Does my box need bracing?
08-18-2005, 06:50 PM
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Low frequency sound waves are omnidirectional and the human ear cannot locate the origin of sound waves below 80 Hz. This attribute allows subwoofers to be placed anywhere they sound best and allows the use of single subwoofers. Multiple subwoofers provide benefits of increased low frequency power and extension while helping to smooth out frequency response in a given area making two or more subwoofers desirable if possible but certainly not necessary in most cases.
The enclosure walls should be constructed of a high strength material that will not leak air. The most common materials are Medium Density Fiberboard (MDF) and High density particle board. For enclosure volumes less than half a cubic foot, 1/2” to 5/8” material is the minimum. On Enclosures greater than half a cubic foot 5/8 or 3/4” is recommended. Thicker is better, in that it is more rigid. A rigid wall is crucial. When a woofer moves out, the air within the enclosure is rarefied (thinned). If the walls are not of sufficient strength the walls will bend inward, which in turn causes a cancellation of the front wave.
If any wall of the enclosure spans more than 18” it is recommended that the enclosure be braced. This can be accomplished by attaching a 1”x2” piece of wood to the opposite walls of the enclosure. Remember to account for the volume of air that this brace takes up.
Walls should be attached with glue and either screws, nails or staples. Most of the strength of the enclosure comes from the glue, so be sure to use a good wood glue. When using screws, be sure to pre-drill the holes, or the wood will split.
It is a good practice to use cleats in enclosures. A cleat is a strip of wood glued along the inside edges of the enclosure. This technique adds strength to the enclosure.
Before mounting the driver to the enclosure, use a bead of silicone sealant (not bathtub caulk) around the inside edges of the enclosure. This will remove any chance for air leaks.
In closing, frequencies below 80HZ are omidirectional, and the design of the enclosure matters very little (cube or otherwise). Brace the box as much as possible, just remember to include the bracing when calculating your internal volume. 90% of your bass response comes from the enclosure. Do it right, and you'll be amazed by the performance of even mediocre subs.
What you may be thinking of regading a "cube" is that studios and theatres should not be designed as cubes because the internal deflection of the frequencies above 80 Hz (which are uni-directional) will result in cancellation or distortion of certain frequencies.
Hope this helps clear things up.
The enclosure walls should be constructed of a high strength material that will not leak air. The most common materials are Medium Density Fiberboard (MDF) and High density particle board. For enclosure volumes less than half a cubic foot, 1/2” to 5/8” material is the minimum. On Enclosures greater than half a cubic foot 5/8 or 3/4” is recommended. Thicker is better, in that it is more rigid. A rigid wall is crucial. When a woofer moves out, the air within the enclosure is rarefied (thinned). If the walls are not of sufficient strength the walls will bend inward, which in turn causes a cancellation of the front wave.
If any wall of the enclosure spans more than 18” it is recommended that the enclosure be braced. This can be accomplished by attaching a 1”x2” piece of wood to the opposite walls of the enclosure. Remember to account for the volume of air that this brace takes up.
Walls should be attached with glue and either screws, nails or staples. Most of the strength of the enclosure comes from the glue, so be sure to use a good wood glue. When using screws, be sure to pre-drill the holes, or the wood will split.
It is a good practice to use cleats in enclosures. A cleat is a strip of wood glued along the inside edges of the enclosure. This technique adds strength to the enclosure.
Before mounting the driver to the enclosure, use a bead of silicone sealant (not bathtub caulk) around the inside edges of the enclosure. This will remove any chance for air leaks.
In closing, frequencies below 80HZ are omidirectional, and the design of the enclosure matters very little (cube or otherwise). Brace the box as much as possible, just remember to include the bracing when calculating your internal volume. 90% of your bass response comes from the enclosure. Do it right, and you'll be amazed by the performance of even mediocre subs.
What you may be thinking of regading a "cube" is that studios and theatres should not be designed as cubes because the internal deflection of the frequencies above 80 Hz (which are uni-directional) will result in cancellation or distortion of certain frequencies.
Hope this helps clear things up.
08-19-2005, 07:12 AM
#12
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exactly. that's the word i was looking for. cancellation. what i had heard from a local stereo shop, was that a cube shaped box increases cancelation, and causes the bass to be a lot more quiet than you'd expect. godo info above^^^. perhaps that should be set as a sticky somewhere. very useful 
