Acoustics

A Quadratic Diffuser has a series of wells or troughs and each trough has depth at a diffused quarter wavelength on the depth, half wavelength on the width. You can position the diffuser vertically and you’ll get horizontal diffusion or you can position the diffuser horizontally and get vertical diffusion. So whatever the position of the quadratic diffuser, you will have the inverse in terms of diffusion.

Our Quadratic Diffuser Absorber units in a customer’s house. These units are an acoustic

• Vocal rooms: Reflection management is the key for vocal rooms. How are you going to do it? Are you going to use absorption? Are you going to use some diffusion and some absorption? Are you going to use variable acoustics where you can decide based on the timbre and the tone of the singer’s voice? How are we going to deal with the lateral reflections? What combination of absorption and diffusion are you going to use? Always remember that with absorption, the rate is always frequency dependent so you always want to keep that in mind.
• Live rooms: With live rooms you have reverberation times you have to deal with. Direct versus reflected energy. The live room should be large enough to minimize low frequency resonances, that’s always a hope when we’re doing live rooms. You want it big enough so you can get the big, middle and upper frequency sound that you want but make sure it’s big enough so it can handle the low frequency resonance. You can treat rooms and make the bass sound good but there’s just nothing like a larger room when you’re dealing with longer frequencies or longer wave lengths. So it’s really good to have a room that has the correct volume. Variable acoustics on the side walls can be a combination of absorption and diffusion. It all depends on your room size, it all depends on your room usage. It sounds a little complicated, it looks a little complicated but once you get into it you can usually figure it out. So we have low frequency absorption, we have Helmholtz resonators, diaphragmatic absorbers; each room requires a different application of all technologies and it is regardless of what you hear and it is a blend of art and science.

There are 5 common room acoustic problems that people commonly face in recording studios the world over. But to understand them you first need to accept that there are three, and only three, things that happen to sound energy within your studio. It can either be absorbed, reflected, or diffused. That’s it. There are no other characteristics that we can assign to sound energy in our studios, unless we come up with some new laws of physics.

In your studio, you need to be concerned with all three. All three have an impact on your sound within your room whether it is a project studio that you set up in a spare bedroom or a full blown brick and mortar studio with different live, voice, and music rooms. Lets start with absorption and those nasty low frequency “bass booms” we talked about in Chapter 1.

1. Low Frequency Management:  The first acoustic reality and treatment myth that we must address is low frequency energy management. This is the most important element of the top 5 room acoustic mistakes you are making in your studio. Let’s start with an accurate definition.

• • Low frequency energy is any energy that is less than 100 cycles. This definition comes about because you need different absorption technologies for treating energy above 100 Hz. in small room acoustics than you do below 100 Hz. These sound absorption technologies require drastically different approaches to effect treatment and management.
  • Treating energy below 100 Hz. requires mass and depth or distance. Treating energy above 100 Hz. can be accomplished with technologies that take up much less space and can be wall hanging units like foam. The difficult management happens below 100 Hz. Get that out of the way and your mids and highs will pop. As such, low frequency treatment provides a good dividing line from a room acoustic treatment perspective so let’s take a look at what you need.
  • Treatment Is A Must: Low frequency energy below 100 Hz. must be treated. The acoustic power of this energy is covering and smothering certain frequencies within your music that you are not hearing at all because of these room modal issues. Therefore, it is a musical imperative that they must be dealt with. You would not put up with a piece of gear that did not reproduce certain frequencies in its output and likewise you cannot put up with that in your room. This is your product that you produce which reflects your musical talent and production skills. Mess with that at your own risk! You can’t have things missing here. There is a lot of important music from 30 Hz. – 50 Hz. and it must be heard. It is the foundation on which the rest of the sonic presentation exists for. Do not short change this area. Your product will suffer and you will miss sounds that you need to hear during the recording and playback process.
  • Treatment Myths: The treatment myth is that you can get rid of low frequency issues in your room by placing a box filled with building insulation (otherwise known as a bass trap) or foam around your room. First of all, all you can do with frequencies below 100 Hz. within a room is manage them. Certain lower frequency issues can never be eliminated and thus a reason why some people move to larger rooms. Any concern for dealing with this area of the top 5 room acoustic problems you are facing in your studio, must be taken seriously.
  • Make Your Room Smaller: It’s actually counter intuitive but in order to manage your low frequencies, you must make your whole room smaller using the correct technology, namely, diaphragmatic absorbers. You make it smaller by adding this proper low frequency technology around the room boundaries. You do not use boxes filled with building insulation (the aforementioned bass traps…which are good for one thing, trapping dust!) or foam. They do not have the acoustic horsepower to deal with 30 Hz. 40 waves of energy. Using these technologies is like using a feather to stop a tornado.

2. Appearances Are Deceiving: The second myth is that you can set up your studio any way that looks good or “cool”. Unfortunately, the laws of physics don’t give a damn about “cool”. They are simply there to dictate what you can and cannot do. I see studios every day that put decor ahead of acoustical needs. I have a simple question in such situations… “do you hear with your eyes or your ears?”

So here are some simple rules.

• • Speakers must be equal distance from both right and left channel side walls. You cannot have one speaker closer to the side wall than the other. Your seated position must be located a certain distance from your speakers and rear wall. Here is why.
  • Sound Energy Is Constant: Sound energy moves at a defined speed, around 1,130′ per second. Reflections from the side walls will be slower than the straight line sound that comes directly out of your speakers to your ears because it has to travel a bit farther leaving the speaker and then striking the wall. It is that straight line sound that is the purest. It does not contain room sound, but it soon will.
  • Side Wall Reflections: Reflections traveling from both side walls will transverse the direct sound or straight line sound coming from your speakers. It is the proper slowing down of this energy that you must accomplish with correct room treatment technologies. You need the sound energy striking the side walls to have even time signatures, so you can apply the correct rate and level of sound absorption technology. To achieve even time signatures, you need even distances. This is another critical issue in the top five room acoustic mistakes you are making in your studio.
  • Sound Triangle: Your speakers and listening position are a “sound triangle”. The speakers and listening position form the apexes of a triangle that must be moved as a single unit. It is that positioning of all 3 items that must balance with room dimensions and low frequency pressure levels. There is only one position of the “sound triangle within your room that will give you the best frequency response within your room. Most of the time the best position is not what looks the best within your room. Are you concerned with appearance or good sound?
    
    

4. Watch Rates And Levels:  The third common acoustic problem that we see in most studios is that absorption rates and levels for sound absorption treatment can be all over the map. A lot of people will buy a product that absorbs a certain amount of energy and that since it performs on a limited frequency basis, they assume it can do everything acoustically within their room. It cannot, no matter what the manufacturer claims. Remember those laws of physics?
   
   
   • Minimal Absorption: You must absorb at a rate and level of absorption that does just enough to minimize the “acoustical damage” it causes upon your signal. There is no need to eliminate large amounts of your sound energy through absorption. Converting acoustical energy to heat using the process of absorption, eliminates sound forever. Ever been in a room that is just too dead? It is called “dead” for a reason.
   • Reflections Are Rate and Level Sensitive: Reflections from your room wall or boundary surfaces must be controlled at the correct rate and level using sound absorption technology. Most companies will tell you to absorb as much energy as you can to manage the reflected energy. If you do this, you “destroy” the acoustic energy and convert it to heat. You do not want to “destroy” sound energy in order to manage it, at least not all of it. You need to take just a little from each reflected frequency, that it slows down just enough, so that its arrival at your listening or monitoring position is less than the direct or straight line sound from your monitors or speakers. You want the time signature of each reflection to be below the time signature of the direct sound.
     
     
5. Don’t Forget Ceiling and Floor:  Our fourth myth is that the ceiling and floor do not contribute any reflection issues that must be managed. Do you have ceiling treatment in your studio? Most do not. It is very important. Remember your side wall reflections that we needed to slow down, so that they arrived below the time signature of your direct straight line energy from your speakers? Well guess what, the ceiling and floor reflections actually arrive before the side wall reflections do.

• • Ceiling And Floor Closest Surfaces: Think about it. You are closer to the floor and ceiling in small rooms than you are the side walls. Floor and ceiling reflections enter your mix and music play back presentations. They must be managed with the same approach as the side walls. They account for 15 – 20 % of what you’re hearing. They need to be respected and treated.
  • Absorption Or Diffusion: Ceiling reflections can be treated using diffusion or absorption technologies. Each treatment has its own certain acoustic presentation, so you must decide what is the room’s use and what are you trying to do with music within the room. If it is a control room, everything must be heard within the mix and less room sound during monitoring is usually desired. Absorption technology, including low frequency technology, is generally used and located upon the ceiling to minimize ceiling reflection distortions. If your room is for music playback and listening enjoyment then a different room acoustic treatment is needed on room boundary surfaces.
    
    

5. Room Size And Volume Critical: Our fifth myth is that you can locate your new music room in any room size that you currently have available. Sorry, we see a lot of this and there are simply some room sizes that have a certain width, height, and length dimension that you cannot use because the real, low frequency energy, < 100 Hz., cannot be managed at all by current room acoustic product technologies no matter how good they work. In certain room volumes and dimensions, there is no treatment for the low end disease. Find another room size. Sometimes, only a foot here or there will make the difference. Middle and high frequencies also require minimum room distances to be completely heard without room distortions. The Top 5 Room Acoustic Problems You Are Facing In Your rooms It’s critical that you manage your low frequency energy, so that you can hear every note from the lowest 30 cycle note on an electric bass to the bass drum attack and decay of each note. Yes, I know it is not easy, but it can be done with the correct technology. Boxes filled with building insulation and foam (bass traps) will not do it.
   
   Room Treatment Balance: Once you have decided upon the use of the room, treat all room boundary reflections, so that those reflections are working with your room usage and not against you. Also choose a room based upon the needs of the music and not any of your human wants or desires. Your music room is not a living room. It is a room to make music in. Choose the room size and volume that gives you a good chance by adding the correct treatment technologies, to achieve a room sound that is energy balanced across the audio spectrum. Sometimes a few feet in just one dimension can make all the difference. I want to give you answers to your questions if you have them. So I’m going to give you a free 30 minute consultation to give you a chance to get your room working for you. I’ll look at the size of your room. I’ll compare it to our database and give you some ideas of what you can do. We’ll work together and work on your particular room with your particular problem. I’ve got to tell you in all honesty, that you won’t have a problem that I haven’t seen or heard a thousand times and you won’t have a problem that we can’t figure something out for. I want to take the simplest path and work from low frequency management on up as it’s easier if we get the bass under control as then we can go from there.