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Or: a shortly about room acoustics

ul. Sportowa 5
15-523 Białystok | POLSKA


Miejsce rozmowy: KRAKÓW/Poland

The topic of listening room's acoustics seems to be well studied. Or at least its importance is recognized by most people. But is it really? I think that „acoustic revolution” is still ahead of us and companies such as ACOUSTIC LAB may be an important part of it.

t's one of those hot summer days and all the windows in the apartment are open. I live in a quiet neighborhood, actually in the countryside, so I can hear the bells from the nearby church. So – it's noon. We are sweating real hard, but in a moment we will close the windows and curtains to listen to my system for an hour. Sometimes sacrifices are necessary for the things we love :)
The meeting you're reading a record of, is devoted to listening room's acoustics and how to improve it. I am talking to MIROSŁAW ANDREJUK, the founder and owner of the ACOUSTIC LAB company.

MIROSŁAW ANDREJUK: My name is Mirosław Andrejuk and room's acoustics is my specialty.

In September, it will be exactly nine years since I came up with the name Acoustic Lab, although it took me a while to register it with authorities.

How did it start?
There were actually two beginnings. First: it started with my dad, who really loved to dance, and music is a must if you want to dance. That is why around 1980 he bought an all-in-one Unitra system (turntable, tape recorder and radio tuner in one) + small speakers or monitors with paper drivers. So you can say that they have always been with us. Monitors - like most cases at the time – were placed on top of tall cabinets, so the sound was actually coming to us from the ceiling. In 1992, my dad built a house and we moved there and this music set moved with us and was placed in a large, 29 m2 room, also with speakers at the top of the tall cabinets.

Mr. Włodzimierz Andrejuk and his Unitra set, 1980s.

Beginning no. 2: a friend of a friend bought JBL E100 loudspeakers. We were teenagers, so when he put them on the balcony and broke all the windows at the neighbor, it was SOMETHING! We were really impressed! So also my colleague wanted to buy a better system for himself. It was 2003. He invited me for a listening session as an adviser and bodyguard in one. It was about spending around two and a half thousand zlotys, which he earned, so - for a high school boy - was really a lot.

Being completely inexperienced future audiophiles, basing all our knowledge on reviews we read in the "Hi-Fi and Music", we went to the Audiofil-A shop to listen to some monitors. The seller invited to the listening room, connected the Denon PMA-495R amplifier to Acoustic Energy Aegis One monitors, and then played the Amused to Death by Roger Waters from the Naim CD5 player. He cued in the eighth track, the sleigh ran across the room, and we looked at each other in disbelief, wondering how it was possible ... Of course my colleague bought the amplifier and speakers, and I decided that I at some point I would have my own audio system.

And what did you buy?
A few months later I bought the same amplifier as my colleague. And because the Unitra speakers did not sound so spectacular, I bought two sheets of a black furniture board, a pair of dome tweeters and woofers, all from Alphard. I used midrange drivers from my dad's monitors and with the help of the colleague I built my first loudspeakers in two days. They sounded terrible, above all they had a boomy bass. There was a lot of it but the quality was horrible.

You started quite young.
Well, yes. And I also started to read multiple reviews looking for my holy grail. I found it in Avance Dana 509, that were highly rated in the „Hi-Fi i Muzyka” review, getting in some aspects of performance an incredible 6/5 grades!!! I looked for them on the second hand market for a while, and when I finally found the add I went to Warsaw to get them.

It was 2004. I was 17 and it was the same year when my dad passed away. That's why I begged my mum to come with me as a bodyguard. We came to Central Station on the bus and continued to Bielany on a tram. The seller lived in an apartment block. He used them in a 20 m2 room paired with entry level Vincent electronics. When he played Kilar and I heard the tympani entering I immediately knew I was going to buy them. I placed one speaker on top of the other, wrapped them with some carton, used some tape to keep them together. I paid for them and we took a taxi to the Central Station.

Avance Dana 509 already in Mirek's room

Due to the traffic jam near Marriot Hotel we moved maybe 20m and it cost us 40 zlotys, so I asked the driver to let us out. I took the speakers and we walked the rest of the way carrying the speakers. Then we took the train home and we got to Bialystok around midnight.

You came home and…
I had to hook the speakers up as soon as we arrived to check out the performance in my room. Unfortunately, with a computer as a source in a 29 m2 room with wooden walls I did not hear such a powerful bass as at the seller's.

So what happened next?
The 2005-2008 period was really hard for me. After my dad died I had to become the „head of the house”. We lived in a 200sqm house and my mum was already retired. It was taught. I was a student at the time and had some part-time jobs to make a living. In a meantime I got injured when playing football and spent three month in bad and then had to learn how to walk again. The silver lining was all the time I had to read about audio.

The speakers placed in a large room „disappeared”, there was no bass, no space. I thought that maybe the cables were a problem. I brought home cables by a new Polish company called Audionova, plugged them in and... nothing changed. I stopped reading reviews but rather tried to figure out by myself what the problem was. Finally, I thought that since I had quite a good electronics, speakers and cables the unsatisfying performance could be caused by room acoustics.

So I reached for Alton Everest's Handbook of Acoustics, I also read dozens of articles published in the Audio Engineering Society and the Acoustical Society of America. Then I started reading books on interior acoustics, exploring the subject of acoustic adaptation even deeper. In addition, I read audio forums from other countries. In Poland at the time, the only owner of a dedicated audio listening room I knew was Adam Mokrzycki, who in 2005 described his room very well. Despite that, the subject of acoustics definitely wasn't something most Polish audiophiles really thought about.

Hat's when you contacted me?
A bit later – on Jan. 7th 2008 I sent an email to „Mr. Wojciech Pacuła, „High Fidelity” chief editor, asking you what CD Player should I buy. I was looking for more bass and warm midrange. You recommended the Xindak CD-06, but I read a lot of opinions of various forums, also listened to audio sellers advice and they all claimed that for a Denon amplifier I should buy a Denon CD Player, and so I did buy the DCD 1290.

Mirek's room in 2004, before room treatment

In April 2008 I found this player at Ebay in Germany – I was looking for one in perfect condition. I won the auction and the courier brought it soon after, fortunately without any damage. So from this moment my system consisted of the Denon DCD 1290 Player, Denon PMA 495R amplifier and Avance Dana 509 loudspeakers.

Were you finally happy with this system?
Well, no, I wasn't… It still didn't sound the way I wanted it to. At the time I met a neighbour, an audiophile - Jacek vel Zydelek. When he invited me over I heard for the first time his 3-way Jamo Concert 11 (D870) speakers driven by a tube preamplifier and push-pull tube powers amps (4xEL34 each) I was amazed. I didn't have the money to buy these speakers so I decided to try with a tube amplifier first.

In 2009, as one of the first customers in the country, I bought a Chinese tube amp, it was the Music Angel featuring KT88 tubes. It delivered more dynamic performance with more power than Denon, but lacked in terms of sophistication and finesse. I tried various cables but it didn't change much. I started to roll the tubes and that resulted in a noticeable difference. Then I met a guy who made Totem Mite clones for himself and a tube amplifier. He said he would upgrade this amplifier for me. And indeed, after his tuning it sounded better. I bought Mullard driver tubes for it and the final result, a warm sound, was what I was looking for and I was pleased and happy with it.

What about room acoustics – you've mentioned you'd already read some manuals.
Yes, it was then that I bought the first microphone, interface and borrowed a laptop from a friend to perform measurements. It was also then, in 2009, when I started to develop first projects of my listening room's acoustic treatments. Since you can't really overdo room's treatment and I knew mere and more about it, also the project evolved becoming more and more advanced. I planned to use more and more items – in no manual was it written that adding three more diffusion panels would worsen the sound… Still, at some point I had to start to implement my project and it did finally happen in 2010.

So you first planned the whole thing and than executed it – that's a very serious approach :)
Well yes, I didn't want to do just something, I wanted to do it right. I had to learn carpentry, varnishing, materials science, upholstery and many other secondary activities. Fortunately, I met some kind-hearted people on my way, who gladly shared their knowledge and skills. Maybe it's Podlasie's innate cordiality. It certainly helped, that dad built a house in a suburban village, where there were a lot of all kinds of specialized workshops.

The final design of Mirek's room

I was very happy with the creative and mental work while designing and enjoyed the physical work too, when cutting, recharging, grinding and painting - and there was about 300 m2 of surface to work on. It's easy to design on paper and in a computer, but it is much more difficult to implement it. That is why I reduced the surface of the diffusers to about 200 m2 that required cutting, manual sanding, priming, sanding again and painting. It took me about six months to build the panels. At times, I felt like letting it all go, but I pushed through. I was young, so I wanted my panels to be visible - so I painted them yellow. It later really haunted me :)

After finishing all the panels, installing them, taking measurement and achieving a high level of satisfaction of the results of my own work I decided, that since I was able to do it for myself I could do it also for other, professionally.

And that's when the Acoustic Lab was born?
The idea for the company was born then - in September 2010 I came up with the Acoustic Lab brand. I didn't want to do it halfheartedly, I wanted to get fully involved. I spend my whole days reading a lot, learning, trying. Earlier, I wrote a bachelor thesis in college, in which I compared various programs for measuring acoustics. The work did not quite fit in the profile of my studies - IT and econometrics - but I succeeded :)

In the same year I was selling speaker cables and a man from Bialystok came for it, Mr. S. I sold them to him, then it turned out that we had a mutual friend and so we began to get to know each other better. He had a very good sounding system based on Grundig GAT electronics (Greg Audio Tuning) and equally old Grundig monitors. It was the beginning of our common chase of a bunny, but at the beginning we took only small steps at a time.

In May 2011 I bought Acoustic Energy Aegis One monitors for a small system in my office (same model as a colleague once had bought and which were my first dream). Initially, they also served as speakers for generating sounds during measurements. I also bought the Jamo C80 subwoofer, also for acoustic measurements, and out of curiosity I created a 2 + 1 system.

The combination of monitors and subwoofer resulted in a large amount of bass on the edge of bands, i.e. in area of 50 - 80 Hz. That is why I bought the Behringer DEQ 2496 equalizer in order to equalize the emphasized frequency range that the sub and monitors played together. After many measurements, tests and moving the equipment around, the sound was evenly matched, however - even in such a basic system the sound quality degradation was obvious after plugging in another device.

The listening room with acoustic treatment and Harpia Acoustic 300B speakers

On August 19. 2011 the first open listening session took place in my listening room. From Kraków came the designer with his Harpia Acoustic 300B loudspeakers, and I organized for the session the Cary Audio 300B monoblocks and a source in the form of an MBL 1531 CD player. It worked pretty well, so in November 2012, for the first time, I participated in the Audio Show as an exhibitor, providing my acoustic systems for the Amare Musica room.

In June 2013, I designed and made an omnipolar sound source in the form of a sphere with twelve drivers. Thanks to the fact that it plays in every direction, it can evenly fill the room with sound, which allows you to measure the reverberation time more accurately. We can ignore the impact of the loudspeaker design, whether it is a closed or open enclosure, bass reflex, Magnepans or electrostatic speakers, because the acoustics are "made" not for the owned audio system, hiding its flaws, but under certain standards. It means in such a way that the room has the least impact on the sounds that reach the listener.

When I measured the room with my speakers in October this year, I replaced the monitors with Jamo Concert 8 speakers. I dreamed of something else of course - I remembered your review of the Hansen Audio Prince v2 speakers well (HF | No. 67) a few years ago. I listened to them at the Soundclub salon and was amazed. Unfortunately, the price was completely out of reach for me, hence the idea to buy Jamo.

And when was the Acoustic Lab actually founded?
In 2014, four years after creating my listening room, after four years of writing acoustic advice on audio forums, after four years, when I had already done several acoustic adaptations and was already recognized as "Mirek from Acoustic Lab", I founded the company as StartUp in Incubators Entrepreneurship. Fortunately, the awareness of what is important in audio was already growing and that acoustic treatment is the basis of good sound.

It is much easier to select other system components - for example, any cable is easy to assess or check, because you can unplug it from your friend's system and take it to your own. The panels are different because they cannot be easily moved. And there is something else - from the beginning I did not want to produce of-the-shelf solutions. I approached each project individually, designing and constructing optimized systems for a given room, guided by the acoustic and aesthetic aspects.. And this made my life much more difficult and I had to wait another year for people to appreciate my offer.

So today people are more aware of the importance of the acoustic treatment?
Now, it is going great. A breakthrough was the year when the Audio Show exhibition was hosted at the Bristol Hotel for the last time. In the Nautilus room, the Wroclaw-based company 4Sound installed a huge number of diffusers on the walls and people who came there saw that it worked, that the acoustic treatment was a part of an audio system. Between 2004-2008, this was the only company really well-known in Poland, but generally people knew nothing about this issue. In the past, there were moments when I wasn't sure if I wanted to continue, and it was difficult to explain to people, that properly sounding room was critical and definitely worth investing in it. I didn't want to do it casually, I wanted to be involved 100%.

It was then that you came up with your diffusers?
Yes, they were ready in July 2014. All the time in my listening room I had diffusers on the right wall in front of the window, which obstructed them quite strongly, which meant that the room was quite dark. That's why I started designing and making prototypes of transparent diffusers. I knew that there were several companies in the world producing plexiglass diffusers. I could have prepared standard 1D diffusers, such as I already had in my lineup, but I wanted something more.

M-diff modules in a living room

I found SMT's S-Wing systems from Sweden online, which I liked because they had a different shape and worked slightly differently than ordinary panels. The sound went inside the system, not into a crack. I didn't want to copy the solution, so I decided to improve this project. This is how the M-diff project was created - a diffuser named after the first letter of my name, which based on the transmission line had much deeper tunnels compared to standard 1D diffusers.

It looked great on the computer screen, but implementation turned out to be a problem. All over Poland I was looking for a company that could bend plexiglass one and a half meters high at a reasonable price. Only the third version was successful, so it cost me quite a lot. I also added some backlit to it.

My orange diffusers on the back wall were 24 cm deep, and M-diff at 24 cm deep had a tunnel 84 cm long, and in addition by using the letter M and an open top some of the sounds from the reflections came out from the sides and some from the top. Thanks to this, the diffuser operated in a vertical and horizontal plane, and - in comparison - the standard 1D only works in one plane.

After placing them on the side walls, two pieces on each side, the music scene widened, virtual sources became better located and - most importantly - I got a better vertical gradation of planes. The vocals went higher, above the height of the speakers, and the guitars or double bass were lower, which meant that I got a more realistic presentation. Their premiere took place at the Audio Show 2014, where I exhibited together with the newly formed Fezz Audio.

And what about your audio system, has it kept evolving?
In 2015, I already had done over a dozen listening rooms in which I improved the acoustics and the more and more orders were coming. So I could invest more in audio. I bought a Velodyne subwoofer with a 10" driver, especially for acoustic measurements. I also replaced capacitors in my Behringer for Nichicon and Elna ones, but they did not improve the sound.

The first reflections – a simulation in Acoustic Lab listening room

On the other hand, the audiophile I mentioned for four years has been persuading me to "solder" something together myself or to buy some "antiquity". I finally listened and bought a DIY DAC for him based on the AD1865 chip - and this was the beginning of my system's never-ending improvement. Thanks to him I replacing individual components in my devices became something normal for me, as I am not an electronics engineer to develop a new device myself. I can only replace components with similar ones but of a better quality, and I am able to evaluate these changes.

In this way chasing the bunny really began: then I purchased the Marz preamplifier (clone of the Marantz 7), then Pass B1. A power amplifier - Chinese, in class D, with an output of 2 x 250 W and above all after three years of listening to the story of Mr. S. who "visited once an audiophile and listened to speakers that made an electrifying impression on him", I bought these 50-years-old loudspeakers. These are large monitors with a 10'' paper woofer and a silk midrange dome. Something like modern ATC SCM 50 speakers, only in a closed cabinet.

| MIROSŁAW ANDREJUK and „High Fidelity” reference system
Or: the sound of Wojtek's system by an acoustics specialist, who's been travelling Poland for nine years, listening to many audiophile systems, finding out their weaknesses and improving their performance.

Text: Mirosław Andrejuk

In 2011 I had a chance to listen to the Harpia Acoustic Marcus and 300B speakers in my room. I remember that Wojtek once had the Harpias and it allowed me to better understand how his system can sound like and what to look for in the future in terms of particular aspects of the sound, and what to pay an attention to. When Wojtek changed the speakers for Harbeth monitors writing that he wanted some warmth in the sound of his system I thought it was strange. I knew Harbeths from auditions at the Audio System showroom and from Audio Shows. Each time they were combined with a low-power tube amplifier, which made the sound sweet, gentle and relaxing. And here they sounded completely different.

The first thing that impressed me was the very dynamic sound with point bass. When needed it appeared out of nowhere and then disappeared almost immediately. Amazing sound speed that can surprise you. Listening loudly, several room resonances arose, but the room shape is quite complex, so the resonances were minimal. For a room with zero bass traps it is exemplary.

Bass, midrange and treble are beautifully sewn together. The overall sound is perfectly neutral, neither warm nor cold. Thanks to this, it is certainly easy to assess the nature of changes in the sound of reviewed devices. Sometimes I personally lacked a bit of warmth in the midrange, depth of the stage and clearer holography that I have in my system. However, the limitations are a small room and distance between speakers.

To sum it up: it is a very versatile system that can play any music genre. Thanks to this listening session I understood how difficult it must have been for Wojtek to configure this audio system. On the one hand, it is to be analytical and transparent to hear all changes and nuances in the sound of the reviewed device plugged into the system, and on the other hand it has to be musical and enjoyable.

Let me add that the stage here is slightly shifted to the right - you can't fool physics. A diffuser would help when placed next to the right loudspeaker in the place of the first reflection, but there is a door to the second room, and - as you know - not everything can be subordinated to audio. ▪

What kind of people approach you?
Various ones. But I noticed that there are a lot of people who tried something earlier, who used some other company's services and it turned out that it didn't sound like it was supposed to. And it's them who as a result of such disappointment often come to me - they are owners of ready-made panels that were simply brought to them and placed against the wall.

So a guy calls you and tells you that he has no treble – what's the next step?
I always ask for photos. They let me see the placement of the system, how big is a room, what's its shape. Some people are reluctant to send photos not to give me a clue regarding a budget they may have for it, which complicates things for me :) I can prepare a room treatment for 10 000 PLN, 40 000 PLN or more. But to do it right we need to have a longer conversation, I need to know more. I need to know a lot about the sound, bass and so on, and what the person is not OK with.

2013 – taking measurements

I usually start by coming to the room and taking measurements. I'm using a Beyerdynamic microphone - it's simple now, because everything can be calibrated using calibration files. I also use FuzzMeasure for Mac. But the most important thing is what you do with the measurements, how do you analyze them and whether you can find defects that you want to fix. And this takes a lot of time.

It is often the case that a person calls me asking for a measurement and is surprised by the amount I give. There are many people who do that for some small price. But then I ask such a person what they actually get for such a low price. It turns out that most often it's just a measurement at the listening position from speakers plus a graph of reverberation time and that's it. I tell them then that they just got what they paid for.

And to get a good understanding of the room you need to make from ten to even fifteen measurements at various points. I take measurements with the help of a subwoofer and a "sphere" with twelve drivers I developed - the point is that the sound propagates in an omnidirectional way. Performing measurements with sound coming only from customer's speakers is simply not enough.

So you take measurements and what then?
Now it is the time to work on measurement results. And only then I get to what customers are most interested in, i.e. what panels they should use. The list usually contains several points - this is the maximum plan. But these are only recommendations, most often it ends with four or five points. It's a pity, because people usually don't know what sort of improvement we're talking about. And that's why I go for measurements I take some panels with me so that they could get a glimpse into what can be achieved in customer's room.

The photos I was talking about help me in assessing what to take with me. If it's a large room, I take more absorbing elements, if it's small, well-furnished, with carpeting on the floor, I take more diffusers. With full adaptation, what I take with me is about 30-40% of what eventually lands in the room. But it's such a big leap in sound quality that it's easier to talk about spending money. Otherwise it's hard to imagine the scale of change.

What can really be done in particular room is a different matter. If it is a living room, obviously there are communication routes, windows, cabinets, etc. These are also visual restrictions, which are easier to deal with today.

So, you've measured the room, the owner has heard 30-40% improvement in room's acoustics, what's next?
I take with me "standard" panels that are part of my measuring system, and - as I said - I believe that each room requires slightly different approach. If the customer likes the panels I bring with me I can always sell them to them – it is their choice. Then I analyse the measurements and present a comprehensive solution to improve the acoustics. We agree on what can and cannot be done and I prepare a quote.

Does it often happen that people who bought some panels later come back for more?
It's just like with audio equipment - when we buy loudspeakers, in a year or two we want to replace them with even better ones. If we really liked the first ones we often go for more expensive model from the same brand. My panels are no different.

There are two types of customers - those who do the full project right from the start and then do not change it, and those who constantly improve something. Usually I see such customers again, two or three times. In such cases, we implement the scenario that I prepared right at the beginning. In addition, awareness of the possibilities increases with the experience – the longer people listen to their system supported but some room treatment the more they appreciate it. In this way people learn what the good sound is, they become more sensitive to a better sound.

White bass trap

Have there been any technical advancements in room treatment recently?
It changes a lot, but mostly in terms of panels finish. There are also more and more companies that produce mass, hence cheap products. There are also those that offer the prettiest things, often rather strange ones. But this is always a compromise. However, it can be done properly - I myself am an example of this. I had these aggressively yellow panels behind my loudspeakers, now I have replaced them with hybrid systems (absorbing and diffusing), which I covered with acoustically transparent fabric printed with the photo of the Grand Canyon.

Are there any new solutions/techniques for calculating panels?
Manfred Schroeder invented 1D and 2D diffuser in the mid-1970s, then fractals came, i.e. diffusers, having smaller diffusers inside. Every few years, new formulas for calculating diffusion panels are created, better optimized, such as those illustrated in the Acoustic Absorbers and Diffusers: Theory, Design and Application by Trevor Cox and Peter D'Antonio.

On the other hand, Frank Sinatra recorded in a studio in 1955, where the absorbent panels were bare wool in a frame, even without upholstery (more HERE). Currently, absorbing panels are also made of wool or foam.

In the industry, international companies are trying to outdo each other in producing more and more sophisticated systems that are a bit absorbing and a little diffusing packed in an interesting form. They are visually attractive, so they can reach a larger group of audiophiles, especially those having their systems in the living rooms. I also offer various visual finishes of the same acoustic panels to make it blend in better with a room.

To wrap it up let me ask you what advice you could give to people who are just beginning to think about room acoustics and have not quite yet got to the decision to call you?
The most common problem of many rooms is an excessive reverberation. For several years now, whether the newly built or renovated apartments often have a living room connected to the kitchen and corridor. People think that since their audio system is in the living room, they need to improve the acoustics of the living room. But one has to actually thing about all these connected spaces as a whole. The sound travels all over the room and returns after some time as a reverb.

If you want to try to hear the difference I suggest a simple experiment – all you need to do is to hang up some blankets, shut the curtains, place some towels all over and see (hear) what's changed. Actually that's how some customers ended up with me - their wife was gone for a few days, and the men hang blankets instead of paintings and found out the sound improved. With more damping everything sounds better. Bringing a rug from other room is another quick solution - the midrange improves. Then it's hard to come back to reality…