To start off here's the music wing I design for SUNY. Rated pretty high up in News Week.https://www.youtube.com/watch?v=dsR4GRhCSeo
Jim Bookhard reviews the Tunable Roomhttp://www.michaelgreenaudio.com/forum/viewtopic.php?t=61
above is from the TuneLand Archives
The Tunable Room has been around for almost 20 years now. Every time I have a chance to make one a part me matures a little more in my art. The most recent room being made is for Bill333 in Chicago. Of course all of the wood is being prepared in Las Vegas at my little "dry" hideaway.
Dry is the key to great sound!
Over the years I have learned to listen to dry and can appreciate the full range tonal bliss that comes from products being in their correct performance environment. Most designers however don't understand the basics of the power of drying. They talk about the shape of cabs, or the finish they use but have know idea about voicing or what it takes to shape the sound of transferring vibrations. to get the best sound as a wood designer in this business you must know the facts of wood and air.
for example: If I were to ask you which weighs more, dry air or damp air? most of you would say damp and that would be incorrect. At the same time green wood weighs twice as much as dry cured wood. I've told you for years that understanding the balance of power when it comes to your audio chain will make or break your system. A little study and experience goes a long way.
Interested? Read on.
The total amount of water in a given piece of wood is called its moisture content (MC). Although we are accustomed to the fact that 100% signifies the total amount of something, the MC percent of wood can be greater than 100%. This occurs because the water can weigh more than the wood, and the MC of wood is usually based on the ratio of the weight of the water to the weight of the wood after it has been dried (see Equation).
Equation 1: % MC = weight of water in wood ÷ weight of ovendry (OD) wood
The general range of moisture content for green (undried) hardwood lumber can range between 45% and 150%. The standard method of determining the relationship of water in wood is to:
1. weigh a wood sample before drying to obtain the combined weight of the wood and water;
2. dry the wood sample in an oven at 103 ±2° Centigrade (100°C = boiling point of water) for (approximately) 24 hours;
re-weigh the wood sample;
repeat steps 2 and 3 until the current weight equals the previous weight (the wood sample is now ovendry (OD), sometimes referred to as bone dry);
apply Equation 2 for determining % MC of the wood.
Equation 2: % MC = (weight of wood before drying - OD weight) ÷ OD weight
From the equation above, when the water weighs more than the wood, the % MC will be greater than 100. The OD weight is not a natural state for wood, and the sample must be weighed immediately after being removed from the oven. Because wood is a hygroscopic material (meaning that it readily takes up and retains moisture), it is impossible to prevent moisture from entering dry wood. As soon as the OD sample is exposed to the air, it will start to take in moisture from the air.
Why Dry Wood?
Some important reasons to dry wood include:
Better usability. Wood shrinks as it loses moisture and swells as it gains moisture.
Less likelihood of stain or decay during transit, storage, and use.
Increased strength. As wood dries below 30% MC, most strength properties increase.
Better “hold.” Nails, screws, and glue hold better in seasoned wood.
Better finishing. Paints and finishes adhere better to seasoned wood.
Better heat insulation. Dry wood is a better thermal insulator than wet wood.
Water and Wood
A commonly mistaken belief about lumber is that once dried it is permanently seasoned in its final dimension. A dry piece of wood will exchange water molecules with the surrounding air according to the level of atmospheric relative humidity. Loss or gain of moisture in wood products may cause such troublesome results as shrinking or swelling, interference with paint adhesion, and increased susceptibility to decay and stain.
Water is found in wood in three forms. Free water is found in its liquid state in the cell cavities or lumens of wood. Water vapor may also be present in the air within cell lumens. Bound water is found as a part of the cell wall materials. As wet wood dries, free water leaves the lumens before bound water. Water can be removed from wood fairly easily up to the point where wood reaches its fiber saturation point (FSP). The FSP is defined as that MC where the cell wall is completely saturated with (bound) water, but no liquid water is present in the cell lumens.
Wood does not start to shrink until it has dried below its FSP. FSP for most wood species falls in the range of 25 to 30% MC. It becomes increasingly hard to remove water from wood after reaching the FSP. Remember, it is only after water begins to leave the cell walls that the wood begins to shrink and its strength begins to increase.
How Wood Dries
Wood will seek an equilibrium moisture content (EMC) in relation to the relative humidity (RH) and temperature of its surroundings. That is, as wood is dried below its FSP, the amount of moisture leaving the wood will be determined by the relative humidity of the atmosphere surrounding the wood. For wood to air dry, the moisture content of the air must be less than that of the wood.
Lumber drying is usually accomplished by evaporating the moisture from the surface of the wood. Wood dries “from the outside in”; that is, the surface of the wood must be drier than the interior if moisture is to be removed. Moisture will move from an area of higher moisture content to an area of lower moisture content within the wood. When the surface moisture evaporates from the sides or ends, moisture moves from the interior toward these locations. This process continues until the wood reaches its EMC. At this point the moisture content is equal throughout the piece of wood. Thicker lumber exposed to the same drying conditions will take longer to reach its EMC than thinner lumber.
Wood dries along the grain up to 15 times faster than across the grain. Therefore, a board will dry at a faster rate from its ends. However, because a board is usually many times longer than it is thick, most of the moisture loss occurs across the grain and out the surfaces of the piece. In other words, the moisture travels across the grain at a slower rate, but it has to cross a much shorter distance and, except near the ends of the board, it dries more through the surfaces.
The rate at which lumber dries is controlled both by the rate of evaporation from the surface and by the rate of movement of the water within the piece. As long as the moisture can move from the interior to the surface at a fast enough rate to keep the surface moist, the drying rate will be increased if the surface evaporation rate is increased.
This can be accomplished by:
Increasing the air across the surface of the wood. As long as the RH is low enough, the air will continue to dry all exposed surfaces of the wood.
Increasing the temperature of the air surrounding the wood. Warmer air holds more moisture; by increasing the temperature, the moisture-carrying ability of the air is increased.
Reducing the RH of the air. Water evaporates faster into the drier air.
When I'm working on a project I basically am living in a kiln, sanding, curing, drying, finishing, voicing, and most importantly listening to the sound of what the process is giving me. Sometimes this gets me in trouble because I know people want and need deadlines, but in my world the product tells me when it is done and those of you who heard the difference between finished and not can tell big time.
An evaporate environment makes the difference between good and bad, and between better and extraordinary.
Let me give you another example: Many people think that these heavy MDF cabs are the strongest cabs out there. Not so! a big heavy MDF cab done in a moist shop will not be able to withstand nearly the amount of shock that a thin dry piece of wood will. The more the wood is dried the stronger it becomes. This is what separates the hobbyist from a pro in the world of music reproduction.
So as I get into The Tunable Room the first and deal breaking subject is "understanding dry"