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Visiting the Pure Acourate Sound Project in Germany (MHE 2024 -> Hall 3, Box K05)


The P-Experience: Pure Acourate Sound, PuRiFi and a Porsche

Visiting the Pure Acourate Sound Project in Germany 

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.





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.


[album]172 [/album]


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.

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.


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.




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.

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 capacative limits. Resting cocentrated, 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  can clinical 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-overed 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 defence of unmolested bitperfect reproduction ofthe 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 listenings 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 ;-)


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 .

Part 2 with commented listening of some  playlist tracks, some reflections, many documents and two other xperiences from that trip (yes - with Porsche) will follow tomorrow ;-)


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