Many people we speak with about designing a sound room have no idea where to start acoustically. Not only do they not understand acoustics and how the room influences their sound, but they don’t know how to go about planning to handle all the acoustical issues that the room will produce when you put energy into it. Most rooms are existing rooms that are now going to be a sound room. Some are new rooms that can be built from the foundation up.

First Things First

The first acoustical issue that must be addressed in all rooms no matter existing or new construction is low frequency energy control. In existing rooms we have a predetermined size we must deal with. Those room dimensions will dictate what low frequency issues we will be faced with. Since we can’t make the room larger to minimize low frequency issues, we make it smaller. We make it smaller by using powerful bass absorbers that absorb at high rates and levels of low frequency absorption in the appropriate room positions. In new construction and design, we have the flexibility of making the room dimensions more favorable from the beginning and can minimize low frequency issues by choosing the correct width, height, and length.

No reflections

Reflection control from the room’s boundary surfaces or walls is our next acoustical concern. The direct sound from our loudspeakers is the sound we want to hear the most of. The direct sound is the sound that leaves our loudspeakers and travels in a straight line from our speakers to our ears. Unfortunately, or fortunately, depending on which school of thought one subscribes to that wanted, direct, sound has to be produced in a room and then the direct sound strikes all the room walls eventually and now we have direct sound and room sound. We want a balance of both room sound and direct sound. This balance can be achieved with time and patience, blended with current diffusion and absorption technologies.

Speaker Size

Choosing the correct speaker size for the room is also critical. Bigger is not necessarily better. More energy introduced into a small volume room, will only make our low frequency issues larger. Side wall reflections will cause difficulty at the listening position and the reflections will cause acoustic distortions at the listening position by confusing our brains with the reflected/direct sound mix. Controlling and choosing the correct speaker size is especially critical when one is dealing with low frequency drivers such as a sub woofer. One must choose the correct sub woofer diameter to “match” the volume of the room. We don’t need a 12″ diameter driver in a small room where low frequency issues are always a concern.

Low frequency control can be managed with the appropriate room size. Speaker size should match “room size”. make sure all side wall reflections are managed correctly for proper sound stage focus and clarity.

The Sonic Issues

Robert Green, in the April issue of Absolute Sound examines how speakers interact with the room and especially the floor. His discussion focuses on the frequency range from 100Hz.-300Hz. This is the frequency range where are vocals are present. He sums up his position by stating:

“Somewhere between 100Hz.and 300Hz. there is typically a deep and quite wide trough in the in-room frequency response. The problem is not primarily the speaker’s anechoic response, but the speakers not being designed to interact with the floor correctly. Some of the designers who presumably cannot figure out how to deal with this contend that it is not a problem and that floor bounce is a natural thing. This is nonsense. The natural floor interaction of the original event is already recorded, and whatever floor interaction a system adds, if it does, is spurious and musically devastating.”

Sound Effect

This frequency range that Robert refers to holds the key and emotional connection to our vocals. This is the range where most female and male vocals lie. Male vocals inhabit the range from approximately 150Hz.-300Hz. and female vocals from 200Hz.-400Hz. If we have a dip or trough in the frequency response in this range we lose information. If we can not hear this vocal range because of speaker design issues or room interaction response issues we are doomed if we are going to seek an emotional connection to the music, which has to be our goal.

Bass and Low Frequency
We have the same issues occurring with low frequency or bass energy. Bass notes have long attack and decay modes. It is in this attack and decay process that the true beauty of the bass instruments can shine through. As a bass note is played and is still present in the room, that note will begin to decay. The decay from the first note must be allowed to decay on its own volition and the room response must allow for this decay to unwind on its own and not blur and smear our presentation. Now, a second note follows and the process begins again. It is this attack and decay process that produces a layered bass foundation to our musical presentation where every note is heard in its entirety. The room must be designed to allow this process to occur or we get muddled and confusing bass sounds and we all know what those sound and feel like.

Solution

In order to allow for a tight layered bass response we need a large room. Unfortunately, most people do not have the ability to have a room at least 30′ long to allow for natural bass energy room response to occur. Acoustic product manufacturers claim that end users must “live” with the bass issues and focus on the middle and high frequencies for product design and acoustic control which are much easier to design for. This is nonsense also. Products can be designed to control bass energy attack and decay ratios, so the bass has a tight and layered presentation and we do not need to tear down walls and make the room larger. We also do not need numerous free standing bass absorbers placed throughout the room. In fact, one can take the opposite approach and physically make the room smaller if the bass absorbing technology is designed correctly.

Esperanza Spaulding: Complete Musician

Esperanza Spaulding is a bass player. She is 20 years old. She has the sonic wisdom of someone twice her age. She is also a singer and realizes that both vocals and instruments are separate but related issues. In her interview in the April issue of Bass Player Magazine, she discusses her philosophy on both vocals and instruments and how she feels they are intertwined. When asked by the interviewer about the relationship between singing and playing she said:

Philosophy

“You can think of it like a piano player’s two hands, they generally move independently, and the combination of the two gives you the sound of the chord changes. Singing and playing allows you to be like a pianist in that your aware of how the line of your voice and the line of your bass together form a counterpoint that implies the harmony. The key to creating a good bass line is to remember what was already played and is still hanging in the air. If I play a B in a G chord and I am going to a C7 next, then I want to go back to the B and resolve it up to C because that B is still in the listener’s ears. You have to control how the line resolves into the next harmonic sound: notes are not separate incidents. Great bass players are really in touch with that knowing what was just outlined and what was left unanswered. They only have a single line, but with it they try to weave and sew through all the important notes in the harmonic progression”.

Chicken Skin

Ms. Spaulding knows the importance of one note played and that same note heard correctly in the room in which it is played. She is big on harmonics and how each note contributes to the overall presentation. Look back at your favorite music. You will see that relationship in a vocal harmony or a guitar break. It is that single note or fretboard slide that causes a resonant frequency inside your body that lets you forget everything else at that particular moment and emotionally connect to the music. We all know that sound. It is that sound that causes goosebumps or as my grandma used to say, “chicken skin”. There is no need to explain the cause and the meaning of the “goosebumps” to others. It is immediately understand by all, with no words or explanation needed.

Esperanza Spaulding: Acoustical Engineer

Musicians like Ms. Spaulding are good role models for acoustic design companies to emulate in their product design parameters and their overall acoustical performance philosophy. Every note is important. Every note must be heard and the room and its acoustical design and treatment must allow for this to occur. Acoustical products must be designed to provide the proper amounts of rates and levels of absorption to minimize the surface reflections but not smother them. Each note is important and all notes that follow that first note must be heard in the room. Bass absorbers must have the correct rates and levels of low frequency absorption to provide for the natural harmonic presentation to come through and to be felt and heard. These acoustical concerns must be taken more seriously.

Lessons Learned

Acoustical design companies must take more care in designing their products to allow for musicians work to be heard correctly and in the manner the musician wanted. We need more than fiberglass insulation filled panels and foam filled pillows. We need to control the acoustical issues but remember we are dealing with music first and emotion second. We need to spend more time “voicing” the room and getting the reverberation time and sound stage correct. The bass energy must be controlled, so that layers upon layers of bass lines can be heard and more importantly felt. We need to take that extra step with our acoustical technology that musicians like Ms. Spaulding take in their music. We owe it to the musician and without hesitation, we definitely owe it to the music.