DIY Studio Project
Small rooms have large acoustical issues. Those that realize this are on their way to understanding what needs to be done to manage the two most critical issues we deal with in small rooms: pressure and reflections. Pressure is low frequency energy below 100 Hz. that will not fit into our small rooms. A 50 Hz. wave is 23′ long. Anyone have a 24′ room for it to fit in? Reflections from our wall surfaces interfere with the direct energy from our speakers and distort it.
Modal Pressure Issues
Since none of us have 29′ width or length rooms, we have to work in smaller room sizes and volumes. How many issues our 50 Hz., 23′ long wave, will produce depends on how high of a pressure level we listen at, how many low frequency drivers we have, their diameter and frequency response. Lets forget about sub woofers for the moment and just focus on mini monitors. Some produce energy below 50 Hz. and do a good job at it. What problems will a 23′ long wave cause in a 11′ room ? We know one thing, they will be located at the room boundary surfaces trying to make their escape out of the room. The first boundary surface you must look at in small room is the front and rear walls.
Our data base of 145 built and measured rooms shows that the front and rear walls produce unwanted modal pressure in over 90 % of the room sizes and volumes we have measured. Our data base contains room sizes that begin at 10′ x 10′ x 10′ and go through rooms that are 40′ x 40′ x 40′. A total of 130 rooms out of 145. Yes, that is statistically significant. We can rely on that number and use it to our benefit when we are treating small mix rooms. Of those two options, front and rear walls, the front wall has the greatest unwanted pressure issues. Pressure issues that can be + 12 dB – + 20 dB over acceptable base line measurements. How do we treat such issues?
The Horsepower You Need
First, we need lots of sound absorption power. We need broadband absorption because the unwanted pressure frequency range in the front of our rooms goes from 30 – 200 Hz. Only diaphragmatic absorption has the horsepower that translates to sound absorption power. Our DIY / BDA unit was designed for this frequency range. You can build this unit and add our carbon technology to the cabinet increasing performance of the unit by 35 %. Remember, we need horsepower and we have no space because our room is already to small. Each unit weighs over 200 lbs. Make sure you build them on casters or have a sturdy hand truck for positioning. Reflections from our wall surfaces must be managed with the proper rate and level of absorption.
Roxul, Dupont 703, and building insulation do not possess the correct rates and levels of absorption for music and voice. Music and voice are different and you must match the rates and levels of absorption to the music and voice requirements in your room. Our foam technology took 8 years to develop and does possess the proper rates and levels for music. It won’ t keep your house warm or cool but it will make your music and voice sound natural, life like, and real. We have technology that was designed to treat the low frequency energy in our small rooms, that we can build ourselves and foam technology for the mids and highs that took 8 years to create. Watch how one of our DIY mates down under took advantage of all of this.
Acoustic Foam Absorption Performance Chart
- Acoustic Fields Absorption Coefficient in %
- Auralex Absorption Coefficient in %
- Sonex Absorption Coefficient in %
The red group are rooms that produce so many low, middle, and high frequency energy issues, that large amounts of absorption treatments are required. There is not enough space for diffusion in terms of surface area or distance for wave lengths to fully form. It is the room sizes that are below 2,000 cu. ft. in total volume. The large amounts of treatment surface area, especially in the lower frequencies, will take up so much space that you might not be able to work in it.
The second group (yellow) of room sizes is from 2,000 – 4,000 cu. ft. This group of room sizes and volumes has the necessary space to allow for enough low, middle, and high frequency absorption along with enough space for diffusion. You have the space to place the appropriate low frequency absorption technologies and enough distance for diffusion to work. You will still have issues, especially in the low end but they can be predicted and managed.
The third group (green) is greater than 4,000 cu. ft. It is an ideal grouping of width, height, and length to allow for almost any usage. These rooms have enough distance to allow for appropriate management of all reflection time signatures, unwanted modal pressures, along with enough distances to allow for diffusion to do its job correctly and allow for all diffused wave forms to fully form.
ACDA-10 Activated Carbon
The ACDA-10 is our flagship, activated carbon, broadband, diaphragmatic absorber with low frequency absorption from 30 Hz. – 200 Hz. The face of the unit can be used to support one of our foam absorber thicknesses or one of our mini-diffusors in our MDP line. Units are designed with rigid side and rear walls and a dual wall, front panel construction that increases diaphragmatic action. The inside of each unit contains our activated carbon filters which increase the unit’s Q value through acoustical compliance enhancement. This activated carbon filter process is unique to low frequency absorbers and is patent pending. Solid wood and paint finishes are available. Each unit measures 60″ tall, 30″ wide, and 16″ deep. Each ACDA-10 unit weighs 225 pounds.
All rooms need low frequency energy control, unless you are fortunate enough to have a room that measures at least 30′ in one of it’s dimensions. The ACDA-10 is designed to be a broadband, linear, absorber targeting the 30 Hz. – 200 Hz. range. It is even effective at higher frequencies. With the ACDA-10 unit, you can also control unwanted middle and high frequency reflections through the application of one of our foam thicknesses, mini-diffusors, or a combination of both. You can now have broadband, linear, absorption from 30 Hz.- 6,500 Hz.