In the beautiful surroundings of lake, town, and castle Greifensee, the Klangschloss high end audio show has established itself as one of Switzerland’s main but still intimate show and more. With more are meant the concerts, talks, and culinary enjoyments which are offered with the show.

In 2011 we participated in Klangschloss, along with reputable Swiss loudspeaker manufacturer PSI Audio. Not with our own audio processor yet, but with a provoking 13.1 3D Surround demonstration. The loudspeaker system was fed with a multi-channel sound card driven by an Apple Macintosh, which would convert stereo music to 13.1.

This year, in 2014, we were back. Honored to share a room with loudspeaker manufacturer Klangwerk, or in other words with Markus Thomann, the founder and organiser of Klangschloss.

Markus installed a beautiful 5.1 setup. Left and right loudspeakers were Klangwerk Ella active loudspeakers. The subwoofer was not really visible, it looked like a designer table. A special very compact Klangwerk center loudspeaker was installed very discretely.

Even more discrete were the surround loudspeakers. My wife Renata’s comment to this setup was, that this is the first surround system she saw that she could imagine having at home (great – hurdle one passed – but our current apartment does not have the space for it).

Above, on top of the subwoofer table, you see what Illusonic showed. Our Immersive Audio Processor, fed with stereo and multi-channel PCM signals by an Oppo universal player via HDMI.

Playing plain stereo over the Ella loudspeakers, the system had already a remarkably robust sweet spot and spacious sound. A speciality of Klangwerk is, to design their loudspeakers with very frequency consistent directivity pattern, enabling consistent sound quality in the larger part of a room.

With these features, Klangwerk loudspeakers are also an ideal match for our Immersive Audio Processor. A sweet spot extension by means of center and surround loudspeakers can only work as well as the loudspeakers emit sound consistently into the room.

We played mostly stereo music and stereo converted to 5.1 by IAP, but also multi-channel music and movies. Sound quality of all configurations was well received. The challenging castle acoustic was successfully addressed by Illusonic’s new room equalization system.

Thanks for coming, Max, Lisa, Renata!

Once visitors have heard enough or needed a break, coffee, wine, and food was served on the ground floor of castle Greifensee.

On the second day of Klangschloss, there were a few seminars. The first one was given by renown sound engineer Jürg Jecklin on the history of sound recording from mono to surround. Over the great PSI Audio 5.1 system, installed in the lecture hall, Jürg played many historical and modern recording demonstrations.

I gave a talk about center channel and surround systems. Over the 5.1 system I demonstrated spatial hearing illusions (to demonstrate to the people how our spatial hearing works and what limitations of stereo are) and different usages of center and surround channels. This included also a demonstration of presenting stereo music over a 5.1 loudspeaker system.

We invite you to visit us at High End 2014 in Munich, May 15-18, in Room E222 (Atrium 4.2). We will demonstrate our extended family of high end audio processors.

Besides of the Processors, our amazing sound setup comprises of:

Soulution power amps

Raidho loudspeakers

Vovox cables

Dr. Feickert turntable

mbakustik panels

Additionally, I will give every day a presentation on the High-End Technology Stage: “Strategies for Room Equalization of High End Systems”.

Thursday, May 15, 2014: 12:00 – 12:25

Friday, May 16, 2014: 12:00 – 12:25

Saturday, May 17, 2014: 12:00 – 12:25

Sunday, May 18, 2014: 12:00 – 12:25

Originating as house warming party for our new office in Lausanne city in 2007, the 7th edition of our Pre-Christmas Party took place the evening of Thursday December 5th at our offices in Lausanne.

As always, our office was re-arranged (moved desks and things on the side), and plenty of finger food and drinks were served.

Besides friends and family, friends from local audio industry visited.

Such as from ABC PCB, Digimath, Klangwerk, Merging, Logitech, PSI Audio (Relec), Silent Work, Radio Materiel, Sonosax, Stenheim, and Stereolith.

Also, friends from the reknown local technical university, EPFL, visited (where I still teach an audio course in the fall semester).

We also welcomed friends from Lausanne University UNIL, which we got to know through a hobby bird-related audio analysis project.

At 8pm there was a short review on Illusonic’s year 2013. A highlight was our venture into high-end audio hardware business and our experiences with related trade shows.

Otherwise, the evening was without formal program.

While the first edition of the party still lasted until 5am, we closed around midnight this year. Because we might get older, or more reasonable.

Good night!

Given any signal, no need for multiple microphones or channels, de-reverb attenuates reverberation. It makes a speech signal sound as if the talker is very close to the microphone, i.e. hands-free sounds more like higher quality headset recorded speech.

Also applicable in the professional domain, de-reverb removes annoying room effects from dialogue and interview recordings.

With hindsight obvious, de-reverb is effective against acoustic feedback, acting as a good acoustic feedback controller.

Contact us for more information.

Sons & Sens 2013

In its third edition, Sons & Sens was held for the first time in Montreux, famous for its Jazz festival and beautiful surroundings. Exclusively Swiss high-end audio brands showed their latest and greatest offerings, including a few newcomers, such as Le Son, soundkaos, and us (Illusonic).

A show, not only for sound, but the “Sens” in Sons & Sens stands for other senses, such as local wines, food, chocolate, music, and art. These were implemented with other exhibits and evening social gatherings, resulting in a fresh atmosphere with partly a new audience, besides classic audiophiles.

With a respectable number of 18 exhibitors and its location in Montreux’s glamorous Hotel Suisse Majestic, Sons & Sons seems to be set for growth and more international vibes. This year, the number of visitors was still modest, though, resulting in an intimidate atmosphere. We were happy to have several in-depth interactions with well respected journalists.

Our Room and Setup

Our room was number 211, a junior suite with a balcony and beautiful view on Lake Geneva and the alps behind. Though we closed the curtains of the balcony window, to focus on sound and not distract listeners with too much light coming in.

Besides of the Processor, our 5.0 setup comprised of:

Battery powered 3-channel power amp by Audio Consulting for L, R, C

Two Nagra stereo amps for sub L, sub R, Ls, and Rs

Stenheim 5 main loudspeakers and two sub extenders

Vovox line and loudspeaker cables

An Oppo Blu ray player served as high definition digital source (CD, SACD, Blu ray) to our Immersive Audio Processor.

Before the show opened, we measured the room and set gain/delay trim for each loudspeaker and the sub extenders. Further, we used a single parametric equalizer for mitigating a slight room mode.

Show Report

Here a few reports by others on Sons & Sens 2013:

HIFISTATEMENT, Part 1 (German)

HIFISTATEMENT, Part 2 (German)

home-electronics.ch (German)

6moons.com (English)

We invite you to visit us at Sons & Sens in Montreux, October 11-13. We will demonstrate our revolutionary Immersive Audio Processor.

Besides of the Processor, our 5.1 multi-channel setup comprises of:

Power amps by Audio Consulting and Nagra

Stenheim loudspeakers

Vovox cables

An Oppo Blu ray player serves as high definition digital source (CD, SACD, Blu ray) to the Immersive Audio Processor.

What We Wanted to Show and Demonstrate

The demonstrated Illusonic Immersive Audio Processor is a versatile high-quality digital pre-amp, featuring in addition to the conventional audiophile common interfaces also latest HDMI 1.4a inputs and output.

Why would one want to have an audiophile pre-amp with 16 balanced analog outputs? To implement our unique immersive audio technology, which has the goal to reproduce existing music and movie sound tracks optimally over the given loudspeaker setup. With optimally we mean, enabling a sound experience like in the sweet spot, also for listeners which are not sitting in the sweet spot. Add a center loudspeaker to stereo to get a stable sound stage from everywhere. Or/and add surround loudspeakers to be immersed into the room of the music (no added reverb, but music-extracted room signal). Many setups and up to 16 loudspeakers can be used.

It is about getting great sound, for music and movies, on each seat on your sofa. Or an audiophile home cinema with great 3D immersive sound on each of its seats.

Demo Room Equipment

In the two days before the show, we prepared our demo room. We were lucky and thankful to be able to install highest quality and world-renown audio equipment:

6 Soulution Series 5 power amps

Soulution Digital Player

Dr. Feickert turntable with a Soulution pre-amp

Focal 5.1 setup with 5 Utopia III Viva and Sub Utopia

Vovox cabling (power, XLR, coax, loudspeaker cables)

TAOC racks (Axiss)

mbakustik absorbers, diffusers, and curtains

The central control (“digital pre-amp”) connecting this setup was our Immersive Audio Processor, which additionally connected to an Oppo Blu ray player via HDMI 1.4a.

Fine Tuning and Calibration

The Immersive Audio Processor’s versatile calibration capabilities were used. An initial calibration setting was derived from measurements throughout the 13-chair listening area (resulting in gain trim, delay trim, modest EQs, and bass management settings).

The night before the show, Patrik Schwitter fine tuned the calibration of the system until midnight, to improve low frequency response and to remove some “shoebox” sound which remained despite of the (relatively modest) acoustic treatment. Patrik used our new Immersive Audio Processor calibration tool, which presents an up to 16 channel mixing console with gain trim, delay trim, 5 fully parametric EQs per channel, and the many bass management parameters. Using this tool, Patrik could calibrate the system as he is used to: real-time like with a real mixing console, getting immediate acoustic feedback as he moved any control. This effort paid back, we got many positive comments on the overall sound of the room and system (also for stereo!).

Impressions and Reactions

Throughout the show, we used a single sound setting. No tweaking at all. Our goal is, that one setting is good for all music. That went well, we never felt we would have to change anything.

I was a bit anxious about the prospect of having many audiophile people exposed to our 3-channel stereo (left, right, center) and 5.1 for music and movies demonstration. We have had our system exposed to music professionals, acousticians, and a few audiophile people with good feedback. But it was hard to predict what the shock of listening to an unfamiliar 3 or 5 channel presentation of stereo music would evoke in an audiophile stereo and music lover.

The majority of feedback was overwhelmingly positive. We had many listeners staying long and coming several times again – listening carefully with closed eyes. The range of reaction was from being amazed (for example laughing out loudly as we switched to reference stereo), positive, to being a bit confused but positive. We got only very few negative reactions. Of course we don’t know the thoughts of the many people that just listened without saying anything. But not many people looked distressed or not pleased.

Technology Stage Presentation

Every day, I gave a presentation entitled “High Quality Stereo Reproduction Using a Center Channel”, to explain how a center channel is generated from stereo with the goal of sounding similar to the 2-channel stereo phantom center. I wrote a short version of this presentation as a blog.

Introduction

While our Immersive Audio Processor supports multi-channel surround loudspeaker setups with up to 16 loudspeakers, an economic and thus appealing setup is stereo with an additional center loudspeaker.

Stereo music is reproduced with a center loudspeaker with the goals of providing:

– highest quality

– a vastly improved listening experience for listeners that are not in the sweet spot

In the following, we are describing our strategy and challenges we faced for achieving these goals.

Stereo Sounds Great – In the Sweet Spot

High quality music, reproduced with a high quality stereo system, properly setup and assuming a good acoustic, enable a spatially remarkably faithful and rich listening experience. Phantom sources are perceived between the left and right loudspeakers and the listener is to a good degree immersed into the room/environment contained in the recording.

Much Is Lost – Outside of the Sweet Spot

If a listener is not in the sweet spot, phantom sources are perceived from the nearer loudspeaker. Immersion vanishes, making way to noticing being in the local room and “listening to loudspeakers” as opposed to instruments.

If a listener is in the sweet spot, but turns his head to the side, immersion vanishes, too.

Goal: Great Sound Everywhere

The goal is to enable a great listening experience for everyone, that is, not only for the person in the sweet spot, by using a center loudspeaker. The key to high quality is how the three channels (left, right, center) are generated from the given stereo music. In the following, we describe the three challenges we faced when developing this technology:

Extracting a Center Channel

Timbre of Center

Spaciousness of Center

Extracting a Center Channel

The goal is to extract a signal from the stereo signal, corresponding to the signal a listener in the sweet spot hears as a center phantom source. Localized sound is dry. Thus, a first step is to extract from the given stereo signal its dry part. The next step is to analyze the dry stereo signal and extract dry sound localized in the center. The so-obtained center signal is (scaled and) subtracted from the original left and right channels.

Timbre of Center

A listener’s head and body act as a filter to the arriving sound. This filter is different for sound from the side and center. Therefore, the same signal reproduced as stereo phantom center versus a center loudspeaker has a different timbre. For high quality stereo reproduction using a center channel, the center timbre has to be corrected such that it is similar to the original phantom center timbre.

Spaciousness of Center

A stereo phantom center is perceived as blurred. In contrast, a signal from a center loudspeaker is perceived very compactly. It is as if you “hear the loudspeaker” as opposed to a more spacious object like a stereo phantom center.

A phantom center corresponds to the same signal at the left and right loudspeakers. From these, not only direct sound reaches the listener, but also left and right early reflections. In contrast, early reflections from a center loudspeaker come mostly only from the center direction (back wall, floor, and ceiling reflections). Thus, a center loudspeaker is perceived as more focused than a phantom center.

Additionally, especially at high frequencies, the localization information available at the left and right ears is not precise and consistent for the phantom source, further adding spaciousness to its perception.

To add spaciousness to the center signal, center signal early reflections are added to left and right. The difficulty is to do this without impairing timbre and sound quality. Furthermore, at high frequencies, the energy of the center signal is spread to left and right.

Putting It All Together

The use of techniques for center signal extraction, timbre correction, and increase of spaciousness enables high quality reproduction of stereo signals using a center channel.

Disclaimer

Note that the functionality and functioning of Illusonic technologies and products may be modified at any time without notice. The algorithm descriptions above are for illustrative purpose only.

We invite you to visit us at High End 2013 in Munich, May 9-12, in Atrium 4.2 Room E221. Every hour, we will demonstrate our revolutionary Immersive Audio Processor.

Besides of the Processor, our amazing multi-channel setup comprises of:

Soulution power amps and digital player

Focal loudspeakers

Vovox cables

mbakustik panels

TAOC racks

Dr. Feickert turntable

Additionally, I will give every day a presentation about “High Quality Stereo Reproduction Using a Center Channel” on the High End 2013 Technology Stage:

Thursday 12:30

Friday 16:00

Saturday 12:30

Sunday 12:30

Introduction

Consumer systems often use bass management for convenience and reducing cost. Bass management enables the use of smaller main loudspeakers, by reproducing low frequencies over a subwoofer.

The use of bass management and a subwoofer has been more popular for home cinema systems than for stereo systems,because for most people it is simply not practical having five or more large full range loudspeakers.

For high-end consumer stereo systems, subwoofers are hardly used. Why use a subwoofer if the main loudspeakers are large and truly full band?

While the optimal solution certainly depends on the specific case, there are situations when also high-end systems with full range loudspeakers benefit from bass management.

In the following, we are discussing and explaining bass management and reproduction of low frequencies with subwoofers. Even when all loudspeakers are full range and bass management per se would not be necessary, bass management can have its benefits.

Background: Room resonances

In this discussion, we are concerned about the impact of  relatively late reverberation. Each pair of parallel walls of a room generates room resonances, that is, standing waves between the walls. The frequencies at which these room resonances occur are usually also the problematic frequencies at which reverberation decays too slowly, causing annoying “temporal smearing” and “bass boom” effects.

The figure below illustrates the sound pressure for room resonances occurring between two walls. The lowest frequency room resonance (shown in blue) has a wavelength twice as large as the distance between the walls. Thus, its frequency is:

f0 = c / (2*d) ,

where c is the speed of sound in air (about 340 m/s) and d is the distance between the walls. The frequencies of the higher frequency room resonances f1, f2, f3, … are:

fn = n * c / (2*d) .

When one measures a room, with the measurement loudspeaker and microphone located at two opposing walls, the corresponding room resonances appear as peaks in the spectrum. Above the so-called Schroeder frequency, the room resonances are so closely spaced in frequency that they do not appear as distinct spectral peaks.

Loudspeaker (Subwoofer) Positioning

When loudspeaker and microphone measurement positions are at or near peaks of the standing room resonance waves, as illustrated in the example in the figure above, the resonances appear as peaks in the spectrum. For general loudspeaker and microphone measurement positions, a room resonance may also appear as a notch in the spectrum. This occurs when either loudspeaker or microphone are positioned at or near a zero position of the room resonance.  The figure below illustrates measurement or the room with the loudspeaker at a zero position, resulting in a spectral notch at the corresponding resonance frequency. Generally speaking, for an arbitrary loudspeaker and microphone position, each room resonance may appear as a peak, notch, or something in between.

Note also, that the energy transferred between an omni-directional loudspeaker and microphone by means of a room resonance remains the same if loudspeaker and microphone positions are swapped.

Now consider subwoofer positioning. The previously discussed loudspeaker position corresponds to the subwoofer position and the microphone position to the listening position. Given a pre-determined listening position (e.g. sweet spot of a stereo system), different room resonances are excited with different strength depending on the subwoofer position.

A good subwoofer position is reached when the room impulse response measured from subwoofer to microphone is as frequency smooth as possible. This occurs at a position at which the energy flow from subwoofer through the room resonances to the microphone is as frequency independent as possible.

The above mentioned condition does not yet ensure that the overall gain of the subwoofer signal matches the main loudspeakers. Thus, once the subwoofer is positioned, a gain calibration should be carried out.

The described positioning and calibration procedure may be carried out based on room impulse response measurements (you can use for example the free Room EQ Wizard). Less effort but more skill may required to optmize subwoofer positioning and gain by simply trying out different positions and listening.

Another method which may help for finding a good subwoofer position is to place the subwoofer in the desired optimal listening position and listen at all possible subwoofer positions whether bass is reproduced well. The point at which bass is reproduced well may be a good subwoofer position. This method is based on the above mentioned insight that loudspeaker (subwoofer) and microphone (listening) position may be swapped, while the energy transfer through room modes remains approximately the same.

Subwoofer Positioning II

In the previous section, subwoofer position optimized for a single optimal listening position (“swee spot”), was discussed. Especially for home cinema, but also whenever one intends to have more than one listener at a time, one should not only optimize the reproduction system for a single sweet spot.

One extreme example, to illustrate the problem of single sweet spot optimization, is the following. If the sweet spot is near a zero position of a room resonance, the subwoofer is potentially placed at a position where it excites this room resonance maximally. This likely leads to annoying “temporal smearing” and “bass boom” effects, for listeners which are not exactly in the sweet spot.

A good strategy for full room (or large listeing area) optimization is to measure the room resonances not only at the sweet spot, but at multiple positions. One way to optimize subwoofer position then is to optimize it in terms of spectral flatness with respect to the average room impulse response (averaged over all measurement positions).

Again, a skilled listener may optimize subwoofer positioning for an extended listening area by simply trying a number of subwoofer positions and listening at different positions.

Putting It All Together

So what has the previous discussion to do with a high-end stereo (or high-end surround) system with full range loudspeakers?

Low frequencies, below at least 80Hz, can not be localized by a listener. Thus, for perception of the stereo/surround image, it does not matter where the loudspeaker is, reproducing such low frequencies. For higher frequencies, it is crucially important that the main loudspeakers are at their appropriate positions.

It may be that the position of your main loudspeakers, due to your specific room, is suboptimal to reproduce low frequencies. If yes, it indeed makes sense to use bass managment to remove bass from the main loudspeakers and reproduce it over a well placed subwoofer.

Since in this case full range loudspeakers are used, the cross over frequency is chosen as low as possible, but such that most or all of the bass reproduction problems (“time smearing”, “bass boom”) occur below it.

Montreux Jazz Festival and EPFL (Ecole Polytechnique Federale de Lausanne) organized a press conference to launch the Montreux Jazz Heritage Lab. A fantastic state-of-the-art multimedia cocoon offers the opportuntiy to experience over 5000 hours of concerts from the last 45 years. The multimedia cocoon is powered by our Immersive Audio Processor, to reproduce the stereo Montreux Jazz archive over a 3D 10.1 loudspeaker system.

Montreux Jazz founder Claude Nobs: “I have the feeling to be into the concert hall. It is not just a normal sound. The sound envelops you. You are into the image, into the sound”.

Nicolas Henchoz, EPFL: “The aim of the Heritage Lab is to rethink our relationship with the digital world and to create another experience for AV archives”.

Pictures © Daniela Droz, Tonatiuh Ambrosetti / EPFL+ECAL, 2012.