Explorations in Audio

Karsten Hein

Are you ready to Explore?

In 'Explorations in Audio' I aim to share some practical insights on setting up and optimising an affordable HiFi system. Although one would think that, really, all has been said about HiFi, some surprisingly simple questions still remain, e.g.: 'Is digital superior to analogue?' 'Do cables matter?' 'Can digital cables pick up interference?' 'Should speakers be placed on spikes?' 'Has evolution in HiFi made older gear obsolete?' 'Where should I place my sub?' 'Which room correction works best?' - On the other hand: 'Are these really the right questions?' - We shall see.

What's new in eiaudio?

While the entries in this blog are divided into the three distinct categories above, you will find a mixed listing of the most recent postings below. The most recent article is shown first. If this is not your first time visiting, the listing below is a good place to quickly check if anything is new.

Your input is more than welcome, as long as you follow the basic audiophile rule of ‘ear over mind’. This means that you do not comment based on what you think you know, but only on the basis of your own listening experience. Please feel free to suggest gear for testing as well as leave comments on the descriptions provided here.

  • 28. Watts, Sound Pressure, Decibel

    28. Watts, Sound Pressure, Decibel

    02/12/2022

    Author: Karsten Hein

    Category: High Fidelity

    My first memories of leafing through advertisements for HiFi gear stem from mail order catalogs during the early 1980s. There were a handful of units presented on each page with small numbers linking the photos with crammed description boxes that provided a short list of specifications. Due to the fact that the concept of mail order required for purchase decisions to be made remotely, without the possibility of sensory feedback, I remember weighing my interest based on two criteria: the aesthetics of the design and the wattage output of amplifiers. In terms of design, I found myself veering towards shiny buttons, bright lights, and large power meters. When it came to watts, I was inclined to follow the simple rule of ‘the more power, the merrier’. Luckily, I did not have the means to make a purchase myself, and my parents objected to purchasing from mail order catalogues altogether.

    In later years, I sometimes came across such HiFi systems at friends’ houses and was surprised to find loudspeaker cabinets that were made of resonant chipboard with smallish-looking drivers that were often surrounded by painted or glued-on silver rings to make them look more impressive. The amplifiers claiming to offer 1,000 watts of power output weighed half of my 40 watts receiver and sounded rather tame and weak-chested. Taking a look inside, there was little electronic basis behind the large power meters to back up the bold claims. But how then was it possible that the technical specifications did not translate into superior sound quality and power output? At that time, I did not have a good explanation for this phenomenon and only made a mental note that I had better be careful when purchasing gear, in order to receive real value for money and not fall for inferior quality.

    Many years have passed since my early explorations, and I have since learned that a HiFi system’s ability to play music clean and loud depends on four basic factors: 1. the continuous (not peak) power output potential of the amplifier into a given Ohm load (rated in watts, RMS); 2. the maximum power handling capacity of the loudspeakers at that Ohm load; 3. the loudspeakers’ power sensitivity level (dB, at 1W/1m), and 4. the preferred listening distance from the speakers. The distance is important, because the listening volume halves as the listener’s distance to the speakers doubles. The decibel (dB) rating itself is measured at 1 watt input and one meter distance from the loudspeakers. Decibel is a logarithmic scale to measure volume that was introduced by the American Bell telephone company to measure signal loss on long runs of telephone lines.

    Zero decibel was defined as being near silence for adult listeners, and ten decibel were defined as ten times this amount. With the scale being logarithmic, twenty decibel were defined as ten times louder than 10 decibel, thus resulting in 100 times the sound pressure level, and so on. Following this scale, a balloon exploding at 150 dB is one quadrillion times louder and normal conversation is one million times louder than a volume level near silence. The table called ’Sound Pressure — Sonic Event — Decibel’ provides an overview of everyday sounds, their decibel ratings, and the corresponding sound pressure levels on a linear scale from near silence to the most deafening sound. Hearing loss from high listening volumes is usually the result of a combination of being exposed to a very loud sound over a longer time period. While a popping balloon may have the potential to surprise or even frighten us, there is little risk to our ears.

    The decibel scale proved to be useful for sound pressure level measurements and is also said to be much closer to the human perception of sound volume than the linear scale. However, it does not match the human ear exactly. Humans perceive the listening volume to double with every increase of six decibel. The table ‘Sound Pressure — Sonic Event — Decibel — Human Perception’ therefore aims to bring some perspective to this difference. According to the human ear, a popping ballon is approximately twenty-five times louder than near silence, not one quadrillion as the linear scale would suggest.

    The table ‘Amplifier Power — Speaker Decibel Output’ contrasts the characteristics of two contemporary loudspeakers: the British Tannoy XT8f dual-concentric towers and the German Duevel Planets. The table shows that it takes ten times the amp power for the speakers to play 10 dB louder, regardless of the loudspeaker chosen. In calculating the necessary amplifier power, I factored in 3 dB headroom, which I felt to be realistic for real-life indoor applications. The Tannoy towers started from a commendable sensitivity rating of 91 dB 1W/1m. Listening from 9ft or two meters distance, one watt of power produces 79 dB. This volume level is comparable to being in a noisy restaurant and should be sufficient for most applications. At full 100 watt capacity, the Tannoys produce 99 dB of sound pressure at two meters distance (which is the equivalent of having a running motorcycle in the room) or 89 dB (similar to a person shouting) at 10 meters distance. This should be plenty of sound pressure to entertain the occasional party.

    The Duevel Planets are rated at 85 dB (1W/1m) and come in at 73 decibels when listening at two meters distance. They reach the Tannoy’s comfortable 79 dB at four watts only, and, at this time, the amplifier already needs to do quite a bit of work. At their maximum 50 watts capacity, the Duevels produce 90 dB (shouting) when listening at two meters distance and 80 dB (noisy restaurant) at ten meters. This means they are less equipped to power living room parties than the Tannoys. The nine decibels in resulting difference will make the Tannoys seem 1.5 times louder than the Duevels.

    As we can see for these findings, human the human perception of sound pressure is not linear. With perceived volume doubling every 6 dB, it is more similar to the logarithmic decibel scale. Amplifier watts are only meaningful when they are also quoted as continuous and not as burst or peak power. In fact, peak power output can be ten times higher than continuous output, if the capacitors are large enough. Amplifier output wattage depends on the Ohm rating on the connected speakers. An amplifier rated at 8 Ohms will produce much higher power into a 4 Ohm load. Sufficient amplifier wattage paired with high sensitivity and high power handling capacity on the side of the speakers will lead to high sound pressure levels, if so desired.


    Jörg Hegemann
  • Duevel Planets

    Duevel Planets

    17/11/2022

    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Loudspeakers

    When I first met Alexi, this was during our role as fathers of elementary school children. However, it did not take long before we discovered our mutual interest in home audio equipment. I was intrigued by the fact that he was a seasoned technician in electronics who had preserved the heart of an explorer and did not, on principle, object to the significance of interconnects. As I found out, he even ran a pair of single-wired Kimber cables from his NAD streamer amplifier to his speakers. From this combination, I took it that there was likely to be some room for meaningful conversation.

    As it turned out, Alexi's speakers were a pair of smallish-looking omnidirectional 2-way towers with down-firing bass ports. They had the words ‘Duevel Planets’ printed on them and each cabinet held two shiny spheres suspended above its upwards-pointing drivers. The woofer-to-midrange driver featured a kevlar diaphragm, whereas the soft-dome tweeter was recessed behind a horn construction. The otherwise non-frills cabinet had a clean anthracite colour coating and was raised 40mm off the ground by four rubber absorbers. These also served as acoustic decoupling from the floor.

    However, no matter how long I looked and pondered over the design, I did not have the faintest idea of what to expect from these speakers, especially, because they came from a small German manufacturer of whom I had never heard. Alexi informed me that Duevel was the founder’s family name and that the Lower-Saxony-based company specialised in building omnidirectional loudspeakers, most of which were larger and also heavier than the Planets. He further told me that the Duevel Planets had been praised as unrivalled in the sub-1,000 EUR category, and performed near the level of this manufacturer’s far more expensive models. I was hard-pressed to believe this account and fully expected their sound signature to resemble their physical appearance: small, airy, slightly metallic and tonally thin, perhaps.

    When Alexi first started his convenient NAD streamer amplifier, my impression was that the music sounded a little thin and disorganised. I had trouble discerning an accurate center stage image but could also see that the distances from the speakers to the front wall and the distance between the speakers and the listening position were not the same for both channels. The speakers had clearly not been set up taking into account the specific resonance frequencies resulting from the room's dimensions. Although the NAD amplifier offered on-board software for room-adaptation as well as a microphone for calibration, this feature had not yet been fully employed. The random overlapping of frequencies and heavy smearing of running times I could have easily taken as confirmation of my suspicions towards the design.

    I spoke to Alexi about my concerns regarding the positioning of his speakers in the listening room and also offered to lend him a power amplifier from my stock in order to test his speakers with this. However, we agreed to first swap loudspeakers for a few days: He would get my Tannoy XT8F, while I would audition his Duevel Planets. At the time, I thought that he was getting the better deal for sure, but I think we were both excited to get new insights and gather experience with different loudspeaker designs. As it turned out, dragging the large and heavy Tannoys over to Alexi’s house in our children’s handcart proved to be quite a challenge, whereas the eleven kilo Duevels could easily be carried and pulled over to our house. This was the Duevels' first obvious benefit.

    We decided to set his Planets up in our upstairs listening room, which was of considerable size and had slanted walls that helped to deflect some of the reverberations. The Duevels were going to replace a pair of Epicure EPI 500 that had been my favourite speakers due to their natural bass and tonality for some time. We gave the Epicures a final audition, playing tracks from 2Cellos, Diana Krall, and Norah Jones and then placed Alexi’s Planets in the exact same position. We played the same tracks again and were both more than a little surprised at how tonally similar the Planets sounded. Alexi remarked that the Duevels had slightly sharper imaging than the Epicure, and I noticed a mild leaning towards analytical and technical sound on the side of the Duevels.

    In this first position, the Planets were positioned directly on our hardwood floor with one meter distance kept between the bass driver's central axis and the room’s front wall. Happy with the findings of our first listening session, Alexi and I parted ways. Over the next few days, I came back to the Planets to experiment with different placement options. I noticed that bass response and depth of soundstage strongly depended on the triangular relation between the speakers, the room’s front wall, and the listening position. And although I did realise that this was the case with all speakers, the effects seemed more pronounced due to the omnidirectional nature of the design. The front wall became an integral part of the listening experience, and differences in shape, texture, and firmness of that wall would have an effect on how the music sounded.

    Bass became stronger as I moved the Duevels closer to the front wall. I found that imaging stayed remarkably sharp until about 50cm distance. Whereas at one meter wall distance I had been lacking bass punch and the lower frequencies of vocals, the speakers sounded tonally richer and fuller when nearer to the wall. Of course, the wall distance will affect room resonances and bass modes relative to the seating position, and I was glad to see bass increasing again once the speakers were positioned further than one meter from the front wall. In one instance, I moved the Planets to a position half-way between myself and the listening position and was pleased with the immense depth of stage I was experiencing.

    Judging from their looks alone, I would have thought that the upward thrust of the drivers paired with the two spheres would make the Planets susceptible to imbalances caused by the room dimensions. In our upstairs listening room with slanted walls, the left speaker only had about 50 cm of air above, whereas the right one had about three meters of empty space above it and also plenty of room to the right. However, my concerns were unfounded, because the spheres served as fixed points of first reflection, radiating the sound around the speaker rather than up. As a consequence, the Duevels sounded just as balanced as all the loudspeakers I had auditioned before them. If anything, the center image felt more natural.

    As I was still feeling a little bothered by the Planets’ accurate and technical sound, I experimented with pads and carpets that I placed under the speakers. This helped shift the balance from listening to the character of a microphone towards hearing the voice of a human singing. I would suspect that the best option would have been to place a thick board underneath the speakers and to decouple this via felt pads. But since the Planets were not mine, I did not want to make the investment. Instead, I achieved good results by placing felt pads or floor matts underneath the four feet. Either way, the speakers benefitted from some form of additional decoupling from the hardwood floor. The floor matts had the advantage of keeping the bass reflex at the prescribed distance.

    I found that the Duevels were capable of creating a naturally-sounding sound stage that was both deep and wide. This impression grew stronger with increased distance to the room wall. Given their relatively small size and shape, however, placing these speakers midway towards the listening position would make them stumbling blocks in most listening rooms, exposing them to the risk of being toppled over to one side. Their more monumental brothers and sisters, on the other hand, would present more obvious obstacles and also resist the occasional collision without the immediate risk of damage. This could be worth a consideration when deciding to make a purchase.

    At the correct relative distance to the wall and seating position, the Duevels produced a tonally correct sound that was neither thin nor boomy. Vocals sounded clean, open, and realistic once the correct coupling towards the floor had been achieved. Imaging was surprisingly sharp for an omnidirectional speaker system, and the developers Annette and Markus Duevel were obviously in control of the relevant acoustic dimensions when they designed these speakers. I was surprised by the accurate phantom center despite the uneven layout of the room. And I was even more astonished by the persistent stage effect as I was walking through the room. Similar to a living room concert—and we have had some of those—the stage did not change position. It seemed as if the Jazz combo was still playing in the exact same position, no matter from where in the 70 sqm room I was listening.

    From the listening impression alone, it was difficult to believe that the Planets were entry-level speakers that had been sold for under 1,000 EUR. With my eyes closed, I would have assumed that I was listening to far taller speakers with a heftier price tag. With the eyes open, there were some indicators that the price was perhaps justified. Inspecting the Planets from the floor upwards, I first stumbled over the affordable-looking rubber feet that kept the speakers suspended without the addition of a defined base plate with spikes towards the ground. The binding posts, too, were designed to only take one set of bananas or spades without the option of bi-wiring. Given the limited mass of the woofer, I did not feel that there was need for bi-wiring, however, the absence of this option did not strike me as state-of-the-art.

    The cabinet itself was a simple box of medium density fibre that had been neatly colour coated. Although my wife rather liked the look, I would have preferred a more reassuring instrument-like appearance using real wood veneer. The font and style of the lettering did not exactly scream High End design, either. Instead of well-seasoned and sophisticated, these speakers looked young and cool. And this coolness-factor was further accentuated by the two seemingly cold spheres hanging suspended above the drivers. Since both of the drivers were pointing upward, keeping them clear of dust might prove to be a challenge. The mouth of the tweeter’s horn had a metal grille to protect it from children’s fingers, however dust and cleaning liquids passing the grille would remain out of reach. Non of this, however, appeared to have been an issue on my test specimens that still looked clean and in great shape. Perhaps a testament to Alexi’s good care.

    In my listening tests, I enjoyed how the Planets maintained stage size and instrument location. The fact that some of the music was reflected upward gave string instruments a life-like appearance. The speakers did not betray their position nor the materials used on the cabinet or spheres. They did not sound wooden, boxy, or metallic. Even in our large listening room, playing music at volumes of between 60 and 80 dB was possible without audible compression (measured from the listening position). Duevel rated the Planets at 50 watts RMS per channel, and our Dynavox VR-70 tube amplifier had no difficulties driving them. Low-bass presentation was sufficient and even surprising given their size. I could not detect any phase issues, and their timing was excellent. Rated at 85 dB (1W / 1m), the Planets would benefit from large amplifiers despite their relatively low power tolerance.

    Although I could not find any information on frequency response, the thought that anything was off or amiss never once crossed my mind while listening to them. Sonically, the Planets were close to some well-regarded classic speakers and did not follow the path of so many modern showroom squeakers. Astonishingly, this character remained largely in tact when walking though the room. On very rare occasions, I missed the piercing power and attack of piano keys, especially when the Planets were standing further away from the wall. And I did notice that the full extent of tonal balance needed at least 60 dB of volume. Below this, the treble seemed slightly dominant. This did play a role at least once when we had guests for dinner, and I was looking for some mild background entertainment. In this scenario, I would have wished for stonger bass foundation to support tonality.

    I never played music at volumes where the size of the woofer seemed to matter. And after listening to Jazz albums by Diana Krall, Helge Lien Trio, and Jamie Saft (among others), I was pleasantly surprised how well the Duevels played Jörg Hegemann’s fast and furiously dynamic CD album “High End Boogie Woogie” that included some wonderful double bass runs. Due to their omnidirectional characteristics, experiencing the music with friends and sharing a similar experience, all at the same time, was possible for the first time. Audiophiles will agree that sharing the pleasure of listening is often a challenge, because, given the narrow sweet spot, we can only guess what the other person is hearing.

    While a sceptic at first, I could see that omnidirectional loudspeakers such as Alexi’s Duevel Planets had a deserved place in the heart of HiFi enthusiasts. Given Annette and Markus’ command of this technology, it was fair to say that the Planets shared some highly audiophile characteristics and were fun and easy to listen to over extended periods of time. Omnidirectional speakers had the potential to create a more natural stage that maintained its realism in many positions of the room. For those of us who prefered to listen to acoustic instruments played by small combos, these speakers provided the perfect setting. As all audiophile speakers, the planets had been designed to perform best at living room volumes. Any deviation from this (be it higher or lower) would produce less-than-ideal results.

    For my part, I decided to hold on to the Planets for a few more days and enjoying the music before returning them to their rightful owner. I was also looking forward to helping Alexi in calibrating his own NAD system to his listening room, first with my Tannoys and then with his Duevels. I now knew that they were well worth the fuss.

    Test system: Marantz CD-17 via HiViLux Reference SP/DIF cable on Cambridge DAC Magic 100 via HBS Silver Solid-Core Interconnect on Dynavox VR-70 via Belden 9497 in Y-wiring on the loudspeakers

    Specifications

    • Type: floor-standing 2-way loudspeaker
    • Design: omnidirectional, vented cabinet
    • Frequency response: N.N.
    • Power handling (RMS): 50 watts
    • High-frequency driver: soft-dome tweeter, horn-loaded
    • Midrange-to-bass driver: dynamic, kevlar diaphragm
    • Diameter of spheres: 98mm and 58mm
    • Distance between spheres: 48mm
    • Crossover frequency: 4,100 Hz
    • Power sensitivity: 85 dB
    • Nominal impedance: 4 Ohms
    • Dimensions: (H) 840mm x (W) 260mm x (D) 156 mm
    • Weight: 11 kg
    • Country of manufacture: Germany
    • Year(s): 2012

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  • Sanken 2SC3519A Class A/B Amp Project

    Sanken 2SC3519A Class A/B Amp Project

    12/11/2022

    Author: Karsten Hein

    Category: Explorations

    Tag(s): Power Amplifiers

    Looking at some modern amplifier designs, one might think that the process of signal amplification is infinitely complex and requires lots of patented electronic components and integrated circuits for signal enhancement and sound shaping. It may therefore seem counter-intuitive that some of the best-sounding amplifier designs have taken the opposite approach, following a less-is-more philosophy. Audiophile listeners believe that each additional part in the signal path leads to a deterioration of the original signal. It was out of this understanding that the developer of the Sanken Class-A/B amplifier presented here started his project.

    Sanken have an excellent name for building quality transistors and contributed to some legendary amplifier designs, such as the Japan-made Luxman L-10 model of 1976-1982. The Sanken 2SC3519A therefore came as a natural choice and are able to handle currents of 15 amperes and maximum operating temperatures of up to 150° centigrade, just in case the operating temperature should ever be an issue. This project's aim was to build a powerful and tonally correct linear amplifier that delivered lots of clean power with ease. An optional three-band parametric equaliser was to allow for exact tonal adjustment to accommodate the room and the loudspeakers, if doing so should become at all necessary.

    The Aschaffenburg, Germany based developer was neither new to the industry nor was this his first amplifier design. On the new Class A/B design, he started out from a generous 250 VA toroidal transformer paired with high-quality capacitors as power supply. There was one amplifier board per channel with each holding four Sanken 2SC3519A transistors. In the amp's prototype version, the transistors were mounted on two overly large heat sinks that were a total of three rack slots high. While the amp itself would also have fit into a two-slot housing, starting from the larger cabinet was more practical when making last-minute changes to the design. Given the size of the heat sinks, the amplifier did not become warm, not even in combination with our 83dB low-sensitivity 4 Ohm Epicure 3.0 speakers.

    11 Nov 2022 — Listening Test 1:

    Turning on the Sanken Class-A/B amplifier for the first time, I immediately noticed that it provided far stronger amplification than our existing Hafler, B&W, and Dynavox power amplifiers. At 160 WPC, the Sanken was also the strongest amp in our range, offering 15 watts per channel more power than our Hafler XL280 amplifier. The Sanken’s input sensitivity was set at 1.4 volts, and its ultra-strong amplification reminded me of amplifiers from Quad which similarly appeared to be brimming with energy. Bass was exceptionally tight, and this reminded me of the H&S Exceptional tested some time ago. Indeed, the developer confirmed that the damping factor should be near 800:1. The Sanken amp provided lots of effortless control which worked well with our power-hungry Epicure 3.0.

    There was lots of attack and crescendo. The music was able to free itself from the speakers better than with our Hafler amp and was thrust more deeply into the room. The resulting musical experience felt more intense and immediate. The sound was dry and, in combination with the Epicure, maintained a solid centre image. The sound was tonally rich with sufficient but not overly presented high frequency resolution. The sound was captivating and easy to listen to over long periods of time. The parametric equaliser had not yet been connected, but I did not feel the need to make any adjustments during my test.

    Although I enjoyed listening to the amplifier a lot, its strong amplification served to highlight a weakness in our Dynaco PAS-4 preamplifier. Some weeks earlier, the Dynaco had begun producing a mild hissing sound. This proved to be borderline unbearable in combination with the Sanken Class-A/B amplifier, and has led me to have the Dynaco serviced. On occasion I noticed distortion that sounded like overdrive-clipping. At first, I thought that the clipping might have been present in the music, but when it appeared again, I was not so sure. And, upon restarting the amp without giving it a longer break, I noticed a recurring inner vibration that seemed to fade in and out. This might have been caused by the large transformer. But as I was not sure this was a strictly mechanical effect, I thought it best to list it here.

    [Revision in progress…]

    Specifications

    • Type: class A/B power amplifier (prototype)
    • Transistors: 4x Sanken 2SC3519A per channel
    • Transistor type: bipolar (BJT)
    • Transformer type: toroidal, 250 VA
    • Power output: 160 WPC, 8 Ohms
    • Frequency range: 1-100,000 Hz (+/- 3 dB)
    • Signal damping: 800:1
    • Input type: cinch/RCA
    • Input sensitivity: 1.4 volts
    • Signal to noise ratio: (to be determined)
    • Total harmonic disortion: (to be determined)
    • Rise time: (to be determined)
    • Slew rate: (to be determined)
    • Dimensions: (W) 244mm; (H) 165mm; (D) 250mm
    • Weight: 8.4 kg
    • Country of origin: Germany
    • Year: 2022

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  • Tang-Band W8-2314 Project

    Tang-Band W8-2314 Project

    07/11/2022

    Author: Karsten Hein

    Category: Explorations

    Tag(s): Loudspeakers

    In autumn of 2022, I was asked to take part in the development of a loudspeaker. The design had been created by a friend in the industry and was based on Tang Band’s coaxial W8-2314 driver. The Tang Band chassis used a bamboo-paper composite to create a rigid light-weight midband diaphragm and a coaxially mounted inverse dome tweeter made of an aluminum-magnesium amalgamate. Powered by a neodymium engine, the combined driver unit was capable of producing an impressively wide frequency response that ranged from a low 38 Hz to an ultra-high 40,000 Hz. Instead of being mounted inside a ported cabinet, as recommended by the producer, the W8-2314 driver was built into a cloth-dampened open baffle design and its bass cut via crossover. Its bass was supplemented by an open-baffle dipole design featuring four dynamic 28cm paper composite drivers.

    3 Nov 2022 — Listening Test 1: I set the speakers up in our spacious upstairs listening room that featured irregularly slanted walls and a 4.5m heigh ceiling at its centre. Setting the open back dipole up in the exact position of our Epicure EPI 500 speakers proved to be too close to the rooms front wall. Both soundstage and mid-bass seemed overly compressed. In steps of a few centimetres I pulled the cabinets forward until the sound stage seemed right and bass was tight. At this point, the Tang Band driver was 107m from the room’s front wall. The listening triangle was at a relatively short 2m. The provisional crossover could still be adjusted in three steps, and I ended up with step 3, which was most likely the highest cut-off frequency and seemed to offer the cleanest sound.

    In this setting, however, it also became apparent that the bass cabinet was still suffering from resonances that interfered with the upper bass to lower midband creating some smear in this section. At this point, there was no inner bracing to support the cabinet construction, and since the four drivers required four large holes drilled into the sides, some rigidity was lost. It was difficult for me to judge what the speakers would sound like once these resonances were eliminated. On the other hand, I enjoyed the open-baffle bass sound that seemed very natural in our listening room. I could well imagine that a central bracing might have a positive effect. Perhaps bitumen matts could be applied to quiet the cabinet. Looking at the narrow gap between the left and right facing drivers, I thought that physically connecting their magnets in the middle somehow might cancel out cabinet vibrations. It might also be possible to provide an electronic filter to cut the most relevant resonance frequencies.

    [Revision in progress…]

    Test system: Marantz CD-17 via HiViLux Reference SP/DIF cable on Cambridge DAC Magic 100 via HBS Silver Solid-Core Interconnect on Dynavox VR-70 via Belden 9497 in Y-wiring on the loudspeakers

    Test environment: 14m x9m listening room with irregularly slanted walls and 4.5m ceiling height at its centre. Listening distances in equilateral triangle of 2m. Midrange driver to front wall distance 107cm. Resonance absorption towards the floor: 8mm high and 40mm wide steel ronde + 4mm high and 40mm wide felt cushion. Resonance-to-midrange absorption via knobbed rubber acoustic isolation pads 12mm high and 40x40mm in square.

    Specifications

    • Type: 3-way, open baffle
    • High and mid frequencies: Tang Band type W8-2314
    • Low frequencies: dipole of dynamic bass drivers
    • Power handling: 150 watts RMS
    • Power sensitivity: 85 dB (1W / 1m)
    • Nominal resistance: 8 Ohms
    • Frequency range: (?) - 40,000 Hz

    Tang Band W8-2314

    • Frequency range: 38 - 40,000 Hz
    • Power sensitivity: 90 dB (max.)
    • Power handling: 100 watts RMS
    • Tweeter: 2.5cm dome, aluminum-magnesium
    • Midrange driver: 20cm dynamic, bamboo fibre
    • Movable mass: 23.14 grams
    • Nominal impedance 4 Ohms (3.6 Ohms)
    • Bass drivers: 28cm dynamic, paper compound

    Cabinet Dimensions

    • Bass Cabinet: (H) 700mm; (W) 250mm; (D) 368mm
    • Top Cabinet: (H) 250mm; (W) 250mm; (D) 368mm
    • Combined: (H) 970mm; (W) 250mm; (D) 368mm
    • Country of Manufacture: Germany
    • Year: 2022

    Digitising Records
  • Epicure 3.0

    Epicure 3.0

    15/10/2022

    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Loudspeakers

    When my good friend Luigi called to say that he had come across a pair of Epicure 3.0 speakers in Berlin, I was at first a bit puzzled why he was telling me this. The German capitol was located five car hours from Frankfurt, and I could not imagine how I might transport two 30kg tower speakers over a distance of 550km in any other way than by driving to Berlin myself. Nevertheless, I thanked Luigi for keeping me posted on new opportunities and said that I might consider these Epicure speakers for review someday. In the days that followed, I did some research on the 3.0 model and became even more interested in listening to them perform. I also remembered that we had good friends in Berlin who just might be spontaneous enough to pick them up for us, until we could find a way of transporting them to Frankfurt.

    In a spur of the moment decision, I contacted the seller in Berlin and bought the speakers. That same evening, I wrote to our friend Enrico in Berlin telling him about my purchase and the difficulties involved. Luckily, Enrico said he would be interested in supporting me and the eiaudio project by picking up the speakers. I was relieved to hear this, because I knew that the Epicures would be in good hands with him. As it turned out, Enrico had to drive from Berlin Bernau in the north all the way across town to Steglitz in order to pick them up. To both our surprise, the Epicure were on sale from their original owner and came with all the documents relating to the purchase. The owner himself informed Enrico that he had bought these speakers at a time when he was still a university student, long before starting his career and, later, his own business. He had simply enjoyed listening to them for the greater part of 40 years. That was a good sign, indeed.

    Once the Epicure 3.0 were safely stored at Enrico’s house it took me another month or so to find a professional carrier who would pick up the speakers and deliver them to our doorstep, labelled as ‘additional cargo’ as part of a larger delivery. I had found out that the Berlin-based freight company ‘KLTransporte’ organised regular transports between Berlin and Frankfurt that made additional cargo loads possible in most weeks of the year. To assure a safe journey, Enrico wrapped each speaker in multiple layers of bubble foil and indicated the exact positions in which the speakers could be touched and carried. It was due to his mindful preparation and support that the moving company was able to take all necessary precautions and deliver the Epicure 3.0 in one piece. I was truly grateful to all involved for making this new exploration possible.

    On the images I had found on the Internet, but also in the photos that Enrico had sent me, it mostly looked as if one side of the Epicures’ truncated pyramid shape was off balance somehow. I am not sure what might have caused this first impression, but unpacking them at our house provided me with affirmation that they were indeed perfectly balanced. And although I had used a folding ruler to check the speakers’ approximate size and position in our room, I was surprised by how monumental and accomplished they looked in real life. The rounded edges, the unconventional pyramid shape, but also the high-quality waxed American walnut surface on all sides suggested that these loudspeakers were not to be taken lightly.

    Similar to our EPI 500, the 3.0 were decoupled from the floor by means of a wooden base. But different to the EPI 500, the base itself was decoupled from the floor by means of four scantlings, with one scantling placed in each corner. In my attempts to get the EPI 500 to sound right, I had applied the same method of raising the base with great success and was pleased to see this confirmed. As the speakers of this era were mostly designed to be placed on American living room carpets, I achieved the most natural tonality by placing them on 5x40mm felt pads, sometimes in combination with 8mm thick steel plates. The base itself served to raise the bottom of the cabinet off the floor and allowed for the binding posts to be hidden from sight underneath the speakers, thus contributing to Epicures’ clean look from all around.

    For those of us conducting lots of experiments with loudspeakers, the hidden position of the binding posts could become a bit of a nuisance, and I was further surprised to find that the supposedly original G.R. plugs had been upgraded (most likely by the company itself) to more convenient wire clamps that sadly were too puny to accept the hollow beryllium-gold banana plugs of my confectioned Belden speaker cables. In search of a quick solution, I grabbed a disused run of Belden 9497 cables and simply clipped the bananas off at one end. I then slipped the tinned copper Belden wires directly into the clamps. This did the job of connecting the speakers to our Hafler XL280 power amplifier, and, as usual, the initial sound emanating from the speakers proved to be quite horrible. With the cables and speakers having been dormant for many months prior to my purchase and with one end of the cables having freshly been clipped, there was obvious need for homogenisation of materials and perhaps fluids. 

    Another aspect leading to the at first poor sonic impression was the positioning of the speakers in the listening room. At first, I had simply placed them at the markers that had worked well with our Martin Logan electrostatic speakers, and this was obviously not the perfect position for the Epicure 3.0. In this position, the speakers were standing too far apart, far from the room’s front wall, and toed in towards the listening position. On the Epicures, this placement led to an over-accentuation of treble and lower bass with a complete absence of bass punch. It was clear to me that the room was interacting unfavourably with the speakers, and I was reminded of an Excel spreadsheet that I had received from a fellow audiophile called Peter Englisch. This spreadsheet permitted the calculation of favourable speaker placement positions simply from entering the room dimensions. It seemed that the process of placing the Epicures would present a good opportunity for me to work with this new tool. Based on the dimensions of our main listening room, I received the following values:


    Speaker-to-wall distances in centimetres:

    • Front Wall: 70 / 112 / 252
    • Side Wall: 59 / 94 / 212
    • Floor-to-Woofer: 35 / 56 / 126


    The Front Wall distance was measured from the room’s front wall to the woofer-plain (near the voice coil); the Side Wall distances were measured from the left and right side walls to the centre-axis of the bass drivers, and the Floor-to-Woofer distance was measured from the room’s flooring to the centre-axis of the woofer. Speaking to Peter Englisch about how to best work with the values, I was reminded that, while the front wall distances should be identical between the left and the right channel, the side wall distances should not be the same. The need for different distances between the side walls resulted from the listening position normally being located midway between the speakers. If the speakers were also positioned symmetrically within the room’s walls, the result would be a cancellation of frequencies in the listening position.

    I ended up with a front wall distance of 70 centimetres (which was 10-30 cm less than I usually positioned our speakers at) and a right channel to wall distance of 94 centimetres. The floor to woofer distance was naturally at about 56 centimetres with the Epicure 3.0. On the left channel I could not quite match the prescribed value, because of a door being in the way. I added round 5mm high and 40mm wide felt pads underneath the four scantlings to decouple the speakers from our hardwood floor for more tonality. The speakers were placed in parallel to the front wall to improve channel separation and bass agility. The Epicure 3.0’s freestanding invert-dome tweeter provided linear frequency response over a super-wide dispersion angle and was said to show variations by 3dB over a 180° angle only. This resulted in the speakers sounding relatively balanced anywhere across the room and even outside the listening room. When standing right next to the speakers or grabbing a cup of coffee from the kitchen, the emanating sound remained natural and balanced, more so than we were otherwise used to.

    The Epicure 3.0’s unusually wide dispersion angle and its flat frequency response over the whole bandwidth was accompanied by excellent phase linearity resulting from the front plate being slanted backwards towards the pyramid top. Earlier models of manufacturers such as Cabasse, KEF, B&W, etc., had added additional cabinet boards under the bass and midrange drivers to reach a similar effect, but Epicure’s soft edge, soft slope approach would also lessen the unpleasantness caused by sound waves hitting on sharp edges. The pyramid structure had the advantage that the reflecting surface around each driver was proportional to the driver’s size, thus minimising harsh refractions. The tweeter and the midrange driver were housed in their own separate compartments, and there was little interference between the chassis that would jeopardise acoustic integrity. This resulted in low distortion, reduced time-smear, excellent transient response, and, above all, natural tonality.

    On the 3.0 model, Epicure made use of a relatively large 140mm ferrofluid damped midrange driver that was allowed to mechanically roll off at 6 dB per octave from 75 Hz towards the woofer. Its potential high frequency content was kept from interfering with the tweeter via crossover at 2,600 Hz and 18 dB per octave. The bass driver was kept clear of the midrange by sloping at 12 dB per octave. Next to the active ferrofluid damping of the tweeter and midrange drivers, the model 3.0 eliminated internal resonances through a combination of bracing and anti-resonance matts. The resulting effect was a linear frequency response from a very low 32 Hz to 10,000 Hz over an impressive 180° angle. Needless to say, shoppers today would be hard-pressed to find loudspeakers that deliver a similar performance. And measured from the sweet spot, frequency response over the whole spectrum of human hearing was quoted at 32 to 20,000 Hz with a mere 3 dB variation towards the fringes.

    With their high level of resonance absorption, the Epicure 3.0 turned out to be power hungry. Sensitivity was rated at a low 83 dB, which would have made them a companion for beefy amps. I did achieve good results driving them with a 40 WPC Dynavox VR-70 tube amp and with a 145 WPC Hafler XL-280 solid state amp. Epicure actually recommended amplifiers from 30 to 500 watts, and I can confirm this to be realistic, if the lower watts amplifiers are tube driven. Ferrofluid cooling made the speakers withstand even high levels of continuous power without any immediate danger of them overheating. Their impeccably flat impedance curve at 4 Ohms made the choice of amplifier relatively easy. With the foam grills in place, especially those covering the tweeters, listening at slightly elevated volumes proved to be more rewarding. However, for greater musical detail and nuance, the grills needed to be removed. Sadly, removing the frameless frontal grills without running the risk of breaking them in the process had long since become a challenge on my specimen. Perhaps to compensate for its wide dispersion angle, the tweeter’s output could be attenuated in -3dB steps. This could be a practical feature, for instance when highly reflecting side walls contributed to the amplification of the output signal in an undesirable fashion. 

    In my extensive listening tests, the Epicure 3.0 played all kinds of music program, film score, and effects with ease. While their specific sonic character was not immediately noticeable and would be difficult to spot by the casual listener, these speakers certainly had the potential to surprise. Their linear response made them sound rather inconspicuous until the music program itself demanded attention. From the beginning, I was perplexed by the Epicure 3.0’s bass response and extension to which there was no warning. While other speakers would let you guess their intrinsic abilities by the sound signature they produced, the Epicure were capable of dishing out bass attacks without even the faintest hint of having this ability. And these bass moments could either be surprisingly low or astonishingly loud, depending on the music chosen. I would have expected this kind of bass from a subwoofer, perhaps, but I had never actually heard a subwoofer that was so well integrated with the music and not once seemed misplaced.

    In our setup, the Epicure 3.0 performed well in terms of smoothness, balance, and natural tonality. They were not the most exciting sounding speakers in and of themselves, but they were always ready to accentuate the music when this was called for. I enjoyed the natural sound and kick of percussions and the many tonal layers by which the music was presented. In the field of tonal separation, the model 3.0 was similar if not superior to the EPI 500 series. Stereo imaging was not as wide and crisp as on the EPI 500 when sitting in the sweet spot, but it was far superior to the EPI 500 when listening from almost all other positions in the room. In my nightly sessions I noticed that the model 3.0 took the whole room into the acoustic equation which had its advantages when it came to maintaining lots of musical nuance. Some listeners had described the Epicure’s freestanding tweeters to have an ambience effect, however, this was something that I did not notice as outstanding or even care for so much.

    Listening to the performance of the Epicure 3.0, it was difficult for me to imagine that these had been relatively affordable speakers at the time that could be purchased by a university student. But then again, the 70s and 80s were still about showing customers what was possible in HiFi, and the Epicure 3.0 did strech those boundaries.

    Specifications

    • Type: 3-way tower speaker
    • Design: acoustically damped, closed-cabinet
    • Bass driver: 320mm paper-cone woofer, dynamic
    • Midrange driver: 140mm, paper-cone, dynamic
    • High-frequency driver: 25mm, paper inverse-dome
    • Ferrofluid damping: on tweeter and midrange
    • Crossover frequencies: 475 Hz and 2,600 Hz
    • Frequency response: 32 Hz - 20,000 Hz (+/- 3 dB)
    • Tweeter level attenuation: -6 dB, -3 dB, and flat
    • System resonance: 32 Hz (-3 dB)
    • Nominal sensitivity rating: 83 dB (1 Watt, 1 m)
    • Practical power sensitivity: 3,6 Watts (91 dB, 1 m)
    • Nominal impedance: 4-Ohms
    • Amplifier requirements: 30 (min) - 500 Watts (max)
    • Solid-state amplifier: 100 WPC recommended
    • Speaker terminal: G.R. plugs, base-plate mounted
    • Grille material: acoustic foam, frameless
    • Cabinet finish: hand-rubbed American walnut
    • Dimensions: (H) 105,2cm; (B) 2x42cm; (T) 2x21,6cm
    • Weight: 30.00 kg, each
    • Country of manufacturing: United States
    • Year(s): 1978-1986

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    Karsten