base trap question

[lund101]

In my basement I am going to recess my tv into my front wall for looks and for acustic treatments reasons.I plan on mostly absorbtion for the front wall and side walls up to the speakers because I have a narrow basement! Now on the sides I am going to use panels that are 2ft in hieght at ear level which will leave me about 2 ft from the bottom of the panel to the floor. My thought now is in the space below my side absorbers can I build and use the bass traps that COF has suggested in these forums if so how deep do they have to be? I've heard at least 6 inches? <BR>I guess this question is mainly aimed at COF but please anyone let me hear your ideas.<BR>p.s. I also plan on treating reflection points as well'/idealbb/images/smilies/1.gif'

[crazyoldfart]

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<DIV>How deep they need to be is not an easy question. It depends on what material you use for the panel membrane and which fiberglass you use inside. Also, you want to vary the tuning frequency so they are not all the same. One way to do that is to vary the depth. Another is to change the amount or type of compressed fiberglass on the inside. The third way is to vary the material used for the membrane between materials with difference densities. </DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>I would make the depth at least 4 inches. Deeper panel traps will be tuned to a lower frequency, but if your room in narrow, you will need more upper bass absorption than deep bass absorption.</DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>The deepest tuning can be attained by placing the trap over a corner so that the depth varies from almost nothing to as much as 1.5 feet (for a 2 foot wide panel). </DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>Good luck!</DIV>

[lund101]

what about different surface area like a panel that is 2'x4' and one at 2'x6' and so on all 4" deep?

[crazyoldfart]

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<DIV>Good call!!!</DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>Varying the surface area is another way to change the tuning for three reasons:</DIV><BR>
<DIV>1. The resonant frequency of the panel membrane will change due to the change is mass.</DIV><BR>
<DIV>2. The cavity behind the panel will be a different volume, and thus a different resonance. </DIV><BR>
<DIV>3. The amount of fiberglass in the cavity will change. </DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>Just remember, you absolutely MUST completely seal the cavity behind the panel. Absolutely no leaks can be allowed or the affect will be ruined. This is the hardest part because of the difficulty AND the permanence of the caulk on your walls. </DIV>

[lund101]

just thought I would give my dimensions WxLxH - 10'8"x23'x7'8"

[crazyoldfart]

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<DIV>The lenth is 3x the height, which will be your largest problem. </DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>The length and height modes that fall on the same frequencies are:</DIV><BR>
<DIV>73.6 Hz</DIV><BR>
<DIV>147.5 Hz</DIV><BR>
<DIV>221.0 Hz</DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>The other non-redundant modes are:</DIV><BR>
<DIV>25, 49, 53, 98, 106, 123, 159, 172, 197, 212, 246, 265, and 295Hz (there are more above 300Hz, but they will be controlled by acoustic materials and furniture. </DIV><BR>
<DIV>&nbsp;</DIV><BR>
<DIV>I would focus your tunings to these frequencies. Standard wall mounted traps will not get low enough to work at 73Hz, but the&nbsp;other two modes can be addresses with wall panels. The 73Hz issue can only be handled with corner panel traps or similar. </DIV>