Music Rooms

I get the privilege of going into many rooms and environments that are devoted to sound play back or recording. Anyway you look at it it is a room dedicated to sound and the reproduction or recording of it. I have been in both types recently and I am glad to report that the passion that drove all of us to this business is still alive and kinda well.

Larger Studios

Those of my clients and friends who run larger studios are struggling to try and keep their rooms full of expensive equipment full of engineers using it. They are struggling with lowering their rates to attract more business or keeping their position in the marketplace by keeping their rates in line or ahead of studios that offer less. All of this business stress drains the life out of their appreciation for the music. It is very sad to see.

Small Project Studios

My friends and clients that have smaller studios are divided into two groups. There are those that are extremely busy and there are those that are not busy at all. The busy ones seem to be doing a little bit of everything and everyone is busy. They are using their rooms a lot, so they become more aware of all the acoustical issues that they don’t like and have been living with.

Busy Bees

Since they are busy, they have the cash flow to now address the acoustical issues in their rooms. There are really two main areas that need treatment in the smaller studios and the first one that everyone has in common is low frequency issues. Everyone hears low frequency resonances in a certain room position at a certain frequency. They need special high performing sound sponges in these areas. They have to be small and powerful because space is at a premium in small studios.

Reflections/Reverb Times

Reflections and high or higher reverberation times are also an issue. Numerous reflections from their wall surfaces are becoming more noticeable even if they are already treated with some type of room acoustic treatment. Not only is the reflection from the side wall becoming interfering with the direct sound from their monitors because they realize that they do not have the proper amount of absorption for the pressure levels that they listen at.

Reverberation Times

Small project studio owners are not happy with their overall reverberation times in most of their rooms, period. Most notice and comment on the room still being “too hot” after they have treated it when the room was built. I recently added new foam to a 35 year old vocal room that has been in use all that time for vocals and voice overs. The new breed of voice overs seem to want more absorption in the male and female vocal ranges.

Music First

With all of this activity in the rooms and the desire to make acoustical changes, the music for a brief time gets to be first again. People are excited about improving their sound quality in their rooms and everyone is on the same page of music. It is amazing to me that when the music is first, everything seems to move more easily and when the room sound improves the music benefits.

Hi-Fi Passion

I am also seeing something occur that I have really never seen before. I am seeing long time, hi-fi, two channel, listeners willing to make structural changes to their room to improve the quality of their systems. I mean serious structural changes like building new walls and removing others, even within a living room. I have two clients right now who fit into that category.

Audio/Video

Both have their systems set up in the main living room of their homes. One system is audio and video with a large flat panel hanging on the wall between the left and right channels. The second client has an audio only two channel system set up. His video screen is in the other room. No mixing of technologies for this client. This is an audio only room. Make no mistake about that.

Side Walls First

We will be building new side walls on both systems, so that side wall composition and distances are equal for primary reflection management at the listening position. One must have the same distance for both channels and it is a good idea to have the same material density for each side wall also. We will be using absorption technology for reflection time management at the listening position.

Low Frequency Resonances

Low frequency room modal resonances will be controlled in both rooms by using either frequency specific low frequency absorbers or a more broadband approach depending on the frequency and amplitude of the resonance. We will focus on the area directly behind each rear ported speaker and work out into the room from that starting position.

Quadratic Diffusion

We will even spec in some diffusion for front and rear walls. Both clients are very serious about their sound and know that they have the quality level of equipment to produce it they are just not hearing it They are both tired of the room getting in the way of their equipment and the sound quality. They are so tired, that they are willing to move walls to get it. Now, That’s what I call passion.

Music is all of our passions and must come first. It is this passion that helps me reset my human clock if you will. Day to day business and personal issues seem to creep in where ever they can. They are like water. They find every place to get in and dampen our spirits. We can not let this happen, especially in today’s times. Close the door in your studio or listening rooms, sit down and then close your eyes. Press play. Hear the reason and passion all rolled into one. It is just between you and the music where it has always been. Carry this passion with you.

Much About Nothing

There is much sensationalism and hyperbole when it comes to acoustic products. Claims are shouted about solving this room acoustic problem with the addition of this or that product on this or that wall hanging device. Sound energy issues and the room distortions they create within a small room acoustic environment are never solved. The best objective to shoot for is good sound energy management within the room itself.

“Bass Absorbers”

One of the areas and I think the area that most acoustic companies contribute to is the claims made for low frequency or bass absorbers. First, the name bass absorber is not accurate. We do not absorb bass with current technologies, we absorb some of the bass, never all. It is not as the name implies a complete bass absorption remedy at any frequency nor in any room location.

Low Frequency Definition

Another area of concern in the literature is the definition of low frequency. Is low frequency and bass the same? I went into a group of different audio forums and asked for a definition of low frequency. I received 18 responses, all with different answers. Many acoustical product’s companies have artificially generated newer and much higher frequencies ranges for low frequency and this “frequency creep” in always in an upward direction that tends to favor that specific companies developed product. I have even seen 400 cycles labeled a low frequency. Really?

Low Frequencies < 100 Hz.

Lets focus on frequencies below 100 Hz. and use this as our domain. There are few absorbers in the marketplace that go into this range and are designed for operating only in this range. Absorption coefficients and even Sabins measured do not show much absorption activity at 30,40,or even 50 cycles. With these necessary levels to be reached, we also need to absorb at a rate that has a sonic impact within our room. A faster rate is much more desirable, since we are asking a small amount of real estate in the form of an absorber, to deal with 30 and 40′ waves of energy.

Sound Management

Deal or manage the energy is what our goal should be. We can not control it to a point that it is ruler flat throughout the entire 20 Hz.-20,000 Hz. range. We can reduce pressure levels and lower their amplitudes, so that we can force the room response into some type of acceptable parameter. Room acoustics and the treatments that go with it are always about compromise in some form or another.

Helmholtz Resonators

There are many different ideas on what constitutes a low frequency absorber design. Two basic designs that have stood the test of time are Helmholtz resonators and diaphragmatic absorbers. A Helmholtz resonator is a coke bottle. It is a cavity that is filled with air and that cavity has a specific length. Air inside the cavity reacts with air at the neck opening and this creates a spring type action. Change the length or volume of the cavity and one can change the frequency. A 8 oz., glass, coke bottle resonates at 185 Hz.

Diaphragmatic Absorption Process

Diaphragmatic Absorption

A diaphragmatic absorber is a little more complicated but works on a similar principle of resonance. The air inside our cabinet or diaphragmatic absorber works in sympathy with the movement of the front panel or diaphragm. This vibrational dance slows the air movement of the wave down as it enters the cavity or cabinet center. Inside the cabinet is sound absorbent material that not only must absorb the resonances generated because of internal cabinet dimensions but it also must “over absorb”, so that it lowers the cabinet’s Q value by a large amount.

Cabinet Surface Density

The density of the cabinet walls, the depth of the cabinet, and cabinet fill material are important in the overall performance of a diaphragmatic absorber. If one increases the cabinet depth and increases wall density along with it, lower frequencies of resonance can be obtained. Frequencies above the cabinet’s resonant frequency will be absorbed.

Cabinet Fill Material

If one uses a cabinet fill material that is highly absorbent, higher rates of absorption above the cabinet’s resonant frequency can be obtained. The cabinet’s density and depth determine the level or frequency of resonance of the unit, but the quality of the internal cabinet fill material is critical to how fast absorption occurs at any frequency above the cabinet’s designed for resonant frequency.

Cabinet Fill Rate Critical

The internal cabinet fill has an impact on the rate of absorption above the cabinet’s resonant frequency. At lower frequencies within our small room acoustical environments it is favorable to have as low as level or frequency as we physically have space for within the room. It is also good to absorb that energy as fast as possible within the space confines we are given to work with. This increased rate comes with proper fill testing.

Walter Sabine

To determine if a “bass absorber” is capable of absorbing at its sated frequency of resonance and beyond one must look at a unit of measure termed a Sabin. A Sabin was named after a famous and well respected engineer called Walter Sabin. A Sabin is a unit of sound absorption. Think of one square foot of an open window as having a Sabin value of one. An open window regardless of size is a perfect absorber because once sound passes through it does not return. It is gone forever, unless of course you live in Manhattan where your neighbor’s building is 6″ from yours.

Sabins Above 20

A good bench mark for comparing low frequency or bass absorbers as they are called in the literature is to look at how many Sabins are absorbed by the companies testing procedure or lack of procedure. If one does not see Sabin measurements above 20, especially below 100 cycles, then one will need a lot of these units to have an impact on any low frequency issues.

There is a lot of confusion in the sales literature when it comes to low frequency absorbers. Low frequency definitions are created to suit the individual companies product’s performance. A good, low frequency, energy absorber will be as large as a floor standing speaker and probably weigh more, but if designed correctly can assist one well in managing low frequency issues in our small room environments. It may be big and heavy but it will earn its keep.

Reflections Are Good

Reflections from our room’s walls, floors, and ceiling all contribute to an ultimate end. Their final destination is to aid us when properly managed within the room to achieve a sense of spaciousness in our sonic presentations. Audiophiles would use the term “air”. Whatever it is called it can be raised or lowered in its presentation value to achieve a balance of some type between direct and reflected energy from our loudspeakers.

Olive And Toole

There is much in the literature about the level of reflections and the delay of said reflections. Olive and Toole did work in this area. Reflection levels when compared with decay rates of same produce this region of time measured in milliseconds that produces a home for spaciousness or “air” with our two channel systems.

Optimum Range Determined

When one compares the direct sound energy to reflected, Olive and Toole found that reflected energy delays that were in the 0 – 20ms. range were most suitable for hi-fi listening because in this range the ” reflection audibility threshold varies little with delay.” Since the human ear can detect 1 ms. time differences in reflected energy signals, we have a 19 ms. range to work within for our room tuning efforts.

Science And Art

This is why room tuning is both art and science. Olive and Toole gave us the science but individuals vary between these time domains. We have all seen this. We go listen to someone’s system to listen and immediately notice this or that about the sound. We compare it to what we like and look for the variables that we want to manage. I have noticed some individuals like delays in the 10 ms. range and some in the 15 – 20 ms. range. Most prefer the 15 – 20 ms. range.

Air Where?

Within this range is found our “air” or spaciousness. Air can be defined as the space or distance between each of our instruments and vocals that occupy our sound stage. Between our speakers is a three dimensional sound field that has a height, width, and if the room is correctly treated, a depth that can actually come close to imitating a live event. I say come close but not completely. There is no sonic substitute for a properly balanced live presentation in a room acoustically treated for music. This level of spaciousness is directly proportional to the time relationship between the direct sound and all reflections that impact upon it.

Image Size And Positioning

Referring back to our sound stage example, we now have two other variables to consider. These two variables are image size and image position. Our three dimensional sound field presented between our loud speakers and hopefully extending well right of the right channel and well left of the left channel in the horizontal dimension. We also have our sound field also extending beyond the ceiling and deeper and longer than the room length. Within this satge we will “see” images.

Instrument And Vocal Images

One will be able to point to the drummer and his image position on our sound stage. We can also do this with guitar and other instruments. Vocal image is usually center stage. With different levels or reflection levels from side walls as compared to direct sound beyond that exceed our time range, we can get these images to shift from their recorded position in the mix to right center or even left center stage.
Obviously, image shifting is undesirable.

Free Space Sound

The best sound that we will ever hear is sound in free space. Free space sound is sound that is in free space. It is not locked up in a room with four walls, ceiling and floor. Take your stereo up in the mountains, elevation 8,000 feet and very quiet. Set up a simple two channel system, play music. No room, no reflections, no bass boom, just pure music.

Rooms Are Distortion

Our rooms produce distortions because they are rooms. They are a space created from nothing. If you raise walls from a floor and put a ceiling on it, one has created a room. The size of the room and its associated volume produces distortions due to the room’s dimensions. These distortions range from low frequency to low, middle frequencies. Low frequency issues are created by the room’s measurements. This low frequency distortion can result in +20 dB – 30 dB bumps in our room frequency response below 80 cycles.

Low Frequency Distortions

Low frequency energy issues produce many very severe distortions that minimizing them by choosing the combination of room width, height, and length from the beginning that produces the best room modal separation. There are room ratio guidelines available to assist one in determining these correct ratios. It may even be necessary to make the room physically smaller in order for it to have better low frequency response.

Box Of Pressure

When we build a room with floor, side walls, and a ceiling, we are building a box for sound pressure to be trapped in and surfaces for energy to bounce off of producing reflections. Reflections from room boundary surfaces take on a life of their own. They even disguise themselves with a new name. If a lot of reflections are concentrated in a room area, we call that a comb filter. It is called a “comb” filter because its sonic signature looks like the teeth of a comb.

Mode Coupling

If we take a normal room size dimension, we have three axis that room modal resonances can be located with. Well, located is used loosely. The axial mode is the modes that occur between the two parallel walls to the right and left of the listening position. These are also termed right angel reflections. A tangential mode is when we add in resonances that occur between the side and end walls in our room. If we add the floor and ceiling to the mix we now have 6 surfaces which are called oblique modes. These modes create pressure patterns that are strong on one side and weak on the other. Add in all the fundamentals that go with each frequency and you have a room that is talking to itself. It must be taken to a doctor.

Comb Filter Not For Hair

Behind this mass of “comb teeth” is hiding our real sound. Unfortunately, the comb filter effect is so pronounced that it will mask certain frequency ranges completely. Sounds and music found within this masked domain are not heard very well. The sound and music is there it is just that by the time some of it fights through the comb filter, one can not recognize the music.

Comb That Hides Music

Comb filters distort and hide the music from us. Comb filters can occur between the walls and listening or monitoring position. One can have a comb filter notch from the console to the monitoring position. Obviously, this is deadly if one’s goal is to produce a balanced mix. No amount of golden ears will be able to hear through that soup in the mid range and no one wants to fight that all day.

Furniture, Walls, And Us

Furniture and side walls can create a comb filter. Any two surfaces that can trap energy in some manner between each of their respective surfaces and cause time delays in the original signal, can produce a comb filter. Even our bodies could, if all other variables were addressed and in place. Once energy gets “trapped” between each surface, it gets angry and shows its teeth.

Speaker / Boundary Issues

The next issue of distortion is called the speaker boundary interference. These are issues that deal with low frequency pressure build up as a result of the speaker’s close proximity to the wall or as the name implies boundary. The direct sound from our loudspeaker is the sound that travels in a straight line from the speakers to our ears. The reflected sound from our room’s walls,floors, and ceilings produce their own set of difficulties.

Room Critical Band

However, sound also is radiated from our speaker sides and rear especially with lower frequencies and definitely with rear ported speakers. This lower frequency energy interacts with the room’s physical dimensions. Some of the room dimensions are a favorable ratio to low frequency waves and no resonances are produced. Other room dimensions can play havoc with certain frequency ranges from 30 Hz. – 200 Hz. This is not the frequency band that we want any resonances in. One could say that just as human hearing has critical bands that the brain processes information with and this 30 cycle to 200 cycles is a critical room band.

Stay Away From Our Vocals

Based on the size of most rooms that have less than 20′ in any direction, this is a critical low frequency band and the beginning of the low middle bands where are vocals both male and female begin to take form and shape. We do not want any resonances artificially boosting certain frequencies and smothering completely others when our vocals are directly impacted.

Reflections

The reflections created by speaker/boundary impact can confuse the direct energy from our loudspeakers. Our total sound is the sound of our system interlaced with the room sound. One can not have quality room sound by adding different speakers or amplifiers. All you will get for the additional expense is more or less of what the room will permit you to have acoustically.

Room And System Balance

Quality two channel sound is always a balance between room and system. They both count 50% towards the total sound, so therefore with their 50% contribution to our final sound, we must take the room treatment just as seriously as we did our equipment.I see many good systems that are capable of so much more sound because of each components quality levels. The room is in the way.

Diffusion Brings Air

Lack of diffusion is viewed as a room distortion because room boundary surfaces that are properly treated with diffusion sound more natural and realistic. It is easy to place too much absorptive materials naturally in the room especially if the room is used for living and listening. Diffusion technologies properly positioned bring more “air” or realism to our musical environment. Using absorption is manage reflections, one runs the risk of absorbing energy to manage it. Once energy is absorbed it is converted to heat and thus is lost forever. Diffusion can minimize the negative effects of reflections without converting them to a different energy form.

Our rooms are “boxes” that contain sound pressure and reflections. All of these issues cause some type of distortion on our musical signal. Low frequency pressure causes bass boom and room modal resonances. The speaker and walls are the genesis of most of these issues. Lack of proper diffusion in our box makes for an unrealistic presentation with our music sources.

Most Powerful Magnetic Generator

I have been reading about some of the current findings and research that has been going on with the study of the human heart. Researchers are finding that the heart is much more than a muscle to pump blood through the body. In fact, the whole body, not just the heart actually moves blood through itself. The heart is also one of the most powerful magnetic generator and receivers known for its size. It is this feature that is the communication web for the brain and heart.

Neural Cells In Heart

I always thought the heart was independent in some way from the brain especially when it comes to music. Researchers have found that 60 – 65% of the cells of the heart are what they call neural cells which are just like brain cells. So our heart is composed by a margin more than half of brain cells. Does our heart think like our brain? What do these brain cells within our heart actually do.

Its Own Nervous System

Science has also discovered that the brain and the heart are linked together in many more ways than originally thought. They have discovered that the heart has its own nervous system and one could consider the heart as a specialized part of the brain. I think that is the reason our hearts connect to the music quicker than our brains do. Our hearts store memories with their “brain” cells and these memories are interpreted with the nervous system of our hearts so we can then emotionally connect to the music.

Emotional Connection

When I hear a song from the past, I am immediately transported back through time to where and what I was doing when I originally heard that particular sound. I do not remember what was the specific year of the song but I do remember what I was doing at that time and where I was geographically in my life. I even can remember other groups or songs that I was listening to at the same time. Perhaps the heart stores the emotional connection I had with the music back then and now when I am hearing the song again, it recalls those emotional connections for me.

Heart Felt

I am sure others have felt this experience. You are somewhere and you hear an old song and are immediately transported back through time and space into the same dimension if you will of where you were when you first heard that song and really connected to it. I think this could be the reason we can listen to the same song over and over again without getting tired of it. Our brains may be tired of hearing it and our friend’s brains may be also equally tired of hearing it, but our hearts like the feeling of the song and transmit that feeling through its nervous system into ours.

Coherence

The topic of coherence is a big part of the heart and brain. Coherence in this instance refers to two forces working together to achieve a larger goal. It is similar to synergy but not quite the same. In synergy, we have two forces that melt together to form a new entity that is greater in either positive or negative ways than each individual component. Coherence is two forces working together for just the sake of working together and generating positive energy.

Rhythms

Our hearts rhythms are tied to our emotions through coherence. Our heart’s rhythms reflect the actual emotion that each rhythm is connected to. All of these rhythms interlace together to produce a field of energy that can be likened to a radio wave. A radio wave modulates energy and music is attached to those modulations. It radiates out from the heart in 10′ distances.

Modulations

As these “modulations” move along they were produced or enter twined with emotions. Emotions are attached to experience and every emotion adds to the rate and level of energy modulations. These modulations can add energy to the field through these modulations and cause changes in the energy field.

Chi

Many religions use this coherence between the heart’s rhythms and emotions to produce a field that one can focus on and control to accomplish many internal system objectives. A person’s Chi or energy field can be tapped into by the individual and made to work in positive ways. Studies are underway with using this energy field as a form of healing both physically and spiritually.

Heart Felt

When the brain and heart form a coherence to produce an energy field, the brain takes a back seat to the heart. This causes the brain to become more connected to the body. When the brain takes the lead there is less connection to the body. When the heart is in the forefront, there are many changes. Mental chatter and both blood pressure systems become more balanced and in synch with each other. William Teller describes this electrical transmission chain:

“The major centers of the body containing biological oscillators can act as coupled electrical oscillators. These oscillators can be brought to synchronized modes of operation through mental and emotional self-control and the effects on the body of such synchronization are correlated with significant shifts in perception.”

Heart First For Music

With all of this coherence between our body systems such as the heart and mind we are beginning to see that our hearts are really the mechanism that we relate to music with. If we can measure heart electrical modulations from a physical distance of 10′ and these modulations are attached to emotions then our brain’s need to get out of the way and listen to the heart. I always tell people that the only sound in your room that matters is the sounds that you emotionally connect to.

Dedicated Audiophiles

There are two different levels of audiophiles. There are those that have a dedicated room only for two channel playback and listening. These dedicated audiophiles take care in the equipment they match together to produce the sound that they are seeking. They match amplifiers with speakers with cables to produce a sonic synergism that can be quite amazing and emotionally connecting for that audiophile. They pay the same care and attention to their room sound. There is one chair that is placed in the best area for room and listener. No reservations are necessary at any time.

Not So Dedicated

Other audiophiles are serious about their equipment and match components together to achieve a certain sound from their system. Unfortunately, they have it placed into a room that has other functions attached to it. Usually it is a living room with some type of video presentation screen on the front wall. It can also be a family room with a fireplace or some other visual distraction. Listening time is by a schedule that takes into account the schedule of others in the domicile.

Hybrids?

Our latest project concerns a blend of both of these types. This project involves components of both major groups. The room is not dedicated to hi-fi, but that is all one can do there. Well, one can watch video on the screen, but mostly the room is an audio room. The owner has just purchased a new amplifier and speaker system and when he got it placed in his room, he realized that the sound was not what he wanted, so he called me.

Room Treatment Requirement

He stated that after 40 years of buying new equipment, he has finally realized that he must deal with the room and have the room acoustically treated if he is to even begin to hear what his new system is capable of. Even though I admire this person’s courage and persistence, I can not help but think how behind we are in teaching people about the music that is in their room and that they need proper room acoustic treatment to hear it. The room wants to keep the music for itself. Room acoustic treatment releases the music from the room’s control and lets the listener hear it properly.

Right Side Wall/Glass Window

Right Side Wall Issues

Our issues with the room begin with the side wall reflection surfaces. The right channel side wall reflection surface is not an usual wall construction. It is a wall of glass because it is a large window. Our right channel, first side wall reflection point is a large piece of glass.

Left Side Wall/Album Closet

Left Side Wall Issues

The left side wall is at a different distance from the left channel as the right channel glass wall is. It is at a different distance because it is a closet without a door. Well, it physically resembles a closet without the doors. As you can see, no shoes on the walls, just albums and cds.

Front Wall/Equipment Rack

Front Wall Issues

The front wall has a horizontally positioned equipment rack. It is not just individual components with space between them but a solid rack of equipment that takes up a lot of precious acoustical space. There should not be anything that occupies the space between the left and right channel speakers. Anything that sits in this place, has an impact on the sound stage. It is best left free of clutter.

Room 15′ Wide

Narrow Room Width

The room is long behind the listening position. Our length dimension is 25′. However, our width dimension is at 15′, so we will have to deal with low and middle frequency pressure issues in the axial room resonance domain, especially since the Usher speakers are rear ported.

Acoustic Objective 1

Our first approach is to deal with the right channel, side wall reflection area. The glass must go, at least while we are listening to music. However, we must only make it go when music is listened to. The rest of the time it must be a window. We will need something that is movable and acts like a wall. It must be easily positioned and then re positioned somewhere else, when we need to look out the window.

Objective 2

Our primary left side wall reflection point is really an acoustical closet. It is a cavity with its own resonant frequency. It is another speaker into the room. It is a very unwanted speaker. The acoustical closet also delays reflection times at the listening position because it is two feet deeper in distance than the right side walls. This difference in physical distance makes for uneven arrival times at the listening positions.

Objective 3

The front wall extends out into the room about two feet because of the equipment rack. The amount of equipment has been assembled and placed into a very critical area that effects sound stage image depth along with instrument and vocal separation. This area needs to be less cluttered and more spacious.

Objective 4

Low and middle frequency build up in the front of our room is an issue and must be dealt with within that room’s physical area. We will need powerful sound absorption technology for both low and middle frequency ranges.

Side Walls Proposed Solution

This will be a project where we will alter the left and right channel side wall distances to make them more equal. The right channel distance altering will have to serve two purposes. It will have to temporarily cover the window and then provide the surface area for proper room treatment technologies. It will have to do this when listening to music and then get out of the way for window viewing easily.

No More Acoustic Closet

Our left channel acoustical closet will have to go. We can not have a cavity that close to the listening position producing sound energy of its own. We also will have to adjust the distances to equal out between left channel and right channel speaker primary reflection points. We can turn this closet into an area for low frequency absorption technology.

Front Wall New Build

We will have to move the equipment and free up that space for more sound stage depth. The front wall will also have to incorporate the low frequency absorbing technology and provide a platform for our equipment to sit upon.

Watch for our build out solutions in Hi-Fi Room Tuning Project #2.