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Building broadband absorber the easy way

Building broadband absorber the easy way

One of the greatest challenges of any studioroom is adapting the acoustics to such a level that it doesn’t interfere too much with the audio coming from your monitors. One thing that get noticably better after you’ve added some soundimprovements is the stereo-image. Because the first reflections will be absorbed or have changed direction, direct information from the monitor will enter your ear first and not the reflections that make it harder to notice the balance. Also, it will greatly improve recordings if they are done in the same room, simply because there’s less reflections. There are a few options you have regarding soundimprovement and they are not all that expensive.

The simplest improvements and most obvious are ofcourse adding big bulky, soft couches and chairs. Put them at the rear wall, opposite your monitorposition and they’ll suck up a lot of mid and a bit of low end. But only for a portion, this is not enough for adjusting the acoustics to a level that it’s reasonably ‘dead’. Since you cannot fill the complete room with couches and chairs you can setup large open cabinets filled with different size books. These cabinets will work as sound reflectors or rather, scatterers. This will help in avoiding standing waves at certain frequencies as well as absorb a few in the mid and high end. But still, you cannot fill your room with books, let alone the fact that you must have so many books…

ABIMG_0002As most of the walls are clean and plainwhite you could consider hanging broadband absorbers. The panels made here are about 1,5m high and 1 meter wide. The panel is filled with aixfoam triangle shaped foam of 5 centimeters height. There is a potential health hazard in using Rockwool, if you use this be sure to cover the whole panel, back and front, and not only the front. The small fibers that Rockwool releases over time do get into your lungs, and can have nasty consequences.

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The whole constructions is made from a hardboard-back with big 63mm holes in it. This is to let sound enter the panel from the back as well as from the front. The sides of the panel are just plain wood of 56mm height. The side are glued and nailed together to make a solid construction. Then 3 plates of Aixfoam panels of 1m by 50cm are added and glued to the back with Bison Construction Glue. The whole panel is covered with a fabric which is quite open of structure. I choose this nice gray linnen fabric. You can test this fabric by putting it to your ear and listen for not too much damping. Also if you blow on it lightly it should be able to let air pass. If you choose a fabric that is to thick, to tight it won’t deliver a very good performance absorbing the audio. The fabric is tackered onto the panel.

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The panel is constructed 7 cm of the wall so there’s a gap between the panel and the wall. This is to let the panel not only catch audio from the front but also to catch sound that is reflected back from the wall. I would say this is a double action panel. Also you could do a bit of ‘tuning’ of which frequency center you would like to catch mostly. But since these absorbers are broadband, they are mostly effective in the mid and higher frequencies.

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By hanging these panels onto the walls you’ll notice a good improvement of your mid and high frequency acoustics. All the first reflections on the side walls are absorbed. This should result in a remarkable better stereo image. Now you could add some absorber above your head for absorbing the first reflections coming from above, more on that later.

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