was quite impressed by PASP, thus absolutely excited by the “Micro” design - as this is exactly was he was looking for.

This Pure Acourate Sound Project isn’t made for quick decisions, you may need to hear it and get involved within this experience of the unknown (for most of us). Only a small number of audiophiles may have tasted such a 5-star menu, thus we - the majority – have the need to get acquainted to this type of almost distortion-less reproduction.


The full system will be presented at the MHE 2024, in Hall 3, Box K05, with the team happy to make you smile.

The designer, Dr. Brüggemann has a speaker slot about his project involvement at the MHE XPERT stage in the MHE press center at Friday, 10th of May, at 12h sharp (in German), he follows directly after the presentation by Klippel’s Ellis Blackford Strout at 11h sharp (in English).


Active Member
Jul 3, 2020
French side of Europe
Gallery no 2 - The heads of PASP

the core team

Dr. Brüggemann with Markus

Markus Grelka

Party at Klippel ;-)
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Joachim Gerhardt


Addicted to Fun and Learning
Forum Donor
Aug 7, 2023
Old hard Oak Wood for reincarnation in speaker enclosures ;)
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