REFERENCE LISTENING ROOM PROJECT



THE ROOM



It took me a long time to finish my dream project, a dedicated reference listening room. Investing the time, money and painstaking efforts into the making of a personal ultimate man cave is surely less of blink affair than acquiring something much more eye-catching like a new upmarket car or high-end watch. In the long run at least for yours truly it was a spot-on decision, both personally fulfilling and business-wise. 

One of the Slovenian most recognized master chefs was once asked in the interview, why the competitors are repeatedly coming to taste his preparations. In a half-joking tone, he replied that they do come with their fancy cars, but those machines cannot blend and smooth the tongue delights in the form of his unforgettable and unmistakable sweets and sauces. His investment in upper echelon kitchen accessories was deliberate and something that let him stick out of the crowd. 

I found this analogy most convenient when I'm asked about the need for a dedicated listening space to my colleagues or readers. And the question pop-up more frequent that one would imagine. 

Of course, there is no such thing as a perfect solution. The point is to work with what is essential and realistically possible. This includes the space, time, funds and nonetheless a one's will to enter into the uncharted territories.

My adventure began with the renovation of my grandfather's house. The first plan was to keep the most of the old walls intact and just rebuilt the new house on top of this foundation. 

Well... As many of us learned over the years, the construction work rarely goes as planned...

The nearby road was rebuild at the same time as the initial construction took part and the heavy compressors' tremors have shaken the foundation so much that all the walls crackled. I had to tear everything apart and start from scratch. As it turned out this was a "happy accident", but one that required way more time and funds to complete from what I've planned to. 

Past 25+ years I've traveled intensively and had the luxury to experience music in various listening rooms, venues, professional studios, and interesting sonic chambers. I've been always inspired by the acoustics of small, historic Italian venues, where acoustics provided one of the kind experience. 

I've dug deeper and went through numerous white papers, writings, essays and talked with many acousticians and owners of the studios, state of the art dedicated listening rooms.  When I've finally connected the dots I've distinguish a particularly and common trait. It turned out that it was something that has intrigued and interested me from childhood; the Golden ratio/Fibonacci sequence. 

Most of the acoustic spaces that left a profound and lingering impression on me were considerably or entirely based on this specific math. From that the ground zero all of the measures and applicable room size calculations were based on the Golden ratio. 

According to what I've could work with the room size was finalized with the following measures: 5.4 m (wide) 8.2 m (length) 3.16 m (height).

All the walls are made of brick wall construction with special acoustic plaster overlay. I've almost gone with full concrete walls, but at the final check-up of the project, two or three similar undertakings (one at the audio manufacturer) were designed in this way. The result was (using their words) horrific and one of the clients who committed to such a plan decided to tear down the listening space entirely as with was unbearable to deal with the lower register, mid and upper-bass frequencies booming and wobbliness.  

So I've stopped for a while and prolonged my research. I've also hired professionals from various fields of acoustics and they all proposed the clay red bricks as the final material for the walls. Bricks act as semi absorbers for the lower frequencies and some of the spaces I was most impressed with (what I've discovered almost a bit too late) were entirely made with them. A personal point taken about asking too many questions. I've asked too little...

I wanted the absolute left and right room mirroring with perfectly identical side arrangement. The first idea was the acoustical curtains that were moveable along the complete 8.2 wall length. And for a while, this was a practical and workable solution.

All the walls in the room are already covered by the special plaster compound that involves lately discovered sound-absorbing paint. This solution doesn't solve all the reflections issues, but it does work to a certain extend. So once I've spent prolonged time with different top tier speakers, I've started to experiment. First by moving the speakers around the room, then by moving and at last removing the acoustical curtains.

The main Kaiser Acoustics Spline diffusors (120 cm x 120 cm) were moved at the middle of the walls and the reflection points where the echo was heard and measured were covered either with two graphics/paintings and with the two pairs (black/white) PYT Audio SMAD Reference panels. 

Paintings serve as an absorber with the special acoustic compound behind the graphics. The second echo points, closer to the back wall are occupied by four PYT Audio SMAD Reference panels. As stated above, the main side walls energy congestion and partially room modes are handled by a pair of Kaiser Acoustics Spline diffusors. 

The main, back wall is covered with a large RD Acoustics Hybrid circle pattern absorption Acoustic Diffuser (3 x 2 m). Below the Hybrid diffuser (foam/wood) there are twelve PYT Audio SMAD Reference panels. The left and right critical corners are damped with ten large highly concentrated acoustic foam bass traps, where the front side is covered partially with the wooden inlays. 

Over a few occasions with Dr. Roland Gauder from Gauder Akustik, in our talks, he was very evocative about the ceiling and the floor utterly importance, how these two are far too often overlooked, and how priorities are given to everything else.

So again, I did my homework, talked with professionals and we did the calculations and researched the proper materials.  

I've ended up with a perforated ceiling that acts as a broadband absorber/diffuser with multiple zone sandwich construction. The sandwich consists of different layers of special, lately introduced acoustical foam, air compartments, wood and a triangle-shaped attic space filled with 45cm of fiberglass insulation. 

The floor is a bit different affair. Here the theories and practical implementations clash. At least what I've learned and what it was strongly advised from multiple sources was the absence of soft materials and floating grounds. 

For my room I've chosen the 30 cm solid concrete floor with dedicated 15 cm subfloor acoustic plaster (mixed with concrete) overlay, that is covered with one piece acoustical carpet. 

What is perhaps unusual about the floor is a hidden star-shaped copper wire grounding scheme. This is quite large and based on the mix of esoteric and actual science. Additionally, I've also installed a massive copper rod outside of the house. It is buried in the earth as advised by professionals. I'm still exploring the potential of both and this is reserved for the future. Presently I'm using Nordost QKore 6 grounding unit connected to various Nordost full grounding cables loom. Four Entreq Olympus ground boxes along with single Entreq Olympus Ten ground box and cable Entreq full ground cable loom are also in place.

Technically inclined would want to know at least the basic acoustic measurements and facts. The reference room has 0.47s average RT60 time and the room noise floor is around 27dB. Yes, 27dB! You can literally hear your thoughts as my wife loves to put it :). This allows me to truly hear and discern all of the subtle details that are crucial at the evaluations. Of course, the quietness is important with testing any kind of product, but it's really an asset with the examination of the upper echelon products, where the differences can sometimes be very subtle. 

To achieve this sound sealing I've only used two special sound glass (soundproof) seven-layer windows (RI - RW = 35 dB) that are both placed at the golden ratio calculated position. In front of them, there is a single SMT Wing transparent diffusor that adds to the taming of unwanted reflections and energy bursting.

The rest of the room I wanted to keep windowless to avoid the problems associated with the glass reflections but wanted as much as possible daylight in the room. Luckily the positioning allows the sun to show appear in the morning at the left side and show up in the evening on the right side. This ensures an enormous light source and I don't have to use any artificial lighting until its dark. For my kind of work that blends listening, photographing and writing it's essential and inspiring. 

The back wall host the massive custom soundproof/sound trap door (RI - RW = 45 dB) that partially act as a bass absorber. Sort of a quasi bass black hole. On top of the door, there are three PYT Audio SMAD Reference panels at the reflection point. 

According to the room size and the speed of the sound, the room modes are mostly congested at 31.76 Hz - B0, 66.44 Hz - C2, 126.06 Hz - B2. These are dealt with proportionally.

You can check the complete reference listening system here.•

Matej Isak