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Building a Listening Room

Building a Listening Room

Building a dedicated space for music listening is the ultimate commitment to the hobby. It’s expensive and complex, and when you’re finished there’s no guarantee that the room will sound good. But if you take that plunge and the stars align, a room specifically designed for optimizing sound quality can allow a high-end system to realize its greatest potential.

I recently realized a lifelong goal of building a serious listening room and will share my experience with you. Although I had built two homes before with dedicated rooms, this one is more ambitious. In addition to creating an optimized platform for evaluating some of the world’s finest audio equipment, the new room is also designed around the requirements of my job. I’ve been reviewing high-end audio equipment for 30 years, and for 30 years I’ve hauled big and heavy gear through the front door of a house. To avoid damage to the new house (and preserve domestic tranquility), the listening room has a secondary door that opens to a third-car garage with no step. (The room’s main door opens to a hallway in the house.) The third-car garage is a staging area for gear coming and going, as well as facility for box storage—a surprisingly important consideration for reviewers. In addition, the room is acoustically isolated from the rest of the house, saving my wife from being subjected to my musical tastes (which admittedly aren’t for everyone). I wanted to be able to listen to any music, at any hour of the day, at any listening level. This is our last house, and I wanted to get all the details right.

Before telling you about the room’s design and construction, I’d like to state that a dedicated room is most certainly not a prerequisite to musical enjoyment. My description of the room’s AC power a few issues ago prompted more than one reader to accuse me of elitism (“That was the most elitist bunch of crap I’ve ever read. A study in one-upsmanship par excellence.” See Letters, Issues 283 and 286). The letter writers believed that optimizing the AC power to an audio system is symptomatic of audiophile overkill, and of turning an audio system into nothing more than an object of status.

Elitism actually has nothing to do with it. The pursuit of fidelity in music reproduction has been a lifelong endeavor for me, ever since my brother Stephen introduced me to the joy of music at the age of 12. I’ve worked in audio all my life, from selling stereos to put myself through college (degree in Recording Engineering), recording studio owner and recording engineer, college teacher (recording engineering), CD mastering engineer, and audio writer for the past 30 years. Building a serious room—one in which I will enjoy music for the rest of my days—is a logical and natural extension of everything I’ve done in my life. Moreover, a good-sounding room is a great boon to my work—it is a platform for evaluating products that is commensurate in quality with the products themselves. My goal for this article isn’t “one-upsmanship” but rather to share with readers my experience and the techniques in the hope that they will benefit others who are considering building their own listening rooms.

Planning the Room: Size and Dimensional Ratio
The first step in any room design is choosing the room’s size and dimensional ratios—the ratio of the length to the width to the height. This ratio has a very large effect on the room’s sound, particularly in the bass. Good room ratios spread out the room’s resonant modes more evenly, resulting in smoother and more linear bottom octaves. Explaining the importance of room ratios is beyond the scope of this article (The Complete Guide to High-End Audio’s chapter on room acoustics breaks it down), but know that the length-to-width-to-height ratio is the crucial starting point.

Fortunately, acoustic-design consultant John Brant has created an excellent tool on his website (jhbrandt.net) for evaluating room dimensions. The free downloadable spreadsheet performs a detailed acoustical analysis on any set of ratios that you enter. The tool plots all the resonance modes graphically, shows you if the resonance distribution meets the “Bonello Criterion,” and suggests ideal ratios, among other analyses. In addition to the dimensional-ratio spreadsheet, the site includes many other valuable resources for room design. Art Noxon, founder of Acoustic Sciences Corporation, inventor of the famous Tube Trap, and consultant on my room explains room ratios in the sidebar accompanying this article.

In practice, the listening room’s dimensions are also influenced by real-world considerations such as the amount of real estate you’re prepared to commit to the room and how the room fits into the floorplan of the rest of the house. It’s easy to forget that the listening room is just one part of a house and must integrate with the rest of that house in many ways. Keep in mind that good room ratios span a spectrum in which you’ll get good sound. Generally, the larger the room the better the sound (assuming good dimensional ratios); a large room spreads out the resonance modes more smoothly than a small room does, resulting in flatter bass. My room is 27′ long and 17′ wide, and the ceiling is 11′ tall. After living with the finished room for about three months at the time of this writing, I’m very happy with the size and feel of the space.

Once you’ve decided on the room’s dimensions, the next consideration is the room’s wall construction. There’s a wide spectrum of framing and construction techniques that improve the room’s sound quality as well keep sound in the listening room from getting into the rest of the house. You must decide how important this sound-proofing is to domestic harmony, and then choose the wall-construction technique that fits your budget and needs. I’ll share with you just a few examples of the vast range of wall constructions. But first you should know that a wall’s “transmission loss” (reduction in sound amplitude from one side of the wall to the other) is specified as an STC (“sound transmission class”) rating. The higher the number the greater the wall’s attenuation of sound. A standard 2×4 wood-framed wall (16″ on-center) filled with insulation and with 1/2″ gypsum board (drywall) on both sides is specified as STC-35—not a very high value. With music playing at a moderate level inside this room, standing just outside the room you would be able to clearly hear and identify the music. The next step up is to use 2×6 plate with 2×4 studs that are staggered. This costs next to nothing, but increases the STC rating. For a nominal additional cost you can use 5/8″ Type X Sheetrock on the wall outside the listening room and gain a few dB of additional transmission loss. Acoustic supply houses sell gypsum board composed of two layers of gypsum separated by a viscoelastic polymer (SoundBreak XP from National Gypsum, for example) that blocks more sound than does conventional drywall. You can also hang vinyl material inside the wall for even greater isolation. Double drywall adds to the transmission loss. I’ve mentioned this small sample of materials and techniques to illustrate that you can dial-in the amount of isolation you need, and balance it against your budget, with great precision. The gypsum board manufacturers (USG and National Gypsum, for examples) publish a wealth of useful information about the various wall-construction techniques and their sound-blocking performances. As Art Noxon explains in the sidebar, however, soundproofing and optimizing audio quality inside the listening room is more complex than simple soundproofing. The wall inside the listening room should be treated very differently from the wall outside the listening room, as we’ll see.

One of the problems of frame construction is that bass energy from inside the listening room puts the wooden-frame-and-drywall structure into motion—a bass impact, for example, makes the wall move. That wall motion, unfortunately, converts the stored mechanical energy in the wall back into sound after the transient is over (Fig. 1). Art Noxon has called this phenomenon “wall shudder.” Wall shudder colors the bass tonally because the walls will vibrate at their natural resonant frequencies, adding energy at that frequency. Moreover, the wall movement is chaotic. It doesn’t take much wall motion to hear tonal coloration because the acoustic output of a vibrating object is a function of the object’s excursion (how far it moves) and its surface area. With a large surface area such as a wall, even a very small excursion can produce an acoustic output.

Wall shudder also distorts music’s dynamics. Some of the transient’s acoustic energy is turned into structural resonance of the wall, diminishing the transient’s attack and thus the sense of suddenness and dynamic life. Then, as the wall releases that energy over time, the transient’s decay is smeared. The result is a distortion of an instrument’s dynamic envelope and thus a diminution of music’s dynamic expression. Moreover, wall shudder masks the delicate spatial cues that our brains need to form the sense of a fully developed soundstage, the space within it, and the impression of bloom and air around instrumental outlines. All these subtle forms of distortion add up and contribute to a hi-fi system sounding like a facsimile rather than like the real thing.

Another way in which listening rooms color the sound is familiar to anyone who has set up a full-range speaker: tubby and lumpy bass. The listening room selectively reinforces some frequencies and cancels others, with the frequencies reinforced and canceled determined by the room’s dimensions and the speakers’ and listener’s positions. This is one reason why some sort of bass trap is essential in every room.

To summarize, the three primary problems inherent in music-listening rooms are: 1) sound leaking from the music room into the rest of the house; 2) wall shudder; and 3) excess bass that requires bass traps in the listening room.

After evaluating the possible construction techniques for my room I chose one that simultaneously solves all three of these problems. This technique was developed about 25 years ago by Art Noxon and has been used successfully in many listening rooms and recording studios around the world. Called the ASC Iso-Wall System, it is a building method that achieves excellent isolation of the listening room (sound proofing), nearly eliminates wall shudder, and absorbs excess bass. It’s remarkable that Iso-Wall addresses these three major problems with a single construction technique.

Before describing ASC Iso-Wall, I’ll tell you about the listening room’s wall construction. The listening room adjoins the house on just two walls and only partially on one of those walls (the third wall adjoins the garage, the fourth the outside perimeter). The walls adjoining the hallway and garage are framed 2×6. The wall that partially adjoins the kitchen and dining room is a double 2×6 wall with an unbridged air cavity. This wall construction is more effective in reducing the transmission of sound, but is expensive and consumes some of the room’s real estate. I used it on this wall because it happened to work out with the rest of the floorplan. The ceiling height of the rooms surrounding the listening room is either 10′ or 9′, lower than the listening room’s 11′ height. This is advantageous because the surrounding rooms’ ceiling framing helps to reinforce the listening room walls and give them greater structural rigidity. In addition, one of the room’s long walls is connected to a perpendicular outer wall, adding stiffness.

In designing an Iso-Wall installation for my room, Art Noxon specified an elaborate framing structure that would further reinforce the external side of the listening room walls. It involved screwing and gluing, rather than nailing, the wall structure together. The plan included other non-standard and labor-intensive framing techniques. Unfortunately, this special framing was outside my budget. (Builders and subcontractors don’t like to do things that are outside the ordinary, and quote very high prices to discourage custom work.) Still, if you have the budget, the glued and screwed walls, along with the upgraded framing structure, should strengthen the walls and transmit less bass, as well as making the walls less prone to vibration.

I did, however, adhere to Art Noxon’s specification that I damp the 2×6 studs by attaching strips of 5″-wide and 1/2″-thick plywood to the side of each stud, with two strips of ASC’s WallDamp, a self-adhesive viscoelastic damping material (Fig. 2), between the stud and the plywood over nearly the entire stud length. I went to my local Lowe’s and loaded up a lumber cart with sheets of plywood and wheeled it to the lumber-cutting area. The lumber-cutting guy wasn’t enthusiastic about the prospect of making 80 cuts in ten 4′ by 8′ plywood sheets. But it turned out he was interested in audio, and after discovering the purpose of my odd request, fed the sheets through the saw while I stacked the strips (I was prepared and brought hearing protection).

Back at the raw-framed listening room, I conducted an experiment to understand the effect of the stud dampers. I hit an undamped stud with a hammer and listened to the ring. Then I repeated the hammer strikes after installing the stud damper. The undamped stud rang for a long time; the damped stud produced a dull and short-lived thud. The difference was so dramatic that I recorded the experiment on my phone. Many weeks later, just before the drywall went up, I applied strips of ASC WallDamp viscoelastic material on the stud edges that face the house side of the wall for additional wall damping (Fig. 3).

After the insulation had been blown into the walls, I started the Iso-Wall installation in earnest. You can see an overview of the entire Iso-Wall structure in Figs. 4 and 5. The first step is to attach with construction adhesive and a few small nails a “perimeter gasket” to all the wall and ceiling edges—on the upper and lower stud plates along the ceiling and floor lines, on the stud edges where the walls meet, and around window and door frames. The perimeter gasket will support the entire edge of the drywall wall. Next, a strip of self-adhesive “wall-bearing felt” is attached to the floor where the floor meets the walls. You can see the black perimeter gasket and white wall-bearing felt in Fig. 6 (and in some of the subsequent photos).

Once the gasket and felt are installed you’re ready to attach ASC dRC-1 resilient channel to the studs and ceiling joists. Resilient channel is a “Z”-shaped strip of somewhat flexible metal that acts as a spring between the framing and the drywall. The resilient channel is attached to the studs, and the drywall to the resilient channel. Conventional resilient channel is commonly used between adjacent condos and apartments where STC-45 sound isolation is part of the building code. ASC has taken the resilient-channel concept to a much higher level, modifying a conventional resilient channel by facing it with ASC’s WallDamp viscoelastic material. The channel is laid out in horizontal strips across the studs and screwed to each stud it crosses. A small rectangle of WallDamp viscoelastic material (called a StudPad) is located between each stud and the dRC-1 channel to help damp vibration transfer (Fig. 7). The dRC-1 channel forms a spring bed for the drywall. The ceiling is treated the same way, but with a slightly different resilient channel (ASC’s dRC-2) and closer spacing between the channels.

The release paper on the WallDamp strips along the resilient channel is removed and panel adhesive applied to the face of the perimeter gasket. The first layer of drywall is laid up vertically and screwed to the channel’s wide face. The drywall is thus affixed to the channel rather than to the studs. The channel’s springiness “floats” the drywall on the channel, reducing the energy transmitted from drywall motion to the framed walls and ceiling. It is essential that every drywall screw goes into the channel and not into a stud—an errant screw that penetrates the stud will “short out” the structure and reduce its effectiveness. Chalk lines snapped on the drywall are essential to avoiding this problem. Fig. 8 shows my room with the channels installed. You can also see the perimeter gasket (black strips along edges and around the door) and the wall-bearing felt (the white strip along the floor at the wall).

The next step is to apply WallDamp Strips (1.5″ by 48″ by 1/16″ thick) along the perimeter edges of each plane of drywall, around the wall perimeters, door and window openings, and over the vertical drywall seams. Then WallDamp Squares (4″ by 4″) are applied to the drywall face 12″ on center (Fig. 9). Remember that the WallDamp Strips and WallDamp Squares are self-adhesive, requiring that you remove a release paper on both sides of the strips and squares. It’s a job in itself to clean up the backing paper from these strips, squares, and rectangles, but it has to be done or you’ll end up with a floor literally covered in it.

You’re now ready for the second and final layer of drywall, which is also installed vertically and with its seams offset from those of the first layer. Again, the drywall is screwed through the two drywall layers into the resilient channel, making sure that no screws penetrate the studs. The drywall is thus rigidly attached to the wood-framed wall only along the wall edges where it meets the perimeter gasket. The central area of each wall essentially “floats” on the flexible resilient channel rather than being rigidly affixed to the studs.

Finally, you seal all the drywall joints and corners, and around electrical boxes, light fixtures, door jambs—anywhere there’s not a tight seal. I went through 17 tubes of oversized (29-ounce) acoustical caulk. Don’t scrimp on the caulk; tiny gaps can allow a surprising amount of sound through, a phenomenon called “flanking.”

Although I installed the Iso-Wall system myself (except for hanging the drywall) it was a much bigger job than I anticipated. Attaching the resilient channel to the ceiling is particularly challenging for one person. If you hire out the work, I recommend that you be on-site at all times to make sure that the contractor is precisely following ASC’s installation procedures. A drywall contractor with experience installing resilient channel is recommended, but you still must monitor the process closely. Incidentally, you can download a PDF of the Iso-Wall installation guide from ASC’s website.

The resulting wall structure—viscoelastic damping sandwiched between two drywall layers—forms a classic constrained-layer damping system. Constrained-layer damping is widely used in many industries and is a science unto itself. When the wall is flexed by the acoustic pressure of low-frequency sound inside the room, sheer forces in the viscoelastic layer dissipate that energy as a minute amount of heat in the viscoelastic material. Remember that the resilient channel allows the interior surfaces of the listening room to bend but not vibrate, which is a key element in a constrained-layer damping system. The walls and ceiling are turned into giant diaphragmatic bass absorbers. Moreover, the energy dissipated in the viscoelastic damping is energy that’s not putting the walls into structural resonance. The framed structure is rendered quiet and inert.

A small tweak is to specify different densities of drywall for the two layers. One layer of standard drywall and one layer of moisture-resistant drywall will do the trick. The idea is that the different wallboard densities will exhibit different resonant characteristics, and thus distribute the resonant energy that remains over a wider band but at a lower amplitude.

The Iso-Wall construction technique solves the three main problems with listening rooms: 1) it greatly reduces wall shudder; 2) prevents sound inside the listening room from getting out; and 3) absorbs excess bass energy by virtue of the flexible walls, turning them into giant membrane bass traps.

Between the stud dampers, the damping rectangles between the resilient channel and the studs, the damping material on the channel, and the damping between the layers of sheetrock, there are several hundred pounds of ASC WallDamp viscoelastic material built into the room. The goal is to make the room as inert as possible, reducing the amount of wall resonance and shortening the decay time of the resonances that remain. When you think of the extraordinary effort that some loudspeaker designers put into creating inert and well-damped speaker enclosures, it makes sense that one would want similar performance from the structure in which the loudspeaker is operating.

To realize the room’s full isolation (sound-proofing) potential, the door between the listening room and house must be carefully considered. At a minimum you should use a solid-core door with a door-seal kit such as ASC’s DoorKit. For greater isolation, consider installing a full-on studio isolation door. The specialized acoustic door I chose (the Studio 3D from Acoustical Surfaces) weighs 300 pounds, is 2 1/4″ thick, has a robust three-point latch system, and cost about $4000. It has an STC rating of STC-56. As massive as this door is (it feels like opening and closing a bank vault), it’s still the weak spot in the room’s isolation. To achieve full soundproofing (such as would be required in a recording studio in Manhattan) a double-door structure is required. Nonetheless, in my application the door is highly effective and in practice works as intended.

Incidentally, because I have two doors going into the listening room (the 300-pound isolation door to the house and a standard solid-core door to the garage) I was able to compare the sound-proofing effectiveness of the two doors. The solid-core door performed much better than I thought it would, attenuating the sound quite well. But it was no match for the acoustic isolation door. When standing in the hallway in front of the door with music playing at a high level in the listening room, you can detect that music is playing on the other side but it’s not nearly loud enough to disturb anyone. Move a few feet away from the door and the sound is barely detectible. Mission accomplished.

The materials cost for my room was about $13,500—$8500 for the ASC Iso-Wall products (ASC supplies a kit with the appropriate amount of dRC-1 and dRC-2 resilient channel, WallDamp strips, squares, and StudPacks, perimeter gasket, and wall-bearing felt,), $4000 for the isolation door, and $1000 for plywood stud dampers, screws, acoustic caulk, and miscellaneous supplies. That’s on top of the cost of the additional layer of drywall. At the next level, Art Noxon will design a custom ASC Iso-Wall System for your room for a consulting fee. He will also specify all the surface acoustic treatments for the interior of the room once the Iso-Wall has been installed.

The finished and painted room looks just like any other room in the house—the acoustic infrastructure is completely invisible behind the drywall. The room is now ready for surface treatments. I treated the inside walls with the Acoustic Geometry Pro Room Pack 10 that I had been using successfully in my temporary rental house (see my review in Issue 291).

AC Power
The AC power to a listening room has a greater effect on sound quality than one would expect. I followed the guidance of Shunyata Research founder Caelin Gabriel in specifying my room’s power. Although one can spend an enormous sum on a custom AC-power system, I employed a few simple and inexpensive techniques that Caelin Gabriel has found to be effective. I had a good head start on the AC power; my home’s power is supplied from its own transformer at the street. I have rooftop photovoltaic solar panels but have no idea whether this confers any sound-quality benefits.

AC power to the listening room is supplied by a separate sub-panel located right outside the listening room. The room’s five dedicated 20-amp AC outlets for the audio system are wired with identical lengths of 10AWG on the same phase. Thinner 12AWG wire is standard, but don’t let the electrician scoff at the need for 10AWG and talk you into the easier-to-manage 12AWG. The thinner wire will limit instantaneous current delivery to the power amplifiers. Identical lengths ensure that each component in the audio system sees the same ground potential. I specified five dedicated lines for equipment-placement flexibility. In practice, I need only three: one for each power amplifier and a third for the front-end components. During the build, cable manufacturer Audience sent me a small sample of its new in-wall AC cable, but it was too large in diameter to fit through the conduit that the electrician had already installed. I had used Audience’s earlier generation of in-wall AC cable in another house with excellent results.

The five dedicated lines terminate in floor plugs. The electrician wasn’t able to install the audio-optimized AC outlets (the same ones in Shunyata’s AC power conditioners) because the slightly oversized Shunyata outlets didn’t fit in the rings he had installed in the floor. Consequently, the electrician installed the stock AC outlets so that we could pass the electrical inspection. (The electrician and project foreman both thought the AC power requirements were bizarre and unnecessary—not to mention their opinion of the Iso-Wall construction.) Although I was disappointed at the time, the situation turned into a valuable learning experience. Two weeks after moving in I got the reference system up and running (see sidebar). I spent the next eight weeks listening to the system powered by the stock outlets. I then got another electrician to modify the existing floor-plug rings to accept the Shunyata AC outlets. I was thus able to listen to the effect of the custom AC outlet independently of any other variables. I was beyond shocked by what I heard. In my previous house I had compared dedicated AC lines and custom outlets to stock AC with stock outlets, but never to just the outlets themselves. After replacing the stock outlets with Shunyata outlets in the new room, the bass was fuller and deeper, textures were more densely rendered, dynamics wider, and the sense of individual objects existing in space was heightened. Replacing your AC outlets is a relatively inexpensive upgrade (see Neil Gader’s review of the Furutech GTX-DR NCF AC outlets in Issue 291).

By one standard, this room’s design and construction are expensive and elaborate. But it is by no means the state of the art. One can spend a lot more money on a room’s construction and AC power. For example, Magico founder Alon Wolf spent $250,000 building the factory’s listening room (it looks and sounds magnificent). I know people who have spent on their AC ground more than I spent on my entire room—it involved, in part, a copper ground rod buried in an electrolytic slurry of precise chemical composition that must be constantly kept moist. One can spend seven figures building a listening room. Wonder what a multimillion-dollar room looks like? Go to keithyates.com to see what’s possible at the state of the art.

I chose a construction technique that I thought would give me the best performance for my budget. Unfortunately, building a listening room as part of a house entails financial demands from the room simultaneously with the substantial financial demands of building an entire house. During the many long hours working on the listening room, alone with my thoughts, I wondered if what I was doing was worth the expense and effort. Did I go far enough? Did I go too far? What details had I overlooked? Would the room sound any better than a conventional room? I know several audiophiles who have built expensive dedicated rooms that sounded awful. Until you set up a pair of speakers in the room and listen, there’s no way to know how the room will sound.

So, Was It Worth It?
It was thus with great anticipation that I listened to the first music in the new room. I brought to the house the system I’d been living with in the temporary space—Piega C711 speakers, First Watt F7 amplifier, Berkeley Alpha DAC Reference Series2 MQA, Aurender W20, Berkeley Alpha USB, Wireworld cable. It took only a few seconds into the first track to hear that this same system sounded dramatically better in the new room. It was a wholesale transformation, not a matter of minor improvements in a few areas. The sound had a solidity in the bass, a sense of effortlessness on dynamics, and an expression of music’s rhythmic flow that I had not heard before from this equipment. There was a quiet between the notes that heightened the impression of realism.

But it was only after living with the reference system (see sidebar) and its much deeper bass extension and wider dynamic scale that I came to fully appreciate the room’s contribution (or more precisely, lack of contribution) to the sound. For starters, bass in the new room is extremely linear, smooth, and highly resolved in pitch and dynamics. The Wilson Benesch Eminence loudspeaker has extraordinary bass articulation on its own, but I could hear that the room was allowing this speaker to reveal nuances of texture, dynamic shadings, and pitch that I’d never heard before on familiar recordings. Every new LP or digital file was like a voyage of discovery, hearing detail in bass lines that had previously been blurred—the individual notes had been relatively undifferentiated in timbre and pitch.

Kick drum, the rhythmic foundation of much music, had a solidity and dynamic impact that were startling. Instead of the kick drum sounding like a low-frequency thump, the system conveyed details about the mechanism by which its sound was created, including the beater hitting the drum head and the resonant ring of the drum. I could hear fine detail in the lowermost octaves. Moreover, the sound of kick drums varied more from recording to recording than I’ve heard before, suggesting that their “sameness” I’ve experienced in the past was the room’s sonic signature imposed over the drum’s sound.

I could use just about any piece of music to illustrate this precise sense of pitch, bass articulation, and dynamic agility, but I’ll choose one that many of you are undoubtedly familiar with and one in which the sonic improvement rendered a large difference in musical perception: “Diamonds on the Soles of Her Shoes” from Paul Simon’s Graceland. The track starts with just the gorgeous vocal harmonies spread out across the soundstage, then the lone guitar, and then the drums (a couple of pick-up beats on low-tuned toms) come in followed immediately by the remarkable fretless bass guitar playing of Bakithi Kumalo. I’ve heard this track on many systems, but never one like this. The suddenness of the drums was startling, and the fluid bass playing pulsated with energy, vitality, and the joy of music-making. This sense of life continued throughout the song, anchored by the tight kick drum and Kumalo’s extraordinary inventiveness in playing his instrument. It was absolutely sensational and thrilling. This precision in the bottom end was apparent on just about any music, and proved a defining quality of the new room.

Several years ago when reviewing a speaker with heroic cabinet construction, I used the term “self noise” to describe how the speaker didn’t seem to add a low-level “chatter” or chaotic noise to the music. The speaker had a spooky sense of realism, with instruments appearing seemingly out of nowhere with startling immediacy. The speaker also resolved very low-level textural and spatial cues that were lost by most loudspeakers. As a result, the sound had a delicacy and density of information that accurately conveyed instrumental timbre, while also vividly portraying the size of the recorded acoustic and the spatial perspectives between instruments and between the ensemble and the surrounding hall. I’m hearing those qualities in the new room, and I speculate that it’s because the Iso-Wall structure is doing for the listening room what the inert speaker cabinet did for the loudspeaker—reduce the low-level chaotic motion that imposes a threshold below which information cannot be resolved.

Hi-fi systems have always seemed to me to change their character on loud peaks, or when the music is played loudly. On the peaks the sound congeals; individual instrumental textures tend to be smeared into a single big sound; and the sense of space collapses. The sound on peaks becomes less liquid and more mechanical, the music losing the pristine clarity the system is capable of delivering during quieter passages or at lower volume. I had always assumed that this was simply part and parcel of reproduced music—a characteristic of amplifiers being pushed, or the mechanical structures in loudspeakers reaching their limits. We’ve all had the experience of bracing ourselves, or tightening up, anticipating a loud passage on a familiar poor recording that is shrill or distorted. I think that we tend to do that on a micro scale on any recording simply because of these expectations. But hearing the system in the new room made me realize that much of this congealing of the sound on musical peaks is the room distorting, not the speakers or amplifiers. After the bass clarity and dynamic fidelity, the next most dramatic and musically significant aspect of the room’s performance is the absence of this phenomenon. High-level peaks maintain the same clarity, resolution, and timbral quality of the lower-level signals. I had the feeling that an artificial limit had been lifted from the music, allowing its full dynamic expression. Moreover, peaks had a sense of ease and effortlessness that encouraged higher playback levels and simultaneously greater relaxation and involvement. And so I can play the system louder and still maintain the sense of ease and clarity of individual musical lines.

After discovering the importance of the listening room’s contribution to sound quality, I consider it another component in the signal path and will list the ASC Iso-Wall System as part of my reference system in future reviews.

In Retrospect
Needless to say, I’m beyond thrilled with the new listening room. It has exceeded expectations in every way and, indeed, has been revelatory. In relation to the expense of building the house, the cost of the Iso-Wall and studio isolation door ($13,500) was incremental. Even if you hire out the Iso-Wall installation the cost is still reasonable when viewed in context of the price of today’s high-end systems. If you have the chance to build a house, the cost of ASC’s Iso-Wall is without question the best allocation of your audio budget.

What would I have done differently? Given the enormous sonic improvements I heard, I can imagine that the glued-and-screwed walls and elaborate framing structure Art Noxon specified would have elevated the sound quality to another level. I also would have hired someone to help me with the installation; it’s a huge amount of work for one person, particularly one whose day job is largely sitting at a computer. But overall, it was well worth the research, time, effort, and expense. It was also a great learning experience. Building the room was a small price to pay for realizing a place specifically tailored to reviewing and enjoying music with wonderful fidelity for the rest of my days.

The Reference System

The first system in the new room is a combination of products that will be long-term reference components in addition to short-term review samples. Watch for upcoming reviews. Here’s the rundown:

Digital sources: Aurender W20 server, Berkeley Alpha Reference Series2 MQA DAC, Berkeley Alpha USB interface, Audience Au24 USB cable, AudioQuest Wild Digital AES/EBU
Analog sources: Basis Audio Transcendence turntable with SuperArm 12.5, Air Tight Opus cartridge, Moon 810LP phono- stage
Electronics: Constellation Altair II preamplifier, Hercules II power amplifiers
AC power: Shunyata Research Hydra and Triton, Sigma AC cords
Cables: Shunyata Research Sigma (balanced)
Equipment racks and amplifier stands: Critical Mass Systems Olympus, CenterStage2 isolation
Surface acoustic treatments: Acoustic Geometry Pro Room Pack 12

By Robert Harley

My older brother Stephen introduced me to music when I was about 12 years old. Stephen was a prodigious musical talent (he went on to get a degree in Composition) who generously shared his records and passion for music with his little brother.

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