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Reviewer: Srajan Ebaen
Financial interests: click here
Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo boost, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz Hifi, Tidal Hifi, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref, AURALiC Vega, Denafrips Terminator-Plus and Gaia [on review]
Preamplifier: Vinnie Rossi L2 Signature with WE VT52/300B or Elrog 50/300B, Nagra Classic, Wyred4Sound STP-SE Stage II, Vinnie Rossi LIO (AVT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1 monos, SIT3, F5, F6, F7; Goldmund/Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics NC500 monos; LinnenberG Audio Liszt monos
Loudspeakers: Audio Physic Codex; Cube Audio Nenuphar; Kroma Audio Mimí; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & VI & Submission; German Physiks HRS-120; Eversound Essence; Fram Midi 150 & 120; Acelec Model One; AudioGE Teddy [on review]
Cables: Complete loom of Allnic Audio ZL3000 and Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Black Cat Cable redlevel Lupo; Ocellia OCC Silver; Audio Art Cable Reference 75Ω clock-sync cables
Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps/sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands
Sundry accessories: Acoustic System resonators
Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room, hence no wall behind the listening chairs
Review component retail: €7'500/pr
Out-of-the-blue reward. If you've reviewed for 20 years, soon at a clip of at least one review/week, unexpected rewards do happen. For me, one such hit in the wake of signing up for Simon Audio's i5 integrated whilst agreeing to package it with Aurai Audio's M3 speaker. I knew nothing about that speaker. I only knew that Simon Lee's friend Alain Pratali of Marseilles had designed it. I'd never heard of Alain.
Neither had most anyone else. "Very few people know of me even though I was in audio for 35 years. 25 years ago I developed the Oracle Audio 1000 and 2000 CD players and amplifiers for Jacques Riendeau. My very first design was the Crystal DAC with a Philips CDM 12 transport, I²S system and nine power supplies for which I had developed a signal path without feedback, capacitors or DC offset servo, just a clean differential approach.
"Back then I also made products for Simon like a phono stage. Today I'm retired but love tech and audio so keep working on projects that interest me. Five years ago Simon wanted to offer a range of speakers. So I developed for him everything he asked for including working with the most desirable drivers from Accuton, AudioTechnology and Supravox. I didn't give up when he subsequently ran into problems with April Music. Now it's 2020 and here we are again under a new name." As it turns out, the aurai or aurae were ancient wind nymphs. With a speaker's job that of moving air, that made perfect sense.
The M1 is a 90dB/6Ω 8" two-way with a 1" tweeter loaded by a "custom horn machined from acetal* to one micron tolerance". Above it sits a ceramic Accuton mid/woofer for 33Hz-18'500Hz bandwidth in a 38kg box of 113x26x38cm HxWxD. The 3'400Hz filter has a compound 6dB+12dB electrical slope and 12dB+12dB acoustical function. Bass loading combines quarter-wave tuning with a 33Hz port.
* Acetal or polyoxymethylene aka POM is commonly known under DuPont's brand name of Delrin®, an engineering thermoplastic where two separate oxygen atoms single-bond to a central carbon atom for a general structure of R²C(OR')².
"There are many magical things about these Accuton drivers. They can sound from dark to very very shiny. It's all up to the speaker designer's approach and taste. Fundamentally, our German ceramic drivers have one huge advantage. Due to the low resonance at the outer edge of their pass band, they operate as true pistons. The real challenge actually isn't whether the membrane is ceramic, diamond, beryllium, aluminium or bakelite. It's their surrounds that cause problems. One must know how to work around them.
"All tweeters without a wave guide have lobing functions relative to frequency. I've tested them all. With our horn's ellipsoidal profile, we only have one lobe and exactly the same energy across the entire pass band. The tweeter I developed isn't a standard soft dome though. Its membrane is polymer, the total moving mass below 0.12g. For a dynamic not ribbon driver, that's exceptionally low weight. I've tested all possible filter permutations and slopes to pick what touched and moved me most. I focus on impulse response and in-phase transients to get a very natural open sound."
Then there was Antoine Rouault. "I've been making speakers for the last 10 years and worked with Alain since 2016. Alain does speaker design, I take care of all the manufacturing and shipping. I build M1 cabinets from 24mm Finnish Birch ply which greatly limits resonances harmful to the sound. Bespoke filter parts come from Rike Audio of Germany, terminals from WBT and book-matched grain-oriented veneer options under polyurethane varnish are cherry, walnut, padouk and santos rosewood."
Alain again: "I control the tweeter level with magnets. Everything is set on the motor. By removing or adding a magnet, we adjust the level and overshoot. Think of a car with a big engine but no brakes. It's useless. Everything is a matter of balance. A good tweeter values the whole. We don't hear it per se but it gives life to all the micro information. Here is the tech and the curve.
• The blue curve is without added magnets.
• The red curve has a magnet in the opposite field to achieve max output of ~96dB.
• The green curve shows what a 5mm teflon magnet does in the attractive field.
"With full-power extension to 18'500Hz and a 10mm voice coil, it gives 6dB of tuning range without shelving resistors. It's how we dial our tweeter's output to a customer's taste. Most important about this is that we control overshoot. For that purpose, magnets or autoformers are the royal way. But there's more. This tweeter uses a floating system to avoid screws or extra glue. Now it works without tension and far fewer mechanical vibrations. Its shape is like a Western Electric 555 motor placed in front of a 2" Altec diaphragm."
"To me the legendary WE555 is the holy grail. I work with many horns where this concept is ideal. The diaphragm could be aluminum or a bakelite-type phenolic. The shape is a classic dome like an Altec Lansing or JBL. Yet it's not the membrane material but diaphragm geometry which is most important. I'm presently working on four different tweeter designs in fact."
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